Clean Energy Trainer Experiment Guide

Clean Energy Trainer Experiment Guide

Clean Energy Trainer Experiment Guide April 2011 Version 1.0 © Heliocentris Energiesysteme Energiesysteme GmbH Rudower Chaussee 29 12489 Berlin Germany All rights reserved. reserved. No part part of this Experiment Experiment Guide may be reproduced, stored in a data retrieval system or transmitted by any means without the prior written permission of the issuer. The following exception applies: photocopying pages pages from the manual for instruction for or by lecturers is allowed. Components of the Clean Energy Trainer are Trainer are protected by patents and / or utility patents. Clean Energy Trainer is a trademark of Heliocentris Energiesysteme GmbH, Germany. We reserve the right to make changes.

Contents 1

Lesson Planning ............................... ............... ................................ ................................. ................................. ................................ ................ 5

2

Solar Energy................................ ............... ................................. ................................ ................................ ................................ ...................... ...... 7 An overview of of all experiments ...................... ........... ...................... ...................... ...................... ..................... ..................... ...................... ............. 7 Learning the different different features features of a solar cell ..................... .......... ...................... ...................... ...................... ...................... ............... .... 9 Experiment 1 ........................................................................................................ 9 Worksheet 1 ...................................................................................................... 11 Answers 1...................... ........... ...................... ...................... ...................... ...................... ...................... ...................... ..................... .................. ........ 13 Determining the the power characteristic characteristic curve of a solar cell. ................ ..................... ........... .................... .......... 15 Experiment 2 ...................................................................................................... 15 Worksheet 2 ...................................................................................................... 17 Answers 2...................... ........... ...................... ...................... ...................... ...................... ...................... ...................... ..................... .................. ........ 19

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Wind Energy................................ ............... ................................. ................................ ................................ ................................ .................... .... 23 An overview of of all experiments experiments ...................... ........... ...................... ...................... ...................... ..................... ..................... ..................... .......... 23 Learning the different different features of a wind generator ..................... .......... ...................... ...................... ...................... ............... .... 25 Experiment 1 ...................................................................................................... 25 Worksheet 1 ...................................................................................................... 27 Answers 1...................... ........... ...................... ...................... ...................... ...................... ...................... ...................... ..................... .................. ........ 29 Determine the characteristic characteristic curve of a wind generator ..................... .......... ...................... ..................... .................... .......... 33 Experiment 2 ...................................................................................................... 33 Worksheet 2 ...................................................................................................... 35 Answers 2...................... ........... ...................... ...................... ...................... ...................... ...................... ...................... ..................... .................. ........ 37

4

Electrolysis ...................................................................................................... 41 An overview of of all experiments ...................... ........... ...................... ...................... ...................... ..................... ..................... ..................... .......... 41 Observe the the characteristics characteristics of water during during an electrolysis ..................... .......... ...................... ...................... ............... .... 43 43 Experiment 1 ...................................................................................................... 43 Worksheet 1 ...................................................................................................... 45 Answers 1...................... ........... ...................... ...................... ...................... ...................... ...................... ...................... ..................... .................. ........ 47 Determining the the characteristic curve of an an electrolyzer ...................... ........... ..................... ..................... ..................... .......... 51 Experiment 2 ...................................................................................................... 51 Worksheet 2 ...................................................................................................... 53 Answers 2...................... ........... ...................... ...................... ...................... ...................... ...................... ...................... ..................... .................. ........ 55 Calculating the degree of efficiency of an electrolyzer electrolyzer ..................... .......... ...................... ...................... ...................... ........... 57 Experiment 3 ...................................................................................................... 57

Clean Energy Trainer - Experiment Guide

1

Contents

Worksheet 3 ...................................................................................................... 59 Answers 3 .......................................................................................................... 61

5

Fuel Cells ......................................................................................................... 65 Initial experience with fuel cells ..................................................................................... 67 Experiment 1 ...................................................................................................... 67 Worksheet 1 ...................................................................................................... 69 Answers 1 .......................................................................................................... 71 Determining the characteristic curve of a fuel cell ............................................................ 75 Experiment 2 ...................................................................................................... 75 Worksheet 2 ...................................................................................................... 77 Answers 2 .......................................................................................................... 79 Calculating the degree of energetic efficiency of a fuel cell .............................................. 83 Experiment 3 ...................................................................................................... 83 Worksheet 3 ...................................................................................................... 85 Solutions 3 ........................................................................................................ 87

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Renewable Energy Sources ............................................................................. 89 Production of hydrogen from renewable energy sources ................................................... 91 Experiment 1 ...................................................................................................... 91 Worksheet 1 ...................................................................................................... 93 Answers 1 .......................................................................................................... 95 Optimal adaptation of renewable energy sources............................................................ 97 Experiment 2 ...................................................................................................... 97 Worksheet 2 ...................................................................................................... 99 Answers 2 ........................................................................................................ 101 Operating several consumers with fuel cells .................................................................. 103 Experiment 3 .................................................................................................... 103 Worksheet 3 .................................................................................................... 105 Answers 3 ........................................................................................................ 107

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Preface Renewable energies and their importance for safeguarding our way of life have now become a matter of general awareness. Their benefits are indisputable. The utility of hydrogen as a fuel has also gained an increased focus in recent years. This Experiment Guide can help explain renewable energies to your students in an entertaining manner and familiarize them with the interrelationships of renewable energy sources and hydrogen. This manual makes the utility of energy conversion comprehensible and promotes an understanding for practical application.

Curriculum aspects

Among other things, this manual can help to communicate the following aspects: 

Principle of solar cells



Principle of wind generators



Chemical reactions



Electrolysis



Faraday's laws



Principle of fuel cells



Efficiencies



Dimensioning of various components of renewable energies



Influences on systems of renewable energies



Conversion of different energy forms



Science and technology in a regional, national and global connection.

Here at Heliocentris we hope that your students will gain experience using our product which will provide them with an understanding of energy sources, hydrogen and fuel cells and pique their general interest in the subject of sustainable solar-hydrogen technology. If only the masculine or feminine form is used in parts of this manual, this is only used for readability and simplicity. Persons of the respective other gender are always included.


3

1

Lesson Planning This Experiment Guide includes 13 experiments covering various thematic blocks from renewable energies. Each of the experiments is accompanied by a worksheet with questions about the experiment as well as a corresponding answer sheet. A fundamental description of the components and the basic action sequence can be found in the Instruction Manual.

Overview

This Experiment Guide contains instruction material covering the subject of renewable energies. This manual is subdivided into the following topics: 

Solar energy



Wind energy



Hydrogen and electrolysis



Fuel cells



The combination of multiple renewable energy sources

There are two to three experiments and two to three worksheets for each topic. The sample solutions for the experiments and the worksheets can be found on the answer sheet. We recommend the following instructional sequence:

Recommended sequence planning

Duration [min]

Social form

Development phase Theoretical part

15

Instructor lecture

Consolidation phase 1 Experiment

20

Group work (3-5 students per group)

Recapitulation 1 Comparison with students

10

Instructor or student lecture, active participation

Consolidation phase 2 Worksheet

25

Individual work or in pairs

Recapitulation 2 Comparison with students

20

Instructor or student lecture, active participation

Activity

Table1-1 Sequence planning

With a 45-minute school hour, the sequence can be discontinued after Recapitulation 1 and resumed in the subsequent hour. At the beginning of each chapter there are didactic explanations for all experiments and a checklist. Prior to the experiment, go through the checklist together with the students. Plan for time at the end of the experimentation to collectively put away the materials.


5

Lesson Planning

TIP

Familiarize yourself with the Clean Energy Trainer before you conduct the experiments during the lesson. For this purpose, read the I nstruction Manual. Conduct the experiments on your own before using them in the lesson. You become familiar with the experiment and can recognize any potential difficulties which your students may encounter.

TIP

Make sure that each student has a copy of the experiment sheets. Consider additional tasks for groups which finish with an experiment before others. However, do not hand out the second worksheet to the "stronger" students ahead of time. The questions on the worksheets may be partly investigated by the students themselves.

The following applies for all experimentation: 



6

If the USB data monitor is used as an energy source, a different energy source (max. 2 V) can take its place. Comparable consumers can always be used instead if the USB data monitor is used as a consumer. There are sample answers on the answer sheets which make no claim to completeness or correctness. They are provided to give possible solutions. If your students arrive at different solutions this does not mean that these answers are not correct – they are only sample solutions.


An overview of all experiments

2

Solar Energy

Experiment 1 - Learning the different features of a solar cell Summary

Worksheet theme

The students become familiar with the typical features of a solar cell in this experiment. In this process, they investigate the influence that the intensity of illumination and the angle of incidence have on the behavior of the measurements of a solar cell.   

Degree of difficulty Advance knowledge Learning objective

Checklist

Easy 

Electrical circuits

The students expand their knowledge in recognizing that the distance, the angle and the brightness of a source of light influence the power of a solar cell. The students learn the importance of close observation in science and the importance of being able to concisely formulate the observations which were made.  

    

TIP

General questions about solar energy Questions about the experiment Comprehension questions and calculations for the power of solar cells

1 solar module USB data monitor - USB cable - PC or laptop with installed software Magnetic bed 1 lamp (at least 75 W) 2 cables, 1 black, 1 red 1 measuring tape Objects for shading (film, thin paper, etc.)

Have the students summarize their observations on an additional sheet of paper.


7

Solar Energy

Experiment 2 - Determining the power characteristic curve of a solar cell Summary

Worksheet theme

In this experiment the students investigate when the solar module can give off its maximum power. Using measurements of current and voltage, they create characteristic curves for varying light irradiation and recognize the maximum power of the solar cell.   

Degree of difficulty Prior knowledge

Medium    

Learning objective

Checklist



    

8

Creation of a current/voltage characteristic curve Creation of an power characteristic curve Calculating electrical power Electrical circuits

The students expand their knowledge when recognizing that there is a range of values in which the solar cell provides its maximum power. The students expand their knowledge in determining the MPP (Maximum Power Point) of a solar cell. 

TIP

General questions about the solar cell Questions about the experiment Comprehension questions about characteristic curves and the power of a solar cell

1 solar module USB data monitor - USB cable - PC or laptop with installed software Magnetic bed 2 cables, 1 black, 1 red 1 lamp (at least 75 W) 1 measuring tape 1 color transparent film

In this experiment you assign different groups with different tasks. For example, Group 1 draws the characteristic curves for varying light intensity, Group 2 draws the characteristic curve for solar modules connected in a series or parallel, Group 3 draws the characteristic curve for different angles and Group 4 draws for different distances.


Learning the different features of a solar cell

Experiment 1 How do the measurements behave depending on the angle of irradiation?

Fig.2-1 Experiment 1 setup

1. Set up experiment as shown in Fig.2-1. 2. Adjust the distance of the lamp to the solar cell to 50 cm. The angle of irradiation should be approx. 90°. 3. Start the software and select the S OLAR MODULE tab. 4. Switch the operation mode to M AN UA L

MO DE .

5. Switch on the lamp. 6. Change the angle of the solar module by hand. The distance to the solar module must always be the same. Make sure that the magnet base always remains in the same position. 7. Observe the measurements and make not of the observations.

How do the measurements behave depending on the intensity of illumination? 1. Set up experiment as shown in Fig.2-1. 2. Adjust the distance of the lamp to the solar cell to 50 cm. The angle of irradiation should be approx. 90°. 3. Hold various objects (films, sheets) between the lamp and solar module and observe the measurements and make note of observations.


9

Worksheet 1



Questions about the experiment 1. How do the measurements behave depending on the tilt angle? 2. How do the measurements behave depending on the intensity of illumination? 3. What general statements can be made about the measurements with a continuously increasing intensity of i llumination? 4. What factors does the angle of irradiation depend on? 5. What can contribute to shadowing?

General questions 6. What is solar energy? 7. What is solar electricity and what does photovoltaic mean? 8. What is needed to feed solar electricity into the mains power grid? 9. How is a solar cell assembled?

Comprehension questions 10. We only consider voltage values in the experiments. Why is the current value always the same? 11. Is the generation rate of electricity the same every day of the year? Why or why not? What could be a solution for this? 12. What factors does the ideal current yield depend on? 13. What physical size can the current and voltage values of the solar module reach?


11



Answers 1 Questions about the experiment

1. How do the measurements behave depending on the tilt angle? 

The observation shows that the solar module exhibits the greatest voltage value with an angle of irradiation of 90°.

2. How do the measurements behave depending on the intensity of illumination? 

Observation shows that the solar cell exhibits increasing voltage values with increasing illumination.

3. What general statements can be made about the measurements with a continuously increasing intensity of i llumination? 

The greater the intensity of illumination, the higher the voltage.

4. What factors does the angle of irradiation depend on? 

It is crucial that the number of photons of the light source meeting the surface of the solar module is as high as possible. This is the case if the surface which is met by the light is especially large and the intensity of the irradiation is especially high.

5. What can contribute to shadowing? Shadowing can have the following causes:     

Clouds Trees Buildings Other solar modules Incorrectly selected installation location

General questions 6. What is solar energy? 

Solar energy is the Sun's energy transmitted through irradiation. Irradiation energy is released during the conversion of hydrogen to helium in the Sun (core fusion) and results in light and heat. The Sun radiates more energy to the earth in an hour than the entire world population consumes in a year. Without this energy, life on earth could not exist.

7. What is solar electricity and what does photovoltaic mean? 

Solar energy is the current which is generated by the photovoltaic effect in solar cells. Photovoltaic (abb.: PV) is the technology with which the sun's energy is converted into electric direct current.

8. What is needed to feed solar electricity into the mains power grid?


13

Solar Energy



The direct current produced by the solar cells is guided to the inverter. This device converts the direct current into alternating current.

9. How is a solar cell assembled? 

Solar cells are normally made of thin silicon disks. Through precision contamination of the pure silicon with foreign atoms, a negative conductive layer and a positive conductive layer are created. An electrical field is generated in the transition zone between the two layers.

Comprehension questions 10. We only consider voltage values in the experiments. Why is the current value always the same? 

No consumer is connected. Therefore, no current flows.

11. Will the generation rate of electricity be the same every day of the year? Why or why not? What could be a solution for this? 

The rate of generation of electrical energy is not the same every day because the sun's irradiation varies depending on the weather and the time of year. A motorized mount for the solar module could be constructed, which automatically follows the optimal angle of irradiation to the Sun.

12. What factors does the ideal current yield depend on? 

The ideal current yield depends on a number of factors. 

  

Material of the solar cells (silicon monocrystalline, silicon polycrystalline, semiconductors, etc.) Size of the solar module Location Conditions at the location (shadowing, temperature, etc.)

13. What physical size can the current and voltage values of the solar module reach? 

14

The power.


Determining the power characteristic curve of a solar cell

Experiment 2

Fig.2-2 Experiment 2 setup

When does the solar module provide maximum power? 1. Set up experiment as shown in Fig.2-2. 2. Adjust the distance from the lamp to the solar cell to 50 cm. The angle of irradiation should be approx. 90°. 3. Start the software and select the S OLAR MODULE tab. 4. Switch on the lamp. 5. Switch the operation mode to AU TO MA TI C MO DE and start the measurement. 6. Record current and voltage values in a table and calculate the power. 

The power P is calculated with the formula     .

7. Draw the power characteristic curve. 

Click on P OWER C HARACTERISTIC CURVE in the software and compare with the power characteristic curve which is shown.

When does the solar module provide maximum power with a low intensity of illumination? 1. Hold a film between the lamp and solar module and re-start the automatic measurement. 2. Record current and voltage values in a table and calculate the power. 3. Plot the power voltage characteristic curve into the power voltage characteristic curve from the previous experiment (only if a previous experiment was conducted).


15

Solar Energy



16

Click on P OWER CHARACTERISTIC CURVE in the software and compare with the power characteristic curve which is shown.


Worksheet 2



Questions about the experiment 1. When does the solar module provide maximum power? 2. When does the solar module provide maximum power with a low intensity of illumination? 3. What is a characteristic curve? 4. How is the maximum power point of the solar module calculated? 5. Has the MPP (Maximum Power Point) of the solar cell changed with a lower intensity of illumination? Can a generalization be made? 6. Which graphic visualization is best suited for reading the MPP? 7. Is the MPP constant? What does the MPP depend on?

General questions 8. What are the advantages of solar electricity? 9. In what areas does solar electricity make the most sense? 10. What are the disadvantages of solar cells? 11. Who is credited as the inventor of the solar cell? 12. When was the first solar cell created? 13. Do solar cells generate direct or alternating current? 14. What is the name of the component which converts direct current into alternating current? 15. What is built into an inverter for PV systems so that the maximum power of solar cells is achieved? 16. What types of solar cells are there? Which have the highest degree of efficiency? Which are the most affordable?

Comprehension questions 17. Does a solar cell behave similarly to other power sources, such as batteries, when connected in a series and in parallel? 18. If one solar cell within a series of connected solar cells is destroyed, is the current flow interrupted? 19. How could the problem from the previous question be solved? 20. Is the efficiency of solar cell comparable with that of a diesel engine? 21. How does a characteristic curve in the current/voltage characteristic curve behave if the resistance is doubled? 22. Known or estimated? How high is the annual energy output [kWh] of a photovoltaic system for an average single family home? Clean Energy Trainer - Experiment Guide

17

Solar Energy

23. How many of the solar modules used in the experiment are required to operate the following devices? Unit

P [W]

Computer

400 W

Car radio

40 W

Mobile phone

2W

Hair dryer

2,000 W

Light bulb

2.4 W

Number of solar modules

24. Can a light bulb be damaged if 20 more modules are connected in parallel than the number of modules calculated above?

18




Answers 2 Questions about the experiment 1. When does the solar module provide maximum power?  

The solar modules has a maximum power approx. 1.7 V and 145 mA (with one 75 W lamp). This can be seen from the current/voltage characteristic curve. The curve represents the power.

I / mA

Current/voltage characteristic curve

300 250 150 100 50

0,3

Power characteristic curve 1

0,6

0,9

1,2

1,5

1,8

2,1

2,4

0,6

0,9

1,2

1,5

1,8

2,1

2,4

U / V

P / mW 250 200 150 100 50

0,3

U / V

2. When does the solar module provide maximum power with a low intensity of illumination?  


The solar module has a maximum power approx. 1.7 V and 70 mA (with one 75 W lamp and a film covering). The MPP has shifted.

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Solar Energy

Power characteristic curve 2

P / mW 250 200 150 100 50

0,3

0,6

0,9

1,2

1,5

1,8

2,1

2,4

U / V

3. What is a characteristic curve? 



A characteristic curve is a graphic visualization of two physical sizes which are independent of one another. This visualization is representative for a specific component. The characteristic curve is represented as a diagram in a twodimensional coordinate system.

4. How is the MPP (Maximum Power Point) of the solar module calculated?  



From the power characteristic curve. Or: The MPP can be determined from the product of the measured voltage and current values. Or: The rectangle with the largest surface area under the current/voltage characteristic curve corresponds to the maximum power. The respective current and voltage values indicate the MPP of the solar module.

5. Has the MPP of the solar cell changed with a lower intensity of illumination? Can a generalization be made? 

Yes, the MPP is measured with lower voltage and lower current and therefore is lower. The lower the irradiation, the lower the current and voltage values of the MPP.

6. Which graphic visualization is best suited for reading the MPP? 

The characteristic curve.

7. Is the MPP constant? What does the MPP depend on?  

The MPP is not constant. It depends primarily on the intensity of illumination.

General questions 8. What are the advantages of solar electricity? 

20

The Sun is the greatest and most secure energy source. Clean Energy Trainer - Experiment Guide

Solar Energy

  

Solar energy is a clean and free energy. Solar energy can be used directly on site. There are no transportation costs and thus no large line losses. Solar systems are technically mature, have a long service life and increase the value of a house.

9. In what areas does solar electricity make the most sense? 

Areas with high solar irradiation (long duration of sunshine and largest possible angle of irradiation, such as in the Sahara Desert).

10. What are the disadvantages of solar cells?    

Solar energy depends on the weather. Solar energy is only usable during the day. Large surfaces are needed for solar modules (except for the roof of a house, because this surface is not used otherwise) The production of solar modules is expensive.

11. Who is credited as the inventor of the solar cell? 



Alexandre Edmund Becquerel observed that a battery which sits in the sun has a higher output that batteries sitting in the dark. The photovoltaic effect was explained by Albert Einstein in 1905 with the Quantum Theory. The theory states that light is both a particle and a wave. These particles can, if they have sufficient speed and come into contact with metal, release electrons from the metal matrix and produce an electron flow.

12. When was the first solar cell created? 

The first solar cell for the generation of electricity was built in 1893. The first solar cell with silicon was developed in 1954 for space travel.

13. Do solar cells generate direct or alternating current? 

Solar cells generate direct current.

14. What is the name of the component which converts direct current into alternating current? 

This components is called an inverter.

15. What is built into an inverter for PV systems so that the maximum power of solar cells is achieved? 

An MPP tracker is built into an inverter, making it possible to activate the maximum possible power .

16. What types of solar cells are there? Which have the highest degree of efficiency? Which are the most affordable?  


Monocrystalline, polycrystalline and thin film solar cells. The monocyrstalline solar cells have the highest degree of efficiency (16-18 %), but are the most expensive to produce.

21

Solar Energy



The most widely available material for thin film solar cells is amorphous silicon. The amorphous solar cells are the least expensive, however they only have a degree of efficiency from 6-8 %.

Comprehension questions 17. Does a solar cell behave similarly to other power sources, such as batteries, when connected in a series and in parallel? 

Yes, when connected in parallel the voltage remains the same and when connected in series the current strength is the same.

18. If one solar cell within a series of connected solar cells is destroyed, is the current flow interrupted? 

Yes, if the destroyed solar cell can no longer produce current, the entire circuit is paralyzed.

19. How could the problem from the previous question be solved? 

With a bypass diode.

20. Is the efficiency of solar cell comparable with that of a diesel engine? 

No, modern diesel engines achieve a degree of efficiency of 45 %. The energy delivered by the diesel engine, however, is generated using fuel, which is only available to a limited extent. The degree of efficiency, therefore, is not comparable, because the sun is an entirely different energy source than diesel fuel.

21. How does a characteristic curve in the current/voltage characteristic curve behave if the resistance is doubled? 

The power characteristic curve remains the same.

22. Known or estimated? How high is the annual energy output [kWh] of a photovoltaic system for an average single family home? 

3000 to 4000 kWh

23. How many of the solar modules used in the experiment are required to operate the following devices? Unit

P [W]

Number of solar modules

Computer

400 W

1,000

Car radio

40 W

100

Mobile phone

2W

5

Hair dryer

2,000 W

5,000

Light bulb

2.4 W

6

24. Can a light bulb be damaged if 20 more modules are connected in parallel than the number of modules calculated above? 

22

No, it enables a greater current consumption of the light bulb. The light bulb will only accept as much current as it requires at the time. Clean Energy Trainer - Experiment Guide


3

Wind Energy

Experiment 1 - Learning the different features of a wind generator Summary

Worksheet theme

The students become familiar with the typical features of a wind generator in this experiment. In the pro cess, they investigate the influence of the rotor blade positioning, the direction of the wind and the number of r otor blades have on the electrical power of the wind ge nerator.  

Degree of difficulty Prior knowledge Learning objective

Checklist

Advantages and disadvantages of wind generators Questions about the experiment

Easy 

Electrical circuits

The students expand their knowledge in recognizing that the rotor blade position, the wind direction and a different number of rotor blades influence the power of a wind generator. The students learn the importance of close observation and the importance of being able to concisely formulate the observations which were made.   



Wind generator Fan USB data monitor - USB cable - PC or laptop with installed software 2 cables, 1 black, 1 red

Experiment 2 - Determine the characteristic curve of a wind generator Summary

The students become familiar with the characteristic curve of a wind generator in this experiment.

Worksheet theme

Questions about the development of wind generators

Degree of difficulty

Medium

Prior knowledge Learning objective

Checklist



Characteristic curve as a means of characterization of wind generators

The students expand their knowledge by drawing the characteristic curve of a wind generator. The students expand their knowledge when recognizing that there is a range of values in which the wind generator provides its maximum power.   



Wind generator Fan USB data monitor - USB cable - PC or laptop with installed software 2 cables, 1 black, 1 red


23

Wind Energy

Experiment 2 - Determine the characteristic curve of a wind generator

TIP

24

In this experiment you assign different groups with different tasks. For example, Group 1 draws the characteristic curve with a varying rotor blade position, Group 2 draws the characteristic curve with 45° changing wind direction and Group 3 draws the characteristic curve with varying wind strengths.


Learning the different features of a wind generator

Experiment 1 How do current and voltage behave with a varying rotor blade position? 1. Set up experiment as shown in Fig.3-1. 2. Affix all rotor blades on the wind generator. In doing so, affix the rotor blades so that they are unbent. 3. Switch on the fan. The fan must be set up directly facing the wind generator with distance of approx. 50 cm. 4. Start the software and select the W I ND GENERATOR tab. Switch the operation mode to M AN UA L MO DE . 5. Change the position of all rotor blades evenly by rotating. 6.

Make note of any observations.

7. Find the rotor blade position with which the wind generator provides the highest no-load voltage.

How do current and voltage behave with fewer rotor blades? 1. Set up experiment as shown in Fig.3-1. 2. Optimally position the fan.

Fig.3-1

3. Start the software and select the W I ND GENERATOR tab. 4. Switch the operation mode to M AN UA L

MO DE .

5. Remove the rotor blades successively. Make sure that they are aligned symmetrically. 6. Enter any observations in the following table. Number of rotor blades 6

5

4

3

2

1

U [V]

How do the measurements behave with varying wind direction? 1. Align the rotor blades optimally. 2. Turn the wind generator and observe the measurements.

How do the measurements behave if the air flow is disrupted? 1. Turn on the wind generator and fan. 2. Hold various objects between the fan and wind generator and observe the measurements.


25

Worksheet 1



Questions about the experiment 1. How do current and voltage behave with a varying rotor blade position? 2. How do current and voltage behave with fewer rotor blades? 3. How do the measurements behave with varying wind direction? 4. How do the measurements behave if the air flow is disrupted?

General questions 5. What is wind energy? 6. What is a wind turbine? 7. What is a wind generator? 8. What are the advantages of wind energy? 9. What are the disadvantages of wind power? 10. What dangers can arise with the use of wind turbines?

Comprehension questions 11. Why is wind energy such a heavily debated topic in politics when it is very environmentally-friendly? 12. Why do most wind turbines only have three rotor blades? 13. What are the common features of a windmill and a wind turbine?


27




1. How do current and voltage behave with a varying rotor blade position? 

The angle of inclination of the rotor blades has a significant influence on the power of a wind generator. If the rotor blades are not aligned favorably, the rotor may not rotate.

2. How do current and voltage behave with fewer rotor blades? Number of rotor blades

U [V] 

6

5

4

3

2

1

3.2

3.2

3

2

0

0

On this small wind generator it is better to use several rotor blades. With large wind turbines more than three blades are less effective. The major difference with a common wind turbine is the aerodynamic active principle: the wind generator from the Clean Energy Trainer is a resistance rotor (flat fins) comparable to wind generators ("Western mills") still partly in use in the USA and Australia. With this principle, "the more the better" applies; in practice, three rotor blades are common and up to 150 are possible. With current wind turbines the rotor blades are shaped in a similar manner to airplane wings. Due to the lift which arises, they are called lift-type turbines. For mechanical reasons the optimal number of rotor blades is three. Constructions with one, two or more than three rotor blades are also possible from an aerodynamics perspective.

3. How do the measurements behave with varying wind direction? 

The wind generator rotates best when the rotor is aligned perpendicularly to the direction of the wind.

4. How do the measurements behave if the air flow is disrupted? 

The current and voltage values drop considerably.

General questions 5. What is wind energy? 

Air masses which move have kinetic energy. They are similar to water masses which move. This kinetic energy has been utilized by mankind since time immemorial, e.g. for wind and water mills.

6. What is a wind turbine? 

A wind turbine utilizes the energy of air masses and converts it into electrical energy.

7. What is a wind generator? Clean Energy Trainer - Experiment Guide

29

Wind Energy



Our small wind turbine in the Clean Energy Trainer is referred to as a wind generator. Wind generators are normally small wind energy plans which have a simple setup and no connection to the mains power grid.

8. What are the advantages of wind energy? 



Wind turbines use the energy from moving air in order to generate electrical current. There will always be wind as long as the Sun exists and it is available free of charge. Wind turbines do not generate any harmful exhaust gases.

9. What are the disadvantages of wind power?  

 

It is difficult to predict when and where a lot of wind blows. Due to limited capacities in the mains grid, insufficient energy can be taken from some wind turbines with heavy wind. These wind turbines can then generate less energy than is possible and may even have to be switched off with an overload of the mains grid. Wind turbines can destroy beautiful landscapes. Offshore construction is elaborate and expensive. A whirring sound is created by the moving rotor blades, which is stressful for many animals and even people. Modern wind turbines are aerodynamically optimized in such a way that the development of noise is significantly reduced.

10. What dangers can arise with the use of wind turbines? 



The rotor blades can accelerate with an uncontrolled load so that the resulting force can be so high that it destroys the plant. In the winter, frozen blocks of ice can fall from the plant or be swung around. Normally there is also an automatic shut-off device for this purpose.

Comprehension questions 11. Why is wind energy such a heavily debated topic in politics when it is very environmentally-friendly? 

Many consider wind energy unprofitable. Wind turbines would destroy the landscape without generating a lot of energy. In many cases the influence on animals caused by wind parks is considered problematic. Energy policy is closely associated with lobbying; therefore all interests of the respective proponents and opponents must be questioned in discussions of the advantages and disadvantages.

12. Why do most wind turbines only have three rotor blades? 

30

The rotor blades of a wind turbine can have a diameter up to 100 m and weight up to 20 tons. The more rotor blades, the higher the inertia of the rotor, because the higher the mass, the higher the inertia. Wind turbines with five or six rotor blades would move much more slowly. Most of today's wind turbines have three rotor blades. Several test objects over several years have shown that this number is the most effective. Clean Energy Trainer - Experiment Guide

Wind Energy

13. What are the common features of a windmill and a wind turbine? 


Windmills also use wind energy and are a forerunner for wind turbines.

31

Determine the characteristic curve of a wind generator

Experiment 2 How can the maximum power of a wind generator be achieved? 1. Set up experiment as shown in Fig.3-2. 2. Use a wind generator with three rotor blades. 3. Align the wind generator and the angle of inclination of the rotor blades in such a way that the highest possible no-load voltage is achieved. 4. Start the software and select the W I ND GENERATOR tab. 5. Switch on the fan (Level 2). 6. Switch the operation mode to AU TO MA TI C MO DE and start the measurement. 7. Record current and voltage values in a table and calculate the power. 

The power  is calculated with the formula     .

8. Draw the power characteristic curve. 

Click on P OWER CHARACTERISTIC CURVE in the software and compare with the power characteristic curve which is shown.

9. Equip the wind turbine with six rotor blades.

Fig.3-2

10. Set the fan to Level 3. 11. Align the wind generator and the angle of inclination of the rotor blades in such a way that the highest possible no-load voltage is achieved. 12. Select the operation mode AU TO MA TI C MO DE . 13. Record current and voltage values in a table and calculate the power. 14. Draw the power characteristic curve. 15. Determine the maximum operating point from the power voltage characteristic curve.


33

Worksheet 2



Questions about the experiment 1. How can the maximum power of the wind generator be achieved? 2. What does the power characteristic curve look like at Level 2? 3. What does the power characteristic curve look like at Level 3? 4. How can the maximum power of the wind generator be determined?

General questions 5. When did people come up with the idea for utilizing wind energy? 6. When was the first wind turbine for generating current built? 7. Which country has the largest installed total power of wind turbines? 8. How much surface area is required to generate one MW of wind energy? 9. How much area will a wind park cover in order to replace a nuclear power plant (1,700 MW)? 10. What percentage of the surface area of Germany cover in order to replace all nuclear power plants in Germany? 11. What is a full load hour?

Comprehension questions 12. How is wind created? 13. Does the sun's irradiation at the equator have an influence on the wind in Europe? 14. Can one state that the energy source "wind" is inexhaustible? 15. Why are wind turbines built near the coast? Why does more wind blow near the coast? 16. How high are the costs for a wind turbine per installed kW? 17. When do wind energy and solar plants pay themselves off? 18. Why does a wind turbine require a gear unit?


35



Answers 2 Questions about the experiment 1. How can the maximum power of the wind generator be achieved? 

Select the highest possible number of rotor blades and optimize the angle of inclination and distance and alignment of the fan.

2. What does the power characteristic curve look like at Level 2?

P / mW 500 400 300 200 100

1

2

3

4

5

6

7

8

U / V

3. What does the power characteristic curve look like at Level 3?

P / mW 500 400 300 200 100

1

2

3

4

5

6

7

8

U / V

4. How can the maximum power of the wind generator be determined?


37

Wind Energy



The power voltage characteristic curve arises from Point 8. The maximum is the maximum power.

General questions 5. When did people come up with the idea for utilizing wind energy?  

The use of wind energy began 1,000 years before common era in order to move sailboats. The use of wind energy by mills or water pumps first appeared in Persia and Mesopotamia (Middle East) in the 10th Century. Wind mills were first used in Europe in the 12th Century.

6. When was the first wind turbine for generating current built? 

In 1888 Charles F. Brush built the first fully automatic wind turbine for the generation of current in the United States. The rotor had a diameter of 17 meters with 144 rotor blades.

7. Which country has the largest installed total power of wind turbines?   

USA: 36,300 MW China: 33,800 MW Germany: 26,400 MW

8. How much surface area is required to generate one MW of wind energy? 

It is not feasible to set up any arbitrary number of wind turbines in front of one another, because mutual shadowing would occur. The minimum distance in the primary wind direction should correspond to eight times the rotor diameter; the minimum distance crosswise to the wind should be four times the rotor diameter. The surface requirement is (here the values fluctuate heavily depending on the power class and the location of the plant) approx. 250 m² per megawatt.

9. How much area will a wind park cover in order to replace a nuclear power plant (1,700 MW)?  

1700 MW * 250 m²=425,000 m² 425,000 m ² = 0.425 km² (In comparison to a nuclear power plant with 1,700 MW) (The calculation is based on the theoretical maximum power of a wind park)

10. What percentage of the surface area of Germany cover in order to replace all nuclear power plants in Germany?     

Total power of the nuclear power plants: 21,457 MW 21,457 MW * 250 m² 5.364 km² (equal to 752 soccer fields) Total surface area of Germany: 357,868 km² 0.002 % (The calculation is based on the theoretical maximum power of a wind park.)

11. What is a full load hour? 38


Wind Energy



One full hour load is only present if a wind turbine runs at full nominal power for one hour. In other words, if a 1,000 kW plant generates 1,800,000 kWh current in a year, that would be 1,800 full load hours. Furthermore: There are 8,760 hours in a year.

Comprehension questions 12. How is wind created? 

The sun heats the surface of the earth differently in different places. The intensity of the sun's irradiation is very high at the equator. Therefore, the air close to the ground is heat up intensively there and then rises to higher layers of the atmosphere. There is a higher air pressure there than in the surrounding area. Since a system is always meant to generate an equilibrium, the atmospheric system strives to equalize the air pressure. Wind is generated as a result.

13. Does the sun's irradiation at the equator have an influence on the wind in Europe? 

Although the equator seems very far away to us, the Sun's irradiation at the equator has an influence on the wind in Europe. Air with a higher pressure always moves towards lower pressure in order to create an equilibrium. That means that the air that has heated up at the equator and has climbed to higher layers of the atmosphere attempts to balance with air masses with lower temperatures and air pressures. The result is air movement, which is also perceptible in Europe.

14. Can one state that the energy source "wind" is inexhaustible? 

As long as the Sun exists and the Earth is heated by it, there will be wind.

15. Why are wind turbines built near the coast? Why does more wind blow near the coast? 

Near the coast the wind is guaranteed through the significantly different heat conductivity of the sea and the land and the air mass movements associated with this. The land heats up much more quickly than the sea over the course of the day. For this reason, the warm air above the land rises quickly. This causes a pressure drop which is equalized by the air flowing in from the sea. The reverse effect occurs at night time.

16. How high are the costs for a wind turbine per installed kW? 

The costs are reduced from year to year. In 2010 the costs for plants in the 100-1,000 kW nominal output ranger were 600...860 € per installed kW. That means that a system with 1 MW nominal power costs 860,000 €.

17. When do wind energy and solar plants pay themselves off?


39

Wind Energy



In consideration of all the expenses involved in the manufacture and the construction of a wind turbine, wind turbines already pay for themselves within a few months. However, these values depend heavily on the location. The amortization of photovoltaic systems also depends on the type and location of the photovoltaic system. Values of 2 ... 7 years must be taken into account.

18. Why does a wind turbine require a gear unit? 

40

Most wind turbines require a gear unit, because the generators which are used require significantly higher rotational speeds than the rotor can provide. The gear unit increases the rotational speed of the rotor for the generator. However, there are wind turbines without gear units.



4

Electrolysis

Experiment 1 - Observe the characteristics of water during an electrolysis Summary

Worksheet theme

In this experiment the students will perform an electrolysis with an electrolyzer. In an additional step the students will investigate the decomposition voltage of water.   

Degree of difficulty Prior knowledge Learning objective

Checklist

Historical development of electrolysis Danger of hydrogen Function of an electrolyzer

Easy 

Recording measurement curves

The students expand their knowledge by learn how an electrolysis works by way of experimentation. They discover the chemical structure of water on the basis of an experiments. The students learn the importance of close observation in science and the importance of being able to concisely formulate the observations which were made.      



Electrolyzer 2 storage canisters 4 hoses 2 black closing caps distilled water USB data monitor - USB cable - 6 V mains adapter - PC or laptop with installed software 2 cables, 1 black, 1 red

Experiment 2 - Determining the characteristic curve of an electrolyzer Summary

In this experiment the students investigate the course of the characteristic curve of an electrolyzer.

Worksheet theme

General questions about water and electrolysis


Medium

Prior knowledge

 

Learning objective

Record characteristic curve Electrical circuits

The students expand their competence by drawing and being able to recognize a characteristic curve of an electrolyzer. The students expand their knowledge in recognizing that there is a range of values in which the electrolyzer delivers the maximum power.


41

Electrolysis

Experiment 2 - Determining the characteristic curve of an electrolyzer Checklist

     



Electrolyzer 2 storage canisters 4 hoses 2 black closing caps distilled water USB data monitor - USB cable - 6V mains adapter - PC or laptop with installed software 2 cables, 1 black, 1 red

Experiment 3 - Calculating the degree of efficiency of an electrolyzer Summary

In this experiment the students will calculate the degree of energetic efficiency of an electrolyzer.

Worksheet theme

General questions and calculations for the efficiency of an electrolyzer


Medium

Prior knowledge

   

Learning objective Checklist

The students expand their knowledge by being able to calculate the degree of energetic efficiency of an electrolyzer.      



42

Recording measurement curves Electrical circuits Working with an electrolyzer (demonstration by teacher) Calculating with multiple physical units

Electrolyzer 2 storage canisters 4 hoses 2 black closing caps distilled water USB data monitor - USB cable - 6V mains adapter - PC or laptop with installed software 2 cables, 1 black, 1 red


Observe the characteristics of water during an electrolysis

Experiment 1 What happens with water during an electrolysis? 1. Set up experiment as shown in Fig.4-1. 2. Fill both storage canisters up to the 0 cm³ mark with distilled water. 3. Close the outlets of the storage canisters with closing caps. 4. Start the software and select the E LECTROLYZER tab.

Fig.4-1

5. Select the operation mode M AN UA L

MO DE .

6. Set voltage to   . 7. Read the quantity of generated hydrogen and oxygen at the following times. Time [min]

Current [mA]

Hydrogen [cm³]

Oxygen [cm³]

1 2 3 4

8. Set voltage to   . 9. Read the quantity of generated hydrogen and oxygen at the following times. Time [min]

Current [mA]

Hydrogen [cm³]

Oxygen [cm³]

1 2 3

At what voltage does water begin to electrolyze into hydrogen and oxygen? 1. Set up experiment as shown in Fig.4-1. 2. Fill both storage canisters up to the 0 cm³ mark with distilled water. 3. Close the outlets of the storage canisters with closing caps. 4. Start the software and select the E LECTROLYZER tab. 5. Select the operation mode M AN UA L

MO DE

and start the electrolysis.

6. Increase the voltage in 0.2 V steps and read the current values. In the process, observe the hydrogen and oxygen storage canisters. 7. Make note of the measurements and observations. Clean Energy Trainer - Experiment Guide

43

Electrolysis

44


Worksheet 1



Questions about the experiment 1. What happens with water during an electrolysis? 2. At what voltage does water water begin to electrolyze electrolyze into hydrogen hydrogen and oxygen? 3. Would the amount of hydrogen generated during the experiment be sufficient to cause an explosion? 4. Is the theoretical decomposition voltage of the electrolyzer or of the water dependent? 5. Why was double the amount of hydrogen as oxygen created? 6. Is there a difference between the observed and theoretical decomposition voltage? If yes, why? 7. Is the creation of hydrogen and oxygen constant during an electrolysis?

General questions 8. What is the decomposition of a conductive liquid with the application of a voltage called? 9. When was electrolysis discovered for the first time? 10. Is hydrogen dangerous? 11. At 11. At what voltage does water water begin to decompose decompose (theoretical (theoretical decomposition voltage)? 12. Where can hydrogen be acquired from? Are there multiple possibilities?

Comprehension questions 13. Is hydrogen also a feasible fuel for airplanes? 14. At 14. At what voltage does an electrolyzer electrolyzer begin to split water? 15. What exactly happens during electrolysis?


45



Answers 1 Questions about the experiment 1. What happens with water during an electrolysis?

Electrolysis with 1.8 V

Electrolysis with 2.0 V

Time [min]

Current [mA]

Hydrogen [cm³]

Oxygen [cm³]

1

0.8

7

3.5

2

0.8

14

7

3

0.8

21

10.5

4

0.8

28

14

Time [min]

Current [mA]

Hydrogen [cm³]

1

1.6

12

6

2

1.6

24

12

Oxygen [cm³]

2. At what voltage does water water begin to electrolyze electrolyze into hydrogen hydrogen and oxygen?

Decomposition voltage of water

Voltage [V]

Current [A]

Observation

0

0.014

0.2

0.014

0.4

0.014

0.6

0.014

0.8

0.014

1

0.014

1.2

0.014

1.4

0.014

1.6

0.054

Bubbles in the electrolyzer

1.8

0.830

Accelerated production of 

2

1.620

Accelerated production of 

3. Would the amount of hydrogen generated during the experiment be sufficient to cause an explosion? 

Yes, a small hydrogen-oxygen reaction is possible.

4. Is the theoretical decomposition voltage of the electrolyzer or of the water dependent? 

The theoretical decomposition voltage general depends on the matter.

5. Why was double the amount of hydrogen as oxygen created? 

There are two hydrogen atoms per oxygen atom in water.

6. Is there a difference between the observed and theoretical decomposition voltage? If yes, why? Clean Energy Trainer - Experiment Guide

47

Electrolysis



The observed decomposition voltage is higher than the theoretical decomposition voltage. The difference is called overvoltage. The overvoltage can be understood as kinetic inhibition, in other words the braking of the reaction.

7. Is the creation of hydrogen and oxygen constant during an electrolysis? 

Yes, if the supplied current ( and the supplied voltage) remains constant.

General questions 8. What is the decomposition of a conductive liquid with the application of a voltage called? 

This process is called electrolysis.

9. When was electrolysis discovered for the first time? 

Electrolysis was discovered by Alessandro Volta in 1,800 (voltaic pile).

10. Is hydrogen dangerous? 



No more dangerous than natural gas or an air/gasoline mixture. Hydrogen is flammable and can result in explosions when combined with oxygen. Basically, all energy carriers must be used with appropriate caution. Hydrogen is innocuous.

11. At what voltage does water begin to decompose (theoretical decomposition voltage)? 

1.23 V (at 25°C)

12. Where can hydrogen be acquired from? Are there multiple possibilities? 

From an electrolysis of water. From hydrocarbons through steam reforming, through the Kvaerner process, chlorinealkali-electrolysis, thermochemical processes or photobiologic through algae.

Comprehension questions 13. Is hydrogen also a feasible fuel for airplanes? 

Yes, it is feasible. There have already been several projects where hydrogen was used as a fuel for airplanes, such as Cyroplane or Hydrogenius.

14. At what voltage does an electrolyzer begin to split water? 

Starting from approx. 1.5 V a clear formation of gas can be observed. Theoretically, this value lies at 1.23 V, however, the overvoltage with this reaction still has to be taken into consideration. Overvoltage results from several material-specific factors and can be regarded as a type of activation energy.

15. What exactly happens during electrolysis?

48


Electrolysis




An electrolyte (this can be solid or liquid or consist of a melt) is decomposed during electrolysis through the application of an electrical voltage. In the process, hydrogen and noble metals are separated at the cathode (minus pole, reduction), cations are discharged. Oxygen and chlorine (with chloride-containing solutions) are separated at the anode (plus pole, oxidation). The anions are discharged at the anode. Water is also always decomposed in the electrolysis of aqueous solutions.

49

Determining the characteristic curve of an electrolyzer

Experiment 2 How does the characteristic curve of the electrolyzer progress?

Fig. 4-2 Electrolysis experiment set-up

1. Set up experiment as shown in Fig. 4-2. 2. Fill both storage canisters up to the 0 cm³ mark with distilled water. 3. Close the outlets of the storage canisters with closing caps. 4. Start the software and select the E LECTROLYZER tab. 5. Select the operation mode M AN UA L

MO DE .

6. Set voltage to   . 7. Increase the voltage as specified in the following table and enter the current values. U [V] I

[A]

P

[W]

U [V]

I

[A]

P

[W]

U [V]

0

1.5

1.8

0.8

1.6

1.9

1.2

1.7

2

I

[A]

P [W]

8. Enter voltage  and current  in a current/voltage characteristic curve and then connect the points. 9. Enter power  and current  in a current/power characteristic curve and then connect the points.


51

Worksheet 2



Questions about the experiment 1. How does the characteristic curve of the electrolyzer progress? 2. At what voltage does current begin to flow in the electrolyzer? 3. What is the explanation for this late current flow? What general statements can be made about the characteristic curve of the electrolyzer?

General questions 4. What is distilled water? 5. Are there any other applications for electrolysis?

Comprehension questions 6. Why does hydrogen burn, but water does not? Although there is even more oxygen in water. 7. What advantages does hydrogen have over natural gas? 8. Is distilled water conductive? 9. Does an electrolysis require DC or AC voltage?


53




1. How does the characteristic curve of the electrolyzer progress?

Table 1


U [V] I

P

[A]

[W]

U [V]

I

P

[A]

[W]

U [V]

I

[A]

P [W]

0

0

1.5

0.015

0.02

1.8

0.8

1.44

0.8

0

1.6

0.16

0.25

1.9

0.9

1.71

1.2

0

1.7

0.38

0.65

2

1.4

2.8

I/ A 1.5 1.2 0.9 0.6 0.3

Power/voltage characteristic curve

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

0.3

0.6

0.9

1.2

1.5

1.8

2.1

2.4

U / V

P/ W 2.0 1.4 1.2 0.8 0.4

U / V

At what voltage does current begin to flow in the electrolyzer? 


Starting from approx. 1.5 V.

55

Electrolysis

2. What is the explanation for this late current flow? What general statements can be made about the characteristic curve of the electrolyzer? 

The characteristic curve does not proceed through the zero point and only starts climbing at approximately 1.5 V. Starting at 1.6 V the current increases exponentially. The decomposition voltage of water must be reached so that a current can flow. In theory this lies at 1.23 V; in practice this value lies at approximately 1.4 to 1.6 V.

General questions 3. What is distilled water? 

Distilled water is pure water (   without impurities). Distilled water is water that is first converted to water vapor and is then re-condensed. In the process, all foreign substances are left in the container. There is pure water in the distillate.

4. Are there any other applications for electrolysis? 

Electrolysis is used primarily for the extraction of hydrogen gases (e.g. chlorine) as well as for the extraction of non-noble metals, such as sodium or aluminum (melt electrolysis).

Comprehension questions 5. Why does hydrogen burn, but water does not? Although there is even more oxygen in water. 

A combustion is an oxidation. If hydrogen is oxidizes, water is the result. Water is also the product of the combustion of hydrogen.

6. What advantages does hydrogen have over natural gas?  

Hydrogen has a higher internal energy. No harmful products arise in the combustion of hydrogen. Hydrogen is non-toxic, CO2-neutral and a reversible energy carrier.

7. Is distilled water conductive? 

No, the conductivity of distilled water is negligible. Water becomes electrically conductive after the addition of ions.

8. Does an electrolysis require DC or AC voltage? 

56

Electrolysis requires DC voltage. With AC voltage the polarity of the electrodes would change continuously and a consistent discharge on the anode and cathode would not be possible.


Calculating the degree of efficiency of an electrolyzer

Experiment 3 How high is the degree of energetic efficiency of an electrolyzer? 1. Set up experiment as shown in Fig.4-3. 2. Fill both storage canisters up to the 0 cm³ mark with distilled water. 3. Start the software. 4. Close the oxygen and hydrogen outlets. 5. Set the voltage to 1.8 V.

Fig.4-3

6. After two minutes, open the water and hydrogen discharges for five seconds. 7. Check the water level. The water must lie exactly at the 0 cm³ mark in both containers. Refill as necessary. 8. Close the water and hydrogen outlets. 9. Set the voltage to 1.8 V and immediately begin the time measurement. Quantity of hydrogen [cm³]

5

10

15

20

25

30

Time [s]

10. Enter the values in a volume/time diagram. 11. Calculate the degree of energetic efficiency of the electrolyzer. 


  

 



  



 : generated amount of hydrogen in m³



 : lower heating value of hydrogen =

    

57

Worksheet 3



General questions 1. What is a degree of energetic efficiency? 2. How high is the heating value of hydrogen? 3. How high is the heating value of gasoline? 4. What is a gas constant?

Questions about the experiment 5. What can be stated on the basis of the volume/time diagram? 6. Why is it important to recognize the efficiency of an electrolyzer? 7. What are the upper heating value and lower heating value? 8. What is a mole?

Comprehension questions 9. What is the difference between the Faraday efficiency and the degree of energetic efficiency? 10. What does Faraday's second law say? 11. What role does the environmental pressure play in the generation of hydrogen?


59



Answers 3 Solutions for the experiment

Volume/time diagram

Quantity of hydrogen [cm³]

5

10

15

20

25

30

Time [s]

25

46

64

83

105

123

60

75

90

V/ cm³ 25 20 15 10 5

15

Degree of energetic efficiency

30

     

45

105

120

t / s

                    

              General questions 1. What is a degree of energetic efficiency? 

The degree of energetic efficiency describes the relationship of the generated usable energy to the used energy.

2. How high is the heating value of hydrogen? 



    =2   

=

 

3. How high is the heating value of gasoline? 



 

 

 

 

 

 

 

4. What is a gas constant? 


The gas constant is a proportionality factor in the ideal gas law. It is the same for all gases. The ideal gas law describes the behavior of ideal gases. The gas constant is the product of the Boltzmann constant and Avogadro constant.

61

Electrolysis

Questions about the experiment 5. What can be stated on the basis of the volume/time diagram? 

Based on the volume/time diagram, it can be determined how much hydrogen is generated with a constant amount of current within a specific time. It can be observed that the increase of volume is directly proportional to the time.

6. Why is it important to recognize the degree of efficiency of an electrolyzer? 

Degrees of efficiency provide basic information about the efficiency of processes and applications. Observations of the degree of efficiency enable direct comparisons of various applications and processes.

7. What are the upper heating value and lower heating value? 

The energy released with the combustion (oxidation) of a material is called the upper heating value  . In the process, the energy which the water vapor caused by the combustion of the material contains as condensation heat is also factored in. In conventional combustion processes this heat is not usable (unlike with condensing boilers, which use the condensation heat). The lower heating value disregards this condensation heat. Chemists primarily use the upper heating value for their thermodynamic observations  ; in technical and physical applications the lower heating value is primarily used  for calculations.

8. What is a mole? 

A mole is the unit for the amount of substance. One mole of a substance contains exactly as main particles as there are carbon atoms in 12 g carbon ( 12C): 6.022*10 23.

Comprehension questions 9. What is the difference between the Faraday efficiency and the degree of energetic efficiency? 

The Faraday efficiency or the current efficiency is calculated from the experimental and the theoretical hydrogen volume to be expected. The degree of energetic efficiency indicates how much of the used energy actually emerges - in this case, how much energy is used for the electrolysis and how much energy (as hydrogen) emerges again in the process. The greater the degree of energetic efficiency, the better the energy was utilized.

10. What does Faraday's second law say? 

62

Faraday's second law establishes the relationship between the amount of generated gas and the amount of current used for this purpose. A mole of a monovalent ion is differentiated from the charging quantity of a mole of electrons. Faraday's second law:       


Electrolysis

11. What role does the environmental pressure play in the generation of hydrogen? 


The environmental pressure has an immediate influence on the gas formation. The arising gases must escape from the liquid against the environmental pressure. The same amount of hydrogen is always produced based on the current. However, with an increasing environmental pressure, a higher voltage is applied in order to cause the same current.

63

5

Fuel Cells An overview of all experiments

Experiment 1 - Initial experience with fuel cells Summary

In this experiment the students find out how a fuel cell is put into operation. They learn by way of experiment that a direct s upply of oxygen positively influences the power of the fuel cell. The hydrogen consumption is observed depending on the time. The influence of direct oxygen inflow is observed.

Worksheet theme

Storage of hydrogen and disadvantages of a fuel cell


Easy

Prior knowledge

   


The students expand their knowledge by learning how a fuel cell is put into operation by way of experiment.      

NOTICE

Working with voltmeters and amperemeters Electrical circuits Operation of an electrolyzer Working with a fuel cell (demonstration by teacher)

Fuel cell Electrolyzer 2 storage canisters 6 hoses USB data monitor and PC 4 cables, 2x red and 2x black

Damage from short circuits! Voltage sources on the fuel cell destroy the membrane. 

TIP

Connect the fuel cell without electrolyzer to USB data monitor.

Explain to your students what it means to "flush the fuel cell". See Solutions, page 71 Question 8.

Experiment 2 - Determining the characteristic curve of a fuel cell Summary

In this experiment the students investigate how the characteristic curve of a fuel cell progresses.

Worksheet theme

Background knowledge for fuel cells


Medium

Prior knowledge

    

Working with the USB data monitor Recording measurement curves Electrical circuits Working with an electrolyzer Working with a fuel cell


65

Fuel Cells

Experiment 2 - Determining the characteristic curve of a fuel cell Learning objective Checklist

The students expand their competence by drawing and being able to recognize a characteristic curve of a fuel cell.       

TIP

Fuel cell 2 Electrolyzers 4 storage canisters 11 hoses 1 hose clamp USB data monitor and PC 6 cables, 3x red and 3x black

When it comes to the individual groups for malfunctions of the fuel cell, it usually helps to flush the fuel cell, which means to open the hydrogen outlet.

Experiment 3 - Calculating the degree of energetic efficiency of a fuel cell Summary

In this experiment the students calculate the degree of energetic efficiency of a fuel cell.

Worksheet theme

Construction of fuel cells


Difficult

Prior knowledge

  


The students expand their knowledge by being able to calculate the degree of energetic efficiency of a fuel cell.       

66

Working with voltmeters and amperemeters Electrical circuits Working with a fuel cell (demonstration by teacher)

Fuel cell Electrolyzer 2 storage canisters 11 hoses 1 hose clamp USB data monitor and PC 4 cables, 2x red and 2x black


Initial experience with fuel cells

Experiment 1 How is a fuel cell operated? 1. Set up experiment as shown in Fig.5-1. 2. Close the hydrogen outlet of the fuel cell. 3. Disconnect consumers from the fuel cell. 4. Start the software. 5. Select the E LECTROLYZER tab. 6. Select the operation mode M AN UA L

MO DE .

7. Set the electrolyzer to 2 V and stop the electrolysis in the software when 30 cm³ have been generated. 8. Open the hydrogen outlet of the fuel cell for one second, then close it again. 9. Generate hydrogen again. 10. Connect the little house to the fuel cell. 11. Make note of observations.

Fig.5-1

How does the hydrogen consumption behave? 12. Disconnect the little house from the fuel cell. 13. Set the electrolyzer to 2 V and generate 30 cm³ hydrogen. 14. Disconnect the electrolyzer from the USB data monitor. 15. Connect the fuel cell to the USB data monitor and switch to the F UEL CELL tab in the software. 16. Set 150 mA in the software. 17. Measure the time, read the hydrogen consumption and enter the values in the table. 18. Repeat the experiment and increase to 300 mA. Hydrogen consumption [cm³]

Small consumer (USB data monitor 150 mA) [s]

Large consumer (USB data monitor 300 mA) [s]

5 10 15 20 25 30

How does a fuel cell react to the direct supply of oxygen? 1. Set up experiment as shown in Fig.5-1. 2. Produce 30 cm³ hydrogen and 15 cm³ water with the electrolyzer. Clean Energy Trainer - Experiment Guide

67

Fuel Cells

3. Start the software and select the F UEL CELL tab. Switch to manual mode. 4. Supply fuel cell with hydrogen. 5. Keep the oxygen directly in front of the ventilation shafts of the fuel cell and observe the voltage values during this time.

68


Worksheet 1



General questions 1. Who is the inventor of the fuel cell? 2. How can the formula       be explained in words? 3. Is the use of fuel cells feasible in space travel? Has this already been attempted? 4. In which areas is the use of fuel cells advantageous today? 5. What types of fuel cells are there?

Questions about the experiment 6. When and why is it important to close the gas outlets of the fuel cell? Why does the fuel cell consume hydrogen rapidly with the hydrogen outlet open? 7. Why must the consumer be disconnected from the fuel cell before experimentation? 8. What does flushing mean in reference to fuel cells? 9. How does the hydrogen consumption depend on the consumer? 10. What happens as purer oxygen is supplied to the fuel cell? 11. Why has the voltage increased?

Comprehension questions 12. How is a PEM fuel cell (PEM = Proton Exchange Membrane) constructed? 13. How does a fuel cell work? 14. How much of the originally used energy can be retained in a fuel cell?


69



Answers 1 Solutions for the experiment Consumed hydrogen [cm³]

Duration with small consumer (USB data monitor 150 mA) [s]

Duration with large consumer (USB data monitor 300 mA) [s]

5

57

27

10

117

52

15

165

77

20

218

102

25

272

184

30

325

215

General questions 1. Who is the inventor of the fuel cell? 

The principle of the fuel cell was discovered in 1838 by Christian Friedrich Schoenbein on the basis of the following reaction.

       

The invention of the fuel cell, however, is credited to the law yer and physicist Sir William Robert Grove in 1839.

2. How can the formula        be explained in words? 

This formula expresses that hydrogen in its elementary form reacts with oxygen to water. This reaction only takes place if an activation energy is supplied. It is exothermic, which means energy is released.

3. Is it feasible to use fuel cells in space travel? Has this already been attempted? 

Fuel cells were used for the Apollo flights and the space shuttles. Fuel cells have been used in space travel since the 1960s in order to generate current, heat and water for the onboard system.

4. In which applications are fuel cells used or have been successfully tested? 

Fuel cells are used for vehicles, uninterruptible power supply, towers for mobile phone networks, mobile electric devices (e. g. laptops), satellites and in space travel.

5. What types of fuel cells are there? 


Alkaline fuel cells, PEM fuel cells, direct methanol fuel cells, solid oxide fuel cells, molten carbonate fuel cells and phosphoric acid fuel cells 71

Fuel Cells

Questions about the experiment 6. When and why is it important to close the gas outlets of the fuel cell? Why does the fuel cell consume hydrogen rapidly with the hydrogen outlet open? 

If the outlets are not closed, the gas escapes to the environment and cannot be used for the operation of the fuel cell.

7. Why must the consumer be disconnected from the fuel cell before experimentation? 

The fuel cell requires hydrogen in order to generate electrical energy. Since no hydrogen was produced yet, a small amount had to be produced before the consumer could be connected.

8. What does flushing mean in reference to fuel cells? Why is it necessary to regularly flush a fuel cell?  

When flushing the fuel cell the hydrogen outlet of the fuel cell is briefly opened. Since impurities can collect on the hydrogen side during the operation of the fuel cell, it must be flushed regularly in order to maintain a sufficiently high concentration of hydrogen in the fuel cell.

9. How does the hydrogen consumption depend on the consumer? 

The hydrogen consumption increases proportionally with the power of the consumer.

10. What happens as pure oxygen is supplied to the fuel cell? 

The voltage has increased.

11. Why has the voltage increased? 

The oxygen content of the environmental air is only at 21 %. A direct supply of oxygen increases the power of the fuel cell.

Comprehension questions 12. How is a PEM fuel cell (PEM = Proton Exchange Membrane) constructed? 

The actual cell unit of the PEM fuel cell is comprised of a polymer membrane which is provided with a catalytic coating on both sides and spatially separated from the gases hydrogen and oxygen. Gas flow plates lie on the outer sides of the electrodes. These gas flow plates have channels through which hydrogen and oxygen flow in order to come into contact with the entire surface of the electrodes. At the same time, any water emerging during the energy production can be discharged through these channels.

13. How does a fuel cell work? 

72

The basic function of the fuel cell is the conversion of the chemical energy which is present in hydrogen and oxygen into electrical energy.


Fuel Cells



If the fuel cell is in operation and there is oxidation at the anode, it means the discharge of electrons is taking place. On the other hand, a reduction takes place at the cathode, which means the absorption of electrons. The fuel (hydrogen) is oxidized at the anode with the discharge of electrons. These electrons flow from the anode, which becomes the negative pole of the cell in the process, through the outer circuit to the cathode, which becomes the positive pole of the cell in the process. At the same time, hydrogen ions wander through the polymer electrolytic membrane to the cathode in order to balance out the charges.

14. How much of the originally used energy can be retained in a fuel cell? 


Through the reversal of water electrolysis in a fuel cell, approximately 25 % of the originally used energy can be retained.

73

Determining the characteristic curve of a fuel cell

Experiment 2 How do the current and voltage behave depending on the consumer? 1. Set up experiment as shown in Fig. 5-2. 2. Close the hydrogen outlet of the fuel cell. 3. Disconnect the USB data monitor from the fuel cell and connect it to the electrolyzer, see Fig. 5-3. 4. Start the software. 5. Set the electrolyzer to 2 V and generate 30 cm³ hydrogen.

Fig. 5-2

6. Open the water outlet of the fuel cell for one second. 7. Generate 30 cm³ hydrogen again. 8. Disconnect the USB data monitor from the electrolyzer and connected it to the fuel cell. 9. Switch to the F UEL CELL tab in the software. 10. Set the USB data monitor to  and connect it to the fuel cell.

Fig. 5-3

11. Make note of the voltage with increasingly greater current. I [A] U [V]

12. Enter values in a current/voltage characteristic and connect the points. 13. Enter values in a current/power characteristic and connect the points.


75

Worksheet 2



Questions about the experiment 1. How can the progress of the characteristic curve be explained?

General questions 1. In 1870 Jules Verne (French author) made an interesting prediction. What did he say? 2. What is a galvanic cell / galvanic element? 3. Why was the fuel cell forgotten when it was foreseeable that coal and oil would one day no longer be available? 4. What possibilities are there for storing hydrogen?

Comprehension questions 5. If more current is produced from power plants than is used, various mechanisms proceed to control this overall production, and the energy is partly stored. What possibilities for saving energy come into consideration? 6. Is hydrogen also available on our planet in the pure form? 7. A company in Germany had fuel cells in the cellar in order to reduce the risk of fire. How can fuel cells reduce the risk of fire?


77





U / V 5 4 3 2 1

100 200

Power characteristic curve

300

400

500

700

800

900

300

400

500

600

700

800

I / mA

P / mW 1000 800 600 400 200

100


200

I / mA

79

Fuel Cells

Questions about the experiment 1. How can the progress of the characteristic curve be explained? 





The theoretically possible voltage of a hydrogen fuel cell in standard conditions is 1.23 V. This value is taken from the thermodynamic data of the reaction of hydrogen and oxygen to water. In practice, losses in the current flow occur through kinetic inhibition of the reaction, internal resistance or insufficient diffusion. Therefore the delivered voltage of an individual cell is actually 0.4 to 0.9 Volts. The difference from measured voltage and thermodynamically potential voltage is called overvoltage. Various factors contribute to this overvoltage: With low currents the characteristic curve is determined by catalytic processes which occur at the electrodes. The increase of the current is accounted for by the speed of the conversion of hydrogen and oxygen, which means through the speed with which electrons cross over the contact surfaces between the gas molecules and the platinum catalyst. This type of overvoltage is called penetration overvoltage (1). Each cell has an internal resistance (2), which - for example - cause is caused through the resistance against the current flow in the electrolyte, the current collector and external wiring. In Ohmic voltage drop can be observed in high flows; the voltage decreases linearly with the increase of the current. The diffusion overvoltage (3) occurs if the gases are consumed faster by the electrochemical reaction at the catalyst than they can reach the catalyst through the diffusion. A typical sign for this diffusion overvoltage is a sudden downward bend of the current/voltage characteristic curve. The voltage increases heavily if the current increases.

U / V 3

1.0 0.8 0.6 0.4 0.2

1

2

80

160

240

320

400

480

560

640

I / mA

Yellow corresponds to a theoretic characteristic curve; black corresponds to a characteristic curve with the fuel cell stack of the Clean Energy Trainer. 80


Fuel Cells

General questions 2. In 1870 Jules Verne (French author) made an interesting prediction. What did he say? 

"Water is the coal of the future. The energy of tomorrow is water, which has been decomposed by electrical current. The elements of water decomposed in this manner, hydrogen and oxygen, will secure the energy supply of the Earth for an unforeseeable time in the future."

3. What is a galvanic cell / galvanic element? 

A galvanic cell is a device for the spontaneous conversion of chemical energy into electrical energy. Every combination of two different electrodes and an electrolyte is referred to as a galvanic element. Therefore, the fuel cell is a galvanic element.

4. Why was the fuel cell forgotten when it was foreseeable that coal and oil would one day no longer be available? 

Based on the invention of the electric generator (1866) by Werner von Siemens, the invention referred to as the "galvanic gas battery" was initially forgotten. The dynamo machine was relatively simply and uncomplicated in connection with the steam machine in regard to fuel and materials and therefore the complex fuel cell was preferred at this time.

5. What possibilities are there for storing hydrogen? 

According to the current standard of technology, hydrogen can be stored as compressed gas, liquid gas, metal hydride or in nanofibers. The cost-effective and resource-saving storage of hydrogen is the crucial element in the implementation of hydrogen technology.

Comprehension questions 6. If more current is produced from power plants than is used, various mechanisms proceed to control this overall production, and the energy is partly stored. What possibilities for saving energy come into consideration?  

The energy is used for the electrolysis, the emerging hydrogen can then be used as a fuel for fuel cells. Water is pumped up to a mountain to fill a reservoir. The water collected on the mountain can then be guided down into the valley and drive turbines in the process.

7. Is hydrogen also available on our planet in the pure form? 

No, hydrogen is only present in the bound form, such as in water or hydrocarbons (biomass, oil, natural gas, coal).

8. A company in Germany had fuel cells in the cellar in order to reduce the risk of fire. How can fuel cells reduce the risk of fire? 


The fuel cell reduces the oxygen content in the room and thereby reduces the tendency of the air towards ignition. 81

Calculating the degree of energetic efficiency of a fuel cell

Experiment 3 How high is the degree of energetic efficiency of a fuel cell? 1. Set up experiment as shown in Fig. 5-4. 2. Close the hydrogen outlet of the fuel cell. 3. Start the software, select the ELECTROLYSIS tab and generate15 cm³ hydrogen. 4. Open the hydrogen outlet of the fuel cell for one second. 5. Generate 30 cm³ hydrogen again. 6. Disconnect the electrolyzer from the USB data monitor.

Fig. 5-4

7. Connect the fuel cell to the USB data monitor, select the F UEL CELL tab and switch to manual mode. 8. Enter current values, observe the amount of hydrogen and begin with the time measurement. Quantity of hydrogen [cm³]

0

5

10

15

20

25

Time [s]

Fig. 5-5

Voltage [V] Current [mA]

9. Enter values in a volume/time diagram 10. Calculate the degree of energetic efficiency of the fuel cell. 







   


  

       

   

 : lower heating value of hydrogen =  : generated amount of hydrogen in m³ : Average value of the voltage in Volts  : Average value of the current in Amperes : Time in seconds

83

Worksheet 3



Questions about the experiment 1. What can be recognized from the volume/time characteristic curve?

General questions 2. What is a degree of energetic efficiency? 3. What material is the membrane of a fuel cell made of? 4. What characteristic must the membrane of a fuel cell have? 5. Which materials are suitable for a membrane? 6. Why are membranes so expensive?

Comprehension questions 7. Why the formula for the calculation of the degree of energetic efficiency of a fuel cell the reverse function of the formula for the calculation of the degree of energetic efficiency of an electrolyzer? 8. What task does the membrane have? 9. Which characteristics must membranes have? 10. What does PEM mean in reference to fuel cells? 11. What happens with the heat in the fuel cell?


85



Solutions 3 Solutions for the experiment

Hydrogen consumption of a fuel cell

Degree of energetic efficiency

Quantity of hydrogen [cm³]

0

5

10

15

20

25

Time [s]

0

23

45

73

88

112

Voltage [mV]

2990

3001

2960

2850

2870

2870

Current [mA]

354

351

349

337

336

337

 

          

 

              

      Questions about the experiment 1. What can be recognized from the volume/time diagram? 

It can be recognized from the volume/time diagram that the hydrogen consumption is proportional to the supplied power. The greater the power supplied by the fuel cell, the higher the consumption of hydrogen.

General questions 2. What is a degree of energetic efficiency? 

The degree of energetic efficiency describes the relationship of the usable energy given off to the supplied energy.

3. What does PEM mean in reference to fuel cells? 

PEM is the name for a membrane in a fuel cell. PEM stands for Polymer Electrolyte Membrane, which is also called a Proton Exchange Membrane. Proton Exchange indicates that the membrane is proton conductive, but is not electrically conductive. Polymer electrolyte means that the electrolyte is a polymer, or in other words a plastic. The membrane looks like an overhead film, but is far more expensive.

4. What material is the membrane of a PEM fuel cell made of? 

The most-often used polymer membrane is made of Nafion from the Dupont company; other membranes are based on polybenzimidazole and phosphoric acid, whereas the polybenzimidazole forms the matrix for the proton conductive phosphoric acid.

5. What characteristic must the membrane of a fuel cell have? 


The membrane must allow protons to pass through. It must be impermeable for both reactive gases and electrons. 87

Fuel Cells

Comprehension questions 6. Why the formula for the calculation of the degree of energetic efficiency of a fuel cell the reverse function of the formula for the calculation of the degree of energetic efficiency of an electrolyzer? 

The reaction in the fuel cell is the opposite of electrolysis. In the electrolysis, hydrogen and oxygen are produced from water and corresponding voltage and current supply. Hydrogen and oxygen are joined together again as water in the fuel cell with the generation of current.

7. Why are membranes so expensive? 

The membranes are provided with platinum and other noble metals as catalysts for the cell reaction. This makes the price very high.

8. What happens with the heat in the fuel cell? 

88

In the experimentation set-up only a little heat is given off to the environment, due to the low power. Fuel cells with high power must be cooled. With water-cooled fuel cells, for example, the heat can be dissipated through a cooling circuit and, if applicable, through a heat exchanger.


6

Renewable Energy Sources An overview of all experiments

Experiment 1 - Production of hydrogen from renewable energy sources Summary

The students become familiar with the combination of multiple renewable energy sources in this experiment. In the process, the electrolyzer is supplied by a wind generator and solar module. The electrolyzer supplies the fuel cell with hydrogen.

Worksheet theme

Photovoltaic power plants and fuel cell vehicles


Easy

Prior knowledge

Working with fuel cells and electrolyzers

Learning objective

The students expand their knowledge by way of experiment in discovering that a combination of multiple different renewable energy sources can secure a constant supply of current.

Checklist

      

Solar module One 75 W lamp (spotlight) Wind generator Fan (min. diameter 40 cm) Electrolyzer 5-cell fuel cell stack 10 cables, 5x red and 5x black

Experiment 2 - Optimal adaptation of renewable energy sources Summary

In this experiments the students will discover how a combination of renewable energy sources must be set up at different locations in order to maintain an advantageous and sensible energy balance. The USB data monitor simulates sun and wind relationships which can be arbitrarily combined; in other words, the USB data monitor is the voltage source and supplies the electrolyzer with current. The students should discover which number of solar modules and wind generators is necessary to be able to c onstantly supply a consumer with current. In addition, they should discover on their own whether an additional electrolyzer with hydrogen storage canister is necessary.

Worksheet theme

Wind parks


Difficult

Prior knowledge

 

Learning objective

Working with fuel cells and electrolyzers Working with the USB data monitor

The students expand their competence by way of experiment in discovering how renewable energy sources must be combined in order to achieve a sensible energy balance in consideration of the efficiency. The students expand their knowledge by way of experiment in discovering that renewable energies are only realizable in combination.


89

Renewable Energy Sources

Experiment 2 - Optimal adaptation of renewable energy sources Checklist

       

USB data monitor and PC Solar module Min. 75W lamp (spotlight) Wind generator Fan (min. diameter 40 cm) Electrolyzer 5-cell fuel cell stack 10 cables, 5x red and 5x black

Experiment 3 - Operating several consumers with fuel cells Summary

In this experiment the students discover which power a fuel cell must supply in order to maintain an advantageous yet economically sensible energy balance. The USB data monitor simulates various consumer profiles which can be arbitrarily combined. The students should discover how the components of this energy conversion chain must be dimensioned in order to be able to supply the selected consumer.

Worksheet theme

Additional renewable energy sources


Difficult

Prior knowledge

  

Learning objective

Checklist

The students expand their competence by way of experiment in discovering how renewable energy sources must be combined in order to achieve a sensible energy balance in consideration of the efficiency. The students expand their knowledge by way of experiment in discovering that renewable energies are only realizable in the combination of various components.        

90

Working with all individual components of the Clean Energy Trainer Basic understanding of energy conversion and storage Knowledge of the principle of conservation of energy

USB data monitor Electrolyzer Solar module Min. 75W lamp (spotlight) Wind generator Fan 5-cell fuel cell stack 10 cables, 5x red and 5x black


Production of hydrogen from renewable energy sources

Experiment 1 Can a consumer be permanently operated with renewable energy sources? 1. Set up experiment as shown in Fig 6-1. 2. Switch on the lamp and fan. 3. After three minutes, simulate various weather situations (day / night / no wind). 4. Observe the consumer.

Which energy source generates the most hydrogen? 1. Set up experiment as shown in Fig. 6-2.

Fig 6-1

2. Predict which energy source "wins". 3. Disconnect the solar module. 4. Align the fan towards the wind generator for three minutes and enter the generated amount of hydrogen in the following table. 5. Switch off the wind generator and empty the hydrogen tank. 6. Align the lamp (50 cm distance) towards the solar module for three minutes and enter the generated amount of hydrogen in the following table. Time [min.]

Fig. 6-2

Wind generator hydrogen quantity [ml]

Solar module hydrogen quantity [ml]

1

2ml 3ml 4ml

Not sensibly usable

2

4ml 6ml 8ml

Not sensibly usable

3

6ml 9ml 12ml

1ml


91

Worksheet 1



Questions about the experiment 1. Which factors must be taken into consideration so that a consumer can be permanently operated with renewable energy sources? 2. To what extent do the previously made statements apply (which energy source has produced more hydrogen)? 3. Can the assumptions be applied in practice?

General questions 4. Where is the world's largest photovoltaic power plant located? 5. The first official applications of solar modules and fuel cells took place in a specific economic area. Which one? 6. How is the energy of the Sun which reaches the earth distributed? 7. Hans Ziegler (German scientist, who conducted research with Wernher von Braun after the Second World War for the USA) opposed the US military in 1958 in a discussion about the energy supply of the second satellite, by the name of Vanguard 1. What did the military not want to believe at this time? 8. What are solar cells?

Comprehension questions 9. When was the first vehicle with solar cells used? 10. What additional advantage could the use of fuel cells in space travel entail?


93

Answers 1



Solutions for the experiment 1. Can a consumer be permanently operated with renewable energy sources? 

It could be observed that the supply of the consumer from either only the Sun or only wind energy is not sufficient. At night or with no wind the consumer could not be sufficiently supplied. If hydrogen was generated as an interim storage and converted into current by the fuel cell, such phases could be overcome. However, everything must be finely attuned.

2. Which energy source generates the most hydrogen? 

Significantly more energy can be generated with the wind generator.

Questions about the experiment 1. Which factors must be taken into consideration so that a consumer can be permanently operated with renewable energy sources? 

Neither wind nor Sun are continuously available 24 hours per day. For times in which they are not available or only very little is available, it would be advantageous to be able to save the energy generated during the day and when there is a lot of wind. The storage and the fuel cell must be designed so that they can also supply the consumer for an extended time at night and with no wind.

2. To what extent do the previously made statements apply (which energy source has produced more hydrogen)? 

The wind generator has generated significantly more hydrogen.

3. Can the assumptions be applied in practice (in other words, for wind turbines)? 

Wind turbines can provide a lot of power with heavy and continuous wind. In order to be able to provide the same power with solar modules, significantly more solar modules are required.

General questions 1. Where is the world's largest photovoltaic power plant located? 

The Sarnia photovoltaic power plant in Canada is currently (December 2010) the world's largest photovoltaic power plant with a power of 80 MW. The solar modules cover a surface of 380 hectares and should be able to supply approx. 13,000 homes with current.

2. The first official applications of solar panels and fuel cells took place in a specific economic area. Which one? Clean Energy Trainer - Experiment Guide

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In astronomy / in space travel.

3. How is the energy of the Sun which reaches the earth distributed? 

30 % is reflected into space, nearly 70 % is lost in the heating of the atmosphere and the Earth's surface and only 0.03 % is used by plants on the land and by phytoplankton in the upper layers of the oceans for photosynthesis.

4. Hans Ziegler (German scientist, who conducted research in 1947 with Wernher von Braun after the Second World War for the USA) opposed the US military in 1958 in a discussion about the energy supply of the second satellite, by the name of Vanguard. What did the military not want to believe at this time? 

That a solar cell in space could provide current longer than a battery.

5. What are solar cells? 

Solar cells are endowed silicon components which can release electrical energy from light. They are constructed similarly to diodes, whereas the charge flow in solar cells is influenced by light.

Comprehension questions 6. When was the first vehicle with solar cells used? 

The first fuel cell vehicle, a tractor with 1,008 cells and a power of 20 HP, was presented in 1959.

7. What additional advantages does the use of fuel cells in space travel entail? 

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After the generation of current, water arises as a reaction product, which can then be utilized (however it cannot be drunk in its pure form).


Optimal adaptation of renewable energy sources

Experiment 2 Which constellation is required at the different locations in order to operate an autarkic single-family home? 1. Set up experiment as shown in Fig.6-3. 2. Generate 30 cm³ hydrogen. 3. Open the hydrogen outlet of the fuel cell for one second. 4. Adjust the storage canister to 15 cm³ hydrogen. 5. Start the software. 6. A location can be prepared in the software (e. g. little wind, lots of sun). 7. Select the number of solar modules and wind generators. 8. Start the simulation. 

The software simulates Sun and wind relationships for 24 hour weeks in 2 minutes.

9. Observe the consumer and the hydrogen level.

Fig.6-3

10. Find the most cost-efficient version for each location. The consumer must be continuously supplied with current in the process. 11. If necessary, connect an additional hydrogen storage canister. 12. Enter the results in the following table. Location

Number of electrolyzers

Number of hydrogen storage canisters

Wind 1 Light 3 Wind 3 Light 3 Wind 1 Light 1

TIP

If the storage canisters are emptied, the fuel cell must be flushed again.


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Worksheet 2

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Questions about the experiment 1. Where could suitable locations on Earth be found for a combination of wind energy, solar energy and fuel cell technology?

General questions 2. What are wind parks? 3. What is an offshore wind park? 4. What is an onshore wind park? 5. What is the world's largest offshore wind park?

Comprehension questions 6. What must be done to convey the current generated by wind turbines over greater distances? 7. Why is it advantageous to construct wind turbines at sea? 8. What factors stand in opposition to the construction of "wind parks" at sea? 9. An inquisitive student goes through a wind park. The student is dismayed to discover that space for several wind generators has been wasted. The students writes a letter to the city inquiring why the wind park is distributed over such a large area instead of building the wind generators closer to one another. What answer would the student likely receive?


99

Answers 2

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Solutions for the experiment 1. Which constellation is required at the different locations in order to operate an autarkic single-family home? 

Different solutions are possible here. In the process, it is important to recognize that there is an optimal point between economically advantageous (in other words, not the largest fuel cell stack, the maximum possible number of solar modules and wind generators) and the actual requirement for each location and each individual current requirement.

Questions about the experiment 1. Where could suitable locations on Earth be found for a combination of wind energy, solar energy and fuel cell technology? 

The ideal locations have high winds and a lot of sunshine. Such locations include the Caribbean or the coast of Queensland in Australia.

General questions 2. What are wind parks? 

Wind parks are a collection of wind turbines. A collection of more than three wind turbines is called a wind park.

3. What is an offshore wind park? 

Offshore refers to wind parks which are outside of the coastal waters or at sea. Offshore wind parks are wind turbines which are constructed at sea.

4. What is an onshore wind park? 

Onshore means "on land". Onshore wind parks are wind turbines which are constructed on land.

5. What is the world's largest offshore wind park? 

The Thanet wind park off the English North Sea Coast has an installed power of 300 Megawatts (September 2010), making it the world's largest offshore wind park.

Comprehension questions 6. What must be done to convey the current generated by wind turbines over greater distances? 

The generated alternating current of wind turbines creates considerable losses in the lines. The losses are so high that no current arrives at the mainland with a length of over 100 km. Rectifiers which convert the alternating current into direct current must be added. In this manner, large distances can be covered with significantly lower losses.

7. Why is it advantageous to construct wind turbines at sea? Clean Energy Trainer - Experiment Guide

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There is a continuous supply of wind at low heights on the sea. Wind turbines on the land (onshore) are heavily criticized in many regions, because they can destroy a beautiful land scape. This is not the case at sea.

8. What factors stand in opposition to the construction of "wind parks" at sea? 

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The generated current must be led over long distances to the mains grid. This is technically complicated, coupled with losses and expensive. Construction at sea represents great difficulty, because it is usually associated with higher costs. There is a discussion as to whether the noise generated by offshore wind parks has a negatively influence on animals living in the water.

9. An inquisitive student goes through a wind park. park. The student is dismayed to discover that space for several wind generators has been wasted. The students writes a letter to the city inquiring why the wind park is distributed over such a large area instead of building the wind generators closer to one another. What answer would the student likely receive? 

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The student would likely receive the answer that the construction of additional wind turbines is inefficient, because the wind turbines would draw the energy out of the wind. Wind generators which are positioned closely to one another would not produce as high yields because the wind generators would "rob" the wind from one another.


Operating several consumers with fuel cells

Experiment 3 How does a solar/wind/hydrogen system to be designed in order to supply different load profiles? 1. Copy the experimentation set-up as shown in Fig 6-4 (use a 5cell fuel cell stack). 2. Generate 30 cm³ hydrogen. 3. Open the hydrogen outlet for one second. 4. Fill hydrogen to 15 cm³. 5. Start the software. 6. Select simulation in the L OAD PROFILE tab of the software. 7. Arrange any arbitrary load load profile.

Fig 6-4

8. The set-up must be designed in such a way that the number of renewable energy sources and storage canisters provide sufficient hydrogen. 9. Start the experiment by clicking the S TART button. 10. Observe what happens. 11. How can one optimize the previous experiment? Make note of the results in a table.

Load profile


Observation (Fan level)

e.g. stove (high), computer (low), air conditioner (high), lamp (LED)


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Worksheet 3

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Questions about the experiment 1. What was discovered through the experiment which was conducted?

General questions 2. What does regenerative mean? 3. In what five main groups can renewable energies be assigned? 4. What power plants exist for the use of solar energy? 5. What renewable energy source has been in use for the longest by mankind?

Comprehension questions 6. How do solar updraft towers work? 7. How do parabolic trough power plants work? 8. How do solar tower power plants work? 9. How do tidal power plants work? 10. In what coastal areas is a tidal power plant less advantageous? 11. What is the cause of flow and ebb? 12. According to physics, there should be no perpetuum mobile. Accordingly, would the rotation energy of the Earth be completely converted into different energy forms one day?


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Load profile

e.g. stove (high), computer (low), air conditioner (high), lamp (LED)

4

2

2

Observation (Fan level) 1

5 cells

Questions about the experiment 1. What was discovered through the experiment which was conducted? 

It is important to know which energy requirement should be covered with the installed system of regenerative energies. It is equally important to know the average solar and wind yields to be expected in the region in which the autarkic house should be. If this is known, the most advantageous combination of regenerative energy sources can be selected for this constellation.

General questions 2. What does regenerative mean? 

The word "regenerative" is the adjective of "regeneration", which means "reproduction, recovery, renewal, restocking". Therefore, renewable energies can also be called "regenerative energies".

3. In what five main groups can renewable energies be assigned? 

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Bioenergy (from biomass in various forms, see the articles Biogenic fuel and Biofuel) Hydropower       

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Embankment dams and dams Tidal power Run-of-the-river hydroelectricity Wave power Tidal stream power Ocean thermal energy Osmotic power (differing salt content of fresh and salt water)

Wind Energy 107


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Solar Energy  

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Wind turbine Solar updraft tower Downdraft energy tower

Photovoltaics (Photovoltaic system) Solar thermal energy (Solar collector, Concentrated solar power) Solar chemical Thermal energy (Solar updraft tower)

Geothermal energy    

Deep geothermal energy Geothermal energy near the surface Enthalpy of vaporization Adiabatic cooling

4. What power plants exist for the use of solar energy? 

Solar thermal power plants (updraft towers, parabolic trough power plants, solar tower power plants)

5. Which renewable energy source has been used by mankind for the longest time? 

Hydropower - flour mills (water mills) were driven by water wheels on rivers and streams.

Comprehension questions 6. How do solar updraft towers work? 

When air heats up it expands and rises. This characteristic of air makes it useful in updraft towers, where large buildings with glass roofs heat the air using the sun's irradiation. The expanding air in the building can only escape through a chimney positioned in the center. As a result, there is an upward air movement in the chimney through which the so-called "chimney effect" is enhanced. This air flow is then used in turbines built into the chimney in order to generate electrical current.

7. How do parabolic trough power plants work? 

With parabolic trough power plants the energy of the Sun is first used to generate heat. In the process, long parabolic troughs are automatically aligned to the Sun in order to bundle the energy of the Sun i n the focal point of the trough. There are tubes in the focal line of the parabolic troughs in which a heat accumulator (usually water) is usually found, which is heated up by the connected solar irradiation to several hundred degrees Celsius. Of course, these temperatures are sufficient to evaporate the heat accumulator. The steam which arises is then used to drive turbines which generate the desired electrical current.

8. How do solar tower power plants work? 108



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In solar towers even higher temperatures can be achieved than in the parabolic troughs. In order to connect as much solar energy as possible, the solar towers use computer-controlled mirrors aligned to the sun to focus the beams on a very small surface. In the focal point of the solar tower there is a heat accumulator, which can be heated to over 1000 degrees Celsius in solar towers. The heat accumulator evaporates and can be used to drive turbines for the generation of current.

9. How do tidal power plants work? 

With tidal power plants generators are driven by the rising water level. A generator can also be driven when the water flows back to the sea.

10. In what coastal areas is a tidal power plant less advantageous? 

In coastal areas with weak tides. For example, the Baltic Sea.

11. According to physics, there should be no perpetuum mobile. Accordingly, the rotation energy of the Earth would be completely converted into different energy forms one day. 


Yes, the earth is also becoming continually slower. However, the effect is so minor that we do not notice it.

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Clean Energy Trainer Experiment Guide

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