Figure 5.26 Power Consumption at 70% Load Profile
Figure 5.27 Power Consumption at 60% Load Profile
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Figure 5.28 Power Consumption at 50% Load Profile
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CHAPTER 6 CONCLUSIONS AND RECOMMENDATIONS
This chapter presents the conclusions and recommendations for the study. The conclusions are based on all the gathered data and relationships from research, experiments, and testings done in the vapor compression system with or without the VFD automated by the microcontroller. Recommendations for this study were made as seen needed.
6.1 Conclusions
The discussions and analysis of different parameters such as environment temperature, power consumption, voltage, and electric current from the previous chapters enabled the comparative analysis of a conventional vapor compression system to a variable frequency driven vapor compression system for air-conditioning application. The Amatrol T7082 Thermal Systems served as the vapor compression system having the Amatrol T7083 Environmental Application System as the air-conditioned space. Through analyzing all the measured and calculated data especially on power and energy consumption, conclusions were made that point out the difference in performance as well as the advantages and disadvantages of the vapor compression system with and without the VFD. Based on the data that can be seen from the previous chapters, it can be concluded that:
As the load increased the temperature also increased. As the temperature increased, the frequency of the compressor also increased, and vice-versa.
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For the variable frequency driven vapor compression system, temperature tend to be controlled depending on the load inside the space. The system maintained an ideal temperature depending on the heat sensed inside the room. Frequency ranges from 45 Hz to 60 Hz.
For the conventional vapor compression system, the operation without VFD showed constant frequency for the compressor which was 60 Hz so the temperature was dependent on what was set by the thermostat which operated in an on-off control.
Voltage was not dependent on the load inside the air-conditioned space as well as on the frequency of the compressor. As frequency and temperature increased or decreased, voltage was still constant.
Electric current was not dependent on the load inside the air-condtioned space as well as the frequency of the compressor. As frequency and temperature increased or decreased, electric current was still constant. There was a percentage difference to the current with VFD to that of without due to friction losses and voltage dropped.
Power consumption was dependent on the load change inside the room. As the load increased, the power consumption also increased, and vice-versa.
- For the vapor compression system without the VFD, the power consumption was constant even if the temperature increased or decreased because compressor frequency was still constant at 60 Hz standard.
- For the variable frequency driven vapor compression system, the power consumption increased as the load increased, and vice versa. It can also be noticed that power consumption with VFD was greatly smaller compared to that without. 77
Because the VFD maintained the desired compressor frequency depending on the room temperature as sensed by the thermistor through the microcontroller.
The variable frequency driven vapor compression system (Amatrol T7082 Thermal Systems with VFD) had a lower power consumption compared to the conventional vapor compression system (Amatrol T7082 Thermal Systems without VFD).
Variable frequency driven compression system had a higher first cost but is more energy efficient compared to the conventional.
- The conventional vapor compression system worked in an on-off control wherein a certain room temperature was set by the thermostat. As the room was cooled and reached the set temperature, the compressor turned off and turned on again at another set temperature for it to turn on. The turning on and off the compressor resulted to higher peak loads during start up which led to higher energy consumption.
- The variable frequency driven vapor compression system worked in variable frequency control. In this control, the compressor‘s frequency was varied. This drive allowed the system to match the speed of the motor-driven equipment to the process requirement. Frequency was varied by the VFD depending on the temperature sensed by the thermistor. The thermistor sent the signal to the microcontroller which automated the VFD. Possible sources of errors and percentage differences on the experiments and testings done in this study includes: (1) the measuring devices such as the digital thermocouple and the power meter; (2) human error; (3) equipment failure; (4) changing environment temperature; (5)
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inefficiency of the reciprocating compressor at low frequencies; (6) open spaces in the air conditioned space and; (7) friction losses and voltage drops. 6.2 Recommendations
For the improvement of this study about the comparative analysis of a conventional vapor compression system to a variable frequency driven vapor compression system for air conditioning application, the following recommendations are made:
Use a scroll compressor instead of a reciprocating compressor for the system. The reciprocating compressor can be run by the VFD but is not that efficient because it is not designed for variable frequency operation. This is why the compressor of the Amatrol T7082 Thermal Systems (2413 BTU/hr ± 28.6 BTU/hr or approximately 1 HP) can only work at a range of 45 Hz-60 Hz. The compressor had failure at frequencies lower than 45 Hz. Scroll compressors are greatly more expensive compared to reciprocating compressors but is efficient at variable speed operation.
Test the VFD-microcontroller set-up in an actual room and in an actual 1hp window type air conditioner (The VFD purchased is designed for up to 2 hp capacity. Dividing the capacity to a safety factor of square root of 3 yields to 1 hp capacity).
Directly connect the VFD (automated by the microcontroller) to the compressor of the vapor compression system. In this study, it is only possible to integrate the VFD to the system by plugging the plug of the Amatrol T7082 Thermal Systems to the socket connected to the supply from the VFD which is directly plugged to the 220 volts main voltage supply. This set up resulted to percent differences from voltage drops and friction losses in the wires.
79
Improve the design and construction of the microcontroller by putting additional relays to the circuit. Also, improving its temperature sensibility by putting additional thermistors (number of sensor depending on the area of the air-conditioned space) to the circuit design.
Maximize certain features of the Delta VFD-B Series Variable Speed AC Motor Drive possible to be integrated in the variable frequency technology such as safe motor start, passwords, 4 acceleration/deceleration times and 2 S-curve selections, automatic energy saving, adjustable V/F curve and automatic voltage regulation, automatic adjustment of acceleration/deceleration time, auto tuning and sensorless vector control, sleep / revival function and master / auxiliary.
Try other automation controls for the VFD particularly the Programmable Logic Controllers (PLC).
For the pursuit of furthering the prototype, it is suggested that a variable frequency driven vapor compression system in a window-type air-conditioner be commercialized. Because of its effective ability to lessen energy consumption, it has a potential strength to penetrate the market.
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APPENDIX A
Drawings / Figures
Figure 1: Typical VRF configuration in an office building.
Figure 2. Heat Recovery VRF System 81
Figure 3 page 337 This typical on-off furnace thermostat has a 3oF temperature swing during its cycle. This is enough temperature swing to be noticeable.
Figure 4 page 337 This furnace is controlled by a variable-speed fan motor and firing rate. It has only a 1oF swing. This will not be noticeable
82
.
Figure 5 page 339The rectifier moved all of the sine wave to one side of the graph.
Figure 6 page 340 Pulsating DC enters the capacitor bank and straight line DC leaves.
83
Figure 7 page 340 When the control system (computer) sends a signal to the base connection the transistor turns on and then turns it off when the signal is dropped.
Figure 8 page341 The choke coil stabilizes current flow
84
Figure 9 page339 A simple diagram of a variable-speed motor drive
Figure 10 page 341Sine coded, pulse with modulation
85
Figure 11 Amatrol T7082 Thermal System S ystem and Amatrol T7083 Environmental Application System
86
Figure 12 Brochure of Hitachi‘s newest Inverter Scroll Compressor Window Type AC 87
Figure 13 NTC Thermistors
Figure 14 PTC Thermistors
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APPENDIX B
Microcontroller Program
' {$STAMP BS2}
x VAR Word
temp VAR Word tempdiff VAR Word time VAR Word timediff VAR Word tempdiffmem VAR Word
sense0: time = 0 HIGH 8 RCTIME 8, 1, temp DEBUG ? temp time = 0
'SPEEDS speed15:
' 45 hz
PAUSE time HIGH 0 HIGH 1 89
HIGH 2 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed1 IF tempdiffmem = 0 THEN speed15
speed1:
' 46 hz
PAUSE time LOW 1 LOW 2 LOW 3 HIGH 0 GOSUB sense IF tempdiffmem = 1 THEN speed14 IF tempdiffmem = 0 THEN speed15
speed14:
' 47 hz
PAUSE time LOW 0 HIGH 1 HIGH 2 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed2 IF tempdiffmem = 0 THEN speed1
90
speed2:
' 48 hz
PAUSE time LOW 0 LOW 2 LOW 3 HIGH 1 GOSUB sense IF tempdiffmem = 1 THEN speed13 IF tempdiffmem = 0 THEN speed14
speed13:
' 50 hz
PAUSE time LOW 1 HIGH 0 HIGH 2 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed3 IF tempdiffmem = 0 THEN speed2
speed3:
' 51 hz
PAUSE time LOW 2 LOW 3 HIGH 0 HIGH 1 GOSUB sense 91
IF tempdiffmem = 1 THEN speed12 IF tempdiffmem = 0 THEN speed13
speed12:
' 52 hz
PAUSE time LOW 0 LOW 1 HIGH 2 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed4 IF tempdiffmem = 0 THEN speed3
speed4:
' 53 hz
PAUSE time LOW 0 LOW 1 LOW 3 HIGH 2 GOSUB sense IF tempdiffmem = 1 THEN speed11 IF tempdiffmem = 0 THEN speed12
speed11:
' 54 hz
PAUSE time LOW 2 HIGH 0 92
HIGH 1 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed5 IF tempdiffmem = 0 THEN speed4
speed5:
' 55 hz
PAUSE time LOW 1 LOW 3 HIGH 0 HIGH 2 GOSUB sense IF tempdiffmem = 1 THEN speed10 IF tempdiffmem = 0 THEN speed11
speed10:
' 56 hz
PAUSE time LOW 0 LOW 2 HIGH 1 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed6 IF tempdiffmem = 0 THEN speed5
93
speed6:
' 57 hz
PAUSE time LOW 0 LOW 3 HIGH 1 HIGH 2 GOSUB sense IF tempdiffmem = 1 THEN speed9 IF tempdiffmem = 0 THEN speed10
speed9:
' 58 hz
PAUSE time LOW 1 LOW 2 HIGH 0 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed7 IF tempdiffmem = 0 THEN speed6
speed7:
' 59 hz
PAUSE time LOW 3 HIGH 0 HIGH 1 HIGH 2 GOSUB sense 94
IF tempdiffmem = 1 THEN speed8 IF tempdiffmem = 0 THEN speed9
speed8:
' 60 hz
PAUSE time LOW 0 LOW 1 LOW 2 HIGH 3 GOSUB sense IF tempdiffmem = 1 THEN speed8 IF tempdiffmem = 0 THEN speed7
sense: HIGH 8 PAUSE 1 RCTIME 8, 1, temp DEBUG ? temp IF temp => 800 THEN cooling IF temp < 800 THEN heating
cooling: tempdiff = temp - 800 tempdiffmem = 0 GOTO comptime
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heating: tempdiff = 800 - temp tempdiffmem = 1 GOTO comptime
comptime: time = (tempdiff*10/30)*25 DEBUG ? temp DEBUG ? tempdiff DEBUG ? tempdiffmem DEBUG ? time RETURN
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APPENDIX C Gantt chart Task
Description
1
Thesis 1 Research Title
2 3 4
Introduction Review of Related Literature and Related Studies Methodology
5
Theoretical Considerations
6
7
Oral Presentation Thesis 2 Further research and study VFD and microcontrollers and PLCs
8
Purchase the VFD and Program the frequencies And everything that is needed
9 10
11 12 11
2
3
4
5
6
7
8
9
10
Weeks
1
2
3
4
5
6
7
8
9
10
Weeks
1
2
3
4
5
6
7
8
9
10-13
Program the microcontroller Integrate the Microcontroller to the VFD/Inverter and test until program works
12
Reserve the HVAC Lab for testing using the Amatrol T7082 Thermal Systems
13
Create a set up to integrate the VFD-microcontroller system to the Amatrol Thermal Systems
16
Study the Amatrol T7082 Thermal Systems and the Environmental Application System, Create heat loads Sources (light bulbs) Data Gathering, Computation, and Evaluation for the Amatrol Thermal System with VFD and without the VFD Formulation of Conclusion, Recommendation, and Discussion of Results
17
Final Presentation / Defense
15
1
Purchase equipments to construct a Microcontroller And study about microcontrollers Design Circuit Diagram and construct the Microcontroller Integrate the thermistor to the microcontroller and calibrate the thermistor in accordance to the program in the basic stamp 2
Thesis 3
14
Weeks
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APPENDIX D
Budget Computation
Sponsored Amount: Php. 30,000 by Modair Manila Co. Ltd., Inc. ITEMS (per receipt) 1.) Delta Frequency Inverter VFD015B21A 2HP 220V 2.) 4pcs. Thermistor 100 ohms 3.) 10pcs. Capacitor
4.) Parts 1 5.) Solid and stranded wires 6.) Parts 2 7.) Parts 3 8.) 5pcs. 80DC-149 9.) 10pcs. Diodes 10.) 12pcs. 1N-4004 11.) Digital Thermometer 12.) Materials for Heat Loads Omni receptable E27 3‖ white 3pcs Omni 1 way switch P3 ST3 CLMB/Philflex flat cord 13.) Materials for Microcontroller 1 BASIC Stamp II PC 401 6pcs OMI-55-2061 (Relay SPDT) 6pcs WA-SH-105D (Relay DPDT) 2pcs LM7805 3pcs 0.1 microfarads capacitor 9P RS232 (F) RA 15pcs 2N3904 3m #22 stranded wire 14.) Materials for Microcontroller 1 3pcs thermistor 10k 3pcs Mylar capacitor 0.1 microF 15.) Materials for Microcontroller 1 12 pcs 1/8 12 pcs 2N3904 ICN-24
SUPPLIER GOTYCO Controls Center, Inc.
PRICE (Php) 13,450
DEECO DEECO DEECO DEECO DEECO DEECO DEECO DEECO Liongco Electronics CJR Hardware & Electrical Supplies ACE Hardware
140 180 50 266 135 254 90 15 12 1, 510 317.75
Alexan Commercial
4, 963.25
Alexan Commercial
55.50
Alexan Commercial
44.50
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switch 16.) Plug 17.) 4pcs Bolts and Nuts x8 18.) 2pcs Plastic Light Bulb Stand 3x3 19.) Other materials 50 Watts Light Bulb 100 Watts Light Bulb 3pcs. Light bulb holder TOTAL
Adams T.S JS Lim Prop. GKH Building Supply GKH Building Supply GKH Building Supply
35 14 64 130
Php. 21,726 - Php. 30,000
Cash / Investment Remaini ng Bal ance / Savin gs
Php. 8,274
99
REFERENCES
Afify, Ramez. June 2008. Designing VRF Systems. ASHRAE Journal . pp. 52-55 Amatrol, Inc. Environmental Applications Learning System – T7083 Retrieved: September 30, 2011 from http://www.amatrol.com/product/t7083.html Amatrol, Inc. Thermal Learning System – T7082 Retrieved: September 30, 2011 from http://www.amatrol.com/product/t7082.html AuCom Electronics Ltd., Variable Frequency Drives (MD) – VFD: Operation Retrieved: September 30, 2011 from http://www.aucom.com/vfd-operation.html Aynur, T.N., Y. Hwang, and R. Radermacher. 2008. Experimental evaluation of the ventilation effect on the performance of a VRV system in cooling mode — Part I: Experimental evaluation, HVAC&R Research 14 (4): 615 – 630. Aynur, T.N., Y. Hwang, and R. Radermacher. 2008. Simulation evaluation of the ventilation effect on the performance of a VRV system in cooling mode — Part II: Simulation evaluation, HVAC&R Research 14 (5): 783 – 795. Aynur, T.N., Y. Hwang, and R. Radermacher. 2009. Simulation comparison of VAV and VRF air conditioning systems in an existing building for the cooling season, Energy and Buildings 41 (11): 1143 – 1150 Aynur T.N., Y. Hwang, and R. Radermacher. 2009. Simulation comparison of VAV and VRF air conditioning systems in an existing building for the cooling season, Energy and Buildings 41 (11) : 1143 – 1150. Aynur, Tolga N. 2010. Variable refrigerant flow systems: A review. Energy and Buildings 42:1106 – 1112 Burt C., B. Busch, F. Gaudi, X. Piao, NFN Taufik. October 2006. Electric Motor Efficiency Under Variable Frequencies and Loads. Irrigation and Training Research Center. California Polytechnic State University. San Luis Obispo, CA 93407-0253 805-756-2379 pg.1 Carrier Corporation, October 2005. Variable Frequency Drive: Operation and Application of VFD Technology Retrieved: September 29, 2011 from http://www.docs.hvacpartners.com/idc/groups/public/documents/marketing/wp_varfreqdrive. pdf Cole, Kenneth S. February 25, 1957. Thermistor Thermometer Bridge: Linearity and Sensitivity for a Range of Temperature. American Institute of Physics. 0034-6748. pp.2 Cooper, Crystal. 2009, June 21. HVACR: About thermistors. Retrieved: October 1, 2011 from http://www.brighthub.com/engineering/mechanical/articles/27687.aspx#imgn_0 Delta Electronics, Inc. Delta VFD-B Series Variable Speed AC Motor Drive User Manual Electronics Information Online (2006), Electronics Information – Microcontroller Retrieved: September 30, 2011 from http://www.electronics-manufacturers.com/info/circuits-and processors/microcontroller.html 100
