FLASHLIGHT THAT RUNS ON THE HEAT OF THE HUMAN HAND Short Description: My objective in my project was to create a flashlight that runs solely on the heat of the human hand. Using Using four Peltier tiles and the temperature temperature difference difference between the palm of the hand and ambient air, I designed a flashlight that provides bright light without batteries or moving parts. My design is ergonomic, thermodynamically efficient, and only needs a five degree temperature difference to work and produce up to 5. m! at 5 foot candles of o f brightness.
Summary: My "outube #ink$http$%%www.youtube.com%watch&v'())*UMkcbjg+feature'youtu.be #ink$http$%%www.youtube.com%watch&v'())*UMkcbjg+feature'youtu.be I chose to investigate the aspect of human energy when I found out that we are like walking -!att light bulbs. he goal of my project became a flashlight powered solely from the heat of the human hand. I decided to use Peltier tiles. If one side of these tiles is heated, and the other is cooled, electricity is produced. /or my flashlight, I would be heating one side with the palm, and cooling the other side of the tile with a heat sink. I calculated that our bodies radiate 5.0 m!%cm1, but only -.5 m! is needed to generate a bright light at the #23. I charac characteri teri4ed 4ed both Pelti Peltier er devices. oth produced produced power power,, but only a few mill mi lliv ivolt olts. s. I ne need ed 1.5 6 7 I ha had d to conver convertt my 3) in inpu putt to 8), 8), an and d th then en run it th thro roug ugh h a oscillator circuit with with a stepup transformer. transformer. My final circuit circuit had only parts and produced a step up ratio of --$. 9o for 5- m6 3) from the Peltiers I obtained 5 6olts 8) which was sufficient to light the #23. he final design included mounting the Peltiers on a hollow aluminum tube which was inserted in a larger P6) pipe with an opening that allowed ambient air to cool the tube. he palm wrapped around a cutout in the P6) pipe and warmed the tiles. he result was a bright light at 5 degree )elcius of Peltier differential. differential. he flashlight worked7
Research: I couldn:t find any idea specific to my topic of the thermoelectric flashlight at all, e;cept for a website websi te called the Ultralow 6oltage 2nergy ?arvester Uses hermoelectric *enerator for attery = /ree !ireless 9ensors>.
9tep in my procedure, involved much research, as I decided to calculate how much heat per cm1 we radiate in our inner palm, where we normally hold a flashlight. I found that an average human dissipates around @5-,---
Metho: B9tep was research oriented, so it is not included hereC. 9tep 1$ )haracteri4ing the Peltier iles$ wo sets of cheap, different si4ed tiles were obtainedH. ile had an area of .@H cm1 and an internal resistance of 5 ohms, and ile 1 was cm1 and had an internal resistance of 1. ohms. I tested the power generated by each Peltier stack on a per cm1 basis. o do this, I taped each tile onto a sAuare aluminum tube. ne side of the Peltiers was cooled by an ice pack, and the other was heated with a 1=volt light bulb connected to a variable power supply. he temperature difference between the sides of the Peltier tile was measured. oth Peltier tiles produced enough power to light an #23, but only at 5- and 0@ m6. I needed 15-- m6 to light the flashlight #23. 9tep @$ oosting the 6oltage. 3irect )urrent cannot be multiplied, but if the 3) is changed to 8), the voltage can be stepped up with a transformer . he answer lay in constructing a simple oscillator circuit with a step=up transformer. o do this I constructed a feedback oscillator with a field effect transistor and wound my own transformers with step=up ratios of 5$15. he oscillator worked, but the #23 did not light up until the Peltier voltage was 1- m6. I needed it to light up at about 5- m6 Bvoltage produced at a 5J) temperature differenceC.
9earching the Internet, I came across an article about energy harvesting0 and the use of a power converter integrated circuit, #)@-KK. he circuit contained /2Fs that would oscillate at voltages as low as 1-m6. !hen used with a recommended transformer, the I) would provide well over 1.5 volts 8). he I) also worked fine as a very low voltage transistor oscillator. My circuit now had only components$ he I), the step=up transformer, a 0L/ capacitor, and the #23. !ith the #23 across the transformer, I was able to obtain good #23 brightness with only 5- m6 3) input across the oscillator. he efficiency of the converter to be about 5-E at -- m6. 9tep $ Physical /lashlight 3esign. I decided to make the flashlight with dimensions of 15mm in diameter and 15mm long. /our of the large Peltier tiles covered Hcm1, and four of the smaller tiles had a combined area of 5.cm 1 . iles were mounted on a milled area of 15mm diameter aluminum tubing, and placed inside a larger P6) pipe, insulated from it by air. he hand griped the tiles through an opening in the P6) pipe. 8ir flowing through and around the aluminum tube cooled the flashlight. he circuit was mounted in the front, and the #23 was centered in the middle of the tube. he P6) pipe was wrapped with insulating foam. I made two flashlights, the / with smaller tiles, and /1, with larger tiles.
Resu!ts: he results prove my hypothesis, that even with all the thermal and voltage conversion losses, there was still enough power in the palm to provide usable light. he actual power at the #23 was difficult to measure accurately because it was an irregular sAuare wave at - k?4. 9o I made a comparative measurement with a light meter and an e;ternal white #23 Bconnected to a 3) power supplyC. I measured the 3) power into the e;ternal white #23, that gave the same amount of light as the white #23 in my circuit. oth #23Fs were identical types, 5mm, 5 degree types from 3igikey. /or my / flashlight, I calculated the theoretical power at the #23 to be around .5 m!. !hen I did the compartive measurement, my prediction turned out to be very close, with a . m!. he /1:s theoretical power was supposed to be around .5 m!, but instead I got 5. m!. he theoretical power calculated, and the actual power obtained were within 1-E of each other7 ravo7
Measurements with a 9pectra light meter showed that both flashlights produced good light and even surpassed the brightness of the pie4oelectric flashlight I made last year. /lashlight / produced @ footcandles of light at a 5), and footcandles at -) Peltier temperature diffrence. /lashlight /1 produced footcandles of light at a 5), and 5 footcandles at -) Peltier temperature diffrence. In outside walking tests at an ambient temperature of -), both flashlights maintained a steady beam of light for over 1- minutes.
"onc!usion: In conclusion, I succeeded in powering a flashlight using only the heat of the hand. I made two flashlights that do not use any batteries, to;ic chemicals, or kinetic energy. hey do not create any noise or vibrations and will always work. he flashlightFs only limitation is its need for at least a 5J) temperature difference to provide usable light. In the beginning of my project, I had hoped and believed that my flashlight would perhaps work, but I did not e;pect my final brightness that I recieved to be as high as 5 footcandles. I am pleased with my results, but do have some future improvements in mind. In the future, I hope to work on improving efficiencies of the converter, increase the flashlight brightness, and perhaps use this technology for powering wireless medical sensors. My uniAue circuit and design has infinite possibilities and uses for the future7 /or e;ample, imagine holding your phone, and at the same time charging it just from the heat of your hand7 r perhaps all school chairs in classrooms having Peltier tiles, and we could harvest the heat and amplify it into electricity using my method. I am very e;cited for the possibilities my project has7 It is but a means of showing what this concept, and what human heat energy, can do. In my e;periment, I had several general errors in my sources and calculations. /or instance, palm temperature, and total skin surface area varies widely between individuals. he skin area was averaged from several sources and varied from .H m1 to 1 m1. 8nother Auestionable figure is the thermal to voltage conversion efficiency of the Peltier tiles. his is a comple; problem in thermodynamics depending on the heat conduction properties of the tiles, contact areas and heat sinks, and is not usually given in the manufacturers specs. he same efficiency figure of -E was obtained from a te;t at 9tanford and an online encyclopedia(, -. he voltage, current, and
temperature measurements I made, were done on /luke meters, and had more precise accuracies which varied from .-E to .E.
Ac#no$!e%ements: C Nodney Oat4 for allowing me use eAuipment and materials in the 3epartment of Mechan ical 2ngineering Machine 9hop at the University of 6ictoria, while under supervision. 1C 8rthur Makosinski for purchasing the parts and he lping me with soldering, mechanical issues, and electronics. @C My teacher Mrs. Paine for her encouragement, and making sure I stay on the task.
&i'!io%raphy an Re(erences: C Physics and 8stronomy nline$ http$%%www.physlink.com%education%aske;perts%ae1-.cfm 1C Makosinski, 8nn. Fire or Ice - Electricity for an Emergency, 6IN9/, 1--. @C he Physics /actbook$ http$%%hyperte;tbook.com%facts%1--%Igor/ridman.shtml C !ikipedia$ hermoelectric )ooling$ http$%%en.wikipedia.org%wiki%hermoelectriccooling 5C Makosinski, 8nn. The Piezoelectric Flashlight - A Novel Way to Generate Green Electricity, 6IN9/, 1-1. HC #aird hermoelectric$ http$%%www.lairdtech.com%Products%hermal=Management= 9olutions%hermoelectric=Modules% 0C 3avid 9alerno, Ultralow 6oltage 2nergy ?arvester Uses hermoelectric *enerator for attery /ree !ireless 9ensorsQ Journal of Analog Innovation, ctober 1--. KC /uturlec$ http$%%www.futurlec.com%ransistors%<@-pr.shtml (C 2ncyclopedia ritannica R hermoelectric Power *enerator$ http$%%www.britannica.com%2checked%topic%5(H5%thermoelectric=power=generator -C 9tanford University, Physics 1- )oursework R hermoelectric *enerators$ http$%%large.stanford.edu%courses%1--%ph1-%weisse%
