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Hybrid Thermoelectric Solar Cell

Novel power harvesting module integrates the energy harvesting abilities of a thermoelectric generator with a solar cell to maximize output

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The purpose of this project is tocreate a small IoT power harvesting module that can use both the light and heat produced from the sun. Solar panels can reach normal temperatures of 95 degrees Fahrenheit and can even get as hot as 149 degrees Fahrenheit (source: https://goo.gl/chraJG). This is because solar cells absorb a lot of radiation as heat. Researchers are looking into how to effectively cool panels so that they can operate more efficiently but this would not be feasible for smaller solar cells. My idea is to utilize this high temperature to produce more electricity during the day. One 40mm by 40mm TEG module can produce 1 volt with 200 mA by using a 20 degree temperature difference. By coupling a solar cell to a colder temperature, We can utilize the high temperature of the solar cell to generate more energy through out a hot day to power IoT devices.

Intro

The purpose of this project is to see if we can create a small IoT power harvesting module that can use both the light and heat produced from the sun. Solar panels can reach normal temperatures of 95 degrees Fahrenheit and can even get as hot as 149 degrees Fahrenheit (source: https://goo.gl/chraJG). This is because solar cells absorb al ot of radiation as heat. Researchers are looking into how to effectively cool panels so that they can operate more efficiently but this would not be feasible for smaller solar cells. My idea is to utilize this high temperature to produce more electricity during the day. The best way to create this temperature difference is to have the colder night air cool a water based heat sink. This cool water is housed in an insulated container so that it slowly get warmed throughout the day. When the solar panel quickly gets hot it will create a temperature difference with the TEG causing it to produce a strong voltage throughout the day. This device can be small and modular . The device should be able to be attached to any sensor and because of its small size it can be attached anywhere to collect data.

Method

One 40mm by 40mm Thermoelectric Generator (TEG) module can produce 1 volt with 200 mA by using a 20 degree temperature difference. By coupling a solar cell to a colder temperature, We can utilize the high temperature of the solar cell to generate more energy through out a hot day. This project will utilize 4 of those TEG modules and couple them with a 5V solar panel. The goal is to produce 5V from the panel and atleast 4v from the TEG modules. If this can be proven, then the next step is to create a smaller scale module that is 40 mm by 40 mm and can produce at least 2 volts totals from both the solar panel and the TEG. The hot side of the TEG module will need to quickly reach the high temperature of the solar panel. Therefore the hot side needs to be conductively  glued with the solar panel. For the module to produce a high voltage the cold side needs to be able to be passively cooled. This project utilizes a water chamber as a heat sink to maintain a cold side as long as possible. The chamber was 3D printed to fit the solar panel exactly and the stls are attached to this project.

 Results, Conclusions and Further improvements.

In the hot weather we are experiencing today, the solar panel easily gets to over 90 degrees Fahrenheit. Furthermore, during the night there is 60-70 degree weather. Therefore there is a 20 degree increase in temperature ATLEAST during the day. The challenge is to harness this temperature change and integrate it into a solar panel TEG hybrid device. 

The results showed that the TEG can give a feasible operable voltage when it is heated. The issue seems to be that it is hard to keep the water cool from the environment. The sun definitely heats up the PLA chamber which help heats up the water at the same rate as the panel. I need to run more tests to confirm these results. I think the theory is sound and some of the data from the project supports this theory. At the least I plugged it into a particle photon to measure the soil moisture of the plants.
To further improve the device I will figure out a way to keep the water cool by using a metal housing with a reflective double wall similar to a Yeti water bottle. If I can show that the TEG can produce the 4 volts I need from the sun, then the next big step would be to create a 40mm by 40mm by 40 mm thermoelectric solar module cube that can be used to power low sensor applications. In the end, this hybrid thermoelectric solar module is quite flexible to provide power to low power as well as relatively higher power IoT applications. It can simply be plugged into any low power device like the particle photon. 

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  • 1 × Solar Cell 5V 80mm by 80mm
  • 4 × Thermoelectric Generator 40mm by 40mm Should produce 1 volt from a 20 degree temperature difference from amazon
  • 4 × Heat Sink 40mm by 40mm same size heat sinks and come with thermal conductive tape to attach to the TEG from Amazon
  • 1 × Solar Cell Lipo charger from adafruit Useful if you want to charge lipo using module
  • 1 × 5V voltage booster Useful to provide 5v exact to you micro controller.

View all 9 components

  • Testing the entire fully assembled module!

    Neel07/16/2018 at 05:56 0 comments

    So I created a fully assembled module using the instructions I posted for this module. I 3d printed and glue a go pro joint so that I could use a suction cup to suction is wherever I want. 

    I had the particle photon collect data all day. 

    The data showed that the solar cell got less than 5v but otherwise it seem to be operating well for a cloudy day.

    The TEG modules only produced .3 volts instead of the 3-4 volts that I was hoping for. The TEG modules were glued to the panel with a thermal glue. I think I got such a low voltage because this was testing in Acadia so the weather was not that hot and sunny on the day. It was only 65 degrees at night and 75 during the day so they wouldn't have been environmental help to maintain a temperature difference. Furthermore the lower level of sunlight may have also made it hard for the panel to heat up from the radiation. Lastly I believe that the water chamber is not well insulated because of the PLA. I think I need to take more tips from the Yeti company so that I can seal the chamber extremely well. I think throughout the day the environment is more easily capable of heating up the water which decreases the temperature difference.

    The good news I got from the data is that the trend clearly shows that the TEG voltage produced increases as the solar cell voltage increase throughout the day. This I believe proves the theoretical idea that the energy absorbed as heat throughout the day can help run these TEGs. The challenge is to now maintain a larger temperature difference.

    Copoed from internal project log

  • Artificial heated module test

    Neel07/16/2018 at 05:47 0 comments

    Well the particle stopped working so I can't do testing throughout the day.  I redesigned the chamber so it has an internal air pocket in the walls similar to a yeti. What I need to figure out is how I can fit reflective walls into the internals of the walls for great insulation.

    I tested it artificially by attaching a blower onto a clamp. I used a laser thermometer gun to keep tabs on the outer surface of the solar panel. This setup was four TEG modules with four heat sinks placed into the water chamber. i didn't want to permanently glue the solar cell to the TEG modules so I had them in contact with each other.

    Surprisingly and sadly the voltage measure was only .1-.3 volts! After removing the solar panel I found out that the TEG was still cool to touch. Apparently a touching contact was not good enough to set up a temperature difference.

    I then wanted to make sure we can set up a temperature difference for atleast a half hour. The water I measured to be 70 degrees so I decided to heat up the TEG itself to 90 degrees.

    Surprisingly the modules produce 3.4 volts for a good half hour.

    The conclusions were that theoretically one could generate extra voltage from the TEG when attached to the solar panel to help power a device!

    The problem is seems is that the contact between the solar panel and TEG needs to be very conductive. 


    Copied from internal project log.

  • Tested solar cell with one TEG in water cooled chamber

    Neel07/16/2018 at 05:32 0 comments

    So I cadded a housing temperature to insert the TEG-Solar module into. The day is once again reaching well into the 90s from a 60 degree night. I taped one TEG Module onto the solar panel and plunged the heat sink fully into the water.


    The max voltage read was close to .1 volts. This is better than before but still not usable for a hybrid system. At least the solar cell is operating well on these sunny days. I suspect that because the TEG does not have good contact with the solar panel, it is not creating a good temperature difference. 

    From a qualitative point of view the solar cell felt hotter to touch while the heat sink felt cooler to touch but not as cool as I hoped it would be after a run. I think the water chamber needs to be redesigned to seal out heat from reaching the water in all directions except from the back side of the solar panel. After looking into the yeti water bottles, I am trying to see if I can use some of there techniques to 3d print a better sealed chamber.

  • Tested solar cell with one TEG

    Neel07/16/2018 at 05:24 0 comments

    I have taped a TEG onto the back of a solar cell. The TEG is attached to the heat sink using the thermal conductive tape it came with. The hot side of the TEG is put into contact with the back of the solar panel. The heat sink is exposed to the surrounding air. I am wondering how well the heat sink works in keeping a temperature difference.

    The day is reached a temperatures at around a 90 degrees. After a full day of exposing the setup to the sun I am sad to say that the max that I recorded on the particle photon was .05 volts. At this point four TEG modules would only produce a max of .2 volts with most likely low amperage. I believe this is because the heat sink is small enough that it is easily heated from the surrounding environment

    I will need to figure out how to passively keep the cold side of the TEG module cool. I will be testing a water heat coupling to see if it will help create a larger temperature difference for a shorter period of time.

    Copied from internal project log 

View all 4 project logs

  • 1
    Attach the cold side of the thermoelectric generator(TEG) to the heat sink using conductive sticky pads

    The cold side of the thermoelectric generator is marked with numbers and letters. Using double sided thermally conductive sticky pads that come with the heat sinks connect them together. The heat sinks will be used to cool the cold side of the TEG

  • 2
    Glue the TEG modules to the back side of the solar panel

    There is a capacitor attached to the middle of the solar panel so the two sets of solar panels will have to be glue slightly apart from each. The side without the numbers should be directly glued to the panel


  • 3
    Wire each of the TEGs in series with each other to produce a theoretical 4V with a 20 degree difference.

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