Thermoelectric Generators as a Renewable Energy Source

[chris26]

Hi everyone. I was searching for discussions on TEGs and bumped into this forum. Can I ask for advice on my project?

The idea is using peltier tiles or seebeck tiles, is it feasible for having the source of heat as human hand, be able to charge a smartphone device or flashlight? The  concerns I'm worried on is about the LTC3108 energy harvester and the current needed for certain applications like charging a phone or a powerbank. I have consulted someone and he told me that his previous problems with TEGs is the output current needed for certain devices. Possible components would be of a buck converter, a Li-Ion battery and a charging module. I feel like I'm having a wrong understanding and background on TEGs and peltier tiles. Thanks! 

[MosherIV]

The idea is using peltier tiles or seebeck tiles, is it feasible for having the source of heat as human hand, be able to charge a smartphone device or flashlight?

The TEG would only see around 10Deg C (ambient temp around 20 and Human = 32) this is not enough for most peltier devices to generate any current.

If you do a search for peltier experiments, you will find some use a candle. This will give temperature grandients of 100s Deg C

Is it feasible to use human hand as a heat source to charge smart phone/flash light battery - NO.

[Marco]

High temperature TEGs can get reasonable efficiencies and might with a bit of science one day even present an alternative to turbines for some applications. They are already used in camping equipment and satellites.

Low temperature TEGs, well maybe you could harvest some energy for some microwatt mote which occasionally transmits some data.

[LabSpokane]

Low temperature differentials yield poor efficiency due to thermodynamics.

Theoretical max. Eff = 1 - Tc/Th

...where temps are in kelvin. What this translates to is that small, low temp differential power generation is usually not practical or cost effective.  I'm coming up with about 5% theoretical efficiency between a 37C hand and a 20C room. And the reality is that the conversion efficiency using a peltier device will be substantially worse than that.

These are always fun projects to think about, but the reality of trying to generate the 5-10W to charge a phone or flashlight in a reasonable time usually renders them impractical.

[Kilrah]

There have been devices made that used TEGs and the temp difference between a hand and ambient to generate power.... they were watches. I.e. yes it works, but supplies around a million times less power than what you'd want for your power hungry devices.

[Kleinstein]

A good TEG device can reach about 10% of the above mentioned maximum efficiency of 1 - T_hot/T_cold. So something like 0.5 % is about the maximum you can expect if ever thing is right. You may also loose half the possible power / temperature difference just to conduct the heat to the TEG.

[JimRemington]

Possible components would be of a buck converter, a Li-Ion battery and a charging module.

See Linear Technology's pages on ultra low power TEG/piezo/solar cell boost converter ICs and modules.
http://www.linear.com/solutions/thermoelectric_energy_harvesting?type=circuit

A distributor gave me one of the way overpriced DC1582B-A demo boards: http://www.linear.com/product/LTC3108#demoboards.

It can blink an LED from hand warmth alone, given a good room temperature heat sink on the TEG.

[chris26]

Thanks for the help. The topic makes more sense to me now. I guess I need to research more on the power and current relationship for power generation for a wide range of devices. Again thanks a lot.

[HighVoltage]

There is a German company, specialized in the TEG
I came across them at one of the last great trade shows in Hannover

http://www.o-flexx.com/en/company/about-o-flexx/about-o-flexx/

From their brochure:
"O-Flexx Technologies is a German technology company that specialises in the field of thermoelectric generators. Our R&D centre and production facilities for both our low temperature and high temperature modules are based in Duisburg.

The O-Flexx technology allows our clients to harvest electrical energy from a great number of heat sources by exploiting differences in temperature. This technology is based on the Seebeck effect, one of three effects from the family of thermoelectric phenomena. The Peltier effect, which describes heat fluxes due to an electric current, is commonly better known.

O-Flexx Technologies owns a broad portfolio of related patents. We have an in-depth understanding of process technology and are proud to work in a close-knit network of R&D partners that includes highly renowned institutes, universities and industry labs in various European countries."

May be they offer something you are looking for.

[amyk]

https://www.eevblog.com/forum/chat/teen-invents-flashlight-that-could-change-the-world/

[Delta]

Sorry Chris, this is a complete non-starter.  There simply isn't the energy available from a warm hand, never mind taking into account the incredibly low efficiencies of low Delta-T TEGs.

Don't waste your effort mate.