Generating Electricity With Heat From the Sun

On November 21, 2007 in General Information

I’ve been doing some research while it is rainy out, regarding generating electricity with heat from the sun..

There are lots of ways to generate electricity from heat, but for the most part they don’t seem cost-effective for the do-it-yourselfer to piece together.

As far as the actual semiconductor you want to use, from what I have found Bismuth (III) Telluride is the best available. Here is an excerpt from the Wikipedia page (with references for you skeptics)

“The properties relevant to thermoelectric efficiency are:

A high Seebeck coefficient (voltage per unit temperature difference). The Seebeck coefficient of N-type bismuth telluride is -287 μV/°C^[1] Seebeck coefficient of P-type Bismuth Telluride is 81μV/K^[2]
A high electrical conductivity. The electrical conductivity of N-type bismuth telluride is 1.1 × 10⁵ Siemens per meter.^[3]
Low thermal conductivity. The thermal conductivity of bismuth telluride is 1.20W/(m*K) giving the compound a thermal insulation value similar to ordinary glass.^[4]“

However, sources for the stuff aren’t abundant. I did find a place you can buy it in Washington, but they don’t list prices and it is probably expensive, not too mention probably hard to work with.

On the upside, there are lots of prefabricated units out there, but I didn’t feel like digging through bunches of them.

So far, the best deal I have found is from http://www.tellurex.com/

They have a 5.7W unit (4.8v, 1.2A) for a cool $43.95, but you have to remember that unless a regulating circuit is employed, load, voltage, current, and power will all vary as load resistance fluctuates.

Here is a link to their FAQ onThermoelectric Power Generation and Here is a link to their “Intro to Thermoelectrics” page

If one designed a system properly, it would be interesting to generate electricity from the sun’s heat as well as light.. For now though if I buy some I will just put them on a wood stove. You have to ensure that the cool side stays cool though or else it won’t generate enough power.