solar heat to electric

[Artic_Knight]

i was hoping to brain storm a DIY project of turning solar hot water to electricity in the most effecient means possible. after all we can get mroe energy from the sun as solar heat than PV cells.  i have seen the thermocouple device that moves heat when electricity is put in and it also generates electricity when heat is put in but this looks to be very expensive to produce a 1kw cell! any ideas?

[Vladokv]

Try to use stirling engine for converting heat to electrisity. Search on Youtube for stirling, and you will see how to built that device, and proof that is stirling best choise for you. It's cheap device, wich reqire some precision in building
Good luck!

[Mr.Entropy]

The problem is that in order to convert heat to electricity, you have to waste some of it.Ã,  That maximum efficiency is (Th - Tc)Ã,  / Th, where Th is the temperature of the heated part, in Kelvins, and Tc is the temperature of the cold part that you're dumping the heat into -- usually ambient air or water.

SeeÃ,  http://en.wikipedia.org/wiki/Carnot_cycle

Lets say it's 20C, i.e., 293K outside, and you use the sun to heat something up to 50C, or 323K.Ã,  The maximum efficiency at which you can then convert that heat to electricity is (323-293)/323 = 0.093, or 9.3%.Ã,  90.7% of the energy you get from the sun is wasted!

So converting the heat from conventional solar-heated water to electricity is a bad idea.Ã, 

Note that the numbers get a lot better if you use concentrating mirrors to heat something up to over 1000K like this: http://en.wikipedia.org/wiki/Solar_power_tower.

Cheers,

Mr. Entropy

[Artic_Knight]

im sorry but the maximum effeciency of electricity from solar heated water is 9.3%? considering PV panels can tap 15-30% and they see usually one spectrum of light where as a black coated solar heat collecter collects multiple light spectrums.... that doesnt make sense! not even with the science of resistance or loss of energy!

[Mr.Entropy]

im sorry but the maximum effeciency of electricity from solar heated water is 9.3%? considering PV panels can tap 15-30% and they see usually one spectrum of light where as a black coated solar heat collecter collects multiple light spectrums.... that doesnt make sense! not even with the science of resistance or loss of energy!

S'true!  That's why people use PV :-)

You have to look at the link.

Mr. Entropy