Heat to Electric Energy

[JaySVX]

I saw this and thought of quite a few practical applications:
http://www.trnmag.com/Stories/2001/1...er_121901.html

If at 40% efficiency, with the size of the diodes, you were to place several thousand on your car, you could increase cooling significantly, as well as remove the need for an alternator to charge your battery, as you could hook these up in line, increasing engine output power, lowering heat, and increasing efficiency, as you be recycling the heat, instead of simply dispersing it into the atmosphere. I can't wait until this technology nears perfection.

[LarryIII]

Thanks for posting it. This is the first that I heard of it.

It's very interesting

[lhopp77]

Strange that this is a 2001 article and reported research result and no current earth shattering news. Maybe it is quietly being used and is now old news.

Lee

[benebob]

I actually think I remember hearing something about this concept from a WW2 book about the Nazis "crazy" schemes to limit the use of foreign resources for their war machine along with the ethanol powered vehicles and wood fired vehicles.

[shotgunslade]

This is only an incremental imporovement on an existing technology. Soviet satellites used a similar technology to generate electricity. Unfortunately, this technology does not overcome the basic limitation of conversion of heat to electricity known as Carnot's law. It all has to do with entropy and the second law of thermodynamics. Electricity is work and work is organized energy. Heat is disorganized energy and only achieves order when there is an orderly flow of heat from a hot place to a cold place. The amount of order that can be harvested from this heat flow is a function of the temperature difference between the hot place and the cold place. The equation is as follows:

Max Theoretical Eficiency = (1 - ( Temp of Cold Place / Temp of Hot place))

These temperatures are absolute temperatures, so add 460 Deg to Fahrenheit and 273 Deg to Celsius.

Note that the article said that 18% was achieved with a source temp of 200 to 300 DegC. Assume the heat is flowing from this hot place to the atmosphere at 30 DegC, the cold place. Using this formula, we get the following:

Carnot Efficiency = (1- ((30+273) / (200 +273))) = 36%

So, they're getting 18% when 36% is the theoretical maximum. Note also that 200 DegC isn't your run of the mill waste heat. A lot of waste heat is available at about 70 DegC, about 160 DegF, which will give you a Carnot efficiency of about 12%, and if the actual efficiency ratio above holds (which it probably doesn't), you would get about 6% efficiency. Probably not enough to go for.

Which is why I always say to architects when they ask whether there's something that we can do with all the waste heat from the air conditioning that we send to cooling towers at 100 DegF. I tell then that they can put together a couple of quadrillion Btu's of that heat and $5 and they can get a cup of coffee at Starbucks.