New Thermocell Could Turn 'Waste Heat' Into Electricity 181
dryriver sends this quote from Phys.org:
"Harvesting waste heat from power stations and even vehicle exhaust pipes could soon provide a valuable supply of electricity. A small team of Monash University researchers ... has developed an ionic liquid-based thermocell (abstract). Thermocell technology is based on harnessing the thermal energy from the difference in temperature between two surfaces and converting that energy into electricity. The new thermocell could be used to generate electricity from low grade steam in coal fired power stations at temperatures around 130C. This would be implemented by having the steam pass over the outer surface of the hot electrode to keep it hot while the other electrode is air or water cooled."
Re:Hmmmm (Score:2, Interesting)
No. If you have a machine that's 50% efficient, where does the other 50% of the energy go? That's right, heat. If you can recover 10% of that heat as electricity, your machine is now 60% efficient. Even if you could recover the theoretical 100% of the waste heat the total energy efficiency is still only 100%, so it doesn't violate the laws of thermodynamics.
Throwing the NOT flag here.... (Score:4, Interesting)
Without going too deep into a lesson on thermodynamics, there is not going to be much chance that this works in a modern power station.
Let me put it this way. Current power stations are already engineered to be as efficient as possible. This generally means they are keeping the phase translations of the working liquid using the minimum temperature differentials possible to avoid entropy loss over the ideal Carnot cycle. Any thermally driven power producing device put in series with the heat exchangers is not likely to capture any more power than will be lost by the increased temperature differential required by the device. If this wasn't true, why don't we just attach a boat load of sterling heat engines (http://en.wikipedia.org/wiki/Stirling_engine) to do the same thing? Reason: It wreaks the efficiency of the power plant by making the temperature differentials higher.. Chances are this new idea has the same problem.
Now, on your car, or other internal combustion engines, there *might* be some application, but I don't think there will be enough power output to make up for the weight increase. There is a HUGE amount of waste heat from your car engine but the question is how efficiently can we capture that and make useful energy out of it? Answer: Not very... Worth looking at because of the amount of heat being just dumped and the high differential temperatures but not likely to be much gain overall.
Re:Nuclear steam (Score:4, Interesting)
The most efficient nuclear power stations in operation today are the Advanced Gas-cooled Reactors (AGRs) in the UK. They use CO2 as a coolant circulating through the carbon-moderator core at over 600 deg C with a generating efficiency of about 41% conversion of thermal energy to electricity compared to steam-moderated PWRs at about 34%. The low cost of uranium fuel per kWh generated means the extra efficiency doesn't help that much in terms of price of electricity generated or operating costs.