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Creating Power From Wasted Heat
Roland Piquepaille writes "Today, about 90 percent of the world's electricity is created through an indirect and inefficient conversion of heat. It is estimated that two thirds of the heat used by thermoelectric converters are wasted and released. But now, researchers from the University of California at Berkeley have found a new way to convert this wasted heat into electricity by trapping organic molecules between metal nanoparticles. So far, this method of creating electricity creation is in its very early stage, but if it can scale up to mass production it may lead to a new and inexpensive source of energy."
How is this "a new source of power" ? it's just improving efficiency by reducing loss.
So now instead of yelling at my kids for leaving the fridge door open I'll have to get them to leave it open every now and then in order to keep the electricity bill down.
I could really dig have a lower electricty bill in the summer rather than a higher one. When can I build a house with this stuff?
So this means global warming is a good thing. With all the electricity we'll be able to make, it's no problem to just run enough air conditions to solve the problem.
Want to improve your Karma? Instead of "Post Anonymously", try the "Post Humously" option.
Computers still are, and probably always will be, a fairly small fraction of electrical consumption. Yeah, data centers are all the way up to 1%... But 1% is 1%. Not a big component... Hell, I'd be more concerned about this - if we replace fossil fuel cars with electric in the next fifty years, electric power used to recharge vehicles will probably become one of the biggest fractions of the total load.
Have you been touched by his noodly appendage?
LED light bulbs are overrated. Compact florescent bulbs are much more efficient, but they aren't a sexy as LED's. Here's some ways to conserve, but no one will do this:
1. No more incandescent bulbs.
2. Live 10 minutes away from work in a condo/apartment instead of the suburbs in a giant house
3. Stop leaving your computer on all day
Actually, #2 is about the only one that really saves the most money. Smaller places cost less to heat/cool, and not driving as much saves a huge amount of energy.
But, oh environmentalists are more concerned about prohibiting housing developments or zoning that actually makes sense.
"But the common man doesn't understand 'efficiency gains' as something significant."
Yeah, they insulate their houses to save on energy bills just 'cause.
Unfortunately, thermoelectric converters based on the Seebeck effect are not going to help with efficiency by a large amount.
Firstly, there is a theoretical limit (Carnot Cycle) to the efficiency of any pure heat engine based on the Second Law of Thermodynamics.
If a quantity of heat Q is taken from a high-temperature reservoir at temperature T2, partially converted into useful work W, and the remainder (Q - W) is deposited into a low-temperature reservoir at temperature T1, then the net increase in entropy is at least
\delta S = (Q-W)/T1 - Q/T2 >= 0.
So the efficiency (useful work generated per unit energy input)
e = W/Q < (T2 - T1)/T2
The waste heat is ultimately deposited into the environment, so T1 can't be much smaller than say 300K.
In a steam engine T2 has to be greater than the boiling point of water (at whatever pressure it is operated), but it is limited by what the materials of which it is composed can withstand. Temperatures of order 1000K are typical. That gives a maximum theoretical efficiency of around 70%. The best steam engines barely reach about half that efficiency.
However, modern power plants (which are not pure heat engines) use a Combined Cycle that can do better by first generating electricity from their fuel with a combustion turbine and then using the waste heat from the combustion turbine to make steam to generate additional electricity via a steam turbine. Their efficiency can reach about 60% of the net calorific value of the fuel.
So you can see that one might be able to shave a few more percentage points off the waste, but it will not at all be the godsend we really need...
IMHO only nuclear power can fulfill that role today.
The "wasted" heat that thermal power plants reject to the surroundings is rejected at a temperature only slightly above ambient. A steam turbine generator has an exhaust steam condenser which operates at a vacuum, where the steam condenses at only a few degrees Fahrenheit above the ambient temperature. There is no significant temperature difference available for the new device to operate with. While thermal power plants do reject over half the fuel energy consumed to the surroundings, it is a myth that this rejected heat can be effectively used. The rejected heat is available at a low temperature, only slightly above ambient, therefore little effective use can be made of it. This is the penalty that the laws of thermodynamics impose on the conversion of heat into work.