Instead of using expensive photovoltaic cells to convert solar radiation to electricity directly, Matteran's solution uses far-cheaper thermal-collection technology to heat a synthetic fluid with a very low boiling point (around 58°F), creating enough steam to drive a specially designed turbine. And although a fluid-circuit system converting heat into electricity is nothing new, Matteran's innovative solution increases the system's efficiency to a point where small-scale applications make economic sense...
So far, Matteran has created only small amounts of refrigeration, but the technology is in place to take the next step, creating a unit with the equivalent cooling of a standard window-mounted A/C that is powered entirely by the sun's heat--something I don't think our carbon-choked planet will be running out of anytime soon.
Considering how hot it has been lately I think this is clever thinking.
I keep getting in this perpetual motion loop though when I am thinking about it.
So say you use some heat to boil the fluid in the machine. This removes energy from the outside and puts it into the fluid. That energy is then used to generate electricity, which is then used to cool the inside of a building. Now as I understand it air conditioning works sort of like a reverse internal combustion engine -- using energy to compress air rather making it cooler, but releasing the energy from the air into the surrounding (outside the building) in the process). So we take that energy and put it outside making the outside hotter, but presumably less hot than it was before because the process of air conditioning is not one hundred percent efficient.
But by that logic you would be both cooling the indoors and the outdoors at the same time, which I know can't happen.
Any kind physicists out there want to help a biologist understand how this is not violating conservation of energy?
(It has been a really, really long time since I had P-Chem.)
Hat-tip: Slashdot.
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I think the first step (generating electricity) needs some explanation. I think the fluid can be heated using some sort of solar collector, just like a collector on the roof to generate warm water for the shower. This can get hotter than the outside ambient temperature, the (theoretical!) limit would be the temperature of the sun. The fluid is then cooled using the ambient temperature, which is still hotter than what you want in the inside of the building, but cooler than initially. This is the principle some solar power plants work by using mirrors to boil water that is used in a gas turbine (and is also mentioned on the web site as an example). The only thing new here is that they use a liquid with a much lower boiling point, and that this allows to use it on a much smaller scale. That's how I understand it.
Now, what you the do with the generated electricity is a completely independent problem. You can use it for an A/C or your computer for further blogging.
Disclaimer: I did study physics, but it is a little bit rusty. I work in a completely different area now.
Hmm. Very hard to say without seeing a diagram. The best idea I've come up with to explain it is a two-phase cycle; an external cycle which drives the described turbine (perhaps a sunshade keeps the upper portions of this cycle cooler so the motion goes the correct way and the system doesn't attain equilibrium) and an internal cycle where the turbine powers a compressor. The internal cycle involves the boiling process you describe, which cools the inside air. The compressor requires work to use, obviously (hence the outside cycle), which is converted to heat energy (the compressor coil is hot), but that energy is radiated to the outside as in a typical refrigerator. The external cycle presumably works because the work done on the turbine cools the fluid, thus maintaining the first law in both cycles. I suppose a way might be found to combine these two cycles, but that is my first-order educated guess.
I'll take a quick stab, inspired by the first comment on slashdot. Let me know if this makes any sense:
The problem isn't conservation of energy, it's the seeming loss of entropy (more cool things = lower entropy). But the conversion of a liquid to a gas is an increase in entropy. To use this as an engine, you would need to find a way to recool the gas into a liquid. That process would also sap energy and increase entropy. I'm not sure if that answers the whole question, but maybe it gets somewhere.
Your mistake is in saying that the AC makes the "outside hotter, but presumably less hot than it was before". The waste heat of an AC system includes all of the power it consumes as well as all of the heat pulled away from the cool side. If your AC is drawing 1kW from the electrical grid, and removing heat from the air at 1kW, that means that its outside heat exchanger has to dump 2kW.
A similar inefficiency works on the generator side. In order to get 1kW of electrical energy out of a turbine, you have to put *more* thermal energy into it. For example, you might shine 2kW of light on your solar boiler and get 1kW of electricity out, but your turbine will have hotter-than-ambient exhaust gas (or the closed-cycle turbine's heat exchanger will stand at hotter-than-ambient) which carries away the other 1kW.
You can see that, in the absence of this whole system, 2kW of sunlight simply heats up the area by 2kW. When you install the solar panel+generator+AC, you're heating up the atmosphere via 1kW out generator turbine exhaust and 2kW of AC heat exchanger exhaust, for a total of 3kW of heat. The additional 1kW is pulled out of the house, cooling it.
OK that makes more sense. So you are saying that the 2 kW sunlight goes into heating the fluid, boiling it, and generating 1 kW of electricity. That electricity is used to pump 1 kW of heat out of the room into the air. In order, to bring the fluid back to the temperature it was so that it can be heated again, it has to radiate off the 2 kW. That would leave a total of 3 kW in the outside system 2 of which are from the sun and 1 of which is from the inside.
And the system can't go on forever because the air conditioner has to be able to radiate off the heat from the fluid in order to cool it down enough so that it can be boiled again and move the turbine. At some point the ambient temperature is such that it can't do that. Is that right?
That's pretty much right.
However, barring engineering details, the system will not stop running at some particular temperature, it will just get less and less efficient as the ambient temperature goes up. If 2kW will produce 1kW of electricity and 1kW of cooling power at 300K ambient temperature, it will produce 600 W of each at 600K ambient, and so on according to the Carnot law ( Efficiency = T1/(T1+T2), where T1 and T2 are the hot and cold temperatures). With less power, you'll see a smaller temperature drop from outside to inside.
The reason that it's not perpetual motion is that ... well, if you stop pumping sunlight into the solar panel, the solar generator stops turning. If you try to use the waste heat from the AC to heat up the solar panel, then the AC won't do as much, because you won't be able to cool the AC fluid down to ambient, only down to the hottest solar panel temperature. The lowered efficiency of the AC will pull less heat from the house, so (even for a massless air conditioner) less than 2kW of heat will be available to continue heating the solar panel. Being less hot, the panel produces less than 1kW of electricity, producing even less cooling and less waste heat, and the whole thing grinds to a halt.
It's all about the Carnot cycle.
The way I read it the difference is just that he's using heat from the sun to drive energy creation rather than photovoltaic cells. So, there isn't a thermodynamic problem, it's just a different way of capturing the energy from sunlight, rather than photoelectric conversion he's using sunlight to directly heat the liquid in the boiler/cell. So the boiler is a sealed chamber, probably with an absorbant interior, that gets a lot hotter than the outside ambient temperature as the sun hits it (like the inside of your car on a hot day). The liquid in the chamber is boiled, steam drives the turbine, and its thermal energy is lost to the turbine and a coolant (ambient outside temp - still cooler than inside your car) leading to condensation and the cycle is restarted.
This is similar to how some people have generated hot water using solar heat, except he's using a liquid that boils more readily in order to drive a turbine.
Other people beat me to this, and I basically agree with what they've said. There are two confusing points in the original description: first, the power generation is entirely separate from the air cooling-- the proposal happens to be talking about using this to run an AC unit, but you could just as well use it to power a computer to surf the Internet.
Second, as Ben notes, the exhaust from an air conditioner is significantly hotter than the outside air, because it's dumping both the heat from the inside air, and the heat generated in running the compressor. This is easily verified by putting your hand in the exhaust stream of a window AC unit.
Big industrial-scale air conditioning units generally use water to carry off the waste heat, which is more efficient that air cooling, as water has a higher heat capacity. This is damnably annoying to those of us with scientific apparatus that needs water cooling, as it means that chilled water is sometimes hard to come by in the summer..
Thanks all for the help. I knew I was confused about something.
Any of you can feel free to forward your molecular biology-related questions. I am all over those.
There are a couple of issues to clear up.
Since, we are talking about using temperature difference to drive
some sort of engine (-or the reverse, wherin we would refer to
the device as a heat pump). Some engine designs can run either way. I seem to recall that Sterling Engine is likely what you are looking for here.
In any case, the energy produces mechanical energy. If the application is air conditioning, we use the mechanical energy of
the first device to drive the second (the heat pump of AC), no need
for the extra cost and inefficiency of electric generation and electrical motors here.
The other item of interest is that thermodynamics gives a maximum efficiency of the difference in temperature divided by the high temperature. This is why we like high temperatures for engines, as
for a given amount of heat (usually created by burning fuel), we get more useful work with a higher temperature working fluid. In this case I think the goal is to make the collector and engine technology as inexpensive as possible, by avoiding high temperatures, and allowing non-concentrating collectors etc, at the expensive of
thermodynamic efficiency -we would need a larger solar collector, but that is Ok as sunlight is assumed to be cheap.