Half a croissant, on a plate, with a sign in front of it saying '50c'
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Green Solar Powered Ice-Based Refrigeration, With Radiative Heat Rejection

Cool your house and your planet
  (+5, -3)
(+5, -3)
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A (slightly complex) refrigeration device that uses no fossil fuels and has the benefit of reducing global warming.

This device has a few stages to its operation:

1. Solar power. Solar cells absorb the sun's energy and store it for night-time use. As batteries use heavy metals, I suggest using a water tower as the storage medium.
1a. Solar cells power motor.
1b. Motor powers pump.
1c. Pump pumps water from low storage tank into high storage tank.

2. Refrigeration cycle. Freeze water at night by pumping heat to a radiative plate. Of course, refrigerants are not great for the environment, so we'll use a peltier junction heat pump. We may need several stages of peltiers, as it's important that we can get the heat rejection plate up to high temperatures - in the hundreds of degrees. But then, this may be too high a temperature for a peltier - maybe use something farly benign like ammonia in a normal refrigeration cycle?
2a. Water turns turbine, generates electricity.
2b. Electricity runs heat pump.
2c. Heat pump pulls heat from water, makes ice.
2d. Heat pump heats radiative plate, sending waste heat to space.

3. Cooling mode. When cooling is needed during the day, solar powered fan blows air over cool water coils that pump water between ice storage and house.
3a. Solar panels run fan, blowing over cold water coils.
3b. Solar panels run pump, running water through cold water coils connected to both an ice storage bath and the house.

Does anyone want to attempt a picture?

Worldgineer, Aug 01 2006

Cosmic Background Refrigeration Inspired by [Bunsen] [Worldgineer, Aug 01 2006]

Attenuation of em waves by the atmosphere http://upload.wikim...eric_absorption.png
Most heat radiation (IR) is absorbed by the atmosphere and re-radiated. [ldischler, Aug 05 2006]

World's Largest Solar Laundry http://www.physorg.com/news73494899.html
Governments will give you money like you are Matthew Lesko to do this, and most of the heat gets pumped underground with the wastewater stream. [reensure, Aug 06 2006]

[link]






       This idea embodies the misconception that it’s heat that’s causing global warming, when the problem is actually insulation--in the form of CO2, H2O, methane, freon, and other gases that disturb the heat balance of the earth. Also, dumping heat this way would be about one or two percent efficient, while just laying a mirror on the roof would be nearly 100% efficient.
ldischler, Aug 01 2006
  

       //embodies the misconception// Yes it does. But it also rejects heat to space, which is a selling point.   

       //laying a mirror on the roof// Great idea. We can use a polished metal for this mirror, add insulation underneath, and use the mirror itself as the radiative surface. Of course, paint one side black and include a means of automatically flipping over the surface at night.
Worldgineer, Aug 01 2006
  

       + I had to read this several times. I can't attempt a drawing but it goes like this- hot
hot
cold
cold
cold
hot
cold
cold
cold
xandram, Aug 01 2006
  

       Ha! Perfect.
Worldgineer, Aug 01 2006
  

       How much energy will be sent into space as a percentage of total heat transfer into the terrestrial surroundings i.e. what percentage is radiative as opposed to convective and conductive?   

       Cool your house - maybe. Cool the planet - unlikely. A mirror would do a better job of that, as [ldischler] pointed out.
Texticle, Aug 02 2006
  

       //How much energy will be sent into space// Some. It will depend on the temperature you raise the plate to. High enough and you'll get a significant fraction off into space.   

       //Cool the planet - unlikely// Wrong - it's guaranteed to. I appreciate your concern about how much it will cool the planet, but you certainly aren't arguing that it won't cool it at all, are you? Yes, a mirror will work wonderfully and I've added it to my design.
Worldgineer, Aug 02 2006
  

       brilliant - but why only available in green ? [+]
monojohnny, Aug 02 2006
  

       //but you certainly aren't arguing that it won't cool it at all, are you? //

Yes, it’s very possible it won’t cool at all. It all depends on what the reference is. All surfaces reflect some heat. If you cover the highly reflective white gravel ballast of a flat roof with solar panels, for instance, you will be absorbing far more heat, even after you subtract the small amount you put out with your hot radiator. In that case, the system is not green at all.
ldischler, Aug 02 2006
  

       Sure, but the roof is already covered with mirrors. I'm placing the solar panels over the existing blacktop parking lot, to keep the electric cars cool.
Worldgineer, Aug 02 2006
  

       Are the cars white?
ldischler, Aug 02 2006
  

       They were, but they aren't washed in order to conserve water.
Worldgineer, Aug 02 2006
  

       /but you certainly aren't arguing that it won't cool it at all, are you? /   

       That's precisely what I'm arguing. This system will never reject more heat into space than it absorbs.   

       Bad science, unless I don't know what good science is.
Texticle, Aug 02 2006
  

       Never? Please explain how you come to this conclusion.   

       (semantically you're correct, just as a sponge can never reject more water than it can absorb - but I doubt that's what you mean)
Worldgineer, Aug 02 2006
  

       Good point, Texticle. Worldgineer is being awfully sneaky. Let him get away with Green Solar Power, and next it'll be perpetual motion...

On the other hand, a heat pump can move more heat than it absorbs, so maybe it isn't so obvious that something like this couldn't work.
ldischler, Aug 02 2006
  

       Radiative rejection will be only a (typically small) fraction of the total heat rejected. Conductive and convective heat transfer is 'lost' to terrestrial surroundings, not space.   

       A heat pump moves heat absorbed at the evaporator plus heat generated by motor-driven compression. Combined the total heat is moved to the condenser, where it is rejected. This total wattage is clearly vastly in excess of the motor input power (hence the energy savings made by installing heat pumps), however energy in still equals energy out.   

       If the panel described in the idea was some sort of magic 100% radiative material, and the system was magically 100% efficient, then the energy absorbed would be the same as the energy rejected. Therefore, in a magical best-case scenario, the planet stays the same temperature.   

       This system will never reject more heat into space than it absorbs.
Texticle, Aug 02 2006
  

       //If the panel described in the idea was some sort of magic 100% radiative material, and the system was magically 100% efficient// With that kind of handicap I should be able to come up with something.   

       As [ld] points out, a heat pump can move more energy than it uses. Let's give our heat pump a COP of 3 - a reasonable number for regular equipment even without magical heat sinks. That means 3 times the amount of energy is output than is required for it to run. Our system is pulling heat not just from the building, but from the envirnment due to the kids always leaving the door open. Simplifying our system to just a box with an arrow for energy in to run it, heat in from the environment, and heat out to space, we get three times as much heat radiated out as we do striking our nice 100% efficient solar cells.   

       Now, enough with that sillyness. Even with real efficiencies this system can certainly radiate more energy than would have been radiated if the system didn't exist. And far more than if the A/C was powered by your local coal-fired power plant.
Worldgineer, Aug 02 2006
  

       I'm with World on this. Considering that all of the solar energy that strikes the earth eventually radiates away all by itself (minus the little bit that goes into chemistry), it shouldn’t take too much to improve on that, at least temporarily. In the end, the global flux must balance, but it could be at a lower global temp.
ldischler, Aug 02 2006
  

       /Simplifying our system to just a box with an arrow for energy in to run it, heat in from the environment, and heat out to space, we get three times as much heat radiated out as we do striking our nice 100% efficient solar cells./   

       Yes and no. You'd be rejecting 3 times the energy required to run the system, not 3 times the energy impingent on your system. Energy in equals energy out.   

       If your solar panel system is 100% efficient, you would need a 100% radiative heat sink just to break even in terms of planetary cooling.
Texticle, Aug 03 2006
  

       //If your solar panel system is 100% efficient, you would need a 100% radiative heat sink just to break even in terms of planetary cooling.//

Not necessarily, since the quality of the incoming energy is high, and that of the rejected energy is low.
ldischler, Aug 03 2006
  

       [Texicle] First, thanks for teaching me the word impingent. Awesome word.   

       Second, //You'd be rejecting 3 times the energy required to run the system, not 3 times the energy impingent on your system.// Correct. And with your magical 100% efficient system, 1 of these units of energy strikes the system and is converted to electricity to run it. The system then sucks the other 2 units of heat energy from the surroundings and sends it off into space. Energy in = energy out.
Worldgineer, Aug 03 2006
  

       So with the aid of 100% efficiency and an as-yet undiscovered heat sink material, 3 units from space eventually get rejected back into space. That's breaking even, by my cyphering.   

       It is clear that we disagree. Let's be friends. Tea?   

       [Idischler], please elaborate on energy quality, as I am struggling with that one.   

       Milk? Sugar?
Texticle, Aug 03 2006
  

       That refers to how easy it is to extract work from it. Electrical energy from a wall socket is high quality, while the thermal emission of a room temp object is relatively low quality.
ldischler, Aug 03 2006
  

       Hmmm cool the planet using solar power   

       1 put a big solar panel up shielding the planet
2 convert the solart energy to some other useful form
3 Condense heat in the planet
4 Radiate it out
  

       Looks like 3 is where the planet will have a net gain in heat energy...   

       <Edit> Ummm only need 1...
madness, Aug 03 2006
  

       [Text] Tea would be great. But before I drop this - are you suggesting that I'd need to remove all of the Sun's energy from the planet, and then some, before you'd consider the device to cool the Earth? Break the Earth up into a few million little pieces. On one of the pieces, install my device. That piece has a net loss of energy - one unit is striking it and 3 is leaving from it. Surely you can see that this piece of the Earth is cooling. Now, look at the pieces immediately around this piece. With my device cooling the original piece at 3x the rate that the sun is heating it, that energy is going to have to come from somewhere. So the pieces around my piece cool down. With these pieces being slightly cooler, they will pull energy from the pieces next to them. Repeat. In the end the Earth is (a little tiny bit) cooler.   

       [mad] Why? How is this different from a satellite using solar power to refrigerate instruments (which is often done)?
Worldgineer, Aug 03 2006
  

       [ldischler], thanks for that. Sheesh, whoever wrote the wiki article on energy quality needs to get out more. Am I right?   

       [madness], I’m with you in spirit on that point 3 thing, however we are assuming that this heat sink is in purely radiative heat exchange with the night sky. No energy is dissipated through any other means. Yeah yeah, I know.   

       /are you suggesting that I'd need to remove all of the Sun's energy from the planet, and then some, before you'd consider the device to cool the Earth?/   

       Pretty much, yeah. I consider this device to cool the planet no more than a wind turbine connected to an electric heater would warm it.   

       Now, what’s your poison? I have normal, Earl Grey, and various herbals.
Texticle, Aug 03 2006
  

       I'd like for you to expand on why you think this. We're not talking about a subject that has room for different opinions.
Worldgineer, Aug 03 2006
  

       //We're not talking about a subject that has room for different opinions.// Them's fighting words.
ldischler, Aug 03 2006
  

       Just bear in mind that I'd rather be having a cup of tea now, but nonetheless, here goes.   

       During daylight hours, the earth receives x trillion watts of energy radiated from the sun. Some is reflected, some is absorbed. The amount absorbed does various neat things, like heating the outdoors so the animals don't freeze, and making plants grow. Some energy becomes ambient heat; some energy gets converted to other forms.   

       During nighttime hours, the earth radiates some heat out into space. The quantity that it radiates out is dependent on, among other things, the temperature of the earth's surface.   

       The whole cycle is pretty much in equilibrium.   

       Now, if by various questionable means that you have been lucky enough to get away with, you were able to take some "extra" heat out of the surrounding earth and reject it all of it to space, then the surface temperature of the earth would be reduced by some small amount, which would mean that the earth would reject slightly less heat by itself on that particular night. That 'slightly less heat' quantity would be roughly equivalent to the rejection contribution of your heat sink.   

       My thinking has been changed along the course of this debate, which is good. Initially I was saying that you couldn’t reject more heat than you absorb (due to fundamental practicalities of the design proposed). With theoretical concessions granted (system efficiency, heat sink capability) I now concede that my position has changed. Yes, it could reject some "extra" heat out into space, however it would not cool the planet, as this "extra" heat would be replaced.   

       Good show.
Texticle, Aug 03 2006
  

       We're getting closer on this. But let's look just at our system again. Do you agree that this little piece of land will always be at a lower temperature? If so, then you must see that the average temperature of the earth will be lower. Even if this piece of earth cools off it's surroundings and they radiate less, the only way for the average temperature of the earth not to have dropped is for the average temperature of the earth outside of this land to have actually raised. Unless you can think of a way for the earth's temperature to increase by means of me running this device, we're done. Earl Grey please.
Worldgineer, Aug 03 2006
  

       As a closing remark, I say that this device is impractical and inefficient. However, under the assumptions made earlier, I concede that the planet will be cooled.   

       You win, let's play again.
Texticle, Aug 04 2006
  

       Bloody Hell. Still no link to a picture. I'd try, but I can't comprehend the system completely.
Zimmy, Aug 04 2006
  

       Something qwerky just occured to me --- I am quite happy to imagine that the "earth" does not recieve heat energy from the sun at night...   

       Clearly that aint true... :)
madness, Aug 04 2006
  

       Is the //hundreds of degrees// idea a way of bypassing the greenhouse, by raising the frequency of the emitted IR? I'm tempted to bun you for that.   

       Peltiers are massively inefficient, and waste a lot more heat in operation than they draw from the heat source. Add in all the pumps and fans and energy conversions (which all dump waste heat) and you might end up with something that heats the earth more than it cools it.   

       Don Lancaster did some calculations on using IR lasers to pump waste heat out to space, but unavoidable thermodynamic loss in the mechanism killed it.
BunsenHoneydew, Aug 05 2006
  

       When there are clouds, the radiation and heat do not reach ground level. If we radiate heat upwards, it may cause clouds not to form... stalemate.
pashute, Aug 06 2006
  

       [BH] The hundreds of degrees thing is required for significant radiative heat transfer. But yes, it sounds like a good idea to design the temperature to correspond with a nice clear frequency.   

       It isn't so difficult to find out if this thing will reject more heat than it absorbs. Start with the two surfaces we're considering - the solar panel array and the roof. If the absorbed energy of the solar panels and the roof combined is less than whatever was there before, we're ahead on energy even before we start rejecting heat. Since my roof is all mirrors and I'm shading a blacktop surface with the solar panels... well, it's probably cheating but I started out ahead of the game.   

       [pash] How would this help clouds to form?
Worldgineer, Aug 07 2006
  
      
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