Solar Power Minus the Light

An anonymous reader writes "Popular Science is running a story about a small company trying to take advantage of all the global warming hype. Matteran Energy uses 'thermal-collection technology to heat a synthetic fluid with a very low boiling point (around 58F), creating enough steam to drive a specially designed turbine. And although a fluid-circuit system converting heat into electricity is nothing new, Matterans innovative solution increases the systems efficiency to a point where small-scale applications make economic sense.' Notably, this comes during a record breaking heat wave here in the US. So has the day finally arrived where I can run my AC off of all that heat outdoors?"

Comments

Only solves 50% of the problem

[chriss]

Hm, looks simply like a small sterling engine or mini gas turbine used to drive an AC. They managed to make it cheap so it will be applicable in small installations, but both the sterling engine and the gas turbine (using a fluid in a closed circuit) require a temperature difference, so the machine would not be driven by heat alone. You'd have to cool down the steam after it had passed the generator to make it condensate to a fluid again and pump it back into the thermal collectors. The article does not mention how this should be done or where the energy for this should come from.

Power stations using closed fluid circuits (e.g. nuclear plants) use a secondary circuit to cool the first one after the steam passed the turbine. They are usually located near rivers for this. Larger installations for sterling engines can store heat during the day in a water tank and use the difference in temperature between the water and the surrounding cooler air during the night to drive a sterling engine. This obviously works best in areas where the difference in temperature between day and night is significant, i.e. deserts. I don't think it to be realistic to turn 1/4 of your apartment into a heat/cold storage just to drive the AC.

So in the end they made it cheaper, but inefficient (5%) even compared to solar panels (20%) without offering something that could replace a conventional AC. To achieve this you'd still have to build houses in a smarter way, e.g. isolate the walls from the inside and outside and use them as thermal storage. More energy efficient construction has been done for cold regions (where houses require almost no heating during winter when isolated well, the inhabitants' body heat is sufficient) and warmer regions (traditional buildings build with clay and wind-traps and smaller windows to the sunny side). So it is possible, but do not expect too much from our current architecture.

Re:Only solves 50% of the problem

[Jedi Alec]

this very principle is currently being put to use in a part of the Netherlands that used to be mined for coal. The water in the now abandonded mine-shafts will be used to provide heating in the winter and cooling in the summer.

Re:Only solves 50% of the problem

[B2382F29]

Wow, that would be expensive. Here (germany) you get 2kW (10x200W) for 9000 EUR

Next time please don't pull prices out of your ass.

Carnot efficiency.

[Anonymous Coward]

58f = 14.4C or 287.6K

Now lets be generous and let our panel "superheat" the stuff up to 80C or so, and put the cold reservoir in a bucket of ice.

That gives us a heat source at 353.15K and a sink at 273.15.

Efficiency = 1.0 - cold/hot = 1.0 - (273.15/353.15) = 0.226, or about 23% efficient.

Not great.

Solar powered Air conditioning

[Hal_Porter]

Notably, this comes during a record breaking heat wave here in the US. So has the day finally arrived where I can run my AC off of all that heat outdoors


I guess you're making a perpetual motion joke, but the strange thing is it's not a daft as it sounds.

You could have an electrically powered heat pump to pump heat into the ground in summer, and back out again in winter.

http://www.igshpa.okstate.edu/geothermal/geotherma l.htm

Very popular here in Sweden.

If you insulate your house enough, the energy required to heat or cool it is pretty minimal, so you could generate it from solar panels, at least in the summer. And heat pumps are 3 to 4 times more than resistive electric heaters.

As wikipedia puts it

http://en.wikipedia.org/wiki/Heat_pump

When used for heating on a mild day, a typical heat pump has a COP of three to four, whereas a typical resistive electric heater has a COP of one. That is, one joule of electrical energy will cause a conventional heater to give off one joule of warmth, while under ideal conditions, one joule of electrical energy can cause a heat pump to move more than one joule of heat from a cooler place to a warmer place. Sometimes this is expressed as an efficiency value greater than 100%, as in the statement, "XYZ brand heat pumps operate at up to 400% efficiency!" This is not quite accurate, since the work does not make heat, but moves existing heat "upstream". This does not violate the second law of thermodynamics, because it takes less work to move the heat than to make the heat.

Use Nature's Solar Panels

[giafly]

... by planting Trees nearby. Their shade keeps your house cool, all trees produce fuel for the winter, and if you choose the right varieties they deliver free organic fruit. You'll save power by not having to run your air conditioner so much. Why must some engineers make things difficult for themselves?

Eyesore solution

[aplusjimages]

I bet you wouldn't mind looking at the windmills if I put some porn on them. Eh. You like that. I bet you do. You so dirty.