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New system aims to harness the full spectrum of available solar radiation.
The key to creating a material that would be ideal for converting solar energy to heat is tuning the material’s spectrum of absorption just right: It should absorb virtually all wavelengths of light that reach Earth’s surface from the sun — but not much of the rest of the spectrum, since that would increase the energy that is reradiated by the material, and thus lost to the conversion process.
Now researchers at MIT say they have accomplished the development of a material that comes very close to the “ideal” for solar absorption. The material is a two-dimensional metallic dielectric photonic crystal, and has the additional benefits of absorbing sunlight from a wide range of angles and withstanding extremely high temperatures. Perhaps most importantly, the material can also be made cheaply at large scales.
(Score: 2) by VLM on Wednesday October 01 2014, @12:04PM
I tried all kinds of ideas and never got a net positive.
Strangely enough the best solution although super high labor was what boils down to a black trash bag in a window with a fan blowing in it when the delta T between inside and outside is low. You'd think throwing away a bag every week or so would waste more oil than just burning it directly, but there was a precise sweet spot around 50F where it actually paid off. If your labor is free and the environmental damage of the labor is zero (LOL) etc.
I had trouble thermal modeling passive air collectors, unless you get really optimistic about maint just burning the wood would be net ecologically cheaper.
The problem is we have a really well engineered system for solar collection turned into thermal heating and its called chopping down trees and burning them in a stove. You have to net total system beat that, and its VERY hard to do.
I'm not talking about "I'm not living in a windowless house, I'm gonna have windows, so lets optimize for the most BTU input per sq ft" thats just sound engineering. I was trying to design collectors... something I'd bolt on to my house. The engineering of the total lifetime system costs (economic and environmental) never worked. AFAIK other than fudged books for greenwashing no one else has ever pulled this off either on a very small scale.
I mean, I can build a solar oven that slow cooks food. So "just move house air thru it", right? But on a total system cost basis, once you add the cost of moving the air and the value of the heat gained, you'd be better off just burning the wood used to make it.
(Score: 2) by VLM on Wednesday October 01 2014, @12:09PM
Edited to add one thing thats getting close is solar electric. LOL at that in 1995, but in 2014 I can get about a third of a watt-year for about a buck capital cost. The electric company sells me electricity for about a buck per watt-year. So hooking a heater up to a modern 2014 COTS shipped from amazon solar panel costs about three times as much as paying the electric company to burn coal for me. with the slight problem that most of the heat would be generated in late June and not so much in December given my lattitude. Whoops.
Still, not long after its cheaper to install solar panels than to pay the electric company, figure maybe 5 years, then not long after it'll be cheaper to toss panels on the roof and hook up a heater.
It boils down to copper cables of electricity being ridiculously efficient way to move energy compared to fans blowing air thru tubes or whatever.