5 ms·
If you shine solar radiation on a nice black carbon sphere, practically all of those photons are absorbed, right? The sphere gets hotter, and starts emitting IR
by pbmonster 3y ago
If you shine solar radiation on a nice black carbon sphere, practically all of those photons are absorbed, right? The sphere gets hotter, and starts emitting IR photons.
My idea was to now enclose this sphere in TPV modules - except in places where the parabolic mirror puts sunlight on it Let's say that's half of the sphere (but you could cut this number down if you chose a parabolic mirror with a long focal point).
Now you lose IR photons in across the part of the surface that you didn't cover in TPV modules. But you could but a IR mirror there, that is transparent for most of sunlight.
- leereeves 3y agoWouldn't this process also contribute to climate change by trapping energy on Earth that would have been reflected back into space? Edit: Apparently, yes, current PV solar may also do this: > We found temperatures over a PV plant were regularly 3–4 °C warmer than wildlands at night https://www.nature.com/articles/srep35070 https://www.nature.com/articles/srep35070 But I suspect/conjecture that turning sunlight directly into heat, then turning some of that heat into electricity, would capture even more heat from sunlight. Because some of the heat in the sphere will re-radiate, but much of it will inevitably be lost to convection and conduction.
- binary132 3y agoIsn’t that what all solar energy devices do?
- adrianN 3y agoMaking the earth’s surface darker contributes to climate change, yes (that’s why sea ice loss is particularly bad). When you use the sunlight to make electricity usually the net effect is still positive.
- pjc50 3y agoThere is an "albedo effect", yes, but it's not cumulative while CO2 in the atmosphere is. Arguably there should be a "white roof" campaign for urban areas, it would be a cheap way of reducing the urban heat island effect.
- lazide 3y agoMost desert buildings already do white roofs for this reason (new ones anyway), same with commercial buildings. It usually pays for itself in short order. Most available roof coatings now are also white + extra reflective additives. [https://www.homedepot.com/p/Henry-887-Tropi-Cool-100-Silicone-White-Roof-Coating-4-75-gal-HE887HS018/205049553 https://www.homedepot.com/p/Henry-887-Tropi-Cool-100-Silicon...] [https://maps.app.goo.gl/TwrV57Jt2fGo2obw9?g_st=ic https://maps.app.goo.gl/TwrV57Jt2fGo2obw9?g_st=ic]
- nine_k 3y agoAnecdotally, my apartment building's roof was painted silver-white during the latest renovation of it. I live on the top floor, and I did notice the change: it's less hot in the summer.
- fnordpiglet 3y agoMany major cities already have such regulations even outside desert areas.
- bluGill 3y agoThere are also a lot of HOAs that require black roofs. Something else to write your representative about.
- cma 3y agoThat area over PV plants is tiny relative to the size of the world though even with enough of them to power world electricity usage.