Night time solar is not such a crazy idea...

louis · 2020-02-03 20:16:15

Looks like it might be possible to generate significant amounts of energy at night on solar panels, focussed on infra red.

https://www.sciencedaily.com/releases/2 … 174512.htm

tahanson43206 · 2020-02-03 21:21:44

For Louis re #1

Thanks for posting the link to this story!

It occurred to me immediately that the pro-nuclear power folks would (most likely) appreciate the utility of this invention to vent otherwise lost heat from fission reactors.

The application on Mars is particularly appropriate, because the sky heat sink is likely to be more available than is true on Earth.

Congratulations on a helpful find!

PS ... I'm not sure you picked up that the proposed "solar panels" would actually radiate energy, NOT absorb it.

The electrical flow would be opposite to that of a traditional solar panel.

(th)

Last edited by tahanson43206 (2020-02-03 21:22:11)

louis · 2020-02-04 04:52:04

You're quite right TA - I didn't really understand how it worked and I'm not sure I do now! I was more interested in the ouput! Specifically this para doesn't make sense to me:

"There's another kind of device called a thermoradiative cell that generates power by radiating heat to its surroundings. Researchers have explored using them to capture waste heat from engines."

I'm puzzled because it sounds like you have two radiative heat objects ( firstly an engine and secondly a panel) but nothing to capture the (infrared?) energy. So I'm not clear how the thermoradiative cell's radiated heat energy is captured. Perhaps you can explain..

You might find this helpful:

https://www.nature.com/articles/srep34837

This seems to suggest that the TR cell works by rejecting entropy...which I understand to mean not radiating heat out (or less so than would normally be the case). That makes more sense to me...through the way the sub atomic particles behave, it's trapping energy from waste heat to make electricity. The paper refers to the need to " reject entropy to the environment"...

I guess such a device might be a more efficient way of generating electricity during hours of darkness on Mars than chemical batteries - though I've no idea really...maybe you would simply heat up some big black rocks in a chamber during the day and then use these TR cells to generate electricity at night.

It seems a big temperature difference helps. Presumably Mars could be perfect for that.

Calliban · 2020-02-04 06:04:05

Interesting tech. It uses the thermoelectric effect.
https://en.wikipedia.org/wiki/Thermoelectric_effect

Two dissimilar metals or semi-conductors coupled together with a temperature gradient applied across them. The hotter electrons will diffuse into the colder material, more quickly than colder electrons can replace them. Hence, the temperature difference results in an electrical potential difference. The larger the temperature gradient, the more efficient the process is.

The obvious advantage over a conventional heat engine is the absence of moving parts. The downside is poorer efficiency, typically <10%. The RTGs used on outer solar system probes use thermoelectric generators that are directly coupled in a sandwich between a radioactive heat source and a deep space radiator. So no moving parts at all and excellent reliability. But generally much poorer efficiency than say a Stirling engine.

There have been experiments with wood burning stoves including thermoelectric plates. The hot side is exposed to the hot fire gases; the cold side dumps heat into the cooling jacket. So, for a 10kW stove at full power you get perhaps 0.5kW of DC electric. Not very efficient, but still a good deal because the other 9.5kW goes into producing hot water. The same thing might work in a solar/wind energy storage system. You use excess electricity to heat masonry blocks in a storage heater to high temperature and then generate fairly continuous DC power as you dump the heat into the air or hot water. Only really works if the heat is a useful product in itself.

Solar panels already have a PV junction that could be used in this way as per your link. The downside is the added complication of having to plumb a heat source into the panel and having enough excess heat in the first place. Efficiency no more than a few per cent. Would work best where there are low night-time temperatures.

On Mars, day-night temperature swings are so large that PV panels would not be needed to generate power. Just simple absorber-radiator panels made from local clay or steel, collecting hot and cold in two separate tanks. A heat engine could be run between the two tanks, generating power 24 hours a day. Power density would be poor, but the storage problem is taken care of as part of the package. The technology is also very simple and easy to make. This sort of thing wouldn't work on most places on Earth because we have a thick atmosphere. On Mars, it should work well given that day-night temperature variations are typically up to 100K. The power density of that system is limited not by the intensity of sunlight, but by the amount of heat that can be dumped into space by the radiator panel at night.

Last edited by Calliban (2020-02-04 06:15:23)

SpaceNut · 2020-02-04 18:02:42

Pellitier or quantum dot possibly for the electrical power. The greater the deviation from on to the other makes the higher level of power which could be outputed.

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#1 2020-02-03 20:16:15

Night time solar is not such a crazy idea...

#2 2020-02-03 21:21:44

Re: Night time solar is not such a crazy idea...

#3 2020-02-04 04:52:04

Re: Night time solar is not such a crazy idea...

#4 2020-02-04 06:04:05

Re: Night time solar is not such a crazy idea...

#5 2020-02-04 18:02:42

Re: Night time solar is not such a crazy idea...

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