Solar insolation in space

littleharbor2 · February 4

Was watching the NASA Channel last night and one segment they were talking about the solar panels they use to create electricity in space. While they didn't mention it , it piqued my curiosity as to how much insolation they can get in the vacuum of space. In perfect and exceptional situations we can get 12-1300 watts per square meter, maybe more, on earth. Anybody know what they get in outer space?

BB. · February 4

For our calculations, we typically use 1,000 W per sq meter.

For space:

https://en.wikipedia.org/wiki/Solar_constant

The actual direct solar irradiance at the top of the atmosphere fluctuates by about 6.9% during a year (from 1.412 kW/m2 in early January to 1.321 kW/m2 in early July) due to the Earth's varying distance from the Sun, and typically by much less than 0.1% from day to day.

Remember that solar cells cannot use the "entire" spectrum, so what an actual solar panel can convert to electricity is not 100% of total actual irradiance (i.e., infra red, ultra violet, etc.).

Example:

https://www.researchgate.net/publication/258549615_A_comparison_of_silicon_and_germanium_Photovoltaic_Power_Conversion_for_power-over-fibre

https://qdsolarinc.com/technology/

Image: https://qdsolarinc.com/wp-content/uploads/2020/02/Si-Absorption-e1581357321237-768x490.png

The typical "best laboratory silicon panel on the the ground" is around 26.7% overall efficiency. Best commercial is something like 25%

https://www.tandfonline.com/doi/full/10.1080/23746149.2018.1548305

-Bill

littleharbor2 · February 4

Thanks Bill. I was thinking it would be higher. Aren't they typically very cold out there? I was wondering how much the hi tech satellites PV arrays get. I have seen some pretty impressive "Cloud Edge Effect" power on my array over the years and not even in frigid conditions.

BB. · February 4

A couple of discussion links for ISS:

https://space.stackexchange.com/questions/14256/what-is-the-temperature-of-solar-panels-used-in-space-missions-such-as-iss

https://space.stackexchange.com/questions/23013/how-are-the-silicon-pv-cells-constructed-in-the-isss-solar-panels-are-they-as

The first link says simulated panel temperatures run from -100F in eclipse to +150F in full sun.

The second link has a bit more detail on cell design and construction...

Edge of cloud effects have been described (in my humble opinion) as a lensing effect. So collection from a larger region and focusing to a a smaller area (your panel) would seem to be possible.

It seems that the photon physics of clouds are not what one would expect. Not sure "lensing" is actually the correct theory... "Glories" would seem to be an edge of object lensing effect... However, it may not be accurate:

https://science.howstuffworks.com/nature/climate-weather/atmospheric/cloud-spiral-phenomenon.htm

Image: https://us.v-cdn.net/6024911/uploads/editor/c2/uq6r0zbs4gy3.png

https://www.nature.com/articles/nature.2014.14869

Optical theorists' attempts to fully understand how glories work were unsuccessful until the 1980s, when physicist Moysés Nussenzveig at the Federal University of Rio de Janeiro in Brazil showed that the main cause is a process known as wave tunnelling2,3. This is caused when rays of sunlight reflected by a droplet do not actually hit the droplet — as in the case of rainbows — but merely pass near it. They nonetheless stir up electromagnetic waves within the droplet. Those waves rattle around inside the droplet and eventually tunnel back out, sending light rays back in the direction from which they came. The way waves resonate within the droplet is wavelength-dependent, thus splitting white light into the spectrum of colours.

-Bill

littleharbor2 · February 4

We get a lot of cool views out west of all the rocket launches from Vandenberg AFB

Image: https://us.v-cdn.net/6024911/uploads/editor/zq/45y4dv6gacy2.jpg

littleharbor2 · February 4

I'm really surprised to see the same type cells still being used in modern day satellite PV Here's a photo from one of the linked articles and a photo of one of my vintage panels made with the same type cells. you might need to enlarge the first photo to get a good look.