3 ms·

> It doesn’t but a measure of output from solar panels ignores the storage efficiency which is what we care about here. So why even mention panel efficiency?

by jhgb 5y ago

> It doesn’t but a measure of output from solar panels ignores the storage efficiency which is what we care about here. So why even mention panel efficiency? > First actual array output falls over time You always compensate for it, it's not hard. > Panels on the moon need to be mounted at an appropriate angle for maximum efficiency, cooling, they need wires to move electric from the panel to your power conversion All included in that figure. > electronics to handle that power That is admittedly not included in that figure but PPUs are still fairly lightweight these days. > Don’t forget the moon is dealing with days of full sun panels need to maintain low temperatures for efficiency We've already dealt with these things for geostationary satellites, and those are almost always insolated thanks to their orbit. > and you can’t just dump all that heat into the moon On the south pole you most likely can, since even though there's lots of sunlight, the extreme incidence angle means that the surface is disproportionately cool. > A 50kg array consisting of 25kg of solar panels, at 30% efficiency produces: 25 different 0.2kw panels for 30 percent of the time over 28 days times 24 hours = 25 * 0.200kw * 0.30 * 28 * 24h = 1008 kWh or 1.008 MWh. Heh? A 50 kg array at 200 W/kg produces 10 kW peak and even at 30% capacity factor generates ~2 MWh in a lunar month: 100.324*29.5 = 2.124 MWh. > consisting of 25kg of solar panels I already said that the ~200 W/kg for UltraFlex/MegaFlex arrays includes structures, so there's no "25kg of solar panels". There are in fact no panels at all - on UltraFlex/MegaFlex, individual "naked" cells are attached to the flexible substrate of the array directly. > I have yet to read about an actual working system over 30% water to hydrogen to water. Do you have any citations or is this assuming some unknown breakthrough? No, it assumes perfectly standard system components. But here you have NASA's RFC demonstrating 50% efficiency in 2006 (already fifteen years ago!): https://ntrs.nasa.gov/citations/20060008706 https://ntrs.nasa.gov/citations/20060008706

Retric 5y ago
> UltraFlex/MegaFlex arrays Those fit on satellites in zero g. The moon has gravity so you support them at an angle you need bracing on something else, or for extra long panels connected to a structure you need bracing inside these ultra flex panels. In space panels can radiate from their back sides into space, but that doesn’t work on the moon as it hits 260 degrees Fahrenheit in the day. Look up panel efficiency curves with temperature. Cooling during the day is a major concern for a long term lunar base, but also needed for panels. Further you need cables from wherever they are to where up your using power. Lunar dust again is an issue for solar panels on the moon vs satellites. All added up doubling weight may be generous. > https://ntrs.nasa.gov/citations/20060008706 https://ntrs.nasa.gov/citations/20060008706 Sure, and that worked wonderfully a lab. But, production systems need to worry about a great deal of stuff that doesn’t apply in a lab setting. I don’t mean this dismissively yes I completely agree in theory it could work, but it’s just not working technology yet. I haven’t looked recently so hopefully there is a system demonstration out there.
- jhgb 5y ago
  >Those fit on satellites in zero g. The moon has gravity so you support them at an angle you need bracing on something else UltraFlex/MegaFlex is rated for 3g acceleration on those satellites even when fanned out, why do you think it would have problems with 0.16g? That's one twentieth of what they're supposed to withstand. >but that doesn’t work on the moon as it hits 260 degrees Fahrenheit in the day That's just not the case on the Lunar south pole: https://agupubs.onlinelibrary.wiley.com/cms/asset/60707425-279b-4609-b8e2-307165678391/jgre20604-fig-0011-m.jpg https://agupubs.onlinelibrary.wiley.com/cms/asset/60707425-2... > Further you need cables from wherever they are to where up your using power. High-voltage cables are not that heavy. > Sure, and that worked wonderfully a lab. But, production systems need to worry about a great deal of stuff that doesn’t apply in a lab setting. I don’t mean this dismissively yes I completely agree in theory it could work, but it’s just not working technology yet. Of course you don't; you're just disingenuously moving the goalposts.
  - Retric 5y ago
    > why do you think it would have problems with 0.16g? That's one twentieth of what they're supposed to withstand. You seem to be stuck on just one issue, heat is vastly more of an issue than this. Anyway, flexing isn’t breaking. https://www.americaspace.com/wp-content/uploads/2012/04/LIFE-Phoenix-on-Mars.jpg https://www.americaspace.com/wp-content/uploads/2012/04/LIFE... The actual panel on Mars isn’t flat or particularly big. Now, if we’re assuming the Moon mission is going to be at it’s equator then laying them directly on the lunar surface is fine. But big arrays at an angle need to be rigid or you’re losing poster from a using a worse angle due to the curve, either option means more weight for a given power output. > That's just not the case on the Lunar south pole Sure, and that deals with heat but now the solar array needs to deal with being at the poles.
    - jhgb 5y ago
      This is an absolutely meaningless level of deformation. The array will be perfectly fine in Lunar gravity. And even if it weren't, instead of a fan, you could equally well shape it into a folded vertical curtain hanging from a beam with pretty much the same parameters. > Sure, and that deals with heat but now the solar array needs to deal with being at the poles. "Now"? It needed to deal with being at the pole the whole time. There was never an intention to put it elsewhere.