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It’s surprising but even that author turns up a much more reasonable return on investment than I expected. His calculations suggest it’s possible to repay the e

It’s surprising but even that author turns up a much more reasonable return on investment than I expected. His calculations suggest it’s possible to repay the energy costs, including orbit, after only a few years. Though as he points out there’s lots of elements which are still impractical. Though I wonder if it could be worthwhile given that covering the Sahara with solar panels would change the global climate (particularly Brazil’s) (1). Space based arrays might be a possible way to avoid that. Or perhaps provide a power source for remote areas. A starlink for power would be intriguing. 1: https://www.techtimes.com/articles/257268/20210221/sahara-desert-solar-panels-are-contributing-to-global-warming-scientists-find-out.htm https://www.techtimes.com/articles/257268/20210221/sahara-de...

cratermoon 5y ago
> His calculations suggest it’s possible to repay the energy costs, including orbit, after only a few years. No. No they don't. that's not what his conclusions are at all. How did you even get that? He's comparing space-based vs. land, not space-based vs. nothing. His conclusion is that it's pointless to build solar power collectors in space for terrestrial power applications. In all cases, if you want power on earth, build the solar on earth.
- elcritch 5y ago
  > Add the embodied energy of the other components in space and on the ground, and I could easily believe we get to a year payback—now bringing the total (manufacture plus launch) to two years and an EROEI around 10:1. > If my 100× light-weighting proves to be unrealistic, and we can only realize a factor of ten improvement over our rooftop panels, the solar panel launch cost climbs to three years, so that adding other components results in perhaps a 4:1 EROEI. > In the end, the EROEI is not as prohibitive as I imagined: it’s not a net energy drain as I might have feared. But it’s not obviously better than conventional solar either. His overall conclusion may reach that conclusion, but his EROI give SPS a net 10:1 to 4:1 energy returns even in his worse case. So regardless if its cost competitive to ground based arrays or not, it might have uses and would likely result in net energy gain vs input (including materials).
  - Dylan16807 5y ago
    It's like saying I could drive 80 miles each way to a gas station despite there being dozens of options within 5 miles. I get more energy than I spend, but it's never worth it. Also the gas there is extremely expensive.
    - elcritch 5y ago
      Even in your example there are scenarios it could be worthwhile. What if it’s gas produced in-country and its used as a military fill station? Particularly if it’s always available despite foreign political events. For personal usage maybe it’ll never be worth it, but perhaps it’s worthwhile for other use cases. Solar + batteries might not work if you can’t buy/procur enough batteries, especially for Arctic regions say where days are short. Or perhaps it’ll become possible to use for recharging electric airplanes in-flight. In that case the ability to “beam” worldwide might offset the cost of ground based grid of towers or ocean barges, etc. To be clear, I think it’s very unlikely, just not infeasible. Particularly if antennae tech keeps improving.
      - Dylan16807 5y ago
        > What if it’s gas produced in-country and its used as a military fill station? Particularly if it’s always available despite foreign political events. Except local solar requires fewer resources of every kind than satellite solar. You're more likely in every way to get cut off from the space version. > Or perhaps it’ll become possible to use for recharging electric airplanes in-flight. In that case the ability to “beam” worldwide might offset the cost of ground based grid of towers or ocean barges, etc. That would be cool. But it's a very different problem from grid power. I don't think it counts as a reason to beam dedicated space power to ground stations.
ncmncm 5y ago
Plants (even at their puny 2% efficiency) can utilize only a fraction of a full day's insolation; they are limited by other factors. Thus, there is no need to put solar panels in faraway deserts. Putting them above other land uses -- parking lots, buildings, reservoirs, pastures, cropland -- nearer to use reduces transmission costs. Shading reservoirs, pastures and crops also reduces evaporation, thus saving water. Where water is a limiting factor, partial shade increases yield. Where water is not the limiting factor, reducing water use cuts salt fouling, and enables other uses for the water, including restoring natural habitat. There is absolutely no shortage of land suitable for solar arrays. You mostly see them on dedicated land (besides roofs) just because that is still cheaper.
- ben_w 5y ago
  While that currently appears to be true, it may still turn out to be useful to have PV in a distant desert and connected by a global grid. While batteries+overproduction is cost effective for overnight and even over-winter, we are still in the scaling up process for battery manufacture, and if that turns out to have a limit for whatever reason, solving the nighttime/winter problem can also be done with intercontinental HVDC[0]. And if batteries can do nighttime but not winter, those connections only need to be north-south not antipodal. [0] At least in principal, I don’t know anything about the geological or political restrictions.
  - ncmncm 5y ago
    Battery cost is still plummeting. Iron/air tech is coming to market at 1/3 the cost of lithium, with no conceivable scaling limit. It is not clear whether other storage methods will end up even cheaper than wherever battery cost levels off. If it does. But efficiency of power transmission technology has also radically improved, so that the chief downsides to distant generation are risk of failure of the transmission medium, and of political instability at the remote site or on the route. Anybody dependent on distant generation had better have multiple distant sources. In practice, we will end up with both local generation and storage and long-distance HVDC backup, to accommodate different failures. Countries without trusted neighbors will need more storage.

cratermoon 5y ago

> His calculations suggest it’s possible to repay the energy costs, including orbit, after only a few years. No. No they don't. that's not what his conclusions are at all. How did you even get that? He's comparing space-based vs. land, not space-based vs. nothing. His conclusion is that it's pointless to build solar power collectors in space for terrestrial power applications. In all cases, if you want power on earth, build the solar on earth.

elcritch 5y ago
> Add the embodied energy of the other components in space and on the ground, and I could easily believe we get to a year payback—now bringing the total (manufacture plus launch) to two years and an EROEI around 10:1. > If my 100× light-weighting proves to be unrealistic, and we can only realize a factor of ten improvement over our rooftop panels, the solar panel launch cost climbs to three years, so that adding other components results in perhaps a 4:1 EROEI. > In the end, the EROEI is not as prohibitive as I imagined: it’s not a net energy drain as I might have feared. But it’s not obviously better than conventional solar either. His overall conclusion may reach that conclusion, but his EROI give SPS a net 10:1 to 4:1 energy returns even in his worse case. So regardless if its cost competitive to ground based arrays or not, it might have uses and would likely result in net energy gain vs input (including materials).
- Dylan16807 5y ago
  It's like saying I could drive 80 miles each way to a gas station despite there being dozens of options within 5 miles. I get more energy than I spend, but it's never worth it. Also the gas there is extremely expensive.
  - elcritch 5y ago
    Even in your example there are scenarios it could be worthwhile. What if it’s gas produced in-country and its used as a military fill station? Particularly if it’s always available despite foreign political events. For personal usage maybe it’ll never be worth it, but perhaps it’s worthwhile for other use cases. Solar + batteries might not work if you can’t buy/procur enough batteries, especially for Arctic regions say where days are short. Or perhaps it’ll become possible to use for recharging electric airplanes in-flight. In that case the ability to “beam” worldwide might offset the cost of ground based grid of towers or ocean barges, etc. To be clear, I think it’s very unlikely, just not infeasible. Particularly if antennae tech keeps improving.
    - Dylan16807 5y ago
      > What if it’s gas produced in-country and its used as a military fill station? Particularly if it’s always available despite foreign political events. Except local solar requires fewer resources of every kind than satellite solar. You're more likely in every way to get cut off from the space version. > Or perhaps it’ll become possible to use for recharging electric airplanes in-flight. In that case the ability to “beam” worldwide might offset the cost of ground based grid of towers or ocean barges, etc. That would be cool. But it's a very different problem from grid power. I don't think it counts as a reason to beam dedicated space power to ground stations.

ncmncm 5y ago

Plants (even at their puny 2% efficiency) can utilize only a fraction of a full day's insolation; they are limited by other factors. Thus, there is no need to put solar panels in faraway deserts. Putting them above other land uses -- parking lots, buildings, reservoirs, pastures, cropland -- nearer to use reduces transmission costs. Shading reservoirs, pastures and crops also reduces evaporation, thus saving water. Where water is a limiting factor, partial shade increases yield. Where water is not the limiting factor, reducing water use cuts salt fouling, and enables other uses for the water, including restoring natural habitat. There is absolutely no shortage of land suitable for solar arrays. You mostly see them on dedicated land (besides roofs) just because that is still cheaper.

ben_w 5y ago
While that currently appears to be true, it may still turn out to be useful to have PV in a distant desert and connected by a global grid. While batteries+overproduction is cost effective for overnight and even over-winter, we are still in the scaling up process for battery manufacture, and if that turns out to have a limit for whatever reason, solving the nighttime/winter problem can also be done with intercontinental HVDC[0]. And if batteries can do nighttime but not winter, those connections only need to be north-south not antipodal. [0] At least in principal, I don’t know anything about the geological or political restrictions.
- ncmncm 5y ago
  Battery cost is still plummeting. Iron/air tech is coming to market at 1/3 the cost of lithium, with no conceivable scaling limit. It is not clear whether other storage methods will end up even cheaper than wherever battery cost levels off. If it does. But efficiency of power transmission technology has also radically improved, so that the chief downsides to distant generation are risk of failure of the transmission medium, and of political instability at the remote site or on the route. Anybody dependent on distant generation had better have multiple distant sources. In practice, we will end up with both local generation and storage and long-distance HVDC backup, to accommodate different failures. Countries without trusted neighbors will need more storage.