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by dojomouse
2878 days ago
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I looked into this in a lot of detail about 5 years ago. There were a couple of studies, and one somewhat-active company I saw (Stratosolar - didn't seem to be very well resourced/capable). My main focus was on aerodynamic modelling and panel positioning methods for various structure sizes, and the resulting LCOE. Main issues I found were:
- Weather conditions in the stratosphere aren't well understood; most of the time pretty benign, but there are a bunch of extremes which could have a significant impact on the structural requirements.
- It's basically a tradeoff of panel-cost/conventional-installation-cost vs aerostat-cost/non-conventional-installation-cost. The aerostat is definitely not going to be cheap, so having your panels on an aerostat has to result in a bunch more energy per PV-element than having them on the ground.
- Having the aerostat option come out on top gets more difficult as PV gets cheaper. Let's say you get 2x energy from PV on an aerostat vs installed on the ground. That means the aerostat option will be competitive with the ground option as long as the total installed cost (per watt) is less than 2x the terrestrial installed cost.
If the terrestrial installed cost reduces by a factor of two (and it's reduced by more than that since I did the analysis!), you suddenly have to reduce the marginal cost of your aerostat option by 50% just to remain competitive!
- To be economic and sufficiently robust to expected weather, these structures have to be enormous; the architecture that seemed most promising to me (from memory) was cylinders of length 4km and diameter 1km (roughly 1GW electrical output peak, more like 500-600MW annualised). They're at least semi opaque, and are tethered around 20km altitude (and can drift within a ~10km radius around the tether point). At that altitude they're visible from several hundred kilometers away, and they look huge - 15x the width and length of the largest cruise ships.
- It doesn't help THAT much with seasonal variation away from the equator. Summer output in northern europe is still 2-3x winter output, so you need long term storage or an energy dump. So... I think it's super interesting, but I don't think it'll ever be commercially attractive vs either terrestrial installations, or space. The main nice thing is that it's still pretty easy to get the power back down to earth with high efficiency... in contrast to orbital solar. |
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