Comment by AnthonyMouse
4 days ago
If you only have one of them then the photons would only be available on that side of the earth at any given time and the other side wouldn't have power, but two of them would confuse the animals and disrupt everyone's circadian rhythm and then you'd have to deal with the three-body problem. Even the reactor-facing side would also have issues with the photons not getting through when it's cloudy.
The photons will also create heat and that heat can be used for useful work at any time, even when there are no photons hitting that side of the earth. For example it will evaporate water which will later condense into rivers, where you can put turbines. So it's a kind of fusion power, but less direct. Pure science fiction, of course.
The energy density of gravity-based storage is very low, so it could work in places where you have mountainous terrain and a lot of cheap land, but what do you do after the sites suitable for it are already in use? To make that work you'd need a scalable storage technology with a low enough cost per kWh of capacity to economically scale to multiple TWh of storage in case it's cloudy for an extended period of time.
For example, if you could make batteries at a price of $115/kWh, the cost for enough capacity to sustain the US power grid for a week would be around 24 trillion dollars, and that's just for the batteries and not any of the associated electronics or the land or the photon collectors themselves. It seems like to make your plan work you'd need a scalable storage technology with a significantly lower cost per kWh of capacity.
Using batteries for week-long storage is a bad idea. Lower efficiency, but lower capex, storage technologies like hydrogen would be better for that.
Optimized combinations of batteries and longer term storage typically comes out to maybe 12 hours of batteries, sometimes less.
We wouldn't need the hydrogen until the last few percent of the grid goes renewable; until then natural gas would be fine.
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Three Body Problems are only systematically unsolvable, you can still numerically calculate and manually move them with some algorithm.