3 ms·

While I think this first-principle analysis is helpful, I fear it may be holding Quaise to too high a standard; their goal (AFAICT) is not to provide 100% of th

While I think this first-principle analysis is helpful, I fear it may be holding Quaise to too high a standard; their goal (AFAICT) is not to provide 100% of the energy needs of anywhere; it's a huge win if coal's 10-20% contribution of total power generation (or even just a substantial fraction of that) can be in-place replaced with a geothermal generator. Maybe this tech won't be cost-effective in 50 years as solar continues to get cheaper, but as a transitional bridge technology it could be incredibly impactful in the 10-20 year timeframe. Also, you didn't specify a depth for your calculation; won't the flux be higher the deeper you go (i.e. be proportional to the delta-T)? They are talking about going to 20km which as I understand it is WAY deeper than most geothermal systems contemplate. Their whole bet is predicated on the idea that with the gyrotron they can drill deeper since they don't need to mess with high-temp drill bits.

jjk166 4y ago
> Also, you didn't specify a depth for your calculation; won't the flux be higher the deeper you go (i.e. be proportional to the delta-T)? They are talking about going to 20km which as I understand it is WAY deeper than most geothermal systems contemplate. Their whole bet is predicated on the idea that with the gyrotron they can drill deeper since they don't need to mess with high-temp drill bits. The depth doesn't matter at this scale. 20km deep the heat flux is about 0.3% higher. Things get complicated as you go down into the mantle, but at 20km you're still in the top part of the crust. The only thing drilling deep does is increase your max temperature, which increases efficiency, but eventually you hit the same limit as with any other steam generating plant where you can only handle steam that is so hot and so high pressure. With current technology, that limits the efficiency percentage to the low 40s. Maybe with some technological improvements this can go up a bit, but the carnot efficiency of a heat engine where the water is heated to the point it will decompose is 87%, and there is no way you're even going to get near that in a real plant, so increasing efficiency isn't really going to make a huge difference.
- deleted 4y ago
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bequanna 4y ago
> Maybe this tech won't be cost-effective in 50 years as solar continues to get cheaper As we replace base load with less reliable sources we need to come up with some way of expressing a penalty for availability. Does it matter how cheap solar is if it isn’t available when we need it and storage is not practical?

jjk166 4y ago

> Also, you didn't specify a depth for your calculation; won't the flux be higher the deeper you go (i.e. be proportional to the delta-T)? They are talking about going to 20km which as I understand it is WAY deeper than most geothermal systems contemplate. Their whole bet is predicated on the idea that with the gyrotron they can drill deeper since they don't need to mess with high-temp drill bits. The depth doesn't matter at this scale. 20km deep the heat flux is about 0.3% higher. Things get complicated as you go down into the mantle, but at 20km you're still in the top part of the crust. The only thing drilling deep does is increase your max temperature, which increases efficiency, but eventually you hit the same limit as with any other steam generating plant where you can only handle steam that is so hot and so high pressure. With current technology, that limits the efficiency percentage to the low 40s. Maybe with some technological improvements this can go up a bit, but the carnot efficiency of a heat engine where the water is heated to the point it will decompose is 87%, and there is no way you're even going to get near that in a real plant, so increasing efficiency isn't really going to make a huge difference.

deleted 4y ago
[deleted]

bequanna 4y ago

> Maybe this tech won't be cost-effective in 50 years as solar continues to get cheaper As we replace base load with less reliable sources we need to come up with some way of expressing a penalty for availability. Does it matter how cheap solar is if it isn’t available when we need it and storage is not practical?