If the geothermal plant isn’t ran at or near capacity all the time, the capex takes longer to recoup.
You can’t just, say, run it at 50% for a while, and then at 150% later, because a) ya typically can’t run plant at 150%, and for power generators ya can only run them at whatever you’re contracted to supply, so you’d typically want to run geothermal at capacity all the time.
This is true of anything that requires capital expenditure.
Drilling the well is the expensive part. It heats at a relatively constant rate depending on the geometry. You could size the plant to be exactly matched to the well output--but the generators and such are relatively cheap. So instead you make that part of the plant slightly oversized, so you can run at over the well's capacity when electricity is expensive, and under the capacity when it's cheap. The thermal mass of the rocks allows you to average this out over time.
So there are two capacities, that of the well and that of generation (oversized with respect to the well). On average this varying scheme utilizes the well at 100% of capacity (the expensive part to increase), and the turbine generation at less than 100% capacity (not expensive to oversize).
> They just let pressure build up higher than normal for 6-8 hours and then the turbine generates more power than normal until the pressure falls back to normal levels again.
If the geothermal plant isn’t ran at or near capacity all the time, the capex takes longer to recoup.
You can’t just, say, run it at 50% for a while, and then at 150% later, because a) ya typically can’t run plant at 150%, and for power generators ya can only run them at whatever you’re contracted to supply, so you’d typically want to run geothermal at capacity all the time.
This is true of anything that requires capital expenditure.