But, running a power plant typically requires significant amounts of water to run and cool the turbines.
This 2002 report summary puts the number for wet cooling at around 15,000 gal / MWh.
Fortunately, there are technologies to use much less water: 200 - 250 gal / MWh, a >90% drop. However these technologies are:
- Expensive: ~7x to 17x the wet cooling system cost
- Less efficient:
- power output must be reduced at times when the ambient temperature exceeds the design temperature (to avoid damaging the turbines)
- Output of the heat cycle drops when the output temperature is high.
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Fortunately, BrightSource Energy is using dry cooling so that they "Will use 100 acre feet [~32 million gal] per year, the equivalent of 300 homes’ annual water usage." If every power plant did this, following the logic of my previous post, it would:
- easily beat the ~20% improvement you'd need to be equivalent to all buildings being LEED 3.0 for water efficiency
- would be enough to meet the ~46% improvement you'd need to replace all the water used domestically and industrially.