I didn’t raise any questions during Michael Webber’s talk on Wednesday, but I did consider raising the issue of water, or specifically the relationship between fresh water production and energy production. Whatever Texas’s advantages in energy production, they are somewhat mitigated by our disadvantages in water supply. If one agrees that water production and energy production are related issues, this obviously becomes relevant.
This raises a question which I did not put to Richard nor to Michael Webber but which has been puzzling me. Webber’s article makes it explicit:
We cannot build more power plants without realizing that they impinge on our freshwater supplies. And we cannot build more water delivery and cleaning facilities without driving up energy demand. Solving the dilemma requires new national policies that integrate energy and water solutions and innovative technologies that help to boost one resource without draining the other.
So here’s my question: why do power plants require fresh water? Is the dominant purpose of water not cooling? If not, why is water such a big issue? On the other hand, if cooling and quenching and thermal conduction is the issue, why use precious freshwater instead of sea water?
Note, the following appears in an information-poor infographic (that doesn’t make it into the scanned text) in Webber’s article:
Water Required to Generate One MW-hr
- Gas/Steam: 7,400-20,000 gallons
- Coal or Oil: 21,000-50,000 gallons
- Nuclear: 25,000-60,000 gallons
I suspect that all (certainly most) of the UK's nuclear power stations use sea water, which was a significant factor in their siting.Fresh water has an additional environmental cost in terms of impacting the local ecosystem – there are often restrictions on outlet temperature which may cause power stations to be shut down in hot weather.Of course in all cases the water is not actually used, merely borrowed, so even freshwater could presumably be later used for irrigation – but not first 🙂
Salt water is a lot more aggressive chemically. It can be handled but there is an additional cost
Water used just for cooling can be (and sometimes is) successfully replaced by air cooling. A few weeks ago there was an excellent thread about this by a guest on Joe Romm's ClimateProgress.
check out south africa's nuclear power plant.
I thought I read somewhere (but can't find a handy reference, and Google is for once no help) that seawater *is* widely used for power-plant cooling. Aside from sea-level rise, there is the problem that sea-shores tend to be highly populated too, and nuclear (in particular, though it applies to coal as well) has that NIMBY issue.A steam turbine does need fresh water for the steam generating loop, but I believe that's generally a closed loop rather than taking fresh water from outside.
Concentrated solar power needs large amounts of water. But photovoltaic power plants need little water, mainly for cleaning.
If one agrees that water production and energy production are related issues, this obviously becomes relevant….until today, the only person I had heard raise this issue has been Richard Doctor of Argonne National Laboratory. Can't track it down now, Michael, bu t several months ago Colo released a study that found if the oil shale on the Western Slope were to be exploited fully, ~750k fewer households would settle in Colo. Not a bad thing in itself, but the tradeoff is all that added C to the C cycle. Best,D