"Our greatest responsibility is to be good ancestors."

-Jonas Salk

Friday, June 5, 2009

Water and Energy

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.

Until today, the only person I had heard raise this issue has been Richard Doctor of Argonne National Laboratory. In a talk I saw him give a couple of years ago, he pointed out that increasing water supply takes energy, and increasing energy supply takes water, so that the once demand reaches a certain point one can't treat the problems separately.

It turns out I should have asked the question as it would have been a real softball pitch for Webber. He has written an article on the subject [link to abstract only; article is behind a pay wall] appearing in Scientific American. (While it lasts: here is a scan of the text.)

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? 

I note that Austin Energy's part-owned nukes are on the seashore. Of course, there is sea level rise to contend with... Yikes! 

I suppose that renewable energy (except biofuel) doesn't require significant water in operations. (Capital costs aside.) Isn't this a strong argument for wind and solar? Why aren't they making it?
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
Another argument for natural gas rather than nuclear as the bridge to renewables.

Drop the thousands to convert into the easier to think about KW-hr, which is about the draw from watching a big screen TV for an evening. That would be, depending where you live, between 7 and 60 gallons. (25 to 225 liters). As much as a bathtub's worth on the high side.

So anyway. Is sea water usable instead of fresh water in power plants? 


Dano said...

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.



Anonymous said...

Concentrated solar power needs large amounts of water. But photovoltaic power plants need little water, mainly for cleaning.

Arthur said...

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.

crf said...

check out south africa's nuclear power plant.

David B. Benson said...

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.

EliRabett said...

Salt water is a lot more aggressive chemically. It can be handled but there is an additional cost

James Annan said...

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 :-)