[SustainableTompkins] I hate to drought on your hybrid parade but...

[Shawn Reeves]

In December I visited Kramer Junction, CA, home to several solar 
electricity generation stations. Since they use steam (heated by oil 
heated by the sun) to turn turbines, and the exiting steam needs to 
be cooled before returning to the turbine, evaporation is used to 
cool the steam. Thus, even large scale solar, such as it is in the 
California desert, uses scarce water resources.
How about a back of the envelope calculation?
About half the energy going through a steam turbine ends up wasted; 
let's say half that much ends up as latent heat in the evaporative 
coolant (water). So, to produce 100 kWh of electricity 100kWh is 
wasted; 50 kWh goes into evaporating water; 1 kWh is 3.6E6 J, so 50 
kWh is 1.8E8 (180 million) J. The enthalpy of vaporization is 2260 
kJ/kg. 1.8E8 J divided by 2260 kJ/kg is 80 kg, or 80 liters of water. 
So, for every 10 kWh of electricity I use, I waste 8 liters of water. 
My wife and I use about 10kWh per month, so we waste 8 liters (a very 
few toilet flushes) a month over at the plant, 100 liters a year. If 
we plugged in our hybrid, we'd drive about 3 miles on a kWh. So, 
every three miles we'd blow a liter of water over at the plant. If 
all 12,000 of our annual miles were 5 m/kWh, we'd be blowing 2,000 
liters, or two tons of water a year.
I wasn't to sure on the 3 miles per kWH--according to Idaho National 
Lab, the GM EV1 got 6 m/kWh--but my result (0.3 liters/mile=0.08 
gallons/mile) is one quarter of the claim in the article, 0.32 
gallons per mile.
But water is more renewable than oil, n'est ce pas?

in answer to:
http://www.sciencedaily.com/releases/2008/03/080310094555.htm
-- 
-Shawn Reeves
shawn at energyteachers.org
http://energyteachers.org