[ RadSafe ] Pumped Storage Issue ---Was: Re: Salsman warning

[Brennan, Mike (DOH)]

Additionally, there are a limited number of places where a "high reservoir" can be built without significant (local) environmental impacts.  Building a lake where there used to be a valley isn't that hard, but we now pay attention to some of the other issues.  I am not saying it is impossible, just not as easy or cheap or clean as is sometimes advertised.  And, of course, it is not an energy source; just an energy storage system that looses energy when it is put in, and looses energy when it is taken out.  

An entertaining variation on the theme is not to pump water, but to pump air.  You can get OK energy densities with compressed air, but you can get pretty good densities if you pound it all the way to liquid (yes, some cooling is involved, but if you are halfway clever you can recover energy from that stage).  Liquid air can be used to power vehicles, with about the same range limits as battery powered vehicles.  It can be combined with solar power to increase its efficiency.  It is not an energy source, any more than pumped water storage is, but is it more versatile and easier to site.  

Besides, who doesn't want to play with liquid air? 

-----Original Message-----
From: radsafe-bounces at health.phys.iit.edu [mailto:radsafe-bounces at health.phys.iit.edu] On Behalf Of Stewart Farber
Sent: Friday, April 09, 2010 12:11 AM
To: James Salsman; radsafe at health.phys.iit.edu; Inc.AnaLog Services
Subject: [ RadSafe ] Pumped Storage Issue ---Was: Re: Salsman warning



Hello all,
Some comments on the narrow issue of "pumped storage" as a supposed cheap electric generating source vs. some other sources mentioned by some earlier posts from Mr. Salsman.
 
Pumped storage is simply a way of primarily  taking baseload generated power [from large coal or nuclear stations] to pump water up from some height to something higher during offpeak hours thus storing potential energy.  Pumped storage can also take electricity from any source other than large baseload stations that is not needed at the time of its generation. This would also pertain to excess wind or solar or any source of generated electricity that was not need by the grid when generated. 
 
So pumped storage is a form of load leveling/energy storage. Once the water is pumped up it can sit there for as long as it needs to until demand dictates that more power must be put into the grid. Rather than fire up peaking stations like gas turbines [which are much more expensive to run than baseload stations and take some time to get up to speed to equal a big spike in power demand] grid operators will generally prefer to open a few valves and let water fall to power a water turbine. Remember that when a baseload plant [like a 1,000 MW[e] nuclear or coal plant trips offline, the instantaneous demand of the grid must be met within seconds, or the grid becomes unstable.  So grid operators have things like pumped storage facilites, or many small 10 or 15 kW water turbines that are kept spinning at low speed ready to be brought to full power within a few seconds. For any one portion of a grid, there has to be enough capacity very quickly available
 to equal the generation capacity which might be lost essentially instantaneously.
 
 Large generating plants [like nukes or large coal stations] do not work well being cycled up and down and cycling costs $. As an example of a big pumped storage facility there is the Bear Swamp facility in near Rowe, MA, [site of the former Yankee Atomic Electric NPP for about 40 years]. Bear Swamp facility takes water from the Deerfield River and pumps this water up 770 feet from a lower reservoir to an upper reservoir.
 
Bear Swamp can generate a maximum output of about 600 MW[e] for about 6 hours if the upper reservoir were filled to maximum capacity. But, the process LOSES ENERGY. Electricity [from whatever source] powrs pumps to pump water up when the electricity is surplus. Then the water can be allowed to fall when demand is up and the twin water turbines can go from 0 power to a full power output 600 MW[e] in about  3 minutes when electricity is needed. However, you get LESS electricity out when the water falls from the upper reservoir, than it took to pump that water up to the upper reservoir.
 
So clearly "pumped storage" is NOT a source of newly generated electricity but a recovery of some large fraction of stored excess or baseload electricity [with unavoidable losses] from any of many primary sources of generation.  The cost of a kilowatt hour out from a pumped storage facility, will always be higher than the cost of the initial generated kW-hr which powered the pumps to drive a huge volume of water up to storage.
 
 
Stewart Farber, MSPH
Farber Medical Solutions, LLC
Bridgeport, CT 06604

[203] 441-8433 [office]
http://www.farber-medical.com
farber at farber.info
 
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