[tt] Independent: Greener power to the people: the real energy alternative?

[J. Andrew Rogers]

On Jun 3, 2008, at 9:30 PM, Randall Webmail wrote:
> Somethign I've wondered about for Quite Some Time:   You dig a hole  
> a few thousand feet deep, the bottom of that hole is HOT, by  
> comparison with surface temps.
>
> Like three hundred degrees F.
>
> I don't know what it costs to drill four thousand feet these days,  
> but it's gotta be less than building a nuke plant.


Under *ideal* circumstances, like drilling into a shallow semi- 
crystallized magma chambers like they have in northern Nevada, a  
single geothermal bore -- at *500-600F* -- will generate around 10 MW  
of cheap, continuous power.  Low-grade bores like the 300F one you  
mention above will generate around an order of magnitude less power in  
practice I would guess, though it is still moderately inexpensive.   
Combine this with the fact that bore density in a geothermal field is  
limited to about one per 20-40 acres (or the wells significantly  
interact) and the problem becomes obvious.

Yes, there is a metric buttload of geothermal power potential and it  
is generally quite clean and low impact (they are closed loop and  
there is little surface impact but a sparse pipe network).  But to tap  
geothermal sources like the mediocre ones you mention above, you would  
need to drill something like 60 square miles to compete with a single  
large nuke plant.  Environmentalists have been reliable opponents of  
geothermal projects in the western US deserts, largely because the  
idea of sparse pipe networks over large geographical areas violates  
their sense of aesthetics in the abstract even if the impact on the  
local ecology is pretty negligible, nobody travels to those regions,  
and the terrain is anything but visually pleasing.

The geothermal technology is improving such that it may be possible to  
generate reasonably priced power most places, since the ability to  
exploit traditionally low-grade sources has been improving.  
Nonetheless, some environmentalists are launching attacks against such  
projects using the argument that drilling geothermal is no better than  
drilling for oil in terms of its impact on the local environment.

J. Andrew Rogers