Question:
What would be the feasability of a large, I mean large, number of solar panels
set across an unpopulated area, say the desert? In terms of meeting a city’s
needs, how much power would this generate? How much could it cost? If big
enough, could it replace the environmentally unsound other means of supplying
energy.
Answer:
Here is a a scenario on large scale solar power production.Solar is not a panacea,
but more likely part of a healthy mix of sources. It is unrealistic to expect a
shift to large scale solar power production in the next decade, and possibly
unrealistic to not expect it in the next three. It appears more R&D in the area
is warranted.
Our best data for the economics of large scale solar power production comes
from the experience of Luz, Intl, a southern CA company that recently went
bankrupt (which is a powerfule statement in and of itself). Luz used arrays
of moving parabolic mirrors to focus light on fluid filled pipes mounted inside
vacuum insulated glass tubes, which heated to 735 degrees and exchanged to
superheat steam. This works best in climes where AC is a big part of peak load
(Luz used used natural gas turbines as a backup). A major factor in Luz’s
failure appears to have been inconsistent tax policies. Luz’z plants were
reportedly producing power at about $0.08/kwhr. The tech itself may not be
dead: Socal Edison, a largish utility, plans to put a similar plant online by
1998, storing the heat in molten salt, which has the advantage of leveling
power output. (Have I got that right, Paul, Tom?). Both are solar thermal
tech, as opposed to photovoltaic. (Solar thermal still seem a bit crude, like
we don’t have enough control over silicon to make PV economic. But I digress.)
One of the arguments against solar energy technology is that it would require
covering huge expanses of the Southwest’s scenic desert to provide substantial
amounts of power. Speaking as one who loves the desert and has expended a
modest amount of effort defending it, I think some accommodation could be
reached. There’s a lot of public rangeland heavily damaged by grazing, and the
benefits of cow removal could offset the effects of land consumption for sun
ranching. This scheme would probably be a net environmental plus if ~1% of
receipts went towards habitat restoration and enhancement.
How much land would be required for large scale power production? The United
States’ current installed electrical capacity of 730 gigawatts could be gen-
erated by a solar plant 80 miles by 80 miles, extrapolating from the Luz design.
This is smaller than the DOE nuclear test range and Nellis Air Force Base, for
example. Note that this is the more valuable PEAK power only, and does not
address base load or storage. Land use comes in at ~10 square miles per Gw.
6400 square miles sounds like a lot of land, particularly to most Easterners
and urbanites. Estimate the cost of consuming that much land in terms of
the good and services which would be displaced: assuming only the lowest value
activities are displaced, then the commodity eliminated would be mostly
public lands grazing, at a rate of $1.90 per animal unit month, where an AUM is
about 50 acres (it values greatly, 50 is on the small side for an average value.
Note that comparing land use between solar and grazing, Luz could produce ~10
megawatts on the area required by one cow). That’s 13 cows per square mile,
or about 78,000 homeless cows to supply the PEAK equivalent of US installed
electrical capacity. Assuming a 6 month occupancy, we have a net of ~$1M in
lost revenue for the land. Land availability shouldn’t be a major problem.
If this land were to replace public lands grazing, it would be occur under the
jurisdiction of the Bureau of Land Management, which supervises some 400,000
square miles of land, mostly in the arid west. The BLM is an agency considered
friendly to resource extraction industries. For reasons of geography, the most
efficient locations span a belt from roughly Bakersfield CA to Big Bend TX (the
region of mean daily solar radiation over 700 langleys). CA, NV, and esp. AZ
and NM have large amounts of public land suited to solar power production.
Utah, Wyoming, and Colorado also have decent sites. Idunno about the SE.
The ecological impact would be significant and must be considered. Much of the
land in question is in awful shape from a century of abusive grazing, but still
provides critical habitat. Mitigation of impacts of consuming land for energy
production would require careful site selection. Perhaps areas most disturbed
might be targeted for solar production. Other design criteria could include
avoiding riparian areas, and areas of significant scenic, recreational,
historical, geologic or biological value. In the end siting would be decided
by a combination of arm-wrestling, breast-beating, mud-slinging, ambush, and
name-calling; that is, through the normal political process.
Potential problems of large scale solar power production include initial
investment costs, maintenance, wind, loss of light incidents, and
earthquakes.
Maintenance is a big one: deposited dust degrades the efficiency of the mirrors,
so that frequent cleaning would be required. The problem with this is that it
takes a LOT of water. The water requirements will be a show stopper if not
successfully addressed. Note also that steam turbines in general require a
lot of water, a rather scarce and precious commodity in the arid West. For this
reason, large scale solar may have to wait for PV technology. If the water
issue can be solved, then solar thermal production has strong potential.
Wind is another issue to be considered: the Luz arrays folded up for
protection when the wind was blowing briskly. For this and weather reasons,
a robust design for major solar power production would be distributed across
several plants, hopefully located in relatively wind and dust free areas.