Wednesday, August 18, 2010
Monday, August 16, 2010
For the purposes of a book I'm trying to write, I had two maps of the United States laid out side by side the other day. These two maps are reproduced below, one above the other. The first is onshore wind power potential at 80 meters, from the National Renewable Energy Laboratories in Golden. The second is the percent change in population from 2000 to 2009 on a county-by-county basis, from Census Bureau data. In the first, the lavender and purple areas of the Great Plains are the best wind resources. In the second, the purple areas are counties that lost population. The correlation is not exact, but is certainly there.
Clearly, if the US is to use onshore wind power in a large way, the wind farms are going to built on the Great Plains. Consider the broad characteristics of such a system. The US consumes about 3.9 billion MWh of electric energy each year. Assume that we could eliminate half of that through efficiency and demand management, and that we want to generate half of the remainder from wind. More assumptions: 3.0 MW wind turbines, generating the equivalent of full-power one-third of the time, so 8760 MWh per turbine per year. Do the simple calculations and you get an estimate of about 110,000 turbines.
That figure is too low if reliability is considered. What is really needed is a figure for the number of turbines that need to be installed if we want to produce a certain level of power for a large percentage of the time. For example, based on the above numbers, we might specify that we want to produce at least 110,000 MWh of electricity during 95% of all daytime hours in the year. That's a much more complicated number to estimate depending as it does on a number of probabilistic variables. For our purposes, though, assume that another 50% is sufficient. That raises the required number of turbines to 165,000. (I suspect that number is still too low, and am looking for any work that has been done on stochastic models that would yield an answer that is not just a guess.)
One of the big knocks on wind power has always been that it's intermittent. Given enough turbines (and 165,000 is our guess at "enough"), much of that problem can be addressed by geographic diversity. Scatter the turbines from the Canadian border to the center of Texas, spread them out over hundreds of miles from west to east, and it becomes feasible to produce power at a fairly steady rate. Connect the turbines to a large north-south AC grid. Connect high-voltage DC transmission lines to that grid sending power most of the way to both the East and West coasts. All of that is technically feasible. There may be financing problems, or problems acquiring the volume of rare-earth magnets needed for that many 3.0 MW generators, and so forth. But the concept is straightforward and all of the engineering is feasible.
There is, OTOH, a heck of an operation and maintenance problem to deal with. For example, if turbines have a 30-year expected lifetime, roughly 5500 of them will need to be replaced each year. All the turbines, the entire AC grid interconnecting them, and the source end of the HVDC links are scattered broadly across the Great Plains, an area that is rapidly depopulating. How do we attract the technicians, engineers, project managers, and all the other skilled labor to work and live in that area? An engineer with a spouse and children is going to ask difficult questions. What are the quality of the schools? Who will straighten my children's teeth? Where will my spouse work? How good are the hospitals? How far is it to the nearest cardiac specialist, or neurosurgeon, or orthopedist? In the interior portions of the Plains, the answers to those questions are generally dismal, and getting worse.
Construction of this very large new infrastructure is likely to bring other problems to the rural areas. The West has seen the same pattern play out repeatedly when a new energy resource is developed: the sudden influx of "outsiders" is followed shortly by large increases in drug availability, prostitution, and various violent crimes that the local authorities are ill-prepared to handle. Local infrastructure such as roads is battered to the point it breaks down. There is no reason to believe that building hundreds of wind farms across the Great Plains will be any different. Again, these are not conditions that make it easy to attract skilled labor.
To sum things up, it may be technically feasible to build the wind-power infrastructure necessary to provide a large portion of US electricity. The social difficulties of building and then operating that infrastructure look to be much more difficult. Who are the people who will tend the turbines?