Cost of building and maintaining Interstate Wind System
The cost of building a wind system that generates all of the nation's electricity per year depends on a number of factors:
How long it takes to build the whole system: Since big turbines are rated to last about 20 years, let's assume that we will take 20 years to build the whole system, at the end of which time we will need to start all over again. That is, each year, for the indefinite future, we need to build 5% of our system.
Total generating output: We have to know how much electricity we need. We want to build a system in 20 years. So we would like to know how much electricity we need in 20 years, and generally people assume a certain rate of growth. However, since we know what we are using now, and we don't know whether we can continue on our present course, we will assume the current rate of generation, which is approximately 4,000 Terrawatt hours (one terrawatt is 1000 gigawatts, which is 1000 megawatts, which is 1000 kilowatts, which is 1000 watts; in other words, one terrawatt is one trillion watts).
Capacity: We have to know what fraction of the the potential output of a set of wind turbines actually turns into electricity. Since wind is intermittent, that is, the wind which moves the turbine which creates the electricity is not always blowing, then we have to know how much electricity comes out of, and can come out of, a set of turbines. There are several ways to determine this:
1) In 2009, wind generated 73.886 terawatt hours (TWh) with a capacity of 34.296 gigawatts ( according to the Department of Energy (p.9)) , which is a capacity factor of 24.5, that is, about one-quarter of the maximum capacity of wind was being used.
2) The National Renewable Energy Lab (NREL) estimates that the average capacity factor for new wind turbines is about 39%.
So we can use 33% as a middle ground of capacity. Since we know we need 4,000 terrawatt hours, then we need three times 4,000, or 12,000 terrawatt hours capacity; 33% of 12,000 is 4,000. Capacity is not put in terms of hours, however; just to make things more complicated, capacity is rated assuming that the equipment was producing 24 hours per day. So we have to divide the 12,000 by the number of hours per year, and we arrive at 1,370 gigawatts capacity. However, we probably lose about 10% of our electricity through transmission; so let's assume that we need 1,500 gigawatts of wind capacity.
Now that we have this information, we can try to figure out how much 1,500 gigawatts of wind capacity would cost. So we need:
Cost per gigawatt capacity: According to NREL, the median for a large turbine is about $2,100, while according to the wind industry, it varies from $1,300 to $2,200. Costs are continuously declining, but assuming current fairly large, up-to-date turbines, let's figure $2,000 per gigawatt. Now we can figure:
Total Cost over 20 years: if a gigawatt costs $2,000, and we need 1,500 gigawatts, then we need 3 trillion dollars, or $150 billion per year.