Tuesday, March 29, 2011

How Big Would Solar Be?

Is solar power too big a challenge for a country to take on? If we were to draw all our peak daytime electricity from solar power, how big would that be?

Certainly there are skeptics. I’ve heard it said that you could cover the entire United States with solar panels and still not produce enough electricity for the country.

Others have said that the United States could supply most of its peak energy demands with a $1 trillion investment in solar panels. A group in Congress is proposing a $1 trillion investment in nuclear power plants, so it’s fair to ask what we would get if we put the same money into solar panels.

To address this question, I decided to break it up into two questions:

  1. What would it take to provide one millionth of the United States’ peak electric supply using solar panels?
  2. Could this kind of installation be repeated one million times?

From Department of Energy data, the United States’ installed electric generating capacity is approximately 1 trillion watts. One millionth of this is 1 million watts, or 1 megawatt. A nominal 1-megawatt solar installation using solar panels available today would take up about 7000 square meters, or the roof of a typical big-box store. The going rate for this kind of solar panel is $2 per watt, so the cost of the solar panels would be $2 million if you bought the panels from your local wholesaler. Other electrical components, wire, and hardware would increase the cost of the installation to perhaps $3 million.

Investments on the scale of $3 million happen every day. To repeat that one million times would require, in theory, a $3 trillion investment. That’s a large price tag, but certainly possible. By way of comparison, the United States is expected to spend $3 trillion to import petroleum between 2011 and 2016, based on current prices.

The placement of the simple solar installation on the rooftop of a big-box retail building can’t be repeated one million times. There aren’t that many retail buildings. Yet it seems likely that enough suitable sites can be found. They don’t all have to be the same size, and they don’t all have to be buildings.

The total area of the United States is approximately 10 trillion square meters. About 1.6 percent of the country is paved. The area of pavement, then, is about 160 billion square meters, and much of that is parking lots. Virtually all large parking lots and the adjacent buildings are potential solar sites. Using current solar technology, we would need about 7 billion square meters of solar panels to provide an amount of electricity equal to the current total electric generating capacity of the United States. That’s an area equal to about 5 percent of the pavement in the country.

In short, we could supply the country with all the solar electricity it could use without venturing too far beyond commercial buildings and large parking lots, and we could do it, eventually, just by purchasing and installing the solar panels that the factories are already making. The cost, around $3 trillion, would be money well spent, especially right now. About half of the money would go to pay the wages of factory workers and construction workers, and there are plenty of workers idle in both skill groups.

As sunny as the solar scenario outlined above sounds, we can’t plan on getting all our electricity from solar in the near future.

  • Solar power provides only daytime electricity. Daytime electric capacity is the most important — two thirds of electricity is used during the day, and the peak demand for electricity is on summer afternoons when solar panels are at their best — but we also need nighttime power sources.
  • The existing factories can’t stamp out solar panels nearly as quickly as we could install them. A large-scale investment in solar capacity would start by adding to solar manufacturing capacity.
  • It works out better financially if we go slow and allow time for solar panel efficiency to improve.

Still, a large-scale investment in solar works out better than the status quo, even at current prices. Prices are expected to fall as panel efficiency and manufacturing efficiency improve, so it makes sense for a country like the United States to make solar power the centerpiece of its electric supply plans.