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Concentration of CO2 in the Atmosphere

Parking Lot Solar

A Perfect Solution for Schools and More

George Harvey

Solar panels over a parking lot at the Intel site in Ocotillo, Arizona (Intel Free Press, Flickr,
bit.ly/solar-parking-7)

One great idea for solar systems is to put them up over parking areas. This has lots of advantages, including not just generating electricity, but shading cars and cooling the parking surface. We have a ten-year-old paper on the idea, and found that it still reads as though it were fresh. It is “Making the Grade with Clean Energy: Case Studies of California Solar Schools.” It has information and a number of pictures of solar arrays on parking lots at that state’s schools, and it may be of interest to readers (www.bit.ly/solar-parking-1).

It occurred to us that the idea may be taken too much for granted, and this could slow down its implementation. It has come up often on our pages. Possibly the most recent article Green Energy Times has had that included the subject of solar canopies for parking lots was “A Net-Zero Multi-Family Community,” in the October 2021 edition (bit.ly/solar-parking-2). But we decided to take another look at it.

One thing that readers might ask is how much good it will do to have parking areas covered with solar panels, as a way to address climate change. This can be viewed as a rather simple problem, with two parts. First, we find much land is covered with parking lots. Then we find how much land we would have to cover with solar panels to provide for the current electricity demand of the United States. Please note that the answer to the second question assumes that solar is the only primary energy source, and this would mean that electricity is stored for times when the sun is not shining.

Let’s look at just urban areas for now. The U.S. has 106,386 square miles of urban areas, according to a fact sheet prepared by the Center for Sustainable Systems at the University of Michigan in 2010 (bit.ly/solar-parking-3). According to an article in the Philadelphia Inquirer, about a third of the land area of US cities is taken up by parking lots (bit.ly/solar-parking-4). If those data are correct, there are 35,462 square miles of land area taken up by parking in U.S. cities. That area is a little bigger than the southern half of New England (Connecticut, Massachusetts, New Hampshire, Rhode Island, and Vermont, put together).

Please note, this is just the areas of urban parking lots, and in the case of multi-level parking only takes into account that part that could be exposed to the sun. Another thing we should note here is that these numbers are estimates, and the estimates vary widely, as we shall soon see.

According to the U.S. Department of Energy, the area we would need to cover with solar panels to supply all of the country’s current demand for electricity is about 22,000 square miles. This is about 115% of the combined land areas of Vermont and New Hampshire combined (bit.ly/solar-parking-5).

This is where we will compare estimates. It happens that Elon Musk estimated that 10,000 square miles would suffice. An article in Inverse said he was right, sort of, but to do the job properly and reliably, we would need far more than that. Data from Delucchi and Jacobson’s 100% Solutions Project, found that the U.S. would need to use 0.69% of its total land, or 26,198 square miles (https://bit.ly/solar-parking-6).

If we use that last figure, we can see that we could supply the U.S. with its current demand for electricity with solar systems sited on an area about 74% of the size of its urban parking areas. While this will probably not happen for various reasons, it begins to show the advantages of solar canopies over parking areas. There are other reasons to cover parking areas. Asphalt, in the full sun on a hot day, can have a temperature of 140°F fairly easily. That is hot enough to burn feet and paws; it is hot enough to fry an egg. (How much does that contribute to global warming?)

We would like to remind everyone that the sizes of parking areas that could have solar canopies could range from a single car to as big as a parking lot gets. There are a lot of opportunities here.

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