But it’s hard to think of an urban area that could be better used than a parking lot. In addition to being unpleasant to the eye, they are usually quite large, which means they have a lot of energy-generating potential.
Based on 2021 data studying Co-authored with Pierce, installing solar panels over the parking lots of 3,751 Walmarts scattered across the US could generate the same amount of electricity as about a dozen coal-fired plants. (Even taking into account the fact that solar energy is used part-time, Pierce believes that it is possible to permanently close two, maybe three such plants in sunnier regions, if they cover sites in Walmart supermarkets.) The French government believes that solar canopies can generate up to 11 gigawatts of renewable energy, equivalent to the power of 10 nuclear reactors. it about 8 percent all electricity generated in the country.
Installing solar awnings can be beneficial for drivers as well. They will provide shade in sunny and warm weather, potentially reducing the need for air conditioning when people jump into their cars, and in winter, they will provide shelter from rain and snow. If the vehicles parked underneath are electric, the energy generated can also be fed directly to those vehicles. Currently, most commuters charge their electric vehicles at home, after hours. The freedom to charge for shopping or at work can allow them to avoid peak prices.
Connecting parked electric vehicles to PV awnings can even help balance the grid. Since the traditional grid does not have the capacity to store energy, the power fed into it must match the power drawn – too much power on the grid is a problem. When using solar energy, especially during peak hours of sunshine, this may mean that production must be stopped. But if you could store surplus energy in electric vehicle batteries on site, you could make the most of solar’s potential during periods of peak generation.
“During the day, they can store energy,” Nathanson says of parked electric vehicles. “During peak power, in the late afternoon, they can return power to the grid.” Running so many independent pieces of equipment in conjunction with the grid – and making sure no one runs out of power – would require a fair amount of intelligent automation. You will also need bidirectional charging equipment, which is currently not widely used. But the potential to be smarter with solar power is there.
However, not every parking lot can be turned into a power plant. Some may have too much shade, possibly due to tall buildings nearby. In countries north of the globe where the sun is lower on the horizon, long shadows will be more of a problem, especially in winter. Elsewhere, the panels could reflect sunlight onto nearby buildings or, worse, onto roads, warns Dylan Ryan, lecturer in mechanical and energy engineering at Edinburgh Napier University in Scotland. “Are we going to throw sunlight in the eyes of the people who work across the street?”
However, the biggest problem is the cost: installing a solar panel over a parking space is expensive. repeatedly more than installation on the ground or on the roof due to the need to create a supporting structure. (These costs are likely to be higher in, say, the United Kingdom than in Southern Europe, because there are no sunshades in the parking lots yet.) One of the outstanding issues with the French proposal is how parking operators will pay for these settings. Without subsidies, Pierce says, it’s hard to imagine too many operators installing optional solar canopies because of the investment required.
Of course, parking operators can recoup their upfront investment by charging customers to connect electric vehicles, or they can use electricity themselves in any business that serves their parking lot. Or electricity can simply be sold back to the grid. “Whether you’re selling electricity to the grid or just using electricity in your business, you’ll be paying less for electricity overall,” Pierce says.
None of this means that solar farms should only be in urban areas. But there is a distinct advantage to having more solar energy generated closer to where people live, and there is an obvious need to find a way to do this that is not bewildered by nimbus. The use of parking lots for solar farms solves this problem, and on that basis French legislation is a huge, albeit aggressive, step in the right direction. “You’re taking advantage of what is essentially free real estate,” says Ryan.