|Fig. 1: Solar panel parking lot at the Cincinnati zoo. (Source: Wikimedia Commons)|
Today in the United States, a majority of the adult population has become dependent on cars to transport them places. With that, cities have built parking lots over the years for people to store their cars for a certain period of time. The asphalt and concrete that compose the parking lot absorb the suns energy and retain heat which are the reasons why cities remain so hot. Corporate campuses, hotels, malls, schools, sports arena parking lots are some of the few places that have added solar panels to their parking lots. For example, public spaces like the Cincinnati Zoo, as seen in Fig. 1, have built solar panels for their parking lot facilities.
There are many benefits to building solar panel canopies over concrete lots. They range from adding aesthetic to a large area of land and increasing vehicle fuel efficiency.  Cars can stay cooler underneath the shade during periods of warm weather. People do not have to immediately crank up the air conditioning the second they return to their vehicle, saving energy and expenses. Electric vehicles are also able to charge their cars in the plug-in ports.
The Washington Redskins were the first professional sports team to add a solar panels over their stadiums parking lot. 20% of the FedEx Field's power on game days runs off the solar power and the panels generate all of stadiums power on non-game days.  The costs of spending money on power have declined for those with solar panels which the costs of lighting and operation expenses have increased. Every week in the NFL season, the teams use so much electricity to power their stadiums. Each stadium hosts around six to eight games each fall, which consumes up to 10 megawatts of electricity per game.  With the 8,000 solar panels built at FedEx Field, it can generate up to 2 megawatts of power, leading to the opportunity to save money from extreme electricity bills.
Although many universities and schools nationwide are building solar canopies over their parking lot, the cost is what is holding everyone from adding them.  Today, prices are dropping and building a solar canopy is cheaper now that building a solar roof a few years ago. It may be challenging to find various engineers and designers that can construct a safe working solar canopy. Specialized workers are hired ranging from a geotechnical engineer, structural engineer, drilling excavator, and steel erector. Arranging the groundwork for the system may be difficult to plan and find experts to help out but it is necessary.
The wholesale rate for electricity around the country costs $0.05 per kilowatt-hour, while the retail cost is about $0.10 per kilowatt-hour.  Take the amount of solar electricity needed to power the stadium at 20,000 kilowatt-hour per month, then divide it by 30 days in a month and 24 hours in a day. The stadium will produce an average of 28 kilowatts of energy not always needed.  With the solar electricity price costing $0.05 per kilowatt-hour, then football stadiums are not saving any money at all with their solar panels. Solar panels can only produce energy effectively until the sun goes down on a clear sunny day. When the sun does not shine on a cloudy day or at night time, batteries will be needed to store for later energy use. On top of expensive battery costs, semiconductor inverters are needed to convert the battery power to match the grid. In addition, maintenance will be needed when issues arise. For FedEx Field, the parking lots are mainly only used for game days which only occur during the football season. The big debate is if it is worth spending the millions of extra dollars on solar panels that look aesthetically pleasing and draw attention to the Redskins?
The companies, schools, sports arenas just to name a few, who have built solar panels for their parking lots have saved a significant amount of money spending on power. However, the initial cost to construct the solar panels is what is stopping everyone from investing a significant amount of money to build the system. The process to set the groundwork and then build solar panels takes a while but once the system is completely built, cars will have the option stay cool and businesses can run on solar power.
© Payton Chang. The author warrants that the work is the author's own and that Stanford University provided no input other than typesetting and referencing guidelines. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
 C. Mooney, "The Best Idea in a Long Time: Covering Parking Lots With Solar Panels," Washington Post, 28 Apr 15.
 J. Breech, "Cowboys Stadium Uses More Electricity Than Liberia," CBS Sports, 17 Sep 13.
 P. Poonpun and W. T. Jewell, "Analysis of the Cost per Kilowatt Hour to Store Electricity," IEEE 4456517, IEEE Trans. Energy Conver. 23, 529 (2008).
 I. Penn, "California Invested Heavily in Solar Power. Now There's So Much That Other States Are Sometimes Paid to Take It," Los Angeles Times, 22 Jun 17.