All types of airport operations are going electric as efforts continue to cut emissions from internal combustion engines and other sources of pollutants at the world’s airports.
In order to help meet their own electricity demand or otherwise offset emissions from fossil fuels, increasing numbers of airports are adding renewable generating resources.
The latest airport to join the electrification trend is Royal Schiphol Group which manages four airports in the Netherlands. Royal Schiphol has agreed to financially back enough renewable energy from wind farms around the country to support its operations beginning in 2018.
Taken together, Schiphol, Rotterdam The Hague Airport, Eindhoven Airport, and Lelystad airports will receive enough renewable energy to meet their 200 gigawatt-hour demand. The wind power will be generated by Eneco, whose wind farm development efforts are funded in part by the contract agreement.
Because of the height of their towers, however, wind turbines usually aren’t a good fit for use on airport property. As an alternative, many airports turn otherwise unused land into sites for solar energy facilities.
A July 2014 report by the Energy Department’s National Renewable Energy Laboratory (NREL) estimates that more than 816,000 acres of vacant land within nearly 3,000 airports across the United States could support more than 116,000 megawatts of fixed-axis solar photovoltaic generating capacity, the equivalent output of around 100 coal-fired power plants.
The NREL study says that although airport real estate represents a fairly new place for solar PV, multiple installations worldwide have implemented the technology. These include:
- Indianapolis International Airport in Indiana where a 12.5 MW system has been operating since 2013
- Fresno Yosemite Airport in California where a 2 MW system was built in 2008 to meet around 60 percent of the airport’s energy demand
- Birmingham Airport in England which installed a 50 kilowatt (kW) system on the terminal roof in 2011
- Gatwick Airport in London, England where a 50 kW system was installed some 150 meters from the main runway. The developer spent months negotiating with the United Kingdom National Air Traffic Service and the Civil Aviation Authority over the exact location to ensure the solar panels do not disrupt airport operations.
Siting, like that addressed at Gatwick, may be the most important issue for airport operators. Some solar generating systems result in glare and reflections that can impair the vision of pilots during takeoff and landing, as well as air traffic controllers who are managing aircraft movement.
Solar towers that use hundreds of mirrors to focus the sun’s rays on a boiler high in a tower may be particularly ill suited, for example. The mirrors would create too much glare for pilots and air traffic controllers, and the towers typically would be too high for airport locations. What’s more, thermal plumes created by the facility could cause unstable air around runways.
Because of concerns such as these, the U.S. Federal Aviation Administration (FAA) in November 2010 released a document titled Technical Guidance for Evaluating Selected Solar Technologies on Airports.
The report aims to ensure that solar projects are sited properly and do not cause safety problems. Specifically, the guide seeks to ensure solar installations do not create glint or glare conditions. (Glint is a momentary flash of bright light, and glare is a continuous source of bright light.)
In writing the report, the FAA expressed concern that glint and glare from typical ground-mounted solar energy systems could result in an “ocular impact to pilots and/or air traffic control facilities and compromise the safety of the air transportation system.”
Besides to glint and glare, the FAA also expressed concern about the possibility for interference to communications and navigation systems. Its 2010 report says that solar PV systems typically present little risk of interfering with radar transmissions because of their low profile. What’s more, it says that solar panels emit no electromagnetic waves over long enough distances that could interfere with radar signal transmissions.
To further ensure that solar PV systems are as isolated as possible, installations must be set back from major on-airport radar equipment. For example, the solar fields at airports in Oakland and Bakersfield, California, were had to be set back as much as 150 meters from transmitters.
The NREL report also says that physical methods can be used to cut reflection, glare, and glint. These can include applying anti-reflective coatings or texturing. Neither one has a discernable effect on system performance, the report says, but could help minimize annoying reflection.
Denver International Airport has installed around 8 MW of solar PV on its property, roughly equal to 6 percent of its annual electricity consumption. Installed in three phases, the largest solar array has a generating capacity of 4.3 MW. It includes almost 19,000 PV panels installed at a fixed tilt of 25 degrees.
As part of the design and construction process, panels were brought to the airport and looked at from the air traffic control tower to ensure they would not affect the view. A tracking feature was included as part of a 2-MW array known as DIA that was sited closest to aircraft operations. The tracker is used to help ensure that glare or glint situations from the PV system are minimized.
Not every airport solar PV installation achieves initial success, however. In 2012, south-facing solar panels were installed on the roof of a parking garage at the Manchester-Boston Regional Airport in New Hampshire. Soon after they were installed, air traffic controllers complained of glare from the panels that affected their vision for around 45 minutes each morning. As a result, around 25 percent of the panels were covered with tarps. They were later removed and replaced with 2,210 panels (460 kW each) oriented toward the east.
The new configuration ended the glare, but trimmed overall system efficiency. At that latitude, east or west facing panels are less efficient than those that face south. To compensate for the roughly 10 percent loss, the airport added more panels in an effort to keep the total installed generating capacity about the same.