Airports + Solar: A wise use of space, but how do birds factor in?

Solar array with airplane near Prescott AZ_WS_David Bergman
PV array near Prescott, AZ. Photo by David Bergman

Solar power may seem like an environmentalist’s dream energy source, but it is not without its caveats. Chief among them is that large photovoltaic arrays (solar farms) require space, and frequently the price of that space is a reduction in wildlife habitat. Solar engineers are coming up with creative solutions to this problem such as the solar panel bike path outside of Amsterdam or transparent solar cells (currently in development) that could be fitted over windows. In a recent paper in the journal Landscape and Urban Planning, Travis DeVault and co-authors examine another idea- installing photovoltaic arrays at airports.

Airports are one place that environmentalists and industry agree is it best to keep wildlife, especially birds, away. Airplanes and birds are not a good mix. The famous “Miracle on the Hudson” emergency landing of a jet on the Hudson River was the result of the plane hitting a flock of geese soon after take off. According to the FAA, more than 243 aircraft have been destroyed by birds strikes since 1988, killing over 250 people. A plane may manage to land despite injuries but the bird probably never survives the encounter. Most airports employ active wildlife management programs to deter birds and other wildlife from the airport area to avoid these types of accidents.

Airports also comprise a lot of open space, usually grasslands, necessary for the safe movement of planes. DeVault and colleagues estimate that when all of the airports in the contiguous 48 states are considered together they contain a total area of grassland that is larger than the state of Rhode Island. That is a lot of space. Could that space serve a dual purpose and generate solar power? If this land is already deemed unsuitable for wildlife, why not put photovoltaic arrays here and save good habitat elsewhere?

Sounds like a good idea, but wildlife does not always respond as expected to man-made structures. There is evidence that large photovoltaic arrays might even attract birds that mistake their reflective surfaces for water. So DeVault and his co-authors examined how birds use solar installations at airports. The researchers designated 10 study sites in Ohio, Colorado and Arizona. Each site comprised a pair of locations: an airfield grassland and a nearby PV array installation, so that both the airfield and PV array could be assumed to host similar bird communities. The researchers then conducted surveys to determine bird occupancy and calculated a Bird Hazard Index (BHI). The damage that a bird strike can do to an aircraft is primarily determined by the body mass of the bird and how many birds hit the aircraft. One starling is not as dangerous to a plane as one Canada goose, so simply comparing numbers of birds at airfield grasslands vs. PV arrays would give a false picture of bird strike danger. BHI is calculated by multiplying species body mass by number of individuals observed per hectare and summing across the species for each location.

DeVault and co-authors found no significant difference in BHI between airfield grasslands and PV arrays, suggesting that installing PV arrays in airfields will not increase bird strike risk to aircraft. However the authors point out that their methods likely underestimated bird occupancy in airfield grasslands. In addition, they found that BHI at PV arrays was greatest in the summer when smaller birds used perched on the arrays in their shade. The researchers suggest that if commercial anti-perching devices were installed, they might reduce BHI at PV installations further. These factors, combined with the fact that smaller-bodied birds tended to use PV arrays suggest that PV arrays may actually reduce bird strike danger at airports. Given that airports have a lot of open space and their buildings and other infrastructure use a lot of electricity, installing more solar panels at airports seems like a wise use of space.

Airports + Solar: A wise use of space, but how do birds factor in?

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