The Pros, Cons of Solar, Wind

Aug. 18, 2010
The FAA Tech Center’s Jim Patterson gives an update on the pros and cons of solar, wind technology.

ARLINGTON, VA — During a meeting of regulators, airports, and consultants held here in July, Federal Aviation Administration airport safety specialist Jim Patterson, Jr. shared what his team at the agency’s Hughes Technical Center have learned during a six-year investigation into alternative energies. While much has happened with solar research, he relates, battery storage remains an issue. With wind turbines, size and noise, and the subsequent interference with radar, are issues. Speaking to planners here, Patterson explains that solar and wind have a place at airports, and a place in long-term master plans. Much of what the FAA team has learned will be incorporated into an upcoming guidance document, expected to be out later this year.

The presentation was part of the annual ACC/FAA/TSA Summer Workshop Series, an annual meeting which covers various aspects of aviation, airports, security, and regulatory issues.

Patterson relates that the Hughes Technical Center’ research development group began some six years ago to investigate solar for airfield lighting applications, dealing with the lights on the runways and taxiways. “We were trying to find ways to harness the sun for later use when the sun goes down,” he says. “We started really small with self-contained, light-emitting diode (LED) solar-powered units with no wires.”

As the technology brought more power and luminance, the tech group moved to the runway environment. “Now we’re at the point where some of the manufacturers are creating self-contained units that are so powerful that they actually meet FAA standards for medium intensity runway lights. Over the past few years we’ve seen the technology come a long way; it’s lending itself better to airfield applications.”

Patterson says that light-emitting diodes are attractive because they are bright while using minimal power. “We do have some scenarios where self-contained units aren’t necessarily the best,” he adds. “Maybe we need to take it to the next level, where we’re talking about a full-scale solar array with several photo-voltaic panels and large battery banks and radio communication. We focus more on the airport surface itself.”

For solar, a primary constraint an airport has is to be careful where it puts solar panels — keeping clear of the airport surface where aircraft are operating, according to Patterson. He says that originally there were some concerns within FAA regarding glare that might be generated from the face of the solar panels. “At all of the installations that we have thus far it hasn’t been an issue for any pilots,” he says. “We’ve also not had any complaints from air traffic control facilities. The thought process there was you have a controller in a tower cab that might at a particular angle pose an annoying reflection. Those are kind of myths, if you will.”

The leading challenge with solar today remains battery storage, says Patterson — that is, storing energy during the day for use at night. Much progress is being made, he says, and manufacturers are testing new battery technologies.

“There are all kinds of different rechargeable technologies out there,” he explains. “But that is one of the biggest problems when we talk about airport lighting applications. Yes, we have all this available sun on a nice flat surface; but when the sun goes down we have to go to an alternative source.

“So, all during the day we’ll have to have banked this energy. Really the only way to do that is through the use of battery banks. And you are talking about a lot of batteries. When you consider the lifespan of a solar system, batteries are your weakest link. The solar panels will last 20 to 30 years; the electronics come with ten- to 20-year warranties.

“We haven’t really seen any major efforts to any storing or saving of this energy for use later in the night. I still see that as a technology challenge that we’ll continue to investigate.”

He points out that one of the “downfalls” of self-contained LED units is again the battery, which generally gives way before other parts of the units fail.

Wind Turbines

Wind presents different challenges, says Patterson. The noise of the units is one; another is location, or siting.

“The first thing that comes to mind is the interference with airborne radar, and that could be anything from the radar that’s looking for airborne aircraft or with aircraft on the ground at the airport with ground surveillance systems,” he explains. “You have to be really careful; these turbines create a lot of noise and disturbance with airborne radar; the radar picks up different signals from the turbine as it’s rotating and as it changes its orientation to align with the wind. It’s constantly changing and there’s just no way of isolating that noise that the radar is picking up.”

There are also concerns about obstruction lighting, he says — if a lot of turbines are planned, there could be a situation with obstruction lights.He says that several years ago FAA completed an in-depth study at 14 wind turbine farms to see how they were being lit. “After doing our tour of the country and seeing all of these different sites,” he says “we were able to develop a good, safe configuration for lighting these wind turbine farms. As a result we were able to greatly reduce the number of lights that were required.”

FAA built a test site at Lawton, OK at the Blue Canyon Wind Farm, called the largest of its kind, which had 43 turbines. “We lit just a few at key locations and [today] 13 of the 43 turbines actually have lights on them,” he says. “We required that they all blink at the same time, so the pilot has the feel that it’s a farm — not just a bunch of wind turbines but a large area to avoid as a hazard.”

Another concern is the impact of wind turbines on wildlife, particularly birds. Reducing the number of lights can help make the turbines less attractive to the birds, says Patterson.

“The other big thing with wind turbines would be siting. The majority of turbine designs are very tall — upwards of 200 feet tall. We’re looking at new ones coming out that will be over 500 feet tall. Tall turbines create some issues with object-free zones and imaginary surfaces that we need to keep clean for arriving and departing aircraft.”

That said, he points out that Boston Logan International recently installed some 20 six-foot high wind turbines atop an administration building to harness the energy coming off the adjacent bay. “It was kind of a perfect-sized turbine to lend itself for an airport application,” he comments.

Master Plans

All these considerations, says Patterson, can be taken into account for future master planning. “Limitations on the technology and siting issues are something that airports can work into their master plans to make them more sustainable,” he suggests.

“If I had a favorite it’s probably solar just because we don’t have rotating blades that we have to hide from our radar facilities. There’s always that chance new technology will come out and wind turbines will become more airport-friendly. There’s always that chance.

“We have several research efforts to address that. One is a localized radar system, a sensor, that we can put at the wind turbine that would actually provide radar coverage in that immediate area. There’s a chance that we can take that radar feed and feed it back to the FAA’s airport radar and, between the two communicating, they would be able to eliminate or filter out that noise being created by the turbine, and actually give us full coverage without interference.”

He adds that there’s also work underway with the Military Academy at West Point trying to develop a stealth wind turbine that couldn’t be detected by radar. “If that came forward it would be earth-shattering,” he says. “It would definitely make wind more compatible and something an airport could put in its master plan.”

Future Guidance from FAA

FAA is in the process of developing a Solar Guidance Document, under development by Harris Miller Miller & Hanson (HMMH). Patterson says that at the end of the day it could take the form of an Advisory Circular. It will be a central reference document for airports interested in exploring solar energy, he explains, with baseline information on solar technology and applications.

It will also include FAA requirements and procedures to ensure no risk to pilots, controllers, or operations, as well as case studies and details on FAA funding programs. It is expected to be available to airports by the end of 2010.