Research officials study energy harvesting for future unmanned aircraft

  • Published
  • By Maria Callier
  • Air Force Office of Scientific Research
ARLINGTON, Va. (AFNS) --  The University of Washington's Multidisciplinary University Research Initiative project team is working on airborne solar cells that are dye-sensitized solar cells and expected to power Air Force unmanned aircraft in the future because they are an optimum energy harvesting source that may lead to longer flight times without refueling. 

Dr. Minoru Taya, the lead researcher, and the team are working on the airborne solar cells by using a flexible film and a thin glass coating with transparent conductive electrodes. 

He has found that dye-sensitized solar cells made from organic materials, which use (dyes) and moth-eye film, are able to catch photons and convert them into synthesized electrons that can harvest high photon energy.

A few years ago, the team mounted dye-sensitized solar cells on the wings of a toy airplane. The propeller was effectively powered, but the plane was not able to become airborne because the glass based solar cells they were using were too heavy. Upon experimentation, they decided to use film battery technology, which enabled the plane to fly.

"These kinds of solar cells have more specific power convergence efficiency, very clean energy and easy scalability to a larger skin area of the craft, as well as, low-temperature processing, which leads to lower costs overall," Doctor Taya said.

The team is currently working on dye-sensitized solar cells with higher power convergence efficiencies using bioinspired dyes, which are installed in the wings of unmanned aircraft (airborne energy harvesters).

"Any airborne energy harvester must satisfy additional requirements, like weight and durability in airborne environments. If those are met, then there may even be longer (unmanned aircraft) flight times," Doctor Taya said.

In the meantime, the engineers are researching the challenges of dye-sensitized solar cells' technology and are seeking to learn how durable they are and how well their technology may integrate with other Air Force vehicles. The team is also trying to determine how to build the solar cells in the wing surface of the aircraft and how to store energy harvested from them.

In the end, the team hopes to reach their goal of developing large, flexible dye-sensitized solar cells with higher energy conversion efficiency. Generally, solar cells that are larger have decreased efficiency. Therefore, the team is using a metal grid, which has high surface resistance and can accelerate electron transport for larger-sized flexible dye-sensitized solar cells while maintaining high efficiency.