Energy harvesting for future UAVs (US Air Force experimenting with solar-powered "drones.")

[OKIsItJustMe]

http://www.wpafb.af.mil/news/story.asp?id=123152369

Energy harvesting for future UAVs

by Maria Callier
Air Force Office of Scientific Research

6/3/2009 - ARLINGTON, Va. -- Dye-sensitized solar cells (DSSCs) are expected to power Air Force unmanned aerial vehicles (UAVs) in the future because they are an optimum energy harvesting source that may lead to longer flight times without refueling.

The University of Washington's Multidisciplinary University Research Initiative (MURI) project team, with lead researcher Dr. Minoru Taya is working on airborne solar cells by using a flexible film and a thin glass coating with transparent conductive electrodes. He has found that DSSCs 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 worked and in fact, enabled the plane to fly.

"These kinds of solar cells have more specific power convergence efficiency (PCE), 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," said Taya.

The team is currently working on DSSCs with higher PCEs using bioinspired dyes, which are installed in the wings of the UAV (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 UAV flight times," said Taya.

In the meantime, the engineers are researching the challenges of DSSCs' 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.

"Some of these challenges will be overcome by the researchers working under this AFOSR MURI within the next two years. In order to make the DSSCs' solar energy harvester transferable to the wings of an UAV, additional engineering tasks remain, which may require another project to be funded for five additional years," Taya said.

In the end, the team hopes to reach their goal of developing large, flexible DSSCs 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 DSSCs while maintaining high efficiency.

[HillbillyBob]

1. Now why can't these cells be applied to roofs of houses and

electric cars etc?
My house has 2,000+ feet of roof. We have gone on and energy diet starting several years ago at our previous place where we were renting. That place we cut the power use by about 30% over 4 years (I m an hiv patient so I'm not exactly able to gogogo like I used to). I put a solar powered attic fan and mylar sheeting on the attic floor, that immediately cut our power use for A/C in the summer and lowered the temp inside by 10 degrees. Our power bill totaled about 350 or 375 in the summer and they went down by about 100$. I did other small things like heavy shades that I opened and closed even in winter. In winter I could leave the North side shades closed but open the shades on the south side and did not need heat during the day.

We bought this place 2 1/2 years ago. Though it has no attic I have foam insulated under the sinks where pipes and wires come through. Low flow faucets and shower heads, double insulated the water heater. I still need to insulate the crawl space walls like I did at the other house. I am just not able bodied enough to get under this house as its a lower space. I put foam insulation around the window frames as the original builder did not. Gaskets in the switch and outlet covers, even the light fixtures(part of them anyway). We have replaced the dishwasher with an Energy Star(dw saves water and power using on full loads), also a front load washer (prop the door open to let it dry out!).

If we all did all these little things that even a disabled person can do we could save so much money and energy. Our power bill is 160 170$ and we are not needing ac this summer and we would have had it on for 3 months now at a cost of 350 450$ per month. I am using fans in the windows and changing the direction pulling cooler air from the shaded side of the house. Plus the heavy drapery liners and mylar on the windows. We have to do something about the lack of ceiling insulation there is only 3 inchs in a 12 inch space. The roof is dark shingles and I have about half of it painted with high reflective white paint. I just had surgery 6 weeks ago and dr does not want me climbing a ladder yet.

Our high use was 33,000 kilowatt hours per month, now they are 1100. The goal is 500 and to be able to put in some solar systems. A separate dedicated for the well, for irrigation from the spring and roof rain harvest for the orchard and veggie gardens. We have a solar water heater to install(when Im strong enough and can afford the balance of system) it will also be independent solar powered circulation pumps, it will also drive warm water underfloor heat.

Our main car is also a high miler Nissan(goes too fast all the time..but Im not the one who has gotten a ticket!) 35 mpg. We garden organically (but have yet to find organic fire ant killer), buy local as much as possible, least packaging, least impact.

It is not an over night life change it has taken seven or eight years to get here.
Its not that hard just add a habit at a time.

Now when are those solar cells going to be available and affordable for the public to buy and use?

[OKIsItJustMe]

2. "Now when are those solar cells going to be available and affordable for the public to buy and use?"

Is today soon enough?

http://en.wikipedia.org/wiki/Dye-sensitized_solar_cell#Market_introduction