Friday, April 18, 2008

Of Necessity

Over the last few years, I have reported on the development of all kinds of third generation photon to electron materials. However, one of the possible pathways to a solid state world, dye-sensitive cells, although theoretically very inexpensive, have also been very, very low in efficiency.

Thanks to Renewable Energy News, here is a development from the University of Washington that may change that:

Popcorn-ball Design Doubles Efficiency
of Dye-Sensitized Solar Cells
by Hannah Hickey, University of Washington

A dramatic improvement in the efficiency rates of dye-sensitized solar cells (DSC) has been discovered in Washington. Researchers at the University of Washington (UW) have found that by using a popcorn-ball design -- tiny kernels clumped into much larger porous spheres -- they have the ability to manipulate light and more than double the efficiency of converting solar energy to electricity.

"We think this can lead to a significant breakthrough in dye-sensitized solar cells," said researcher Guozhong Cao, a UW professor of materials science and engineering.

Dye-sensitized solar cells, invented by Michael Gr├Ątzel and Brian O'Regan in 1991, are more flexible, easier to manufacture and cheaper than existing solar technologies.

Researchers have tried to increase efficiencies by varying the surfaces of the cells, making them rougher, and have achieved higher and higher efficiencies. Current lab prototypes can convert just over one tenth of the incoming sun's energy into electricity. clip

One of the main quandaries in making an efficient solar cell is the size of the grains. Smaller grains have bigger surface area per volume, and thus absorb more rays. But bigger clumps, closer to the wavelength of visible light, cause light to ricochet within the thin light-absorbing surface so it has a higher chance of being absorbed.

"You want to have a larger surface area by making the grains smaller," Cao said. "But if you let the light bounce back and forth several times, then you have more chances of capturing the energy."

Other researchers have tried mixing larger grains in with the small particles to scatter the light, but have had little success in boosting efficiency. The University of Washington group instead used only very tiny grains, about 15 nanometers across. (Lining up 3,500 grains end to end would equal the width of a human hair.)

Then, they clumped these into larger agglomerations, about 300 nanometers across. The larger balls scatter incoming rays and force light to travel a longer distance within the solar cell. The balls' complex internal structure, meanwhile, creates a surface area of about 1,000 square feet for each gram of material. This internal surface is coated with a dye that captures the light.

The researchers expected some improvement in the performance but what they saw exceeded their hopes.

"We did not expect the doubling," Cao said. "It was a happy surprise." more

It would be a happy surprise if this kind of research

was funded with say a month of war.

That 10 billion might provide a lot of surprises.

If we just end the war a year sooner,

that 120 billion dollars at 1.00/ watt (now 3.00) would provide

120,000 MWs of solar,

More capacity than Texas,

Enough energy for 20 million homes. (@12,000 Kwh/year)

Continuing to place our faith and resources in armaments and guns

is not a sadly serious certainty.

And placing our confidence and energy in the tools of peace

should not be viewed as a happy surprise.

For we must move from War to Peace,

not as a matter of choice.

But of Necessity.



Blogger katecontinued said...

Oz, I am so grateful for your posts. I grapple with electronic and technical articles. I don't think it is my intellect, I think it is my internalized resistance - culturally learned. But, I get information in spite of this because I keep coming back here. I also know if I don't understand something I can nose around in your 'stacks' or just ask in the comments. Thanks for being there.

8:53 AM  

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