sci.energy

Scientists are now trying to design solar panels using
nanostructures that work like leaves, but better. The goal is 30
percent efficiency in converting sunlight into power – much higher
than the efficiency of biofuels.

“The corn organism is 3 percent efficient in harvesting the energy of
the sun,” Ratner said. “You’ve got to do better than that.” Miscanthus
grass, another source of biofuel, is less than 5 percent efficient.

While conventional solar panels made from silicon are about 18 percent
efficient, “the cost involved in making them is so high,” he said,
“that they’d have to run for several years just to pay back the energy
cost in making them.”

Nanostructures, on the other hand, would use inexpensive materials to
capture sunlight. That’s where the blue jeans and house paint come in.

In artificial photosynthesis, you need a molecule to absorb the
sunlight, but not any molecule will do. (See accompanying video for an
explanation of how photosynthesis works.)

“The molecules that we probably want to use are related to the blue
jean dye that you’ve got,” Ratner said. “It’s a planar molecule, it
has the right shape and it has the right energy properties.”

The dye is called a thalocyanine and is also found in shoe polish.

Once the molecules capture solar energy, that energy must be stored
somewhere – otherwise, it will be given off as heat. White house paint
contains titanium dioxide, and when mixed with the dye molecules,
titanium dioxide holds on to the energy the dye collects.

Turning concept into reality

The next challenge is to develop the right kind of wire to get the
energy back out of the paint and dye mixture.

“Right now, that’s a bottleneck,” Ratner said. “Nobody’s found the
right wire to be compatible with this whole thing.”