Solar cell technology has been making alot of progress in the past two years. Nanotech is steadily increasing the efficiency. Might be up to a potential of 60% efficiency or more.
Here are two new great advances. Solar might actually get efficient enough this decade to be a viable complementary energy source to fossil fuels. Good stuff coming out of our national labs.
trnmag.com
One way to make solar cells more efficient is to find a material that will capture energy from a large portion of the spectrum of sunlight -- from infrared to visible light to ultraviolet.
Energy transfers from photons to a photovoltaic material when the material absorbs lightwaves that contain the same amount of energy as its bandgap. A bandgap is the energy required to push an electron from a material's valence band to the conduction band where electrons are free to flow.
The trouble is, most photovoltaic materials absorb a relatively narrow range of light energy. The most efficient silicon solar cells capture about 25 percent of the sun's energy. Multijunction solar cells combine several materials to capture multiple bands of photonic energy. Today's most efficient combination -- germanium, gallium arsenide and gallium indium phosphide -- boosts efficiency to 36 percent, but is relatively difficult to make and therefore expensive.
Researchers from Lawrence Berkeley National Laboratory, the University of California, and the Massachusetts Institute of Technology have engineered a single material that contains three bandgaps. The material is capable of capturing more than 50 percent of the sun's energy, said Wladek Walukiewicz, a senior staff scientist at the Lawrence Berkeley National Laboratory.
trnmag.com
Researchers from Los Alamos National Laboratory have tapped the efficiencies of nanotechnology to increase solar cells' potential energy production by as much as 37 percent.
Solar cells generate electricity by absorbing photons and directing the resulting energy to move an electron from the low-energy valence band in a material to a higher-energy conduction band where it is free to flow.
Researchers working to squeeze more energy from sunlight are generally aiming for solar cells that can absorb and use a higher percentage of the wavelengths of light in the sun's spectrum. Today's commercial solar cells can use anywhere from 10 percent to 35 percent.
The Los Alamos researchers have found that it is possible to increase a cell's energy production by making each photon move two electrons. "Carrier-multiplication-enhanced solar cells can, in principle, produce twice as large a current as conventional solar cells," said Victor Klimov, a team leader at Los Alamos National Laboratory.
The method could increase what has been thought of as the maximum power conversion of solar cells by as much as 37 percent, depending on the materials used, resulting in a solar cell with a potential efficiency of over 60 percent. The method could also be used to increase the efficiency of other optical components, including amplifiers, lasers, switches and light absorbers, according to Klimov. |
