Auckland, New Zealand [RenewableEnergyAccess.com]
Solar cell technology developed by Massey University’s Nanomaterials Research Centre in New Zealand may one day enable the country’s residents to generate electricity from sunlight at a tenth of the cost of current silicon-based photovoltaic solar cells. Dr. Wayne Campbell and researchers in the Centre have developed a range of colored dyes for use in dye-sensitized solar cells.
The synthetic dyes are made from simple organic compounds closely related to those found in nature.
Green dye is synthetic chlorophyll derived from the light-harvesting pigment plants use for photosynthesis. Other dyes being tested in the cells are based on haemoglobin, the compound that gives blood its color.
Unlike the silicon-based solar cells currently on the market, says Dr. Campbell, the 10x10cm green demonstration cells generate enough electricity to run a small fan in low-light conditions — making them ideal for cloudy climates. The dyes can also be incorporated into tinted windows that trap to generate electricity.
According to Dr. Campbell, the green solar cells are more environmentally friendly than silicon-based cells as they are made from titanium dioxide — a plentiful, renewable and non-toxic white mineral obtained from New Zealand’s black sand. Titanium dioxide is already used in consumer products such as toothpaste, white paints and cosmetics.
“The refining of pure silicon, although a very abundant mineral, is energy-hungry and very expensive. And whereas silicon cells need direct sunlight to operate efficiently, these cells will work efficiently in low diffuse light conditions,” Dr. Campbell says.
“The expected cost is one-tenth of the price of a silicon-based solar panel, making them more attractive and accessible to home-owners.”
The Centre’s new director, Professor Ashton Partridge, says they now have the most efficient porphyrin dye in the world and aim to optimize and improve the cell construction and performance before developing the cells commercially.
“The next step is to take these dyes and incorporate them into roofing materials or wall panels. We have had many expressions of interest from New Zealand companies,” Professor Partridge says.
He says the ultimate aim of using nanotechnology to develop a better solar cell is to convert as much sunlight to electricity as possible.
“The energy that reaches earth from sunlight in one hour is more than that used by all human activities in one year,” said Partridge.
The solar cells are the product of more than 10 years research funded by the Foundation for Research, Science and Technology.
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‘Nano-Manhattan’ 3D solar cells boost efficiency
Unique three-dimensional solar cells that capture nearly all of the light that strikes them could boost the efficiency of photovoltaic (PV) systems while reducing their size, weight and mechanical complexity.
The new 3D solar cells capture photons from sunlight using an array of miniature “tower” structures that resemble high-rise buildings in a city street grid. The cells could find near-term applications for powering spacecraft, and by enabling efficiency improvements in photovoltaic coating materials, could also change the way solar cells are designed for a broad range of applications.
“Our goal is to harvest every last photon that is available to our cells,” said Jud Ready, a senior research engineer in the Electro-Optical Systems Laboratory at the Georgia Tech Research Institute (GTRI). “By capturing more of the light in our 3D structures, we can use much smaller photovoltaic arrays. On a satellite or other spacecraft, that would mean less weight and less space taken up with the PV system.”
The 3D design was described in the March 2007 issue of the journal JOM, published by The Minerals, Metals and Materials Society. The research has been sponsored by the Air Force Office of Scientific Research, the Air Force Research Laboratory, NewCyte Inc., and Intellectual Property Partners, LLC. A global patent application has been filed for the technology.
The GTRI photovoltaic cells trap light between their tower structures, which are about 100 microns tall, 40 microns by 40 microns square, 10 microns apart — and built from arrays containing millions of vertically-aligned carbon nanotubes. Conventional flat solar cells reflect a significant portion of the light that strikes them, reducing the amount of energy they absorb.
Because the tower structures can trap and absorb light received from many different angles, the new cells remain efficient even when the sun is not directly overhead. That could allow them to be used on spacecraft without the mechanical aiming systems that maintain a constant orientation to the sun, reducing weight and complexity – and improving reliability.
“The efficiency of our cells increases as the sunlight goes away from perpendicular, so we may not need mechanical arrays to rotate our cells,” Ready noted.
The ability of the 3D cells to absorb virtually all of the light that strikes them could also enable improvements in the efficiency with which the cells convert the photons they absorb into electrical current.
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