An innovative new twist on solar rooftop panels may lead to a renewable power system thats both more efficient and cheaper.
The proposed system, developed at Duke University, is designed so that sunlight is harnessed to produce hydrogen, which -- oddly enough -- should allow for more energy to be converted into electricity than standard photovoltaics.
Nico Hotz, an engineering professor, demonstrated the effectiveness of his system by pitting it against other solar-power technologies in a head-to-head comparison. During a trial in February and July, he found that the system achieved exergetic efficiencies of 28.5 percent in the summer and 18.5 percent in the winter. This was a vast improvement over conventional systems which was only 5 to 15 percent efficient during the summer and 2.5 to 5 percent in the winter.
And compared to some of the other alternatives such as a standard photovoltaic system, a photovoltaic cell-based system that includes battery storage and a similar photocatalytic hydrogen system, the technology is also the most affordable.
"We performed a cost analysis and found that the hybrid solar-methanol is the least expensive solution, considering the total installation costs of $7,900 if designed to fulfill the requirements in summer, although this is still much more expensive than a conventional fossil fuel-fed generator," Hotz said.
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The paper describing the results of Hotz's analysis was named the top paper during the ASME Energy Sustainability Fuel Cell 2011 conference in Washington, D.C.
The "hybrid" system works a little something like this:
The energy from sunlight is collected and used to heat a combination of water and methanol in a maze of tubes on a rooftop. The tubes, made from copper, are coated with a thin layer of aluminum and aluminum oxide and partly filled with catalytic nanoparticles. This unique set-up is what allows up to 95 percent of the sunlight to be absorbed and heat the water at temperatures of well over 200 degrees Celsius.
Once the evaporated liquid achieves these higher temperatures, tiny amounts of a catalyst are added, which produces hydrogen. The combination of high temperature and added catalysts produces hydrogen very efficiently, Hotz says.
The resulting hydrogen can then be immediately directed to a fuel cell to provide electricity to a building during the day, or compressed and stored in a tank to provide power later.
Issues to consider
Although the roof-mounted system may be able to supply all the building's energy needs in the summer, it might not be enough for winter. But if you take in consideration that if the system was built large enough to supply all of a winter's electrical needs, it would produce then produce excess energy during the summer, which can be sold back to the electrical grid.
(via Press Release)
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