MIT’s Technology Review reports that a study of solar arrays in actual operation shows poorly designed or faulty inverters—devices that convert the DC power produced by solar panels to AC power—can dramatically lower net power output. In one case, inverters were found to be consuming hundreds of watts at night, reducing overall power output by 40 percent. High temperatures caused inverter faults and, because the inverters had to be reset manually, about half the time when the sun was shining the array was producing no power.
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The MIT tech magazine said the the study also found the common practice of linking solar panels in an array to a single inverter means that a problem with one panel in the array causes the sntire system’s output to go down. Inverter-related problems suggest solar arrays might produce nowhere near what they’re supposed to and solar power may prove even more expensive than expected, the study concluded.
One option is to install automatic disconnect circuits, which can cut down on parasitic losses. Presumably inverters that reset automatically after temperature faults—or that can operate better in high temperatures—would also help. Several companies are also developing micro-inverters or other electronics so that if one panel has problems, the rest aren’t affected.
Solar PV on a Roll
Xunlight Corp. successfully demonstrated a high-throughput, wide-web, roll-to-roll photovoltaic manufacturing process to produce high-efficiency thin-film silicon PV modules.
 Xunlight co-founders, Dr. Xunming Deng and Dr. Liwei Xu, hold a 36-cell panel. |
Using its three-foot wide manufacturing line, Xunlight produced 3ft by 5ft and 3ft by 18ft flexible PV modules. The 3ft by 5ft modules demonstrated 8.77 percent initial aperture-area efficiency. After extended light exposure efficiency is expected to stabilize at 7.4 percent.
Toledo, Ohio-based Xunlight develops flexible and lightweight thin-film silicon solar modules. Roll-to-roll manufacturing allows triple-junction thin-film silicon solar cells to be produced on rolls of thin stainless steel substrates, three feet wide and up to one mile long. The stainless steel web is guided through a series of vacuum chambers where nine semiconductor layers are deposited using a plasma enhanced chemical vapor process, and back-reflector and top electrode layers using a sputtering process. Altogether the layers measure around one hundredth the thickness of a sheet of paper.
Xunlight designed, developed, engineered and built its own manufacturing equipment with the help of the University of Toledo’s Thin Film Silicon Photovoltaic Laboratory. Xunlight is backed by $40 million worth of private equity investments from Emerald Technology Ventures, Trident Capital, NGP Energy Technology Partners and Rabo Ventures. Another $20 million in financial support came from the State of Ohio, the U.S. Department of Energy and the U.S. Department of Commerce.
Future Natural Gas Close to Home
Gas hydrates have long excited hydrocarbon geologists. Made up of natural gas and water, these hydrates are thought to exist in great abundance in nature and have the potential to be a major new energy source.
Until recently, however, little proof has existed that gas hydrates could be found in economically viable quantities and locations.
That changed with word in June from the U.S. Geological Survey that the U.S. Gulf of Mexico holds thick and concentrated gas-hydrate-bearing reservoir rocks, which have the potential to produce gas using current technology.
Recent drilling by a government and industry consortium confirm the Gulf of Mexico as the first offshore area in the United States with enough information to identify gas hydrate energy resource targets that have a potential for gas production.
“This is an exciting discovery because for the first time in the U.S. Gulf of Mexico, we were able to predict hydrate accumulations before drilling and we discovered thick, gas hydrate-saturated sands that actually represent energy targets,” said U.S. Geological Survey Energy Program Coordinator Brenda Pierce.
In the case of two offshore exploration sites—the Walker Ridge and Green Canyon drill sites—gas-hydrate-bearing sand reservoirs between 50- and 100-feet thick were discovered. Discovering concentrated gas hydrates in sand reservoirs is making Walker Ridge and Green Canyon prime locations for future research drilling, coring and production testing.