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news digest ♦ Solar


on the deployment of critical on-orbit capability,” says Brad Clevenger, General Manager of Emcore’s Photovoltaics Division. “We appreciate the opportunity to contribute to this important mission for NASA and the U.S. Geological Survey and we look forward to seeing LDCM’s many contributions to earth science.”


AV Solar Ranch One CdTe plant achieves 100 MW


California’s largest operating PV power plant will reach 230 MW once completed this year


First Solar has announced that the Antelope Valley Solar Ranch One project has achieved a peak generating capacity of 100 megawatts (MW)AC connected to the electrical grid.


The project, which is under construction in northern Los Angeles County, is currently California’s largest operating photovoltaic (PV) power plant and will have a generating capacity of 230 MWAC upon completion, expected later this year.


AV Solar Ranch One is California’s largest operating PV solar power plant, under construction in LA.


“Unlike traditional power plants, the modular nature of PV power projects enables us to quickly add substantial volumes of clean energy to the grid throughout the construction process. This shorter ‘time to energy’ is another key advantage of PV solar electricity,” Moore continues.


Dennis Hunter, Deputy Director of Los Angeles County Public Works, congratulated First Solar on its achievement at Antelope Valley Solar Ranch One. “We appreciated the opportunity to work with the First Solar team to reach this operational milestone.”


When fully operational, the facility will generate enough power for 75,000 average California homes and will displace about 140,000 tons of carbon dioxide per year. That’s equivalent to taking 30,000 cars off the road on an annual basis.


GaAs quantum dots


assemble themselves Quantum dots can self-assemble at the apex of a GaAs/ AlGaAs (gallium arsenide/aluminium gallium arsenide) core/ shell nanowire interface. This breakthrough could bolster quantum photonics and solar cell efficiency


Scientists from the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) and other labs have demonstrated a process where quantum dots can self- assemble at optimal locations in nanowires.


This breakthrough could improve solar cells, quantum computing, and lighting devices.


Quantum dots are tiny crystals of semiconductor a few billionths of a metre in diameter. At that size they exhibit beneficial behaviours of quantum physics such as forming electron-hole pairs and harvesting excess energy.


The researchers demonstrated how quantum dots can self- assemble at the apex of the GaAs/AlGaAs core/shell nanowire interface.


Cadmium telluride solar modules installed at AV Solar Ranch One


Initial construction on the solar project began in September 2011 and module installation started in June 2012, providing an average of 400 jobs during the construction phase. Power from the plant is being purchased by Pacific Gas and Electric Company under a 25-year contract.


“We are proud to achieve this important clean energy milestone for California, which was made possible by the tireless efforts of hundreds of individuals working together. We especially appreciate the support of LA County’s Fifth Supervisorial District staff and the departments of Regional Planning and Public Works for their contributions to making this project a success,” says Lou Moore, First Solar Senior Vice President of Engineering, Procurement and Construction.


104 www.compoundsemiconductor.net March 2013


Crucially, the quantum dots, besides being highly stable, can be positioned precisely relative to the nanowire’s centre. That precision, combined with the materials’ ability to provide quantum confinement for both the electrons and the holes, makes the approach a potential game-changer.


Electrons and holes typically locate in the lowest energy position within the confines of high-energy materials in the nanostructures. But in the new demonstration, the electron and hole, overlapping in a near-ideal way, are confined in the quantum dot itself at high energy rather than located at the lowest energy states. In this case, that’s the GaAs core. It’s like hitting the bulls-eye rather than the periphery.


The quantum dots, as a result, are very bright, spectrally narrow and highly anti-bunched, displaying excellent optical properties even when they are located just a few nanometres from the surface - a feature that even surprised the scientists.


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