Public Power - July/August 2008 - (Page 21)

improve its ability to be dispatched. Utilityscale plants now have the technology to use molten salt or other liquids as energy storage media capable of holding temperatures up to 700 degrees F. “That way, you can provide power for another six hours after sundown,” enabling concentrating solar power to compete in off-peak markets, said Solar Energy Industries Association’s Hanis. Because it can be dispatched more readily, “storage is the technology that can make solar thermal very valuable,” said Cara Libby, a project manager at EPRI’s Office of Innovation. Storage needs to last 12 hours to compete at base load, said National Renewable Energy Laboratory’s Margolis, but four to six hours of storage would be enough to help the industry get some of the experience it needs. DOE wants to use storage to enable concentrating solar power to become base load competitive by 2020, he said. Although there’s been some experimentation in the United States, a facility in Spain will probably be the first commercial plant to give molten salt a try. Nevada’s Solar One is expected to experiment with it. Molten salt is slated to be a feature of Arizona Public Service’s $1 billion-plus, 280MW Abengoa concentrating solar power plant near Phoenix. Some experts question whether molten salt is the best long-term approach, while others think it could also serve as the heat transfer fluid used in the collector field. Using molten salt directly in the collectors would save the cost of heat exchangers used between the collectors and storage. But because molten salt has a high freezing temperature, there is potential for the salt to freeze in the field at night, said Chuck Kutscher, another National Renewable Energy Laboratory expert. If that happens, thawing it out properly could be tricky. “The bottom line with storage is APS said it would not purchase concentrating solar power without it,” Kutscher said. “They want their solar power to deliver electricity well into the evening hours after people get home from work.” But storage is not an absolute requirement for every concentrating solar power project, he said. In the nearterm, some utilities may be satisfied using it www.APPAnet.org only to address daytime peaks. Concentrating solar power’s future largely depends on the federal investment tax credit. “While analysts have acknowledged recent growth and remain bullish about the future of solar energy, this growth will be disrupted if the solar investment tax credit expires,” according to Solar Energy Industries Association. As passed in 2005, utilities do not qualify for the investment tax credit. Third parties develop and own concentrating solar power plants and supply power to utilities under power purchase agreements. “It’s of interest to utilities to have these assets not only to guarantee their energy costs over decades, but also to own an asset that has a good return on equity,” said Solar Energy Industries Association’s Hanis. Many recently signed power purchase agreements have exit clauses if the investment tax credit is not renewed. Although photovoltaic systems benefit from state incentives, the future of the investment tax credit will also affect the photovoltaic market. Navigant Consulting estimates that without the investment tax credit, demand for photovoltaic systems in 2009 will total 325 MW, compared to 790 MW if it stays. Direct investment of about $4 billion would be cut in half, as would 40,000 projected direct and indirect photovoltaic industry jobs. Expiration could also accelerate a decline in photovoltaic industry employment rates that Navigant already expects due to increased automation in manufacturing and maturing installation practices. American Solar Energy Society said there were 6,800 direct jobs in the photovoltaic industry in 2006, plus another 800 in the solar heating sector, while it gave no figure for concentrating solar power. Photovoltaic cells of semiconductors absorb photons and convert them directly to electric current. First generation cells include two semiconductor layers, one infused with boron and the other with phosphorus. They join at the “p-n junction” through which flow electrons excited by light. Powerful Network.org What is it? PowerfulNetwork.org is an online resource portal for electric utility professionals and vendors that are looking to buy and sell electric utility products and services. E-mail powerfulmarketing@APPAnet.org with questions on using or participating on PowerfulNetwork.org. JULY-AUGUST 2008 21 http://www.APPAnet.org

Table of Contents Feed for the Digital Edition of Public Power - July/August 2008

Public Power- July/August 2008 Contents Perspective 10 Questions Solar Energy Rising Sacramento's Solar Shares Gainesville Crowns a Conservation Idol By the Numbers Curbing Costs of Outages Reliability Green Energy Hometown Connections Customer Service Parting Shot

Public Power - July/August 2008

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