Solar Performing Brilliantly

Utilities are using solar thermal and PV rooftop networks to power their communities.

by Nancy Spring, Managing Editor

From coast to coast, utilities in the U.S. are putting the sun to work. With large scale solar thermal projects and photovoltaic rooftop installations, the promise of solar power—abundant, clean and renewable energy—is finally being realized, generating power for the grid that can be measured in megawatts not just kilowatts.

SMUD’s first solar array, PV-1, the first utility-scale solar array in the nation, sits in the foreground of the cooling towers at the decommissioned Rancho Seco Nuclear Station. Since PV-1 was constructed in 1984, five more arrays have been built at the site, producing 3.2 MW. Photo: Click here to enlarge image

According to the Solar Energy Industries Association, the solar market in the U.S. is booming. In 2007, the amount of solar power coming on-line increased 55 percent from the year before. More importantly from the standpoint of the electric utility sector, SEIA reseach shows that installations of grid-connected PV systems have been growing faster than off-grid systems since 2001, surpassing them in 2005.

One of the largest U.S. solar installations completed in 2007 is the 64 MW Nevada Solar One project located near Las Vegas, Nevada. Solar One, which went on-line in June 2007, is the largest concentrating solar power (CSP) project built in the last 17 years. Owned by ACCIONA Energy, a subsidiary of Madrid, Spain-based ACCIONA SA, the $266 million project is the third largest concentrating solar power plant in the world. Power contracts have been signed with Nevada Power Co. and Sierra Pacific Power Co.

But these facts and figures pale in comparison to what we expect to see in solar power in the near future.

Fourteen CSP plants with an estimated total of 4,000 MW are in the planning stages today. Many of those projects are in the Southwest, where some analysts believe 200 GW of CSP potential awaits development, but utilities all across the country are looking at CSP facilities:

  • In California, PG&E has entered a purchase power agreement with a 106.8 MW CSP plant that will use parabolic trough-shaped mirrors to concentrate the sun’s heat.
  • In Florida, FPL plans to build a 75 MW CSP facility at the site of one of its gas-fired plants near Lake Okeechobee.
  • The Long Island Power Authority in New York plans to add 50 MW of solar capacity in the near future.

      According to eSolar, a company that develops, constructs and deploys modular, scalable solar thermal power plants, CSP capacity is expected to double every 16 months through 2012, ushering in 14 times the current capacity.

      The solar rooftop network

      While many analysts think most growth will be seen in utility-scale concentrating solar power projects, perhaps the most exciting story is the enthusiasm with which utilities are embracing rooftop photovoltaic (PV) installations. It’s no wonder: there’s no need for expensive and hard-to-site transmission lines when home and business owners provide the real estate for these solar networks right where the power’s needed.

      For PV systems, a 1 MW facility used to considered large, but today the numbers are in the double digits. No longer the distributed generation stepchild, these multimegawatt systems will soon be producing substantial amounts of power for the local grid.

      “- Florida Power & Light plans to install 25 MW of solar photovoltaic panels east of Sarasota, and a 10 MW PV project at the Kennedy Space Center.

      “- Duke Energy Carolinas will buy all the electricity from a 16 MW PV facility that’s planned for a site north of Charlotte, N.C.

      “- Tucson Electric Power owns a 4.6 MW solar array in Springerville, Ariz., and the PV systems on hundreds of its customers rooftops through the utility’s SunShare program. According to TEP, the SunShare program provides subsidies of up to $3,000 per kilowatt of capacity to help its customers reduce the up-front cost of installing solar power systems. TEP’s total solar generating capacity reached 6.1 MW at the end of 2007.

      California has always been quick to adopt new technologies and that’s true when it comes to solar power. From the early days of large solar installations to today’s new and innovative solar programs, California utilities continue to look for innovative ways to use the sun.

      The Sacramento Municipal Utility District is a world leader in the development of renewable power. When SMUD built PV1 in 1984, it was one of the first solar arrays in the world. Located right next to the cooling towers of the closed Rancho Seco nuclear site, the plant has grown over the past two decades, and with the dedication of the sixth installation, now has more than 900 solar panels.

      Recently, SMUD expanded its solar program from large-scale arrays to customer-owned solar energy systems on homes and businesses or integrated into building materials. But the municipal utility wasn’t content to stop there. What about customers who can’t afford to install solar panels on their homes or don’t own a home but still want to use solar power? For them, SMUD developed the SolarShares program.

      SolarShares is the first program of its kind, according to SMUD, and the largest in the U.S. With SolarShares, SMUD will buy solar power produced on a “solar farm” through a power purchase agreement and sell subscriptions to portions of the electricity to interested customers.

      A 1 MW solar array located on seven acres at a turkey farm in SMUD territory now generates renewable electricity for the SolarShares program. For a fixed monthly fee, customers will get the solar power generated by their “portion” of the system credited to their energy bill, as if they owned the system. Depending on the customer’s energy use and the amount of solar power he or she buys, most customers can ensure that between 10 percent and 50 percent of their energy will come from the new SMUD solar farm.

      SMUD calls SolarShares “solar for everyone” and expects other utilities to emulate the program. According to the utility, it will broaden and transform the market for solar by taking advantage of economies of scale to lower the up-front cost to residential customers.

      When the Solar Electric Power Association (SEPA) announced its Top Ten rankings for 2007 in June of this year, Southern California Edison took first place for total solar electric capacity by megawatt (MW). According to SEPA, SCE was the “most solar integrated utility with the most overall solar capacity (MW) and solar capacity per customer.”

      SCE began purchasing renewable energy in the 1980s. Today, the company buys more than 90 percent of all U.S. solar generation.

      SCE’s 2,700 MW renewable portfolio includes 354 MW of solar power from long-standing contracts with the Solar Energy Generation Station (SEGS) concentrating solar thermal (CST) plants. SEPA noted that those contracts gave SCE a head start amassing its large number of solar megawatts, but “with a number of large-scale CST announcements by several other utilities, Southern California Edison’s top ranking may no longer hold once these new plants are constructed.”

      The 354 MW SEGS is one of two commercial parabolic troughs in the U.S. (Nevada Solar One being the other.) SEGS was built in the Mojave Desert in nine stages, with construction ending in 1991. As of August 2008, it’s the largest solar power plant in the world, owned by Terra-Gen Power LLC and FPL Group.

      SCE has plans to build another solar installation that can win the title “largest.” In March, the utility announced it was launching the nation’s largest solar cell installation project, placing 250 megawatts of advanced photovoltaic generating technology on two square miles of commercial building roofs in southern California. The utility said it is on schedule to begin delivering power from the first of about 150 rooftop installations in the fall of 2008.

      SCE points to numerous customer benefits from its new solar program, including locating new generation in areas of growing customer demand and producing power at peak usage periods. “And the clusters of solar modules SCE plans to install will be connected directly to the nearest neighborhood circuit, eliminating the need to build new transmission lines to bring the power to customers,” said SCE in a press release.

      SCE believes its commercial solar roofs program will boost several California environmental initiatives, especially the Million Solar Roofs program that provides incentives to encourage Californians to install solar projects by 2017. SCE’s solar program also supports the state’s Global Warming Solutions Act and California’s renewable portfolio standard.

      Not everyone is happy about the $875 million project. According to a recent article in the San Gabriel Valley Tribune, solar companies, industry trade groups and other stakeholders are afraid SCE could nab a monopoly on California’s solar market. As SCE works its way through these regulatory issues, utilities that hope to make solar power a star in their energy portfolios will be watching closely, because at this point there’s little doubt that solar is a technology poised for major technological breakthroughs and widespread adoption. No matter how utilities are involved, they will play an important role.

      “Based on recent announcements and internal discussions with utilities,” said Julia Hamm, SEPA executive director, “SEPA anticipates that utilities will quickly become the largest and one of the most important customers for the solar industry. Whether solar electric systems are developed by utilities, their customers, or solar companies, the utilities’ proactive engagement with emerging solar technologies is important to the solar industry as a whole.”

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at

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