The bigger the better

US utilities are rushing to construct ever bigger solar farms.

These are heady times for utility scale solar power gener-ation in the US, but it seems that this growth is greatly reliant on government support. A raft of announcements of utility-scale solar projects was depend-ent on an extension to the solar investment tax credit scheme. But now that the US Congress has approved an eight-year extension, it is full speed ahead.

At the end of 2007, the US had just over 3,400MW of installed solar power, including 750MW
of PV, 418MW of utility-scale concentrating solar power, and 2,250MW (thermal equivalent) of solar hot water systems. The US ranks fourth in the world for installed solar power behind Germany (first place with the solar resources of Alaska), Japan and Spain.

Installed grid-tied solar PV grew more than 48 per cent in 2007 compared to 2006. Projects included the 14MW solar PV installation at Nellis Air Force Base and large companies and big-box retailers adding solar to their buildings. The pool-heating market continued steady growth of 8 per cent. And utility-scale grew 18 per cent.

The US bill, passed in early October, included $128bn in tax incentives and breaks including the $18bn solar energy tax credit that offers 30 per cent credit to both commercial and residential solar installations. The industry wants the extension to scale the industry and reduce the costs of solar to compete with fossil fuel.

"Deploying solar projects that can provide power on the scale of a public utility requires a stable investment environment," says Robert Fishman, president, CEO and chairman of Palo Alto-based Ausra, which is working to develop utility-scale solar thermal power plants. "The eight-year extension will allow us to continue developing innovative technologies to meet energy challenges of our future in a cost-competitive manner."

The eight-year extension is expected to create more than 400,000 jobs nationwide by 2016, with 214,000 of those in California alone.

Utility scale

The Solar Electric Power Association (SEPA) predicts that utilities will quickly become the largest and one of the most important customers for the solar industry, expanding solar markets beyond analysts' expectations. Access to the federal tax credit will expedite the timeframe and scale to which this happens.

"US electric utilities' engagement with grid-connected solar electricity has increased significantly in 2008, with major PV and concentrating solar thermal project announcements totalling more than 5,000MW," says Julia Hamm, SEPA executive director. "Without the advantage of the investment tax credit, the only viable financial option was to have these plants be owned and operated by independent power producers who then in turn sell the electricity to the utility."

"It's huge for the industry, it's huge for developing solar in the US market and it's huge in terms of making solar available to every American," said Monique Hanis, spokesperson for the Solar Energy Industries Association in Washington.

Armed with these financial crutches it appears that big is beautiful and a good example of this is Arizona Public Service Co (APS), which has announced plans for a 280MW concentrating solar power (CSP) plant - to be built 70 miles southwest of Phoenix, Arizona.

The Solana Generating Station will produce enough energy to serve 70,000 APS customers. The plant will be built by the US arm of the Spanish company Abengoa Solar and is scheduled to be in use by 2011. Solana will not emit greenhouse gases and will provide APS with more solar electricity per customer than any utility in the US. The facility would be the largest solar power plant in the world today.

"APS is committed to making Arizona the solar capital of the world and bringing affordable renewable energy to all our customers," president Don Brandt explains.

Solana will employ proven technology that can produce and store energy during the day, and then provide energy during times of peak demand. Pending approval from the Arizona Corporation Commission, APS will purchase 100 per cent of the plant's energy output under a 30-year power purchase agreement worth about $4bn.

The Solana CSP plant will use arrays of parabolic mirrors to track the Sun and focus solar energy on a heat transfer fluid - molten salt. Once heated, the liquid converts water into steam, which turns the plant's turbines to create electricity. This technology allows the plant to produce more energy than a traditional solar power plant which only produces electricity when exposed to direct sunlight.

Another utility that is forging ahead with solar power is Pacific Gas and Electric (PG&E) who have announced two utility-scale PV solar power contracts. The two solar farms will generate 800MW of renewable energy - OptiSolar's Topaz Solar Farm at 550MW and SunPower's California Valley Solar Ranch at 250MW.

"These landmark agreements signal the arrival of utility-scale PV solar power that may be cost competitive with solar thermal and wind energy," says Jack Keenan, chief operating officer and senior vice president. "We will continue to explore such innovative technologies as we work to increase the amount of renewable energy we provide."

Utility-scale PV solar projects feature photovoltaic solar modules, which convert sunlight directly into electricity and produce the greatest amounts of power during the afternoons. When PG&E announced these projects during the summer it was contingent upon the extension of the federal investment tax credit for renewable energy and processes to expedite transmission needs.

The 550MW Topaz Solar Farm project will use low-cost, thin-film PV panels designed and manufactured by OptiSolar in Hayward and Sacramento. The project would deliver approximately 1,100,000 megawatt-hours of renewable electricity per year. The project is expected to begin power delivery in 2011 and be fully operational by 2013.

"We are very happy to be working with PG&E to help meet California's requirements for clean, renewable energy and are committed to working closely with the local community," says Randy Goldstein, chief executive officer of OptiSolar. "Our solar farms are quiet and emission-free, with solar panels mounted near ground level to minimise visual impact. Implementing cost-competitive solar power on this scale establishes thin-film PV generation as an important contributor to global sustainability."

SunPower's planned 250MW solar ranch will be located in San Luis Obispo County's California Valley and will deliver an average of 550,000 megawatt-hours of clean electricity annually.

The project is expected to begin power delivery in 2010 and be fully operational in 2012. The ranch would employ SunPower's crystalline PV solar cells, which generate up to 50 per cent more power than conventional crystalline cells.

The company would install its solar tracking systems at the site, which tilt toward the Sun as it moves, increasing energy capture by up to 30 per cent over fixed systems, while reducing land-use requirements.

"Today, high-efficiency photovoltaic technology is a competitively-priced component of utility-scale peak power generation," says Tom Werner, chief executive officer of SunPower.

"Our experience constructing more than 350MW of solar systems on three continents allows us to deliver utility-scale systems quickly and at a scale of hundreds of kilowatts to hundreds of megawatts.

"We design our solar systems to maximise energy harvest while adapting to the natural topography of the site and serving the needs of the

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