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PV vs. Solar Thermal

Distributed solar modules are gaining ground on concentrated solar thermal plants.

Fortnightly Magazine - July 2008

of thin-film technology rapidly have gained ground in both efficiency and price relative to traditional silicon PV, where costs per watt actually have increased slightly since 2004. As a result, thin-film PV has become competitive with utility-scale solar-thermal generation, and also can provide additional benefits in the form of modular development, lower transmission-system interconnection costs, fewer technical uncertainties, and no need for copious quantities of cooling water.

For example, First Solar, the largest manufacturer of thin film Cd-Te technology, reports that process improvements and growing manufacturing capacity has allowed it to increase the efficiency of its panels to 10.5 percent, while reducing module production costs from $2,940/kW in 2004 to $1,120/kW for the fourth quarter of 2007. 12

First Solar is supplying PV panels for a 40-MW solar PV facility in Brandis, near Leipzig, Germany. When completed, the Brandis facility, which currently has 12.5 MW commissioned and 20 MW installed, will be the largest PV generating facility in the world. The project development arm of the same manufacturer also recently signed a contract with SCE to develop a 7.5-MW to 21-MW facility, at a price lower than the 20-year, 2007 California Market Price Referent. 13 The facility is expected to be interconnected to an existing 34.5 kV line near Blythe, Calif., and thus won’t require any transmission-system upgrades.

While not as impressive in sheer scale as 200-plus MW solar thermal plants, modular DCS PV facilities with 20 MW to 50 MW of installed capacity can be placed closer to load centers and can interconnect to existing 69-kV or 115-kV transmission lines. This avoids the need for large-scale transmission investment (and the all-too-common permitting delays) and increases both the potential cost advantage and the likelihood of completing a DCS PV facility, compared to its much larger solar thermal brethren.

Solar-Life Cycle

As with all generating resources, renewable or not, a number of tradeoffs must be evaluated in order to identify the most suitable generating resources with the lowest life-cycle costs. Today, CSP technologies are perceived as having lower life-cycle costs than PV, and policymakers in the Southwest are incorporating greater quantities of CSP into their RPS portfolios. However, CSP technologies also pose a number of risks that affect life-cycle costs in ways that haven’t always been fully accounted. These risks include:

• Potentially significant cost increases due to protracted and risky site-specific development cycles. This can affect regulatory approval if proposed facilities are to be rate-based;

• Reliance on technologies that are not commercially proven;

• Reliance on technologies in limited production that may not be sufficiently available when demand suddenly increases, as has happened with wind resources. This might drive prices higher and cause schedule delays. As a related matter, maintenance costs might be higher than projected, as is typical of commercially immature technologies and one-off designs.

• Environmental risks, especially reliance on scarce—and currently underpriced—water supplies.

• O&M complexities, with each facility requiring miles of pipe and thousands of joints and seals to circulate heated fluid. In the early years of operation of the parabolic-trough CSP plants in the U.S., built