Big solar rising

Utilities Unbundled - Issue 15

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Solar-to-steam plants such as BrightSource’s new facility in Ivanpah, California, have unique advantages over other renewables.

“Concentrating solar power, combined with thermal energy storage, transforms a variable resource into a flexible, dispatchable generator.”

— Joe Desmond, BrightSource

The world’s largest concentrating solar power (CSP) facility – Ivanpah Solar Generating System – recently started its first power production and is scheduled for completion by the end of 2013.

Developed by BrightSource Energy of Oakland, California, in partnership with NRG Solar and Google, Ivanpah will provide 377 MW, using more than 173,500 individually-controlled heliostats.

Each heliostat consists of two mirrors to track the sun throughout the day and reflect sunlight onto boilers that sit atop three 459-foot-tall towers. When the concentrated sunlight strikes the boilers’ tubes, it heats the water to create superheated ‘solar steam’ that is used to power a turbine, creating electricity just like conventional generation.

Even with rapidly dropping photovoltaic (PV) cell prices, Joe Desmond, BrightSource’s Senior Vice President of Marketing and Government Affairs, believes CSP will continue to be attractive to grid operators and utilities: “It is able to ride through changes in weather patterns much more smoothly due to thermal inertia and provide voltage support. But more importantly, CSP, combined with thermal energy storage, transforms a variable resource into a flexible, dispatchable generator,” meaning the power is available as needed.

Utilities are recognizing that CSP can help address the intermittency of PV and wind at scale. “Short-term variability increases the need for frequency regulation,” says Desmond, “and increased variability requires greater flexibility and operating reserves, with more ramping capability to meet output changes.” The net result, as witnessed by countries such as Germany with high rates of both wind and PV, is higher costs to manage the grid.

Since CSP with thermal storage allows CSP plants to be dispatchable, it allows overall higher levels of other variable renewables. Furthermore, CSP technology provides ‘solar steam’ that can be combined with existing or new gas- or coal-fired plants to reduce carbon intensity or “boost” efficiency during certain times of the day.

The fact that CSP is relatively easy to integrate with fossil-fired power plants means it offers a lower cost and lower risk alternative to stand-alone solar plant construction.

An evolving market

Early CSP systems mainly consisted of parabolic trough collectors involving solar concentrators (mirrors), heat receivers and support structures. Most of these systems used synthetic oils as the heat-transfer fluid. This more mature technology accounted for about 95% of facilities in operation at the end of 2011.

Increasingly, however, plants under development are turning to newer solar power tower technology, like Ivanpah’s. By end 2012 this technology represented 18% of CSP plants under construction.

Solar towers can achieve higher temperatures because more sunlight can be concentrated on a single receiver and heat losses are minimized. This allows the use of higher-efficiency steam turbines and higher-capacity factors, which can lower the cost of both generating electricity and storing thermal energy.

Desmond explains that each heliostat is calibrated and controlled to maintain steam at a steady pressure and temperature throughout the day, and that “BrightSource works with utilities in order to design optimal solutions that meet a utility’s specific load profile and requirements.”

A long road

Ivanpah’s development faced challenges similar to those on any large infrastructure project, including permitting, financing and engineering.

“It had been almost 20 years since the California Energy Commission had permitted a solar thermal plant and so, with new technology and new questions, it took quite a bit longer than it otherwise would,” Desmond says.

The project was partly financed by a US$1.6b U.S. Department of Energy (DOE) loan guarantee. “DOE's loan guarantee was instrumental in attracting the capital necessary to finance this innovative project at commercial scale,” says Desmond. Power produced at Ivanpah will be sold to PG&E and to Southern California Edison under 20- and 25-year PPAs.

Significant role for CSP

Beyond the US, BrightSource has operations in China, Europe, Israel and South Africa and sees good potential for both large-scale CSP deployment and industrial applications at a smaller, modular scale.

“Knowing how important affordability is for consumers, the industry is working hard to reduce costs across the board. We’re on the cusp of a major market transformation, and it’ll be interesting to see how that plays out. But, in the end, we're quite positive that there’s a significant role for CSP,” he concludes.

This is an abridged version of the full article in Utilities Unbundled.

For more information on this topic, please contact Bradley Hartnett.