SOLAR-SPEW PLANT HYBRID

CSP-retrofits: A medium-term solution?; Power generators are under increasing pressure around the world to reduce their environmental impact. Bolting on solar capacity to existing conventional plants is one option on the table. But do the arguments for solar augmentation add up?
Oliver Balch, 21 January 2010 (CSP Today)

"The southwest of the United Sates is to set to host two pioneering solar augmentation projects… Tri-State Generation & Transmission Association…[will] commence construction of the twin demonstration projects in 2011, with operations set to start “by 2014 or sooner”.

"The larger of the two projects will be based at NV Energy’s Chuck Lenzie natural gas combined cycle plant. Located north of Las Vegas, Nevada, the 1102MW facility will have a 95MWe solar installation added…to integrate with the plant’s high-pressure stage…[enabling] the plant’s steam turbine to produce the same amount of electricity from less natural gas…[O]ne of the largest proposed integrations in the world, the project will be equipped with a superheated steam design that boosts the efficiency of the solar component."

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"The second demonstration project will be located at Tri-State’s 245-MW Escalante Station, situated in Prewitt, New Mexico…[A] 36MWe solar field [will be added] to the coal-powered plant…The hybrid model will test main steam integration, using solar-derived steam to displace coal-derived steam in the boiler…[again allowing] for the same electricity output with less coal consumption…If successful, it will mark the world’s first large-scale CSP project for mainstream pulverised coal power generation…

"…[O]ther solar augmentation proposals…[include the] Florida Power and Light…75MW parabolic trough project at its combined cycle gas-fired Martin Next Generation Solar Energy Centre [due in] 2010…Around a dozen more retrofit projects are currently under consideration in the United States, the Middle East and Europe…[including] a 1MW experiment plan by Xcel Energy to enhance the capacity of its Cameo coal plant through [parabolic trough technology] CSP…[In] New South Wales, Australia…US-based Ausra Fresnel reflector solar steam generators [are tesing] with existing coal-fired thermal plants…"

Another alternative. (click to enlarge)

"…[T]he argument in favour of [solar augmentation/retrofitting] has yet to be proven…[In recent research by US solar specialists WorleyParsons Group and EPRI] compact linear Fresnel reflector (CLFR)… was found to be [less successful than towers or troughs because]… the typical operation temperature of the technology measures no more than 270°C. This limits the efficiency of the integrated system and results in fewer integration options…Central receiver technology, on the other hand, boasts temperature outlet levels of up to 600 °C…[enabling] superheated steam to be added to the system, thereby increasing the integration options for coal plant steam cycles…[In] trough technology, the synthetic oils employed in the process limit temperatures to around 380 °C…

"Should the technology prove itself, the potential advantages of retrofitting…[include reduced] fuel use and greenhouse gas emissions …[and] solar augmentation plans inevitably impact the design of a power plant…[but] are likely to generate far fewer regulatory hurdles… than a new hybrid or stand-alone CSP plant…Existing power plants are already connected to the grid, forestalling problems with access to transmission that new CSP plants often face…[and] power plants boast the available water resources for cooling purposes that CSP also needs…[Retrofitting] achieves higher thermal to electric conversion efficiency and potentially lower costs compared to stand-alone solar facilities…[and the] solar component implies access to renewable energy credit markets and other fiscal incentives…[Retrofitting]…enables power generators to add utility scale solar without the huge start-up costs of a stand-alone plant…"