Concentrating Solar Power (CSP) – a different kind of solar
US concentrating solar power projects
A lot has been written about solar energy, especially since the call for independence from foreign oil has gotten louder. From the popular photovoltaic (PV) panels, which produce electricity directly from the sun’s radiation, over solar thermal panels to generate hot water for your home or process heat for industrial use, to large utility scale solar thermal arrays.
Latter heat up a fluid to either drive a turbine for power generation or provide process heat for various applications (air conditioning, processes in food and cleaning industry, desalination, etc.). A comprehensive overview can be found, e.g., on NREL's (National Renewable Energy Laboratory) website.
PV systems are getting most of the attention, leaving concentrating solar power (CSP) technologies a little bit in their shadow. CSP designs are worth looking at though, as they do have their fair share of applications.
There are four basic configurations; all of them reflect the sunlight with mirrors, focusing it onto a receiver. Parabolic troughs use a parabolic mirror configuration to concentrate the solar light and thereby heating up a heat transfer fluid in a tube that runs along the focal line. Secondly, central receiver systems, where an array of flat mirrors reflects the sun on a receiver located on a tower in the center (tower power). Then there are dish engine systems with mirrors forming a parabolic dish, which focus the sunlight on a receiver consisting of a power conversion unit. And, the line-focusing Linear Fresnel technology (CLFR), which is a configuration of flat, segmented mirrors that reflect radiation onto one single receiver.
In this article, I would like to focus on the parabolic trough design and talk about some projects in the United States. These predominant systems are conventionally large (utility-scale) power generation systems in the range of 10 MW and beyond and located in the earth’s sunbelt (between ±35 degrees latitude). Based on the concept of converting solar energy by a thermodynamic cycle (via turbines), the majority has an output of 30 MW or more.
Just some examples are the oldest and well known nine operating plants in California ‘SEGS’ (one 14 MW, six 30 MW, and two 80 MW output), partially maintained and upgraded by Siemens Concentrated Solar Power, Ltd. They were built in the 1980s and 1990s and are still operating. Also located in California (Kern County), NextEra Energy Resources is developing the 250 MW Beacon solar project, with plans to get connected to the grid in 2014. Furthermore, they are currently building two 125 MW units with a combined output of 250 MW (Genesis Solar Energy Project) in Riverside County, CA. In Arizona, Boulevard’s Aguila, Burnt Mountain, and Bouse projects have a capacity of 500 MW, which are all in the planning phase.
The company Solargenix, LLC developed an advanced parabolic trough design for a 1 MW plant in Saguaro, Arizona, which was finished in 2006. The 64 MW plant Nevada Solar One in Boulder City, Nevada, uses the same trough design and got connected to the grid in 2007.
Near Gila Bend, Arizona, the 280 MW Solana Generating Station is being built by the Spanish company Abengoa Solar, and operation is planned to start in 2013. It will be one of the world’s largest CSP plants. Abengoa is also constructing the 280 MW Mojave Solar Project, located near Barstow, CA, with plans to begin generation in 2014.
On the Island of Hawaii near Kona, Keahole Solar Power, LLC built a 2 MW plant in 2009, utilizing Sopogy’s Micro CSP panels. The solar field is located on the right shorty after the airport when driving towards Kona, right next to Kaahumanu Highway. The company is currently planning to complete a 5 MW power plant on West Oahu in 2012, with a goal of generating a total output of 30 MW by 2015.
Keahole parabolic troughs
Under development are 500 MW plant for Ft. Irwin, CA (Ft. Irwin Solar Power Project, planned to be finished by 2013) by Acciona Solar Power, and the Hualapai Valley Solar Project by Mohave Sun Power with an output of 340 MW.
The named projects are just examples of power plants in operation, under construction, and in the planning stage throughout the United States. Some projects have experienced a change in technology (from CSP to PV), some got delayed or cancelled due to environmental, economical, bankruptcies, or cultural issues, but the number of CSP plants is steadily increasing and they play an important role in our effort and need to boost production of renewable energy.