Torresol: The New Kid on the CSP Block

Credit to the Green Wombat for first covering this company, and for the graphic below.

Torresol Energy, a 60-40 joint venture between Masdar, Abu Dhabi's $15 billion renewable energy initiative, and Sener, a Spanish engineering company, aims to build a series of utility-scale power plants using concentrated solar power (CSP) technologies, starting with projects in Spain and Abu Dhabi.

Torresol aims to build two solar plants a year in order to reach 320 MW in total capacity by 2010, and 1,000 MW by 2018. Their target geographic areas consist of Southern Europe (especially Spain), Northern Africa, the Middle East and eventually, southeastern USA, constituting a de facto "global sunbelt". I for one would be thrilled if the likes of China and other Asian markets are eventually included.

I'd like to take a closer look at Torresol’s technologies:

The prototypical Torresol solar plant structure consists of multiple rows of heliostats circling a central receiving tower filled with molten salt. The heliostats consist of parabolic troughs that pivot around an axis to track the changing position of the sun through the day. The heliostats concentrate and reflect the sunlight onto the central receiving tower filled with molten salt, which acts as an energy storage conduit. Though the technology was conceived in the 1970s, the company claims to be the first company in the world to apply this molten salt energy storage technology in a commercial plant.

According to the Sandia National Laboratory National Solar Thermal Test Facility, the molten salt, also known as saltpeter, is a mixture of 60% sodium nitrate and 40% potassium-nitrate. Sodium has a high heat capacity and hence, saltpeter serves as an effective medium to store the solar power in the form of heat. Heated saltpeter is channeled into insulated storage tanks where they can be released into a conventional steam-generating system to boil water to generate steam to cycle through turbines to produce electricity.

The upshot of thermal storage is that the ability of the solar plant is no longer subject to the intermittency of solar irradiation—surplus solar energy collected on the sunny days can be stored in the molten salt for discharge on cloudy days or at night. According to Torresol’s website, molten salt storage allows for 15 hours of independent electricity generation without sun irradiation, resulting in electricity production during 6,500 hours a year, 2.5 to 3 times more than other renewable energies such as wind or photovoltaic energy.