Swiss power firm Airlight Energy have built a pioneering concentrated solar power (CSP) plant at the site of one of Italcementi’s cement plants in the Moroccan desert. Power generated from the sun is integrated into the cement plant’s existing heat-recovery systems, replacing a portion of the plant’s fossil power consumption with green resources.
The Ait Baha plant cost around £2.5b, covers an area the size of two football pitches and produces around 0.2 MW of power. Giuseppe de Beni, managing director of Italcementi’s energy subsidiary Italgen, has described it as a “crazy” project. De Beni said, “with €3b I could instead buy more or less three megawatts of wind [power]”.
The plant is however groundbreakingly sustainable due to its modular Fresnel collector system, low-pressure receiver technology and use of hot air in the heat-transfer process rather than thermal oil. The facility can also be used to dry raw materials.
The plant consists of an array of three solar collectors – each 16m high, 216m long and 1,700 tonnes in weight. Taking a day to install, rather than the three months required for conventional photovoltaic mirrors, the collectors use super-efficient ‘Inflatech’ aluminised polyester foils instead of rigid mirrors. Tracing the sun’s path across the sky in the daytime, the collectors store excess energy in gravel pits during the night – an innovation De Beni describes as a “competitive advantage”.
Size is also central to the site’s innovation. Far larger than normal 9.5 metre mirrors enable extremely high concentration when compared to existing CSP systems. The mirrors’ teflon surface also discourages the sticking of dirt and dust to its surface, maximising efficiency. A controlled atmosphere housing complete with fiberglass membranes further protects the reflectors from dust and humidity.
In an interview with CSPToday, Airlight’s chief technology officer Andrea Pedretti said: “The air pipe is at low pressure like a traditional HVAC duct for air conditioning; despite the higher temperature, the technology is simple.” Pedretti continued, “we are able to use air, which requires a large pipe, because our structure is large enough and receiver does not create any shadow on the primary mirror.”
“The collector cost is much less compared to steel or aluminum frame and current glass or aluminum mirror. Our mirror foil is 0.5€/per square meter compared to 20€ per square meter or more for glass mirror. No special materials are used; concrete can be manufactured everywhere” said Pedretti.