Gemasolar Concentrated Solar Power
Gemasolar is a concentrated solar power plant with a molten salt heat storage system, located in the city of Fuentes de Andalucía in the Seville province of Spain. It is the world’s first commercial-scale plant to use solar technology comprising of the central tower receiver, a heliostat field and a molten-salt heat storage system. The plant is of the solar power tower type CSP and uses concepts pioneered in the Solar One and Solar Two demonstration projects. Originally called Solar Tres, it was renamed Gemasolar. It was officially inaugurated in October 2011.
The Gemasolar CSP plant has 2,650 heliostats spread over 185ha of land. Each heliostat has 400ft2 of steel metal stamped surface and is installed in an array around the central tower equipped with a central receiver. The tower is 140m tall, the heat of up to 900°C is used to warm molten salt tanks, which create steam to power the station’s turbines.
The cold and hot storage salt tanks are installed at the ground level and directly connected to the tower. They have capacity to store salts for 15 hours. The cold tank stores molten salt (sodium and potassium nitrates) at 290ºC and the hot storage tank stores the salts at 565ºC. Both the tanks are made up of steel. The largest tank measures 23m in diameter and 14m in height.
Cold salt is pumped up to the top of the tower at the central receiver, where it gets heated up. The liquid salt is carried back to the hot storage tank where it is stored at 565ºC. Salt from the hot storage tank is transferred to the heat exchanger through pipes and condensed to form steam. This steam is used to run the turbine and produce electricity. But unlike other solar stations, the surplus heat can be stored in a hot tank on the ground, allowing it to be used at times with low solar radiation, when the plant does not get enough heat to generate steam directly. The stored salt, which only loses 1% of the heat being stored each day, can then supply this heat and continue generating steam.
Technology incorporated into the Gemasolar concentrated solar power
The central power technology works on two main components – a central tower receiver and molten salt heat storage technology.
The heliostat or the flat mirrors reflect solar radiation on to the receiver located on top of the tower. They are positioned on the ground with the help of Sensol technology that automatically turns the surface of the mirrors towards the sun light.
The heat storage system permits the power plant to generate 1.5 to three times more electricity than any other renewable sources. The molten-salt tank stores the surplus heat produced during solar radiation, enabling the power plant to operate 24×7.
Power from the plant is carried to a substation in Villanueva Del Rey in Andalusia through a high tension wire from where the power is transmitted to the national grid owned by the Seville Electricity Company (ENDESA).
No limitations
Hailed as the world’s first nocturnal solar plant, some believe the technology could be a breakthrough for solar, leading the way to a future where the share of clean and renewable energy plays a major role in the overall energy mix.
In addition to the Gemasolar plant, Torresol already operates two other CSP plants in Spain, Valle 1 and Valle 2, located only about 200km from Gemasolar in Andalucía. There, the company uses more conventional parabolic technology but also reaches 7.5hr of thermal storage.
