Gemasolar Achieves 24-Hour Operation

The 350-MWh per day, 24-hour operations, solar power plant is now a reality. The first commercial plant to use molten salt storage in a central tower configuration with a heliostat field, in operation since May, yielded better than expected results, its developers say.

With its 19.9 MW of rated power, the Gemasolar plant reached peak production levels of more than 350 MWh in 24 hours of uninterrupted operation.

Thanks to its storage capacity, in July Gemasolar was able to supply energy during the hours of highest demand in Spain: 12:00 noon and 10:00 p.m. August is also expected to deliver a significant load factor for the plant.

Gemasolar boasts a storage capacity of some 15 hours at full operation. This makes it possible for it to supply energy to the grid based on demand, regardless of whether there is constant solar radiation, its operators say.

Indeed, with this project, it appears that generating fully dispatchable power from solar energy sources has finally become a reality.

It is expected that Gemasolar will produce an annual net total output of more than 110 GWh by operating for a total of 6,450 hours a year at full capacity.

Inevitably, the summer months are when the plant is at its greatest efficiency, therefore Torresol Energy’s technicians estimate that come mid-September, its equivalent average production time will be some 18 hours at full capacity per day.

The Gemasolar plant, located in Fuentes de Andalucía (Seville), is a property of Torresol Energy, a joint venture between the engineering and technology group SENER and Masdar, Abu Dhabi’s renewable energy initiative. SENER has been responsible for supplying all of the technology and the engineering detail design for Gemasolar, and for leading the EPC and commissioning works of the plant.

As for Masdar, a strategic developer of renewable energy power projects, the company says it is proud of the commercial approach they have taken to funding and operating this facility.

Felicia Bellows, executive vice president of Development for Torresol Energy USA, explains: “Currently we are the only company in the world that is commissioning a commercial central tower project with molten salt receiver capable of absorbing 90 percent of the solar radiation. Gemasolar is Torresol Energy’s flagship project because of its innovative technology, and in the short term we expect to be able to develop similar plants on the South West Coast of the U.S., where there are optimal levels of solar irradiation.”

Frank Wouters, director of Masdar Power, said: “The first months of Gemasolar’s operation have exceeded expectations. Masdar Power believes in introducing and launching new technologies in the clean energy spectrum, and we will continue to explore fresh opportunities to implement such novel technologies that will bring multiple benefits to the community.”

Mercedes Sierra, vice president of SENER’s office in the US, added: “The efficiency of this technology… is proving to be vastly superior to conventional solar technologies, either without storage systems or which can’t reach such high temperatures.”

The Gemasolar installation can reach operating temperatures of more than 500°C, much higher than other types of concentrating solar plant, which use parabolic trough technology. It does not require oil as a heat transfer medium, but rather directly uses the salt as a transfer fluid.

The receiver, located at the top of the tower over 130 metres high, is the focal point of the 2650 heliostats of the solar field (spread across 185 hectares of rural land). These tracking helistats concentrate the solar irradiation at a ratio of 1000:1.

The molten salt is subsequently passed to a heat exchanger which generates pressurised steam to move a conventional turbine. The use of higher temperatures and pressures significantly increases the plant’s efficiency.

Meanwhile, some of this hot salt is stored in order to continue generating electricity while there is no sunshine.

The power generated by the Gemasolar installation is sent through a high-tension transmission line to the substation at Villanueva del Rey, where it will be supplied to the grid.

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