Big day for CSP as Gemasolar feeds the grid for 24 hours

Torresol’s Gemasolar power-tower installation has become the world's first concentrating solar power (CSP) plant to feed an uninterrupted supply of electricity into the grid over 24 hours.

Gemasolar reached the solar-energy milestone less than two months after it was commissioned in Andalusia by Torresol – a joint venture between Masdar and Spanish construction giant Sener.

After commissioning in May, the plant was finally ready to operate at full-blast in late June and benefited from a particularly sunny stretch of weather, according to Diego Ramirez, director of production at Torresol.

“The high performance of the installations coincided with several days of excellent solar radiation, which made it possible for the hot-salt storage tank to reach full capacity," Ramirez explains.

Gemasolar, which uses a 19.9MW steam turbine, is the world’s first CSP plant based on power-tower technology to incorporate molten-salt storage.

Though power-tower technology is still in its infancy compared to the dominant parabolic-trough design, it is seen by many analysts as the future of CSP as it supports hotter temperatures, and therefore higher efficiencies.

Gemasolar uses 2,650 heliostats to heat the central receiver up to 900ºC, which in turn warms the heat-transfer fluid as high as 500ºC.

Only two other commercial-scale power-tower plants are currently in operation – the P10 and P20, both developed by Abengoa in Spain.

But neither is connected to a molten-salt storage system, which over time dramatically increases the productivity of a CSP plant by allowing operators to store excess heat during sunny periods and convert it to electricity during the night.

This removes one of the main downsides of solar energy.

In future, Torresol believes Gemasolar will feed electricity into the grid an average of 20 hours per day – reaching 24 hour operation during the summer.