Solar power’s perennial weakness – its inability to provide electricity after nightfall or during cloudy weather – might be vanishing: The Spanish company Torresol Energy said its solar thermal plant in Seville was recently able to pump out electricity uninterrupted for 24 consecutive hours.

The Gemasolar plant in Fuentes de Andalucía – which began operating barely a month ago – was able to keep the juice flowing using an innovative technique that stores energy in molten salt. This allows for up to 15 hours of electricity production in the absence of solar radiation, stretching the plant’s production into the night and keeping it running during heavy cloud cover.

Torresol Energy Gemasolar solar thermal plant
image via Torresol Energy

While the plant, which can produce enough power to supply 25,000 homes, was able to pull off an around-the-clock cycle of power production, Torresol said it doesn’t expect that level of production all the time. “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,” said Diego Ramírez, director of production at Torresol. “We’re hoping that in the next few days our supply to the network will reach an average of 20 hours a day.”

The 19.9-megwatt capacity Gemasolar plant uses a “power tower” system, with 2,650 mirrors bouncing sunlight to the top of a 140-meter tower at the center of the circle of mirrors. Torresol said a super-efficient receiver absorbs 95 percent of the radiation aimed at it, heating molten salts inside the tower to more than 500 degrees Celsius. The hot molten salts are then stored for use when the sun goes down or when clouds move in.

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