The solar energy industry is getting closer to finding a solution for producing electricity when the sun isn’t shining. It’s a rather salty solution. During the first week in October, a $325 million, “concentrated solar plant” was inaugurated in Spain that uses molten salt to keep generating electricity after the sun goes down. The Gemasolar plant is near Seville, Spain, and was built by a joint venture (Torresol Energy) between Abu Dhabi’s Masdar, a renewable energy company, and Spain’s Sener, an engineering and construction firm. The King of Spain Juan Carlos I and Crown Prince Sheik Mohammed bin Zayed Al Nahyan of Abu Dhabi were at the ceremony. That gives you an idea of the interest in this new facility. According to Masdar, this is the first commercial plant to use molten-salt, thermal storage in a central-tower configuration with a heliostat field. What that looks like is an array of 2,650 large mirrors that focus solar energy onto a receiver on top of a 450-foot central tower. That really heats things up - 930°F. That’s where the molten salt comes in. It is used to transfer the heat at much higher temperatures. These higher temperatures in turn generate hotter, pressurized steam in the turbine, which significantly increases the plant's efficiency. Molten salt retains heat for up to 15 hours, allowing the plant to continue generating during the night. The 19.9-MW plant started operations in May and is expected to save more than 30,000 tons of carbon dioxide emissions per year. Gemasolar can supply electricity to a population of 27,500 households in southern Spain. The annual production of Gemasolar (110 gigawatt/hours equivalent) is equal to the energy generated in a conventional thermal plant burning 89,000 tons of lignite or the converted energy of 217,000 barrels of oil. Torresol was awarded a 25-year, regulated tariff by the Spanish government. It is developing two further facilities -- Valle 1 and Valle 2 -- in nearby Cadiz. These 50-MW facilities will employ parabolic trough technology and have an expected net electrical production of 160 GWh/year each. Both are scheduled to commence start operations by the end of 2011. Total investment in the three facilities came to €1 billion ($1.4 billion). And, therein lies the technology’s Achilles heel. The average cost per kilowatt is high compared to either wind or geothermal energy. It is also a little higher than traditional forms of solar energy. Since it is the first plant ever built, you would expect costs to be higher. The technology does address one of the major problems facing renewable energy, which is energy storage. It will be interesting to see how the technology and the economics play out.