This has been made possible by its innovative technique of storing solar energy in molten salt, a cutting-edge thermal-transfer technology developed by SENER. This system is capable of fifteen hours of electricity production without solar radiation which overcomes fluctuations in the energy supply.
Diego Ramírez, Director of Production at Torresol Energy, explained how it was possible to achieve 24-hour production in record time, after barely a month of commercial operation at the plant: "Gemasolar achieved optimal performance in its systems in the last week of June. 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. We’re hoping that in the next few days our supply to the network will reach an average of 20 hours a day."
The salt storage system allows the plant to stretch its electrical production hours to beyond sunset, regardless of the cloud cover. Thus, Gemasolar, with its 19.9 MW steam turbine, is able to supply electricity to a population of 25,000 households.
Eventually the plant will be able to supply 24hrs of uninterrupted production per day on most summer days, providing a higher annual capacity factor than most baseload plants such as nuclear power plants.
Director of Masdar Power, Frank Wouters said: “The prove-out of both this technology and the commercial approach we have taken to funding and operating the facility are of huge significance to the solar industry and we are very proud of these twin achievements. They will help inform our progress as we expand our portfolio of renewable energy facilities.”
SENER has applied its solar technology with thermal-storage capacity in plants throughout Spain, some of which are already in commercial operation. This system significantly improves performance compared to plants with no storage capacity. In addition, it makes it possible to manage the supply of electricity sent to the network and respond to spikes in demand. In this way, the reliability of solar energy becomes comparable to that of conventional fossil-fuel power plants, which is decisive as the demand for renewable energy increases.
Gemasolar is the first plant to apply the thermal-storage system in a configuration with a central tower and an array of heliostats. The main difference between it and plants with parabolic-trough technology is its ability to reach a much higher operating temperature (over 500°C) by dispensing with oil and directly using salts as a transfer fluid. The molten salts, at over 500°C, make it possible to generate hotter steam at higher pressures, which significantly boosts the plant’s efficiency.
SENER has been responsible for providing the technology, the engineering detail design and for leading the EPC and commissioning works of the plant. Gemasolar’s most cutting-edge equipment includes its receiver, located at the top of the tower over 140 m high, where the 2,650 heliostats of the solar field concentrate the solar radiation at a ratio of 1000:1. This receiver is able to absorb 95% of the radiation from the sun’s spectrum and transmit this energy to the molten salt compound that circulates within the receiver, which is then used to heat steam and operate the steam turbines.
Torresol Energy, founded in 2008, is a joint venture between the SENER engineering and technology group, which holds 60% of the company, and Masdar, Abu Dhabi’s future energy company, which holds the remaining 40%. The company commercially develops, supervises the construction of, promotes and operates concentrated solar power plants in the international market.