There are many conductors of heat; molten salt is one, which can store the heat that the sun provides during the day. This energy can thereafter be used in the night to provide electricity. In the vicinity of Granada, in Spain around 28,000 metric tons of salt, is present in the pipelines along a power plant at Andasol. The aim is to solve the downfall of solar power; absence of sun shine during the night.
In simple terms, the solution is to store sunlight energy as heat energy.
The use of parabolic reflectors in solar-thermal power plants might soon use salt to assure a night and day provision for energy. Most varieties of salt do only melt at around 800 degrees Celsius and it need to be heated way-above that until it changes into vapor. The salt can be used to store the sun’s energy in forms of heat. The hypothesis is like this, the sunlight is used to heat the molten salt. The salt should be placed near the water and through a heat exchanger used to steam the water. This would ensure that the turbine is stimulated during the day through sunlight and during night from the heat of salt.
Salts generally used for fertilization such as regular blend of potassium nitrate and sodium can store enough heat for the power plant to work another eight hours. According to Sven Moorman, the spokesperson for a German company, Solar Millennium, AG the firm that established the Andasol plant in Spain. The production capacity of solar-thermal power plant can nearly double with the use this new technology.
Old Technology in New Environments
The use of mirrors to concentrate the heat of the sun is a very ancient concept. The Chinese and Greeks used it millenniums before us, to ignite fires. This technology has been redesigned in the modern world to provide substantial sources of renewable energy without any CO2 emissions.
The technology has until now been limited in the sense that it works only when sunshine is present. Scientists have extensively tried to broaden the application of the technology. Alternatives such as batteries have been suggested but according to National Renewable Energy Laboratory (NREL), in Golden, Colo the technology is ineffective and costly. Moreover, pumping water uphill for hydropower and compressing air are plausible solutions to sustain renewable sources of energy.
The process of heating salts to a temperature above 224 degrees Celsius can return as much as 93 percent of that energy. Moreover
The Andaso- 1-power plant required a cost approximately of $380 millions to be constructed and is the first of its kind. The practicability of the plant is yet to be seen. However, In America its feasibility has already been demonstrated through laboratories such as NREL and Sandia National Laboratory in Albuquerque, N.M.
Solar Millennium stays ascertain that the technology will be a success. An identical power plant (Andasol 2) has already been constructed. The best thing about using molten salt is that it maximizes the potential of solar energy. It provides substantial amount of energy during cloudy or rainy days or after sunset.
The energy does however come at a cost. The power plant needs a larger surface area to allow for the heating of the salt. For instance, Andasol 1 covers a surface area of 50 hectares (126 acres) with pipes rows. Moreover, molten salt storage tanks are also required.
Nevertheless, the additional cost involved in assuring that the salt technology work does not add up any daily expenses. It pays for itself, as allows energy to be generated during times (night) previously not possible. Yet, the cost of thermal energy still is around twice the cost of coal-fired power plants, ignoring environmental cost. The reason why storage technology is being considered as fundamental is that the peak demand for energy is regularly in the evenings. The time that energy harnessed from the sun fades out.
For instance the Andasol 1 solar power plant, can store a heat of above 750 degrees. However, companies like SolarReserve in Santa Monica, Calif., are trying to innovate the technology and make it possible to boost the heating process of the molten salt. They are focusing on creating a molten solar power tower of 200-MW but this will cost around $800 million. It is risky investment, as the technology has not yet been fully scrutinized.
Solar Millennium is also working on modifying the mixture of salt. This includes new compositions such as lithium nitrate and calcium nitrate. However, lithium nitrate is a bit expensive. However, Bob Bradshaw at Sandia in California, chemical engineer and leader in the research says that there is always price to pay as nothing is obtained for free.
There are other long-term studies that are focusing on storing heat in sand or simply creating tanks full of salt. The priority is to find new storage technology at reasonable cost. The real trigger for renewable energy will only emerge when emissions-free technology gets the attention due. Establishing higher tax on pollution, would immediately give investors the right call for renewable energy to grow and together with storage and energy conservation technology.
Solar Millennium has constructed the first Solar Thermal power plant that uses molten salt to store energy. Andasol 1, might not be the best one but it is at least the first one to show that the technology exist and works.
Source: Scientific America