engineers at empa (the switzerland federal laboratories for materials testing and research) have spent the past four years studying techniques for storing thermal solar energy from the summer months for use in the winter.
empa researchers work on a thermal energy storage process. (empa)
the work is part of the european comtes project, which has three competing techniques being studied for the storage of thermal energy. one project in austria and germany studied the storage of water in zeolites and the second in denmark and austria is studying the storage of heat in phase-change materials that melt and solidify. the third study is being conducted by empa.
in the fall of 2016, according to a report on the empa website, empa has been operating a plant in its lab that has demonstrated the ability to store energy in the long-term, although there is still a long way to go before this technology is commercially available.
the researchers heated sodium hydroxide solutions to evaporate the water to make the solution more concentrated and causing it to store energy. the solution can then be kept for long periods of time and can be transported. the energy is released when the solution comes into contact with water, which causes an exothermic reaction.
using a sea container as a lab area (to prevent damage from a sodium hydroxide leak due to its corrosive properties), the researchers used a spiral-shaped heat exchangers to flow the viscous solution along a pipe, absorbing water vapor on its path and transferring the generated thermal energy into the pipe.
“in the process, 50-percent sodium hydroxide solution runs down the outside of the spiral heat exchanger pipe and is thinned to 30 percent in the steam atmosphere,” the report noted. “the water inside the pipe heats up to around 50°c, which makes it just the ticket for floor heating.”
it continued, “the water from the sodium hydroxide solution evaporates; the water vapor is removed and condensed. the condensation heat is conducted into a geothermal probe, where it is stored. the sodium hydroxide solution that leaves the heat exchanger after charging is concentrated to 50 percent again, i.e. ‘charged’ with thermal energy.”
the comtes project is intended to meet the european union’s goal of reducing the continent’s dependence on fossil fuels and finding new means for producing renewable energy.
according to the comtes website, “thermal energy storage enables a higher portion of renewables to be supplied and because the storage technologies also create better efficiencies, by balancing the availability and the demand, for a range of energy conversion technologies.”
the empa research was also outlined in an article on newatlas.com; read more at http://newatlas.com/renewable-energy-heat-storage-empa/47334.
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