The European AMADEUS project, coordinated by researchers from the Solar Energy Institute of the Polytechnic University of Madrid (UPM) leads in Europe the studies on the storage of energy in molten silicon, as a basis to create new devices that allow energy to accumulate more compactly and efficiently.
In the AMADEUS project, energy is stored in the phase change from solid to liquid silicon. In this way, the researchers take advantage of the high latent heat of silicon phase change, which exceeds the storage capacity of the molten salts by 10 times. “In our concept silicon does not move, and changes from solid to liquid in a single tank, so it is always at temperatures close to the melting point (1414ºC),” explains Alejandro Datas, a researcher at the Institute of Solar Energy of the UPM and scientific coordinator of the project.
The direct storage of solar energy in solar thermal power plants, or the integration of electrical storage and cogeneration in homes and districts are just some of the applications that the new devices resulting from the AMADEUS project could have. It is funded by the Future Emerging Technologies (FET) call of the Horizon 2020 program of the European Commission which is now in its second year of operation out of the three originally planned for its duration.
With a budget of 3.3 million euros AMADEUS (Next Generation Materials and Solid State Devices for Ultra High Temperature Energy Storage and Conversion) is researching into new materials and devices that allow energy storage at temperatures in the range of 1000 and 2000 ºC. Thus, it is intended to break with the 600ºC barrier, rarely overcome by the current systems used in solar thermal power plants.
To achieve this, the experts are working with different metal alloys of silicon and boron, which melt at temperatures above 1385 ° C and will allow storage between 2 and 4 MJ / kg, “an order of magnitude higher than the salts currently used”, the researcher of the UPM adds.
In addition, they are researching the materials necessary to contain these molten metals for long periods of time and achieve good thermal insulation, as well as the devices to achieve an efficient conversion of heat stored in electricity.
Direct conversion of heat into electricity
The project will investigate a new concept (patented by UPM researchers) that combines the thermionic and photovoltaic effects to achieve the direct conversion of heat into electricity. Unlike conventional thermal machines, this system does not require physical contact with the thermal source, since it is based on the direct emission of electrons (thermionic effect) and photons (thermo photovoltaic effect).
“If successful in their development, these new devices will not only be able to work at very high temperatures, but will also simplify and drastically cheapen the system, since they do not require a heat transfer fluid, or pipes and heat exchangers, which today, represent a large part of the cost of these facilities, ” Datas explains.
In addition to the Polytechnic University of Madrid (UPM), the research consortium of the AMADEUS project includes the National Research Council of Italy, the Research Institute of the Polish Foundry, the Norwegian University of Science and Technology, the Hellas Center for Research and Technology of Greece, the University of Stuttgart in Germany, and the company IONVAC Process SRL of Italy.