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How to store solar thermal energy in molten silicon

How to store solar thermal energy in molten silicon

A team of researchers at the Solar Energy Institute (IES-UPM) of the Polytechnic University of Madrid (UPM) is developing a new system that allows storing energy in molten silicon, the most abundant element in the earth’s crust. The finding paves the way for a new generation of low cost solar thermal power plants.

With this system, which is patent pending in the US, the input power, be it either direct solar energy or surplus electricity from a renewable power generation plant, is stored in the form of heat in molten silicon at very high temperatures, about 1,400 degrees Celsius.

Silicon has unique properties that confer it the ability to store more than 1 megawatt-hours of energy in one cubic meter, ie, about ten times more than with the salts currently used in solar thermal power plants, explains the UPM in a statement.

Molten silicon and thermo photovoltaic cells

The silicon is kept molten by thermally isolating it from the environment until such energy is demanded, at which time the transformation of stored heat into electricity occurs. “At these high temperatures, silicon glows with high intensity, just as the sun does, and therefore photovoltaic cells- called in this case thermo photovoltaic – can be used to convert the said incandescent radiation into electricity,” says Alejandro Datas, principal researcher of this project.

In using thermo photovoltaic cells lies the key to this system “as any other type of generator could hardly work at such extreme temperatures. In addition, these cells produce in the order of 100 times more electric power per unit area than a conventional solar cell and are able to achieve higher conversion efficiencies, theoretically even over 50%, “he adds.

Storing up to ten times more energy

The end result is an extremely compact, with no moving parts silent system able to store up to ten times more energy than existing solutions and using abundant and inexpensive material.

It is anticipated that the first application of these devices be in the field of solar thermal energy, where currently used complex systems using heat transfer fluids, valves and turbines to produce electricity would be avoided, said the UPM.

By simplifying the configuration, the cost of energy generated can drastically be reduced, which along with a larger storage capacity, could turn this solution into one of the most profitable of all the alternatives in renewable generation, continues the note.

Residential Sector

Moreover, it says that in the medium to long term these systems could also be used to store electricity in the residential sector and manage all energy needs (electricity and heat) in urban centers.

Recently, the team of researchers at the UPM has secured funding through an Explora project from the Ministry of Economy and Competitiveness with which it will begin manufacturing the first prototype at the laboratory scale. In parallel, researchers are launching a business project (Silstore) with which they intend to industrialize these developments. At the moment, the project has been recognized as one of the best start-ups born in 2015 in the UPM.