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Saturday, 20 July 2019
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Raw materials & technologies, Technologies

Concrete heating

Tuesday, 21 July 2015

An experiment is currently underway in Switzerland: A construction physicist had researchers install six cubic meters of special concrete in the garage of his vacation home.

Concrete formwork for the small batch production of the storage elements. Source: Empa

Concrete formwork for the small batch production of the storage elements. Source: Empa

The concrete stores heat during the summer and releases it in the winter as and when needed, which enables the house to be heated for weeks – sustainably and ecologically.

Mineral ettringite emits water vapour

When the physicist read about the concrete heat storage system in the media in 2012, he was immediately taken by the idea. Researchers from Empa’s Concrete/Construction Chemistry lab had reported that concrete building components produced with calcium sulfoaluminate cement (CSA) might make ideal seasonal heat storage systems. If the concrete blocks are heated to 80 degrees via heating coils with the aid of solar panels in the summer, the mineral ettringite contained in the CSA cement emits water vapour. This leaves behind the dehydrated concrete block, which "stores” the heat virtually loss free. In winter, the process is reversed: water is channeled into the dry concrete, absorbed by the ettringite and heat is released, which can be conducted away via the heating coils. "Could this be the solution to plug the gap between Christmas and February?” wondered the physicist. After a discussion with Empa researchers, he was convinced to attempt the project together.

First drying tests went well

Empa scientists are delighted: "The collaboration is a unique opportunity for us to hone a system that proved itself in the lab for practical use.” They received support from the Swiss Federal Office of Energy. In the spring, against a breathtaking backdrop with a bright blue sky and framed by the Central Swiss mountains towering up to 3’000 meters into the air, a heavy truck finally rolled up. The team unloaded 24 concrete blocks, which had been cast at Empa, and installed them against the rear wall of the garage n Seelisberg. The concrete storage system’s first drying tests went well, even if it was not heated up to the intended 80°C. Apart from CO2 emissions during production and transport, the energy storage system is ecologically sound. And cost effective: one ton of CSA concrete costs less than 383,88 EUR. If it doesn’t work, the energy storage system can be easily dismantled again after the three year test phase thanks to its modular structure.

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