Sun and stone: a simple solution for energy accumulation?

The next generation of sustainable energy technologies could be built with low-tech, ultra-low-cost materials: rocks and the sun. Thanks to a new approach known as concentrated solar energy, heat from the sun is stored and then used to dry food or create electricity.

The team from the School of Materials, Energy, Water and Environmental Sciences (MEWES), Nelson Mandela African Institution of Science and Technology, published in ACS Omega, found that some samples of soapstone and granite from Tanzania are suitable for storing heat solar, thanks to the high energy density and stability even at high temperatures.

Energy is often stored in large batteries when not needed, but these can be expensive and resource-intensive to produce. A less technological alternative is thermal energy storage (TES), which collects energy as heat in a liquid or solid, such as water, oil or rock.

When released, the heat can power a generator to produce electricity. Rocks like granite and soapstone were formed specifically under conditions of high heat and are found all over the world, which could make them favorable TES materials.

However, their properties can vary greatly based on where they were formed, making some specimens better than others. In Tanzania, the Craton and Usagaran geological belts meet and both contain granite and soapstone. For this reason, Lilian Deusdedit Kakoko, Yusufu Abeid Chande Jande and Thomas Kivevele of the Nelson Mandela African Institution of Science and Technology and Ardhi University wanted to investigate the properties of soapstone and granite present in each of these bands.

The team collected several rock samples from the belts and analyzed them. The granite samples contained a large amount of silicon oxides, which added strength. However, the craton's granite contained other compounds, including muscovite, which are susceptible to dehydration and could make the rock unstable at high temperatures.

In soapstone, magnesite was found, which gives it a high density and heat capacity. When heated to temperatures above 980 degrees Celsius, both the soapstone samples and the Usagaran granite showed no visible cracks, while the granite from the Craton crumbled. In addition, soapstone released the accumulated heat more easily than granite.

Overall, Craton soapstone achieved the best performance as TES, which can effectively absorb, store and transmit heat, while maintaining good chemical stability and mechanical strength. However, the other rocks may be better suited for a low-energy TES application, such as a solar dryer. The researchers say that while more experiments are needed, these samples show good promise as a material for sustainable energy storage.

The accumulated heat can be used as a heat source for electricity generation or, much more simply, for other activities that require heating, such as agricultural activities or domestic heating.

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The article Sun and stone: a simple solution for energy accumulation? comes from Economic Scenarios .

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This is a machine translation of a post published on Scenari Economici at the URL https://scenarieconomici.it/sole-e-pietra-una-soluzione-semplice-per-laccumulazione-dellenergia/ on Sun, 02 Jul 2023 17:00:03 +0000.