Scientists in Tanzania discovered that granite, soapstone, and talc found locally in the region have proven to be highly suitable for storing solar heat. Boasting boast high energy density and stability even at high temperatures, these rocks are ideal elements—in addition to salt—for thermal energy storage on a grid-scale level.
Currently, storage systems mainly refer to electrochemical energy storage systems such as lithium-ion batteries, which enable rapid power distribution and help stabilize grid frequencies. However, their exorbitant costs and reliance on materials like lithium, cobalt, and nickel make them unsuitable for long-term energy storage applications.
In light of these challenges, Tanzanian scientists have set their sights on an alternative energy storage method known as thermal energy storage (TES). This approach involves capturing and storing heat in liquid or solid form, which can later be used to drive generators for electricity production. The Nelson Mandela African Institution of Science and Technology and Ardhi University in Tanzania believe that granite and soapstone, both formed under high-temperature conditions and widely distributed worldwide, hold great potential as effective heat storage materials.
▲ Granite (left) and soapstone (right) (Credit: ACS Omega)
Given that characteristics of granite and soapstone vary between regions, the research team embarked on an investigation of rocks at the intersection of Tanzania's Craton and Usagaran geological belts. The results showed that granite samples contain significant amounts of silica, endowing them with high strength. However, samples from Craton also contain white mica, which is prone to dehydration and instability at high temperatures. As for soapstone, the team discovered magnesite, a mineral with high density and heat capacity. When heated to temperatures exceeding 980 degrees Celsius, the talc samples and Usagaran granite showed no signs of cracking, whereas the Craton granite experienced immediate fracturing. Additionally, the team confirmed that soapstone released stored heat more easily compared to granite.
The team concluded that the Craton soapstone exhibits the most promising heat storage performance, efficiently absorbing, storing, and transferring heat while maintaining excellent chemical stability and mechanical strength. Other types of rocks could find application in low-energy storage systems such as solar dryers. Researchers emphasized the need for further experimentation, but these findings demonstrate the potential of these rocks to contribute to sustainable energy storage materials.
(Credit of the first photo: pixabay)