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High temperature thermal energy Storage by Reversible thermochemical Reaction

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New system stores heat energy in chemical compounds

Thermal power plants that store heat for when solar energy is unavailable could solve some of the problems with solar power. EU-funded scientists successfully designed an innovative thermal energy storage system of high heat capacity and energy density that relies on thermochemical reactions.

Energy

With EU funding of the project STORRE (High temperature thermal energy storage by reversible thermochemical reaction), scientists investigated new ways to store the Sun's thermal energy for electricity production for the mid and long terms. Concentrated solar power (CSP) is particularly well suited to accommodating intermittent demand as it can be combined with large-scale thermal energy storage. Contrary to the photovoltaic cell storage technologies, CSP stores the Sun's energy as thermal energy. STORRE demonstrated an alternative means of storage based on a reversible chemical reaction. This is endothermic in one direction to take in the heat for storage, and exothermic in reverse to free heat for the power block. The approach relies on the reversible hydration-dehydration reactions of calcium oxide and hydroxide. The non-hazardous products are easily stored at room temperature and under atmospheric pressure, while their different phases (gas and solid) make their separation easier. Thermochemical energy storage has been hitherto studied at lab scale and has not been demonstrated even in a prototype system until now. Researchers built a pilot storage system with energy density of around 300 kWh that includes a simple counterflow heat-exchanger reactor. The new system featuring CSP technology uses steam as a heat transfer fluid that is generated directly in the receiver tube. This not only allows higher temperatures but also saves on plant components. The maximum temperature of hot steam provided by the receiver was approximately 500 °C. STORRE delivered an efficient thermal energy storage system that along with CSP generation successfully overcomes problems of fluctuating solar energy supply. This new and promising solution brings thermochemical energy storage one step closer to reality.

Keywords

Solar energy, energy storage, thermochemical, STORRE, concentrated solar power

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