Development of Storage Battery Using CO2Gas Hydrate Thermal Cycle

Abstract

The expansion of renewable energy power generation is urgently needed to realize a decarbonized society. However, the high cost of batteries used to adjust electricity fluctuations is hindering the expansion of renewable energy power generation. In this study, we aim to develop a new energy storage method for storing excess electricity by using the unique state change of CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> hydrate. CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> hydrate is produced at about 0 °C under high pressure of several MPa, and can be dissociated at about room temperature. In the proposed system, the cold and warm heat required for the cooling and heating of CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> hydrate is obtained from renewable energy. CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> hydrate absorbs CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> during its formation and releases high-pressure CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> hydrate dissociation. Therefore, the pressure in the reaction vessel becomes high after CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> hydrate dissociation. In this study, an expander is driven by the high-pressure dissociation gas of CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> hydrate and a generator connected to the expander is operated. The amount of electricity generated in this process will be investigated and compared with the amount of electricity generated when the reaction vessel is filled CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> . The amount of electricity generated was greater when CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> hydrate dissociated gas was used to generate electricity than when the reaction vessel was filled only with CO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> .