Uninterrupted renewable power through chemical storage cycles

Energy storage is indispensable to ensure uninterrupted electrical power supply from intermittent renewable energy sources. Carbon storage cycles (CSC) involving cyclic transformation of carbon atoms between carbon dioxide and carbon fuel have the potential to achieve high storage efficiency (∼54-59%) for GWh-level energy storage with much reduced storage volumes compared to other options. During the period of renewable energy availability, the cycle utilizes stored liquid carbon dioxide to synthesize a carbon fuel and then store it in liquid state. When renewable energy is not available, the carbon fuel is oxidized to deliver electricity. The produced carbon dioxide is captured, liquefied and stored for reuse during energy availability. Here, we review the novel features of the CSC, and three exergy based metrics that allow systematic screening of carbon fuel to be utilized in the cycle. Detailed process simulation results are also reported for dimethyl ether, an attractive carbon fuel candidate, which results in ∼57% storage efficiency.