An energy storage approach for storing surplus power into hydrogen in a cogeneration system

Abstract

Hydrogen, as a future energy carrier, can be used for grid power peak shaving and valley filling and has thus attracted widespread attention. However, the most urgent challenge that needs to be overcome is determining an effective method for providing high-temperature heat for water electrolysis. This study proposes a new approach for driving hydrogen production by adopting high-temperature combustion heat from the cogeneration system. Its feasibility and energy conversion performance are investigated. The results show that the power-/heat-to-hydrogen efficiency can reach approximately 0.95. Meanwhile, when hydrogen is continuously produced, the input work of the compressor and the output work of the turbine are always maintained at 245.4 kW and 448.0 kW, respectively. Namely, the thermodynamic parameters of the gas turbine remain unaffected while storing surplus power into hydrogen. In addition, the relative fluctuations of the cooling and heating outputs and component efficiency are controlled within 0.1 and 0.007, respectively. Importantly, the new approach can achieve the cascade utilization of methane, realizing the improvement of low-grade heat. For example, the energy level of solar heat of 650 °C and latent heat of 100 °C could be enhanced from 0.68 to 0.76 and 0.20 to 0.83, respectively. As a result, a higher thermodynamic degree of perfection of the thermodynamic system is obtained. Finally, the results of this study would be applied to store intermittent renewable electricity efficiently in the future.