Design and experimental testing of a 150 kWh thermal battery using thermosiphons embedded in a concrete matrix for power plant flexible operation

One of the options for achieving the global temperature limitation of 1.5 degrees C target, for the mitigation of global warming, is based on the better penetration of renewables into the electrical grid. This has imposed a burden to fossil fuel fired power plants since they are required to operate away from their baseload mode to compensate for the inherent intermittence of the renewable power. Integrating energy storage with fossil plants is an option to achieve their needed flexibility. A cost competitive energy storage option for the solution is based on storing sensible heat in concrete. This paper reports research results and development of a thermal battery cell (TBC) capable of operating at temperatures up to 425 degrees C. A novel concept consisting of a concrete matrix for sensible heat storage, engineered to provide enhanced thermal and mechanical properties, and twenty-two thermosiphon elements, engineered for dual action were designed and fabricated into a single thermal energy storage (TES) module. Research for the development of the components for the TBC was performed in the laboratory. Efficient heat transfer, to/from the storage media, was demonstrated under several charging and discharging conditions with a thermal storage capacity of 150 kWhth and a rapid discharge, making the TBC suitable for fast ramping when integrated with a fossil fuel fired power plant. Efficient radial heat transfer to the concrete was observed due to the well designed spacing and location of thermosiphons in the radial direction. A minimal temperature difference of 2 degrees C, between the thermosiphons bottom and top was obtained, demonstrating the isothermicity of those elements. An overall end-to-end TBC energy-to-energy round trip efficiency of 70% was achieved.

Automated summary

One of the options for achieving the 1.5 degrees C global temperature limitation target is to integrate energy storage with fossil-fired power plants. In this study, a thermal battery cell (TBC) capable of operating at high temperatures was developed for efficient heat transfer and energy storage using concrete as the storage medium. The TBC demonstrated a thermal storage capacity of 150 kWhth and rapid discharge, making it suitable for fast ramping when integrated with fossil fuel-fired power plants. The overall energy-to-energy round trip efficiency of the TBC was achieved to be 70%.