Experimental Study on Performance of a Containerized 3 MWh High-Temperature Solid Heat Storage and Heat Supply System

Containerized high-temperature solid heat storage is a promising solution for flexible co-supply of steam and hot water. This paper conducts an experimental study on a 3 MWh containerized high-temperature solid heat storage and supply system, which can simultaneously provide saturated/superheated steam and hot water. High-density magnesia bricks are used as the thermal storage medium and heated to over 800 °C using off-peak electricity or curtailed renewable energy. Circulating air is driven through the saturated and superheated exchange sections successively by variable-frequency fans, realizing on-demand output of thermal energy. The size of the integrated equipment is 11.8 m × 2.13 m × 2.18 m. Experiments were conducted under direct electric heating mode and thermal storage mode. In direct electric heating mode, the storage is kept at 900 °C. As the circulating air flow increases, the inlet/outlet air temperature difference decreases from 600 °C to 300 °C at the saturated section, and from 350 °C to 70 °C at the superheated section, whereas the output power is increased. In thermal storage mode, an adaptive air-volume regulation strategy was used to maintain stable-power release despite the temperature drop of storage bricks. A complete 24 h storage/release cycle test shows that the effective heat storage capacity is 3.14 MWh, the electro-thermal conversion efficiency is 97.84%, and the superheated steam above 450 °C can be stably supplied.