Dynamic discharging characteristics of absorption thermal battery under different capacity regulation strategies

Thermal battery plays an important role in renewable energy utilization towards carbon neutrality. The novel absorption thermal battery (ATB) has excellent performance but suffers from serious capacity attenuation. To address this problem, two capacity regulation methods, i.e., variable solution flow and variable cooling water flow, are proposed to achieve a demanded discharging rate. The effects of the two regulation strategies on the dynamic discharging characteristics and overall storage performance are comparatively investigated. To demonstrate the adjustability of the output capacity, several stable discharging rates are successfully maintained by the proposed methods. To maintain a higher discharging rate, the stable discharging time has to be sacrificed. As the demanded output increased from 0.5 kW to 6.0 kW, the stable discharging time decreased from 781.8 min to 27.9 min under variable solution flow and from 769.9 min to 30.7 min under variable cooling water flow. With the increase of solution or water flow rate, the energy storage density is improved, while the energy storage efficiency is slightly increased first and decreased later. The regulation method of variable water flow shows relatively lower energy storage efficiency due to the larger pump power. This study could facilitate reasonable development and application of ATB cycles.