The solar energy utilization has great significance regarding the ever-increasing environment pollution and energy shortage issues. To overcome the instability and intermittency of solar energy, various solar thermal storage technologies have been proposed, and absorption thermal storage is promising for its high energy storage density and long-term storage. However, past researches focused more on working pair and neglected the potential of cycle enhancement. In this paper, an absorption solar thermal storage system with enhanced energy storage density from double-stage output is studied experimentally. A prototype with water-LiBr working pair was designed, manufactured, and tested. The long-term heat storage and short-term heat/cold storage were both tested and evaluated for the double-stage and single-stage working modes. Hot water at 75–85 °C was used as heat source in the charging process to simulate the solar energy from non-concentrated collector, and the prototype was able to provide heating output/cooling output at 50/11 °C in discharging process. Energy storage density of 233 kJ/kg (103 kWh/m³) was achieved for heating output with temperature lift of 30–46 °C, which was 2.51 times higher than that of the single-stage system (93 kJ/kg). The proposed system with large temperature lift, multi-function output, and enhanced energy density has proved its effectiveness in solar thermal storage and conversion, which also provides a feasible option for the large-scale utilization of solar energy.

太阳能的利用对于日益严重的环境污染和能源短缺问题具有重要意义。为了克服太阳能的不稳定性和间歇性，已经提出了各种太阳能储热技术，并且吸收式储热由于其高的储能密度和长期储藏而有希望。但是，过去的研究更多地集中在工作对上，而忽略了循环增强的潜力。本文研究了一种利用双级输出提高储能密度的吸收式太阳能储热系统。设计，制造和测试了带有水-溴化锂工作对的原型。对于双阶段和单阶段工作模式，都测试和评估了长期储热和短期储热/冷储。在充电过程中，将75–85°C的热水用作热源，以模拟来自非集中式集热器的太阳能，并且该原型能够在放电过程中提供50/11°C的加热/冷却输出。储能密度为233 kJ / kg（103 kWh / m³）实现了在30-46°C的温度提升下的加热输出，这比单级系统（93 kJ / kg）高2.51倍。所提出的具有大的温度提升，多功能输出和增强的能量密度的系统已经证明了其在太阳能热存储和转换中的有效性，这也为大规模利用太阳能提供了可行的选择。