Experimental and theoretical study on thermal storage performance of sand-based thermal storage floor in rural areas, Inner Mongolia, China

During China's rural clean heating reforms, despite the widespread application of solar-air source heat pump (SASHP) technology, upgrades to heating terminals continue to lag behind. To enhance the performance of renewable energy system , developing low-cost thermal storage terminal is crucial for budget-constrained rural settings. This paper thoroughly investigates the heat storage and release characteristics of a sand-based thermal storage floor (SBTSF) in rural residence, employing both experimental and theoretical methods. Models were developed to compare the performance of SASHP heating systems integrated with conventional radiant floor, SBTSF and PCM floor using TRNSYS software. Results indicate that the SBTSF provides strong thermal storage capabilities, with a heat discharge rate of 350–550 W over 9–12 h, ensuring consistent heating and maintaining indoor temperatures above 16 °C for up to 14 h without additional heat input. Compared to conventional radiant floor, PCM floor outperforms the SBTSF in terms of indoor temperature and energy efficiency. Nevertheless, the performance of SASHP heating system with SBTSF remained highly competitive, with a 36.7 % reduction of overall energy consumption, a 21.1 % enhancement of solar fraction, a 49.2 % improvement of coefficient of performance (COP). Additionally, SBTSF results in a 37.1 % reduction in operating costs, and the payback period is significantly shorter than that of the PCM floor. This study analyzes the heat storage and release characteristics in a real usage environment of rural households, providing a comprehensive comparative analysis that highlights the differences and advantages of various heating terminals, and offers valuable insights for enhancing thermal performance and energy efficiency of renewable energy system in rural areas. • Performance analysis on sand-based thermal storage floor (SBTSF) for rural areas • Performance comparison of conventional radiant floor, SBTSF, and PCM-based floor • Ability of SBTSF to keep indoor temperature above 16°C for 14 hours at night • Comparable thermal storage and release capabilities of SBTSF to PCM-based floor • The SBTSF has a significant investment cost advantage compared to PCM-based floor.