Two-Stage Solar–NaOH Thermochemical Heat Pump Heating System for Building Heating: Operations Strategies and Theoretical Performance

Yujie Su, Yi Yang, Guoqing He (), Renhua Liu and Ding De
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Yujie Su: College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
Yi Yang: The Architectural Design and Research Institute, Zhejiang University, Hangzhou 310058, China
Guoqing He: College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
Renhua Liu: College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
Ding De: The Architectural Design and Research Institute, Zhejiang University, Hangzhou 310058, China

Energies, 2024, vol. 17, issue 8, 1-16

Abstract: Heating buildings with solar energy is challenged by the seasonal mismatch between solar availability and heating demand. Thermochemical energy storage is a promising technology to overcome this challenge because of its high energy density. In building applications, space requirement is also an important consideration. Therefore, both the storage space and collector areas are important considerations, with only the latter often being neglected in previous studies. This paper proposes a novel two-stage thermochemical heat pump heating system based on the working pair of NaOH/H 2 O. We demonstrate that this system can work with a concentration difference (70% wt–30% wt) for the climate in hot summer and cold winter regions in China. The energy storage density based on the discharged solution is 363 kWh/m 3 . With this solar-driven thermochemical heat pump heating system, 35.13 m 2 of collectors and 10.48 tons of 70% wt NaOH solution are sufficient to complete a full charge–discharge cycle and meet the heating demand of a single-family house (winter space heating + DHW: 9370 kWh, summer DHW: 2280 kWh). The theoretical maximum storage for solution (discharged + water tank) is 32.47 m 3 . Compared with the sensible seasonal storage alternative, the collector area is reduced by 12.5% and the storage space is reduced by 59%, with a possible further reduction through optimization. With the potential to be further optimized for space saving, the two-stage solar–NaOH heat pump heating system is an energy-efficient and space-efficient heating system for buildings in the hot summer and cold winter regions of China.

Keywords: solar energy; sorption energy storage; sodium hydroxide; collector area; double stage (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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