Re-allocation and re-distribution of thermal resistance and capacitance of envelopes in solar heating building integrated heat pipes: A climate-responsive strategy

Optimizing the allocation and distribution of thermal resistance and capacitance (RC) in building envelopes helps to improve building energy efficiency. The RC spatial re-allocation concerns how total thermal resistance and capacitance are assigned among building envelopes, and the re-distribution concerns the nonlinear variation of thermophysical properties with temperature. Existing research mostly focuses on building envelopes with constant thermal properties, lacking RC optimization for novel buildings with variable thermal properties. This study concentrates on the building integrated heat pipes (BIHP), a solar heating building with variable thermal properties, and proposes a novel methodology to optimize RC allocation and distribution, covering five climatic zones and three envelope construction types. The results demonstrate that the optimal RC spatial allocation follows a targeted maximum allocation principle, that is, the external wall should be given the largest resistance, and the heat pipe internal wall should be given the largest capacitance. The optimal capacitance distribution of the heat pipe internal wall exhibits a stepped unimodal function within a narrow temperature range, resembling phase change material. For passive BIHP without heating equipment at different locations, the center temperature of the optimal unimodal function distribution varies according to local climate resources, and the temperature span is 2–3 ℃; while for active BIHP with heating equipment, the center temperature remains at 19 ℃ and the temperature span is 1 ℃. This study proposes a dual-dimensional thermal design approach on RC spatial allocation and nonlinear temperature-dependent distribution of building envelopes, providing theoretical support for realizing climate-responsive buildings.