Building Heat Demand-Driven Collaborative Design and Capacity Substitution Mechanism of Building–PVT Solar Heating Systems

Abstract

The building heat demand and the energy system capacity are usually designed independently in solar heating systems for rural houses in cold regions. This leads to oversized system capacity and a lack of collaborative design between the building side and the energy system side. To address these issues, a building–PVT collaborative passive–active design framework was proposed for a typical rural house in Lanzhou, Gansu Province, China. First, a dynamic building thermal model was developed in EnergyPlus. Four typical building configurations, including a baseline house, an insulated house, a sunspace house, and a sunspace house with an intelligent thermal curtain, were established. The hourly heating demand over 8760 h was obtained for each configuration. Then, the hourly building heating demand was used as the unified boundary condition to develop a dynamic PVT heating system model in MATLAB. The responses of the PVT collector area, thermal storage tank volume, and auxiliary heater capacity to building heat demand were analyzed. A CSR was further proposed to establish a quantitative relationship between building heating load reduction and PVT system capacity reduction. Finally, a collaborative multi-objective optimization was carried out using the NSGA-II with the objectives of maximizing the SF and minimizing the LCC. The TOPSIS was adopted to determine the optimal compromise solution. The results show that the integrated passive design combining a sunspace with an intelligent thermal curtain reduces the annual heating energy consumption by 44.0% compared with the baseline house. The reduction in building heat demand simultaneously decreases the required PVT system capacity. The PVT collector area, thermal storage tank volume, and auxiliary heater capacity decrease by 44.14%, 27.55%, and 25.78%, respectively. This indicates that passive building energy-saving measures significantly change the design boundary of the energy system. The proposed CSR effectively quantifies the capacity substitution effect of building-side energy saving on the PVT heating system, and the integrated passive design achieves the highest overall CSR. The multi-objective optimization generates a uniformly distributed Pareto front. The optimal compromise solution achieves an SF of 86.41% with an LCC of 8.34 × 104 CNY. The recommended configuration includes a 50 mm insulation layer, a 40 m2 sunspace, a 12.62 m2 PVT collector area, and a 1.23 m3 thermal storage tank. Compared with the initial design, the optimized configuration significantly improves solar energy utilization while maintaining a low LCC and further reducing the required auxiliary heater capacity. This study establishes a collaborative analysis framework between building heat demand and PVT system capacity. A quantitative mapping method between building heating load and system capacity is proposed. The framework enables integrated optimization of building thermal design and energy system capacity configuration. The proposed method provides a new theoretical approach and practical guidance for the design of solar heating systems for rural houses in cold regions.