Comprehensive evaluation and analysis of a nearly zero-energy building heating system using a multi-source heat pump in severe cold region

The integrated application of multi-energy coupled technology in nearly zero-energy building(NZEB)is promising from the perspective of low-carbon development to achieve the goal of net zero energy.PVT(photovoltaic/thermal),air,and ground sources were combined organically to establish an experimental platform of a multi-source heat pump(MSHP)system,which can realize flexible switching of multi-energy sources.The paper presents the analytical hierarchy process and fuzzy comprehensive evaluation method to comprehensively evaluate the five modes of the MSHP system with regard to energy,economic and environmental benefits.The results indicate that the waste heat of the PVT cavity can improve the coefficient of performance of the heat pump unit(COP)by approximately 8.0%.The initial investment in air source heat pump(ASHP)modes is lower than that of a coal-powered system.The ground source heat pump(GSHP)modes have high stability and their payback period is 8.81–10.66 years.The photovoltaic/thermal-dual source heat pump(PVT-DSHP)mode presents the most appropriate system applied in the NZEB in severe cold region,followed by the DSHP,GSHP,ASHP,and PVT-ASHP mode.When compared with other modes,COP,annual saving cost,carbon dioxide emission reduction,and comprehensive value of the PVT-DSHP mode have improved by 7.07%–29.57%,2.21%–23.88%,3.38%–14.83%,and 27.91%–52.62%,respectively.The study provides important insights into the practical application and sustainable development of multi-energy coupled systems in the NZEB in severe cold region.

Performance of a collector-storage solar air heating system for building mechanical ventilation preheating in the cold area

The application of solar thermal energy to preheat cold fresh air for mechanical ventilation could save a lot of energy and ensure the stable operation of the ventilation system.In this paper,a kind of collector-storage solar air heating system(CSSAHS),in which the thermal storage unit(TSU)is characterized by a dual S-channel for heat transfer,is proposed and the mathematical model for the integrated system was established.The model including the TSU,solar air collector,heat recovery device,and the fan was verified by an experimental study set up in a typical cold city in China.The model has been verified by experiments.The simulation results demonstrate that fresh air is the most important factor affecting storage/release efficiency.The increasing rate of heat release efficiency in the range of fresh air temperature-6-18°C is about 1.58%/°C.The solar heat collector area and the size of the TSU suitable for representative cities in cold regions are optimized based on multi-condition simulation analysis.The CSSAHS can preheat fresh air for 5 h after heat storage and the release efficiency is between 52 and 74%.Compared with other systems,the energy-saving rate of the CSSAHS is 26.5-33.3%in cold winter,and the heat supply ratio of the TSU is 24.4-35.1%.