Experimental evaluation of a capillary heating bed driven by an air source heat pump and solar energy

Abstract

The traditional Chinese kang is a widely used domestic heating system in rural areas in northern China. However, such system could cause serious air pollution due to burning of biomass materials or coal. An improved bed heating system is introduced in this study to reform the traditional kang, using a capillary mat as a heating terminal, an air source heat pump (ASHP) and a solar energy as the heat source. An experimental prototype was built in a residential house in Xi’an, China, and tests were conducted to evaluate the system’s feasibility and performance under different operational modes. Results showed that the system could effectively provide an acceptable thermal environment for a separately heated room and with a reduced consumption of carbon-based fuel. When the system was completely driven by the ASHP, the daily electricity consumption of the ASHP is only 5.5 kWh with a supply water temperature of 40°C. When coupling the ASHP with the solar energy, the daily hours of solar energy utilization ranged from 3.5 to 4.5 h per day when the ratio of the solar thermal collector area to the floor area was approximately 1.0. The available ratio (days of utilized solar energy to the days comprising the full heating season) exceeded 66.0% over three heating seasons. The system was shown to be a feasible and energy-efficient heating strategy for rural buildings.