Configurational analysis of an hybrid system based on an air-source heat pump and biomass boiler for rural areas

Integrating air-conditioning with air-water heat pumps combined with biomass boilers is a very suitable solution in rural areas where there may be renewable support with photovoltaics. Still, in many cases, the availability of energy is not sufficient for the HP operation at full load, or the environmental humidity is so high that it is necessary to carry out defrost cycles at the expense of the comfort of its users. Therefore, it is relevant to study the combination of both technologies based on the design capabilities of the heat pump and the boiler and their partial operating loads, setpoints, and associated controls that allow their integrated operation with the best possible overall efficiency, apart from its better-obtained comfort. In this case, the Design Builder tool has been used to model the typical demand of a rural house under various efficiency standards in Spain. With this demand, the planned installation has been analyzed using TRNSYS to model a regulated inverter heat pump with a PID and a biomass boiler. The installation also includes a buffer tank before covering heating demand. The results show that, depending on essential parameters such as the power ratio of both technologies, heat/cooling ratio, and their activation temperature, solutions with better overall efficiency can be obtained than in the individual case of the heat pump. The model has been tested for diverse configurations connecting the heat pump and biomass boiler, in addition to three typologies of the same house with progressive efficiency standards.