Active indoor air cleaning and heat recovery technology for energy saving of building ventilation

An innovative clean air heat pump (CAHP) which integrated heating/cooling, dehumidification, ventilation, air cleaning and energy recovery in one unit was proposed. The CAHP was proposed based on the combination of desiccant rotor with heat pump, and was designed to maintain a comfortable, healthy indoor environment in normal office, commercial and residential buildings. The desiccant rotor was used for dehumidification and indoor air cleaning; the heat pump provided sensible heating/cooling and regeneration heat for the desiccant rotor.

A theoretical model of the CAHP was established with numerical equations. The theoretical model is used for predicting the volatile organic compound (VOC) removal and energy performance of the CAHP. The theoretical model was validated by experimental data. Validating results showed that the model could be used to predict the performance of CAHP. Numerical simulations were conducted to analyse and optimize the performance of the CAHP. Simulation results showed the CAHP could clean air borne contaminants effectively and could provide an energy efficient choice for ventilation.

Based on the theoretical analysis, a prototype unit of the CAHP was designed and developed. With the prototype unit, laboratory experimental studies were conducted to investigate its energy performance under different outdoor climates including cold, mild-cold, mild-hot and extremely hot and humid climates. The energy performance of the CAHP was then evaluated by comparing with
conventional reference systems. The results showed that to keep same indoor air quality, the CAHP could save substantial amount of energy. For example, compared to conventional air source heat pump, the CAHP could save up to 55.93%, 36.83% and 32.33% of power for ventilation and air conditioning in a test room in summer of Copenhagen, Milan and Colombo. It can save 11.20%, 10.25% of power for ventilation and heating in the test room in winter of Copenhagen, Milan. If compared to a gas boiler system, the CAHP can save 46.86% and56.44% of primary energy use in Copenhagen and Milan respectively.

Overall, the CAHP can clean indoor air with a high VOCs removing efficiency and can hold heating/cooling load in an energy efficient way. The CAHP could be an energy efficient choice for ventilation systems to maintain a healthy, comfortable and productive indoor environment.