18 May 2017
Comfortable, efficient and affordable heating, ventilation and air conditioning (HVAC) systems in buildings are highly desirable to achieve zero energy building (ZEB) effort. Traditional vapour compression air-conditioners hold a lower COP (coefficient-of-performance) (typically 3.2~3.8) because it often operates at a lower evaporation temperature (5~7oC) and a higher condensing temperature (50~55oC) caused by cooling-based dehumidification method that handle both sensible and latent load together. Temperature and humidity independent control or desiccant systems have been proposed to overcome these challenges, however, the COP of current desiccant systems is quite small and additional heat sources are usually used. In this paper, we report desiccant-enhanced direct expansion heat pump based on water-sorbing heat exchanger by desiccant coating that exhibits an ultrahigh COP value of more than 6 without sacrificing any comfort and compactness. The efficiency is double in comparison with current normal room air conditioners, which is a breath-taking and revolutionary progress. This new approach opens up the possibility of designing a ZEB with DDX HP powered by solar PV, and one PV model (265Wp) can effectively handle about 10m2 cooling load in Shanghai in summer.