Weilong Zhang

The performance of regenerative indirect evaporative cooler (RIEC) highly depends on ambient temperature and humidity. To maintain indoor thermal comfort, proper control strategy is essential. Previous research indicates that high-low (H-L) control by using multi-speed technology, is superior to the conventional on-off control in terms of energy consumption and thermal comfort. Under H-L control, fan switches between a high speed and a low speed. The high speed is determined by the peak load. However, the selection of low speed involves with a great sense of subjectivity. Therefore, the influence of low speed on system performance is comprehensively investigated and optimal low speed to high speed ratio (L/H) is determined. An optimization method is proposed by considering annual energy consumption, predicted mean vote, temperature fluctuation and switch frequency of fan speed. Case studies have been conducted in some typical hot and arid regions. The results show that better thermal comfort can be provided under smaller L/H from the aspects of high control precision and small temperature fluctuation. The switch frequency of fan speed and annual energy consumption firstly decrease and then increase with the increment of L/H. H. The optimal L/H is between 0.2 to 0.3 from year-around perspective and comprehensive consideration.

In subtropical Hong Kong, clear glass is normally used as the translucent material for external windows of residential buildings, but it has poor heat insulation performance especially the tremendous solar heat gain in summer. To improve the thermal performance of conventional clear glass, a new heat blocking coating was developed. The coating can effectively absorb the near infrared radiation, so it can reduce the solar heat gain and therefore the energy use from airconditioning systems. In this paper, the preparation of the heat blocking coating was firstly introduced. Then the optical and thermal properties of different types of window glazing were tested in the laboratory. Based on the experimental data, a combined daylight, thermal environment and building energy numerical model of a public rental housing was established to fully simulate the performance of different types of windows glazing. The results indicated that the heat blocking coating can reduce about 275.4 kWh (14.4%) electricity use per year compared to conventional clear window.