Solar-desiccant air-conditioning systems - Solar Energy Sciences and Engineering Applications - page 526

during the summer and South East Asia year round, air temperature and humidity are
high. In addition, as day-long dehumidification is needed compared to other climatic
conditions, the more cheaply available night-time (off-peak) electric energy can be
stored for daytime operation of the system (Hammou and Lacroix, 2006). Enteria
et al. (2010b) show the applicability of night-time electric energy storage for daytime
utilization. Combined solar energy for air dehumidification with ground water source
for air cooling makes the system utilize natural energy sources, such as done in London
(Ampofo et al., 2006).
The vapour compression system operates to remove air moisture content by cooling
the air below its dew-point temperature. However, as the air after cooling to its dew-
point temperate is very cold, reheating of the air is needed before it can be introduced to
the indoor environment. As the Asia-Pacific region is very hot and humid all year round,
in South East Asia and during summer in East Asia especially, the vapour compression
system operates thoroughly to reduce the very high moisture content of outdoor air.
Application of the desiccant material coupled with the vapour compression system
minimizes the operating condition of the latter since the desiccant material handles the
air latent energy content while the vapour compression system handles the air sensible
load (hybrid desiccant). Liquid system applications can have a higher performance
(44.5%) in green building (Ma et al., 2006). The advantage of the hybrid desiccant
air-conditioning system is its operation in part loading (Jia et al., 2006).
Table 16.5.1 shows the development and application of desiccant-based air-
conditioning systems, which are expanding globally. However, in the hot and humid
climate of the Asia-Pacific Region, South America and Africa the system is still not
fully utilized. Therefore, investigations of the system for applications in these regions
should expand the potential of the system for more wide-scale use. The system has
the potential to be a leading air-conditioning technology for energy-efficient, healthy
buildings in hot and humid climates (Sekhar, 2007). As such, it should contribute
significantly to reducing conventional energy consumption and GHG emissions by the
building sector while also providing human thermal comfort conditions.
16.5.2 Temperate regions
Solid-based desiccant air-conditioning systems have actually been applied in many dif-
ferent climatic conditions. In addition, feasibility studies through numerical studies on
the applicability of the system have also been carried out. White et al. (2009) conducted
numerical investigation of the solar-powered solid-based desiccant air-conditioning
system in different Australian climatic conditions. The investigation centred on direct
application of solar energy for the regeneration of the desiccant wheel. The study
showed that the system is applicable in the warm temperate climate of Melbourne and
Sydney, but not in the tropical climate of Darwin due to the hot and humid outdoor
air. The research also showed that solar energy can support building comfort condition
by means of a high ventilation rate.
Bourdoukan et al. (2008) conducted numerical investigation of the solar-powered
desiccant air-conditioning system using an evacuated tube collector. The researchers
showed that collector areas vary with different location due to the required cooling
load. For higher outdoor air humidity content, a higher solar collector area was needed
in each of three geographical locations: La Rochelle (France), 13.4 g/kg; Bolzano