Solar hybrid air-conditioning design for buildings in hot and humid climates - Solar Energy Sciences and Engineering Applications - page 487

Figure 15.2.1 Feasible design approaches of solar air-conditioning.
air-conditioning cycle. Similar to the solar-electric approach, both roof-mounted and
the building-integrated strategies can be considered for the collector installation. In this
approach, auxiliary heating, typically using fuel gas, is needed in case of thermal deficit
in driving the solar-thermal air-conditioning system. The basic system designs include
solar absorption refrigeration, solar adsorption refrigeration and desiccant cooling,
each of which is described below.
15.2.2.1 Solar absorption refrigeration
Absorption chillers have been developed now for almost a century with various work-
ing pairs of absorbent and refrigerant, as well as different system configurations,
including single-effect, double-effect and even triple-effect. For solar energy appli-
cation, single-effect absorption refrigeration is the most popular due to its relatively
low driving temperature. Figure 15.2.2 illustrates the solar absorption refrigeration
system. Solar-thermal gain is firstly collected in the hot water storage tank by the hot
water pump. To drive the absorption chiller, the regenerative water pump feeds in the
hot water from the storage tank. If the driving temperature is not enough, an auxiliary
heater can be used. Chilled water from the chiller is delivered to the air handling unit
so that the conditioned supply of air can be provided to the building zone accordingly.
As the required outdoor air flow rate is less than that of the supply air, return air from
the building zone is drawn back to the air handling unit for the sake of air balancing.