These cost estimates are suggestive at this stage, and without consideration of any benefits resulting from incentives for solar replacement of electrical generating capacity or natural gas consumption. Conventional cooling uses a compression refrigeration cycle. This system will typically operate for 3,000 hours per year. In an absorption refrigeration cycle, a circulating refrigerant is evaporated by heat from an aqueous solution at elevated pressure and subsequently reabsorbed at low pressure, displacing the need for a mechanical compressor. In desiccant cooling, air is dehumidified by absorption of moisture by a desiccant, the dry air is then cooled by an evaporative cooler.
Hot air regenerates the desiccant by evaporating the moisture and exhausting it to the outside.
Natural gas combustion is used for the regeneration of the desiccant material which occurs at 2300 C. Using the same 3,000 effective full load hours of operation per year, this system will consume approximately 982 million Btu of natural gas. These systems are projected to have a COP of 1.5-1.7. A description of the operation and schematic representation of a solar-driven absorption chiller arrangement are below. As noted in Fig. 5, the upper vessel contains the absorber and evaporator, whereas the lower vessel contains the condenser, generator, and heat exchanger. The refrigeration, or chilling effect, takes place in the evaporator.