Adaptation of Solar Energy Driven Absorption Chillers for Air Conditioning in Commercial Building

Abstract: The most recent analysis of energy usage in the country reveled that nearly 50% of the power generation is used for air conditioning and mechanical ventilation most of which is used by commercial organizations. The grid generation mix that contains a high percentage of fossil fuel makes such energy usage environment unfriendly. Although absorption refrigeration is an old technique its economical application is limited to applications where cheap or waste heat energy is available despite decades of R&D, due to low COP, high initial cost and larger size. Heat input at Moderately high (over 120ᵒC) temperature and need to release large amount of heat to the environment through liquid or air cooling makes absorption chiller less conducive in cooling. Yet, being a tropical country, Sri Lanka has a better potential in adopting solar driven absorption refrigeration, if the chillers are operated at low temperature heat input that also promotes efficiency in storage that is mandatory due to fluctuation of energy source, subject to economic feasibility. The project aims designing and modeling of a solar power driven absorption chiller system that is adoptable to a selected medium size commercial organization. The proposed system uses heat energy around 100ᵒC and reusing fraction of energy expelled to the environment by suitably modifying operating parameter and thereby increasing efficiency of the system. Reduction of such heat losses and reducing heat input is achieved with the use of secondary heat exchange (brine) system that optimizes the energy usage. This arrangement will make efficient usage of solar heat storage, even in the considerable absence of solar power. System modeling and simulation of both basic double effect chiller and its modified versions were carried out and compared to evaluate improvement. The simulation of the modified system was used to obtain working parameters of the chiller so that a suitable solar collector, chilled water and heat rejection systems can be designed. Operational conditions of the cooling system are measured by the state sensors that feed inputs to the control system to achieve the optimum efficiency and their technical details are also included in the report.