Active control of external volume flow rates for single effect absorption chillers.

Abstract

Energy efficient absorption chiller cooling assemblies (ACCA) ought to include active speed control of pumps and fans and heat rejection devices as well. Three external circuit pumps can be controlled actively to minimize auxiliary energy consumption. According to monitoring data of a field test with 25 absorption chillers in 16 installations, up to 80 % of auxiliary electric energy consumption is caused by the cooling water pump and the cooler. Reducing a volume flow rate by reducing fan or pump speed by 50% leads theoretically to a reduction of 87% in electricity consumption for the pump/fan. In practice within the field test, a reduction of up to 65% is attained and has been proven successfully by control of reject heat and chilled water cycle pump. Control of hot water flow has a more complex, but promising potential. Lowering e.g. hot water flow rate leads to higher set temperatures for the cooler and/or lower cooling water flow rates, thus saving electric energy.