Integration of absorption refrigeration systems into Rankine power cycles to reduce water consumption: A thermodynamic analysis

A high percentage of the heat that is supplied to thermoelectric power plants is discarded to ambient and must be handled by an external cooling system. This cooling system typically consists of wet cooling towers because of the excellent thermo-physical properties of water. However, the amount of water consumed for power production has reached alarming levels in developed countries. Air-cooled heat exchangers (ACHXs) appear to be the most adequate technology to substitute for wet cooling towers, but the use of this technology has some limitations. The most important limitation is the higher condenser pressures in the cycle, which produce backpressures at the condensing turbine's exit, increases in heat rejection and losses in the net plant efficiency. This paper presents a concept for the use of ACHXs in the cooling systems of power plants using an absorption refrigeration system (ARS) as an intermediary. Heat from the steam condenser is handled by the evaporator of the ARS and “lifted” to a higher temperature level, where the ACHXs are fitted to work. The generator of the ARS is fed by the power plant itself, extracting (bleeding off) some of the steam that flows through the steam turbine at the correct pressure and temperature.