Recent rethinking by concerned CHP designers has focused on exploring smaller footprint alternatives to the use of higher cost heat-recovery steam generators (HRSGs). One such approach involves use of prefabricated and fully integrated steam generators. These units come complete with associated heat exchangers, controls, and pumping systems employing low pressure, non-volatile, recirculating heat transfer fluids (HTF) capable of direct heat extraction of turbine exhaust gas waste heat to generate steam and allow cascading of the remaining captured waste heat to drive absorption chiller(s). They also include space and domestic hot water heating systems enabling greater utilization of available heat reclamation potentials in satisfying highly variable annual building power, heating, and cooling load demands.
Thermal tracking CHP utilization can be optimized through maintaining favorable log-mean-temperature-differentials (LMTDs) at the turbine gas extraction coil, also resulting in a lower exhaust gas temperature discharge to ambient. Various examples of such alternative HRSG cycles will be presented for gas turbine driven chiller and/or generator application, as well as gas turbine combined cycle operation to demonstrate the operational versatility and life cycle benefits of this approach for the above referenced range of commercially available gas turbines.