INTEGRATED COMBINED H EAT AND P OWER AND G AS C OOLING

Abstract

Fully dedicated on-site combined heat and power (CHP) systems
present both challenges and opportunities for large multi-building
projects; particularly when employing a combined cycle approach in the
3-20 MW range 1 . While some distributed power generation systems
hedge their bets through reliance on both the sale and export of power
(e.g., paralleling with a serving utility to achieve favorable economics),
disappointing de-regulation benefits and the failure of energy trading to
smooth out power supply vs. demand cost uncertainty has been a sober-
ing experience for many California customers.
Recent rethinking by concerned CHP designers has focused on
exploring smaller footprint alternatives to use of higher cost heat-recov-
ery-steam-generators (HRSGs). One such approach involves the use of
prefabricated and fully integrated steam generators, complete with asso-
ciated 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 the remaining captured waste heat to drive absorp-
tion chiller(s), and space and domestic hot water heating systems en-
abling greater utilization of available heat reclamation potentials in sat-
isfying highly variable annual building power, heating and cooling load
demands. This is achieved through maintaining favorable log-mean-tem-
perature-differentials (LMTDs) at the turbine gas extraction coil also re-
sulting 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.