Thermodynamical, economical and environmental evaluation of high efficiency gas turbine cogeneration systems

Abstract

The paper evaluates the thermodynamical, economical and environmental characteristics of a cogeneration system composed of a gas turbine and a waste heat boiler (system A). Two other systems for increasing power generating efficiency are also evaluated, namely systems B and C, which are constructed by incorporating a regenerative cycle and a dual fluid cycle, respectively, into system A. It has been estimated that system C satisfies an environmental constraint that the nitrogen oxide density exhausted should be less than 100 parts in 106, and that systems A and B also satisfy this constraint if a small amount of steam is injected into the combustor. The power generating efficiencies of systems A and B, in this case, and that of system C have been estimated to be 33.5%, 38.5% and 41.2%, respectively; i.e. the efficiencies of systems B and C can be improved noticeably compared with that of system A. The economics of these systems have also been evaluated based on the value of a profit index, and the systems are all estimated to be economically viable under the conditions assumed. As a result, it has been shown that it is possible to construct cogeneration systems with satisfactory characteristics of both environmental protection and profitability if system A is used in districts where the heat demand is large, system C in districts where the heat demand is small, and system B in districts with intermediate heat demand.

Exergetic Evaluation of Gas Turbine Cogeneration Systems for District Heating and Cooling

“…A cogeneration system (CGS) composed of a gas turbine power generator and a waste heat boiler, shown in Figure 1(a), has the most simple construction (Pak and Suzuki, 1990). We shall call this system 'System A' hereafter.…”

“…Hence the following two CGSs have mainly been investigated in the present study. A dual fluid cycle CGS (System B) shown in Figure 1(b) is a CGS in which superheated steam is produced at a waste heat boiler by utilizing turbine waste heat and is injected into a combustor to increase gas turbine power when heat demand is small (Pak and Suzuki, 1990).…”

“…In estimating various characteristics of these three systems, simulation models developed by the authors have been used (Pak and Suzuki, 1989a, b;1990). Table 1 shows the exogenous variables and parameters of the models, together with the reference values adopted in performing simulations.…”