1. Introduction
Energy conservation is a key goal of economy and it will
continue to be in near future. The most effective way to meet the
energy demand is to use energy more efficiently. The exergy
analysis [1,2] method is a useful tool for promoting the goal of more
efficient energy-resource use, as it enables the locations, types and
true magnitudes of wastes and losses. The exergy analysis shows
the true measure of loss which is evident from the results of energy
and exergy analysis reported for various types of thermal power
plants of various capacities [3–6]. The popularity of exergy analysis
method has grown consequently and is still growing [7–11]. Habib
and. Zubair [7] quantified irreversible losses in components of
a regenerative Rankine cycle power plant and concluded that
maximum irreversible loss takes place in boiler, and regenerative
feed water heating reduces irreversible loss in boiler and whole
plant. Singh et al. [3] carried out the energy and exergy analysis for
the system components of a typical 50 kW solar–thermal power
plant (STPP) under given operating conditions. The typical 50 kW
STPP uses thermic fluid in solar collector field. The high thermodynamic quality of solar radiation has led the researchers to
explore the efficient conversion of concentrated solar energy into
electrical energy by using thermodynamic power cycles. Solar–
thermal power generation is one of the promising aspects [12] of
solar energy utilization. Techno-economic feasibility of parabolictrough
based MW scale STPP with some incentives from the
government, has been well proven by the successful operation of
about 354 MW capacity solar electricity generation scheme in
California, USA [13]. The feasibility of the direct steam generation
(DSG) process in horizontal parabolic-trough collectors had already
been proven [14]. The first conceptual and pre-commercial 5 MWe
capacity DSG STPP has been presented by Zarza et al. [15]. The only
one feed water heater (FWH) has been proposed in conceptual DSG
STPP, while in a conventional fossil fuel based thermal power plant
feed water preheating is done to improve the plant efficiency [7].
The objective of the present study is to carry out the energy and
exergy analysis of the proposed conceptual design of 5 MWe DSG
STPP [15,16] to pinpoint the location and magnitude of the process
irreversibilities in system. For minimum exergy loss in receiver of
DSG STPP the inlet temperature of water which is governed by the
number of FWH, bleed pressure and mass fraction of bleed steam,
must be optimum. Thus, the investigations are carried out for
various bleed pressure and mass fractions of bleed steam of
proposed conceptual DSG STPP having one FWH in order to evaluate the optimum bleed pressure and mass fraction of bleed
steam to maximize the STPP efficiency. Further, the investigations
are also carried out by incorporating two and three FWHs.