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Performance analysis of Concentrated solar power systems (CSP) integrated
with Natural gas combined cycle (NGCC) power plant
Muhammad Hassan, Maryam Khan, Asiya Mariam
Department of Mechanical Engineering
NFC Institute of Engineering and Technology, Multan, Pakistan
ARTICLE INFO
Key Words
Solar thermal energy
Performance
Concentrated Solar Power
Solar combined natural gas
power plant
Abstract:
This paper provides a brief study of hybrid solar concentrated
power cycles. CSP can be used with thermal storage systems
or triple high pressure power plant as combined cycle. Purpose
of this study is to assets the overall performance and efficiency
of different combined cycles. CSP with thermal energy is a
good reliable and cost efficient option for advance power
cycles. Steam turbines with CSP is more cost effective and
gives the more flexibility for modern cycles. Experiments show
the efficiency increase from 52.315MWe to 64.86MWe when
NGCC power plant combined with CSP. While the conversion
efficiency from solar to electric is 38.85%. Results of
Experiments shows that the higher efficiency can be achieved
by adding solar energy into conventional cycles.
1.Introduction:
Use of fossil fuels is responsible for the major pollution and the climate change if they are being
used at current rate the reserves will be exhausted in near future. The renewable energy resources
can provide a clean and cheap energy solution to many countries. Solar energy is one of the most
common and easily available energy source across the earth. It can have used as thermal energy
source and as electricity source by using PV cells. Solar thermal power plants
are one of the most common source for solar thermal energy the sung light is concentrated by using
parabolic mirrors to a volatile solid, liquid or gas up to a temperature of 400 to 1000 °C to produce
steam this steam can drive an engine coupled with generator or alternator to produce electricity.
Unlike PV cells the STP cannot be used on domestic levels and small scale but can be combined
with large thermal power plants with a fixed capacity to provide cheap and green electricity.
In combination with thermal and wind energy it can meet minimum and maximum energy
demands.
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STP are suitable for the areas which are exposed to sunlight most of the time in full years like
Africa, china, India, Pakistan, Australia and Bangladesh. The power production range of an STP
can be vary from few megawatts to 400MW depending upon the requirement and previous
system installed capacity.
At present situation the CSP technology is used as parabolic trough systems (PTS), Power towers
or central receiver systems (CRS), and parabolic dish engine (DE). Many technologies like solar
tracker are being used in all of these systems to improve the efficiency of overall system but the
PTS is the most efficient among all CSP techniques which captures almost 80% of sunlight and
can the temperature ranges up to 550°C.
From decades NGCC power plants are proved the most efficient technology to convert mechanical
energy into electrical energy and can the efficiency up to 55%. That is the main reason NGCC
power plants are commercially used across the globe for power production.
Combining CSP technology with NGCC power plants in known as integrated solar combined
cycles (ISCC). ISCC becoming a better choice because it exhibits many advantages like 1-higher
conservation efficiency of solar energy to electric energy; 2-hybridization can provide an efficient
reduction in fuel consumption and CO2 emissions as compared to NGCC power plants; 3-
integration arrangements have lower investment costs when compared to solar only and
conventional power plants.
Many of IGCC power plants are working around the world in Spain, Italy, USA, Africa and China.
Most of these plants are using PTC Technology.
In recent Years many studies are being carried out to analyze IGCC power plants
thermodynamically to check their integration points and limits of solar energy absorbed to
calculate its maximum efficiency. The main purpose of this study is to compare the daily, monthly
and yearly electricity production and conversion rate of IGCC and PTC solar design point and off-
design field. A new thermodynamic model of two IGCC plants have been made in Mathcad
environment to check its thermodynamic impact of solar heat integration in a triple pressure IGCC
plant at intermediate and higher pressure sections. This data allows the designers to design the
plant according to operating conditions in different areas. In this study the IGCC plants are
categorized and simulated in two locations Aswan and Egypt.
Configuration and Operation for ISCC System:
The Basic configuration of ISCC plant consists of a PTC solar Field Coupled with bottoming steam
cycle of a NGCC power plant. Two operational strategies for PTCs and ISCC plants which are
considered; direct steam generation technology in which the feed water is heated in PTC pipes and
steam is directly injected into the cycle. In other scheme synthetic thermal oil is used to transfer
the heat. Heat transfer fluid may pass through a heat exchanger and produces saturated/super-
heated steam which is fed into steam turbine and produces electricity. Most of the parabolic trough
system working currently using HTF technology.
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For our study a ISCC power plant is shown in figure 1. A NGCC power plant is coupled with PTC
solar field and solar steam generator modeled in Mathcad environment. NGCC power plant is
using a Mitsubishi gas turbine model M701F4 working on Rankine cycle. The bottoming steam
cycle consists of a steam turbine (ST) unit divided into three stages: the high-pressure turbine stage
(HPT), the intermediate-pressure stage (IPT) and the low-pressure turbine stage (LPT). The steam
turbine is connected to a triple pressure heat recovery steam generator (HRSG) with one reheat at
the intermediate pressure stage. The output power of the NGCC
is 503MWe and its thermal efficiency is 58.78% in nominal conditions.
The working principle of IGCC is derived from NGCC power plant where the high temperature
exhaust gases are passed through a HRSG and then saturated or super-heated steam is fed into
turbine. The solar collector generates an additional amount of steam through SGG and steam is
transferred to HRSG. Now the steam generated in SSG and HRSG can be integrated in two
different ways: power bosting and fuel saving mode. In power boosting the fuel supply to gas
turbine remains same but additional steam is added to increase the power while in fuel saving the
fuel supply is cut up to some extent and integrated steam is introduced to maintain the output.
In our study the power bosting mode is considered where the integrated steam in introduced in IP
stages in normal condition and for peak sun condition it is fed in HP stage
Site selection and solar radiation estimation:
Egypt is one of the most favorable place for solar energy. It has almost 3200h of sunshine annually
and direct normal irradiance of 1970-3200kW/m² from north to south region of Egypt as shown in
fig 3. according to NASA surface metrology Egypt has an average of 12h daily sunshine duration
with a maximum temperature range of 18°C to 38°C and minimum temperature range of 9°C to
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