Solar Thermal Power Station: Pre-Feasibility Study

Pre-feasibility study of Solar Thermal
Power station

Contents
1.0 Introduction:....................................................................................................................................2
2.0 Power generation using Solar Thermal Collectors:................................................................................3
2.1 Heat Transfer Fluids:..........................................................................................................................4
2.2 Types of solar thermal Collectors are:...............................................................................................4
2.3 Comparison of various types of solar thermal collectors:..................................................................6
2.4 Working of a solar thermal power plant:...........................................................................................6
3.0 Selection of appropriateSolar thermal technology................................................................................9
4.0 Energy Storage System........................................................................................................................12
References:................................................................................................................................................15

1.0 Introduction:
About 87% of the World energy demand is supplied by Fossil fuels only less than 13% of
renewable sources of energy is used to supply the energy demand in world wide. Energy
generation by fossil fuels creates a very negative impact on environmental health as the emission
of harmful gases occurs due to burning these fuels. The production of electricity from the
renewable sources are the most environmental friendly method as the renewable sources of
energy are self-replenishing and inexhaustible. The Solar energy is a renewable source of energy,
which is collected from the sunlight. There are many methods to generate electricity from the
solar energy such as PV cells and Thermal collectors. The PV cells utilizes the photovoltaic
technology to convert the sunlight into electrical energy directly with the help of semiconductors
(Mehrara, M. 2007).
Fig1. Total World Energy Consumption
The thermal collectors collects the thermal energy from the sunlight and utilizes the thermal
energy to generate steam and to run a turbine which is coupled with electric motors and
generates electricity. Some of the solar thermal collectors that are being used are parabolic
trough collector, Fresnel lens collector, Heliostat field central receiver system, etc. The flat plate
and the parabolic collectors are used for small and medium power generation capacities. The
heliostat thermal collectors are applicable in higher power generation plants. (Boyle, G. 2004).
Fig2. Illustration of simple Solar Thermal Collector

2.0 Power generation using Solar Thermal Collectors:
The Solar thermal collectors collects the heat energy from the sunlight and utilizes it to generate
electricity with the help of various arrangements such as the reflective mirrors, Heat exchanger,
turbine, Heat transfer Fluid, generator, etc. (the schematic of a simple solar thermal collector is
shown in the Figure2.) The heat transfer fluid are allowed to flow through the tubes which are
placed on the reflective mirrors, when the sunlight hits the reflective mirrors the heat energy is
concentrated into the tubes which in turn supplies heat energy to the HTF. Then with the help of
a heat exchanger the heat transfer takes place. Inside the heat exchanger the generation of steam
is done. The generated steam is allowed to pass through the turbine. The mechanical energy
obtained from turbine is converted into electrical energy with help of generators.
2.1 Heat Transfer Fluids:
The Heat Transfer Fluid is used to transfer the heat energy from the collector to the heat
exchanger. Some of the variables that are considered during the selection of the HTF are its
Coefficient of expansion, Viscosity, Thermal storage capacity, Freezing and Boiling points. The
selection of the HTF is greatly influenced by the environmental conditions in which the power
plant is about to work. For example if a plant is placed in a hot dessert area then the HTF should
have high boiling point, proper viscosity and a proper thermal storage capacity.(Rached, W.
2011).
Some of the most important types of Heat Transfer Fluids are:
Air
Air is an excellent, cheap, and affordable HTF. Air has anti freezing property and it also does not
boil so it is applicable both in extremely cold and hot conditions. On the negative side it has
extremely low heat carrying capacity, also there will be leakage problem in ducts. (Reddy, J. N.
2014).
Water
Water is an excellent form of HTF as it has very high heat carrying capacity and it is cheap and
affordable. On the other hand it has very high freeing point and low boiling point. Water is
applicable in case of low to medium temperature range operation.(Reddy, J. N. 2014).
Oil
Oils generally have high viscosity but the heat carrying capacity of oil is lower than that of the
water. They also have high specific weight of gravity. There are generally 3 types of oils such as
synthetic, semi synthetic and normal.(Reddy, J. N. 2014).
Molten Salt:
The molten salts are found to have greater heat carrying capacity. They are applicable in case of
super heating type of solar power generators. It words under extremely high temperatures.
(Reddy, J. N. 2014).