INDUSTRIAL WAY TO USE NATURAL GAS

GAS TURBINE POWER PLANT

                A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in between.
                The basic operation of the gas turbine is similar to that of the steam power plant except that air is used instead of water. Fresh atmospheric air flows through a compressor that brings it to higher pressure. Energy is then added by spraying fuel into the air and igniting it so the combustion generates a high-temperature flow. This high-temperature high-pressure gas enters a turbine, where it expands down to the exhaust pressure, producing a shaft work output in the process. The turbine shaft work is used to drive the compressor and other devices such as an electric generator that may be coupled to the shaft. The energy that is not used for shaft work comes out in the exhaust gases, so these have either a high temperature or a high velocity. The purpose of the gas turbine determines the design so that the most desirable energy form is maximized. Gas turbines are used to power aircraft, trains, ships, electrical generators, or even tanks.

How does it works?

The combustion (gas) turbines being installed in many of today's natural-gas-fueled power plants are complex machines, but they basically involve three main sections:

i. The compressor, which draws air into the engine, pressurizes it, and feeds it to the combustion chamber at speeds of hundreds of miles per hour.

ii. The combustion system, typically made up of a ring of fuel injectors that inject a steady stream of fuel into combustion chambers where it mixes with the air. The mixture is burned at temperatures of more than 2000 degrees F. The combustion produces a high temperature, high pressure gas stream that enters and expands through the turbine section.

iii. The turbine is an intricate array of alternate stationary and rotating aerofoil-section blades. As hot combustion gas expands through the turbine, it spins the rotating blades. The rotating blades perform a dual function: they drive the compressor to draw more pressurized air into the combustion section, and they spin a generator to produce electricity.

Compressor:- The compressor sucks in air form the atmosphere and compresses it to pressures in the range of 15 to 20 bar. The compressor consists of a number of rows of blades mounted on a shaft. This is something like a series of fans placed one after the other. The pressurized air from the first row is further pressurised in the second row and so on. Stationary vanes between each of the blade rows guide the air flow from one section to the next section. The shaft is connected and rotates along with the main gas turbine.

Combustion chamber:- This is an annular chamber where the fuel burns and is similar to the furnace in a boiler. The air from the compressor is the Combustion air. Burners arranged circumferentially on the annular chamber control the fuel entry to the chamber. The hot gases in the range of 1400 to 1500 °C leave the chamber with high energy levels. The chamber and the subsequent sections are made of special alloys and designs that can withstand this high temperature.

Turbine:- The turbine does the main work of energy conversion. The turbine portion also consists of rows of blades fixed to the shaft. Stationary guide vanes direct the gases to the next set of blades. The kinetic energy of the hot gases impacting on the blades rotates the blades and the shaft. The blades and vanes are made of special alloys and designs that can withstand the very high temperature gas. The exhaust gases then exit to exhaust system through the diffuser. The gas temperature leaving the Turbine is in the range of 500 to 550 °C.

Advantages

There are several advantages to using a gas power plant to generate electrical power as compared to other systems.

i. Gas turbine power plants can be started up and run at full capacity in only 10 to 20 minutes, making them well suited as backup plants for utility companies that require additional electricity immediately.

ii. Because they are smaller than coal or nuclear plants, gas power plants can be built faster and at a lower cost.

iii. Gas turbine systems also require much less water than steam power plants, and they are easily converted into combined cycle power plants, which are much more efficient.

Disadvantages

Gas turbine power plants have disadvantages as well.

i. The power needed to drive the compressor reduces the net outputs, consuming more fuel to do the same amount of work.

ii. The operating temperature in gas turbines is higher than in other power plant systems and can shorten the lifespan of some of the system components.

iii. Furthermore, because the thermal energy is wasted when the exhaust is released, the efficiency levels of gas turbine plants are lower than those of other types of power plants.

UTILIZATION OF NUCLEAR ENERGY

NUCLEAR POWER PLANT

                A nuclear power plant is a type of power station that generates electricity using heat from nuclear reactions. These reactions take place within a reactor. The plant also has machines which remove heat from the reactor to operate a steam turbine and generator to make electricity. Electricity made by nuclear power plants is called nuclear power.

                Nuclear power plants are usually near water to remove the heat the reactor makes. Some nuclear power plants use cooling towers to do this. Nuclear power plants use uranium as fuel. When the reactor is on, uranium atoms inside the reactor split into two smaller atoms. When uranium atoms split, they give off a large amount of heat. This splitting of atoms is called fission.

                The most popular atoms to fission are uranium and plutonium. Those atoms are slightly radioactive. The atoms produced when fuel atoms break apart are strongly radioactive. Today, fission only happens in nuclear reactors. In nuclear reactors, fission only happens when the reactors parts are arranged properly. Nuclear power plants turn their reactors off when replacing old nuclear fuel with new fuel.

Major components of the systems are described below:-

-Nuclear reactors

 A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. The most common use of nuclear reactors is for the generation of electric energy and for the propulsion of ships.

Nuclear reactors usually rely on uranium to fuel the chain reaction. Uranium is a very heavy metal that is abundant on Earth and is found in sea water as well as most rocks. Naturally occurring uranium is found in two different isotopes: uranium-238 (U-238), accounting for 99.3% and uranium-235 (U-235) accounting for about 0.7%. Isotopes are atoms of the same element with a different number of neutrons. Thus, U-238 has 146 neutrons and U-235 has 143 neutrons. Different isotopes have different behaviours. For instance, U-235 is fissile which means that it is easily split and gives off a lot of energy making it ideal for nuclear energy. On the other hand, U-238 does not have that property despite it being the same element. Different isotopes also have different half-lives. A half-life is the amount of time it takes for half of a sample of a radioactive element to decay. U-238 has a longer half-life than U-235, so it takes longer to decay over time. This also means that U-238 is less radioactive than U-235

The nuclear reactor is the heart of the plant. In its central part, the reactor core's heat is generated by controlled nuclear fission. With this heat, a coolant is heated as it is pumped through the reactor and thereby removes the energy from the reactor. Heat from nuclear fission is used to raise steam, which runs through turbines, which in turn powers either ship's propellers or electrical generators.

Since nuclear fission creates radioactivity, the reactor core is surrounded by a protective shield. This containment absorbs radiation and prevents radioactive material from being released into the environment. In addition, many reactors are equipped with a dome of concrete to protect the reactor against both internal casualties and external impacts.

 

-Steam turbine

The purpose of the steam turbine is to convert the heat contained in steam into mechanical energy. The engine house with the steam turbine is usually structurally separated from the main reactor building. It is so aligned to prevent debris from the destruction of a turbine in operation from flying towards the reactor.

In the case of a pressurized water reactor, the steam turbine is separated from the nuclear system. To detect a leak in the steam generator and thus the passage of radioactive water at an early stage, an activity meter is mounted to track the outlet steam of the steam generator. In contrast, boiling water reactors pass radioactive water through the steam turbine, so the turbine is kept as part of the control area of the nuclear power plant.

-Generator

The generator converts kinetic energy supplied by the turbine into electrical energy. Low-pole AC synchronous generators of high rated power are used.

-Cooling system

A cooling system removes heat from the reactor core and transports it to another area of the plant, where the thermal energy can be harnessed to produce electricity or to do other useful work. Typically the hot coolant is used as a heat source for a boiler, and the pressurized steam from that drives one or more steam turbine driven electrical generators.

-Safety valves

In the event of an emergency, safety valves can be used to prevent pipes from bursting or the reactor from exploding. The valves are designed so that they can derive all of the supplied flow rates with little increase in pressure. In the case of the BWR, the steam is directed into the suppression chamber and condenses there. The chambers on a heat exchanger are connected to the intermediate cooling circuit.

-Feedwater pump

The water level in the steam generator and nuclear reactor is controlled using the feedwater system. The feedwater pump has the task of taking the water from the condensate system, increasing the pressure and forcing it into either the steam generators (in the case of a pressurized water reactor) or directly into the reactor (for boiling water reactors).

-Emergency power supply

Most nuclear plants require two distinct sources of offsite power feeding station service transformers that are sufficiently separated in the plant's switchyard and can receive power from multiple transmission lines. In addition in some nuclear plants the turbine generator can power the plant's house loads while the plant is online via station service transformers which tap power from the generator output bus bars before they reach the step-up transformer (these plants also have station service transformers that receive offsite power directly from the switchyard.) Even with the redundancy of two power sources total loss of offsite power is still possible. Nuclear power plants are equipped with emergency power systems to maintain safety in the event of unit shutdown and loss of offsite power. Batteries provide uninterruptible power to instrumentation, control systems, and valves. Emergency diesel generators provide direct AC power to charge the batteries and to provide power to systems requiring AC power such as motor driven pumps. The emergency diesel generators do not power all plant systems, only those required to shut the reactor down safely, remove decay heat from the reactor, provide emergency core cooling, and, in some plants, spent fuel pool cooling. The large power generation pumps such as the main feedwater, condensate, circulating water, and (in pressurized water reactors) reactor coolant pumps are not backed up by the diesels.

Advantages of nuclear power plant

i. The nuclear power plant is more economical compared with thermal in areas where coal field is far away.
ii. There is no problem of fuel transportation, storage and handling and ash handling as in thermal power plants.
iii. Man power required for the operation of nuclear power plant is less. Therefore the cost of operation is reduced.
iv. Nuclear plant occupies less space than thermal power plants, which reduces the cost of civil construction.
v. The capital cost in structural materials, piping and storage are less than thermal plants of the same capacity.

Disadvantages of nuclear power plant

i. Danger of nuclear radiation.
ii. Problem of disposing the radioactive waste materials.
iii. It has to be operated at full load throughout for a good efficiency. So part load operation becomes inefficient.
iv. Capital cost of small size plants is very high.

WIND IS ALSO AN ANTERNATE SOURCE OF ENERGY

WIND TURBINE POWER GENERATION

                

              Wind power is achieved from flow of air using windmills or wind turbines to produce mechanical to electrical energy. Windmills are used for their mechanical power, wind pumps for water pumping, and sails to propel ships. Wind power is one of the alternative to fossil fuels, it is free of cost, renewable, clean, produces no greenhouse gas emitted during operation. The actual effects on the environment are very minimal as compared to other non renewable sources of energy.

                In a wind farm there are many individual windmill/wind turbines which are connected to the electrical power transmission network and further connected to the peripheral power house. A basic process of the power generation of wind turbine is given below.

                                                                           Fig 1:-Block diagram representation

Windmill or Wind  Turbine

A windmill is a mill that runs on the energy of wind by means of blades or vanes(i.e. rotational energy). In earlier times, windmills usually were used to mill grain, pump water, etc. After the further development of windmills in modern days the windmills has taken the form of wind turbines used for generating electricity, or wind-pumps used for pumping water, normally for irrigation purpose.

A wind turbine is a device that converts the wind's kinetic energy(by rotation of its blades) into electrical energy.

Wind turbines are manufactured in a wide range of vertical and horizontal axis types as per the method of power generation technique. The smallest turbines are mainly used for charging batteries for auxiliary power for boats or other light vehicles and to power traffic warning lights. Slightly larger turbines can be useful for a domestic power supply and selling excess unused power back to the supplier or other consumers via the electrical grid. Arrays of large turbines are known as wind farms, and it is becoming an important source of clean renewable energy and are adopted by many countries as a part of their strategy to reduce dependency on fossil fuels without compromising in the supply of electricity.

Wind turbines works on a simple principle. The flow of wind turns two or three propeller like blades around a rotor. The rotor is connected to the main shaft, which rotates an alternator/generator to create electricity.

Wind farm or On-shore wind power

A wind farm is a group of wind turbines in the same location used for production of electricity. A large wind farm may consist of several hundred individual wind turbines distributed over an extended area, but the land between the turbines may be used for agricultural or other purposes. For example, Gansu Wind Farm, the largest wind farm in the world, has several thousand turbines. A wind farm may also be located offshore.

Almost all large wind turbines have the same design — a horizontal axis wind turbine having an upwind rotor with three blades, attached to a nacelle on top of a tall tubular tower.

In a wind farm, individual turbines are interconnected with a medium voltage (often 34.5 kV), power collection system and communications network. At a substation, this medium-voltage electric current is increased in voltage with a transformer for connection to the high voltage electric power transmission system.

Off-shore wind power

Offshore wind power refers to the construction of wind farms in large bodies of water to generate electricity. These installations can utilize the more frequent and powerful winds that are available in these locations and have less aesthetic impact on the landscape than land based projects. However, the construction and the maintenance costs are considerably higher.

Siemens and Vestas are the leading turbine suppliers for offshore wind power. DONG Energy, Vattenfall and E.ON are the leading offshore operators. As of October 2010, 3.16 GW of offshore wind power capacity was operational, mainly in Northern Europe. According to BTM Consult, more than 16 GW of additional capacity will be installed before the end of 2014 and the UK and Germany will become the two leading markets. Offshore wind power capacity is expected to reach a total of 75 GW worldwide by 2020, with significant contributions from China and the US.

At the end of 2012, 1,662 turbines at 55 offshore wind farms in 10 European countries are generating 18 TWh, which can power almost five million households. As of August 2013 the London Array in the United Kingdom is the largest offshore wind farm in the world at 630MW. This is followed by Gwynt y Môr (576 MW), also in the UK.

Advantages

i. The wind is free and with modern technology it can be captured efficiently.
ii. Once the wind turbine is built the energy it produces does not cause green house gases or other pollutants.
iii. Although wind turbines can be very tall each takes up only a small plot of land. This means that the land below can still be used. This is especially the case in agricultural areas as farming can still continue.
iv. Many people find wind farms an interesting feature of the landscape.
v. Remote areas that are not connected to the electricity power grid can use wind turbines to produce their own supply.
vi. Wind turbines have a role to play in both the developed and third world.
vii. Wind turbines are available in a range of sizes which means a vast range of people and businesses can use them. Single households to small towns and villages can make good use of range of wind turbines available today.

Disadvantages

i. The strength of the wind is not constant and it varies from zero to storm force. This means that wind turbines do not produce the same amount of electricity all the time. There will be times when they produce no electricity at all.
ii. Many people feel that the countryside should be left untouched, without these large structures being built. The landscape should left in its natural form for everyone to enjoy.
iii. Wind turbines are noisy. Each one can generate the same level of noise as a family car travelling at 70 mph.
iv. Many people see large wind turbines as unsightly structures and not pleasant or interesting to look at. They disfigure the countryside and are generally ugly.
v. When wind turbines are being manufactured some pollution is produced. Therefore wind power does produce some pollution.
vi. Large wind farms are needed to provide entire communities with enough electricity. For example, the largest single turbine available today can only provide enough electricity for 475 homes, when running at full capacity.

HOW WE ARE EXTRACTING ENERGY THROUGH WATER BODIES

HYDRO-ELECTRIC POWER GENERATION

                Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy, accounting for 16 percent of global electricity generation – 3,427 terawatt-hours of electricity production in 2010, and is expected to increase about 3.1% each year for the next 25 years.

                Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010.China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use.

                The cost of hydroelectricity is relatively low, making it a competitive source of renewable electricity. The average cost of electricity from a hydro station larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour. It is also a flexible source of electricity since the amount produced by the station can be changed up or down very quickly to adapt to changing energy demands. However, damming interrupts the flow of rivers and can harm local ecosystems, and building large dams and reservoirs often involves displacing people and wildlife.^[1] Once a hydroelectric complex is constructed, the project produces no direct waste, and has a considerably lower output level of the greenhouse gas carbon dioxide (CO₂) than fossil fuel powered energy plants.

Conventional dams

                 Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and generator. The power extracted from the water depends on the volume and on the difference in height between the source and the water's outflow. This height difference is called the head. A large pipe (the "penstock") delivers water from the reservoir to the turbine.

Pumped-storage dams

                 This method produces electricity to supply high peak demands by moving water between reservoirs at different elevations. At times of low electrical demand, the excess generation capacity is used to pump water into the higher reservoir. When the demand becomes greater, water is released back into the lower reservoir through a turbine. Pumped-storage schemes currently provide the most commercially important means of large-scale grid energy storage and improve the daily capacity factor of the generation system. Pumped storage is not an energy source, and appears as a negative number in listings.

Run-of-the-river dams

                Run-of-the-river hydroelectric stations are those with small or no reservoir capacity, so that only the water coming from upstream is available for generation at that moment, and any oversupply must pass unused. A constant supply of water from a lake or existing reservoir upstream is a significant advantage in choosing sites for run-of-the-river. In the United States, run of the river hydropower could potentially provide 60,000 megawatts (80,000,000 hp) (about 13.7% of total use in 2011 if continuously available).

Tidal power

                A tidal power station makes use of the daily rise and fall of ocean water due to tides; such sources are highly predictable, and if conditions permit construction of reservoirs, can also be dispatchable to generate power during high demand periods. Less common types of hydro schemes use water's kinetic energy or undammed sources such as undershot waterwheels. Tidal power is viable in a relatively small number of locations around the world. In Great Britain, there are eight sites that could be developed, which have the potential to generate 20% of the electricity used in 2012.

Top four hydroelectric capacities

Currently, only four facilities over 10 GW (10,000 MW) are in operation worldwide:-

Rank	Station	Country	Location	Capacity (MW)
1.	Three Gorges Dam	China	30°49′15″N 111°00′08″E	22,500
2.	Itaipu Dam	Brazil  Paraguay	25°24′31″S 54°35′21″W	14,000
3.	Xiluodu Dam	China	28°15′35″N 103°38′58″E	13,860
4.	Guri Dam	Venezuela	07°45′59″N 62°59′57″W	10,200

World hydroelectric power capacity

The ranking of hydro-electric capacity is either by actual annual energy production or by installed capacity power rating. Hydro accounted for 16 percent of global electricity consumption, and 3,427 terawatt-hours of electricity production in 2010, which continues the rapid rate of increase experienced between 2003 and 2009.

Hydropower is produced in 150 countries, with the Asia-Pacific region generated 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. Brazil, Canada, New Zealand, Norway, Paraguay, Austria, Switzerland, and Venezuela have a majority of the internal electric energy production from hydroelectric power. Paraguay produces 100% of its electricity from hydroelectric dams, and exports 90% of its production to Brazil and to Argentina. Norway produces 98–99% of its electricity from hydroelectric sources.

A hydro-electric station rarely operates at its full power rating over a full year; the ratio between annual average power and installed capacity rating is the capacity factor. The installed capacity is the sum of all generator nameplate power ratings.

Advantages of hydro-electric power generation

i. Low power cost.

ii. Flexibility.

iii. Sustainability for industrial application.

iv. Reduced CO₂ emissions.

 Disadvantages of hydro-electric power generation

i. Ecosystem damage and loss of land.

ii. Siltation and flow shortage.

iii. Methane emissions from reservoirs.

iv. Construction failure can lead to man-made disaster.