CRDI The improvement is mainly due to the common-rail design, which has tubes that connect all the injectorFuel in the common tube or - rail is under a set amount of pressure which causes the fuel to be - atomized or broken down to its smallest particles. This allows the fuel to combine with the air much more efficiently.With proper direct injection, fuel use is highly efficient, with much less waste fuel escaping the system unused. The technology has also allowed CRDI engines to better control the amount of fuel used, the pressure within the system and the timing of both the injection of fuel and the electronic charge applied to make the fuel burn. Injectors in the common rail direct injection engine have controls on the injector heads that allow slight variances in the amount of fuel put into the cylinders

Power PlantsHydraulic Power Plant: Utilizes potential energy of water as source of energy.Primary source is rain fall.Water is collected in natural lakes and reservoirs at high altitude/storing water by constructing dams across flowing streams.Energy of water utilized mat be PE/KE.KE is a function of velocity and mass.PE is a function of height .The KE and PE possessed by water is converted in to mechanical power in prime movers known as hydraulic turbines.Turbine is directly coupled to n electric generator to produce electric power.

Essential elements are :Storage reservoirDamWaterwaysControl worksSurge tankPower house.Storage reservoir:Basic requirement of a power plant.Stores water during rainy season and supply during dry season.Natural or artificial.Artificial by constructing dams across flowing streams and natural are lakes found in high and huge mountains.

Dam:Expensive structure in power plantMasonry, Earth filled, wooden & Steel dams.Masonry is the most common typeGravity, Buttress and Arch dams.Gravity dams are bulky and derive the stability by water pressure by virtue of its weight.Buttress dam, the upstream face is inclined to create a considerable downward force to counter overturning tendency.Arch dam is a solid curved structure resists water pressure by its weight and by transferring the pressure by arch action.Idukki dam in periyar river.

Waterways:These are provided to carry water from reservoir to power house.Includes Canal, Penstock or tunnel.Canals are used when handling large quantity of water.Tunnels are made by cutting mountains when geography prevents the use of a canal.Penstock are made up of steel or concrete.Sloping towards power house and sharp bends are to be avoided to reduce head loss. (Velocity ranges from 2-6 m/s).Control works:Appliances to control flow of water.Includes gates, valves, trash rack etc..Gates 4 discharging excess water during flood period.Sluice gates, rolling gates etc..Valves for controlling the rate of flow to power house like needle valves and butterfly valves.

Trash racks, which take the form of screens, are placed across intake to keep out foreign materials from going through penstock.Surge Tank:Additional storage space fitted in between the main storage reservoir and power house as nearer to power house as possible.Used in high/medium head plants when there is a huge distance b/w water source and power unit, requiring large penstock.

Gas turbine power plant Gas turbines are used for low capacity power generationThese are coupled to applications that need rotary mechanical power such as air crafts, pumps and compressors. Operates on Brayton cycle on open cycle method.

Working principleAir is compressed to a high pressure in a centrifugal compressor.Sent to combustion chamber for help the fuel burn.The heat released by combustion of fuel increases pressure of gas.High pressure gas runs the gas turbine.Generator coupled to GT produces electricity.Power plant is self sufficient as the part of the power produced is utilized to run the compressor.Advantages:1.Small in size2.Quick starting and smooth running.3.Also supplies compressed air in addition to electricity.4.Less environmental problems.Disadvantages:1.Low efficiency2.Solid fuels cannot be used.3. Only for low capacity power generation

Diesel Power plant

Used for low capacity power generation.Usually kept as standby power generating systems.Maximum capacity up to 50MW.A multi cylinder diesel engine is directly coupled to a generator.Compressed air from a starting compressor for initial starting of engine.Fuel pump to supply from fuel tank to fuel injection system.Fuel distribution system. Supplies to individual cylinders.Air required for combustion is taken through air filter.Exhaust gas is removed through silencer.Lube oil is supplied through separate pump and excess oil is returned back through return line.Water cooling is used as air cooling requires high capacity systems.

Schematic arrangement of a diesel power plant

Advantages:Quick starting and smooth running.Economical even for a few capacity power generation systems.Can be used for mobile power generation systems.Part load and overall efficiency is high compared to other power plants.Disadvantages:Maximum power generation capacity is limited .Maintenance requirement is very high.Fuel and lubrication system are very expensive.

Steam Power Plant

Steam power plantA steam or thermal power plant is one in which the prime mover is steam driven; it works on Rankine cycle.Water is heated, turns into steam and spins a steam turbine which drives an electrical generator. After it passes through the turbine, the steam is condensed in a condenser and recycled to where it was heated, this is known as a Rankine cycle.Boiler:In fossil-fueled power plants, steam generator refers to a furnace that burns the fossil fuel to boil water to generate steam.In the nuclear plant field, steam generator refers to a specific type of large heat exchanger used in a pressurized water reactor (PWR) to thermally connect the primary (reactor plant) and secondary (steam plant) systems, which generates steam. In a nuclear reactor called a boiling water reactor (BWR), water is boiled to generate steam directly in the reactor itself and there are no units called steam generators.

Feed water:The feed water used in the steam boiler is a means of transferring heat energy from the burning fuel to the mechanical energy of the spinning steam turbine. The total feed water consists of re-circulated condensate water and purified makeup water. Because the metallic materials it contacts are subject to corrosion at high temperatures and pressures, the makeup water is highly purified before use. Boiler operation:Pulverized coal is air-blown into the furnace from fuel nozzles at the four corners and it rapidly burns, forming a large fireball at the center. The thermal radiation of the fireball heats the water that circulates through the boiler tubes near the boiler perimeter.As the water in the boiler circulates it absorbs heat and changes into steam It is separated from the water inside a drum at the top of the furnace. The saturated steam is introduced into superheat pendant tubes that hang in the hottest part of the combustion gases as they exit the furnace. Here the steam is superheated to 500C to prepare it for the turbine.

The boiler transfers energy to the water by the chemical reaction of burning some type of fuel.Water to economizer-to steam drum- goes down to water wall-rises up-turned in to steam-passes through water steam separators- water is recycled- Steam goes to super heater drum-to turbine.Super heater: In a Thermal plant, after the steam is conditioned by the drying equipment inside the steam drum, it is piped from the upper drum area into known as the super heater.The steam vapor picks up more energy from hot flue gases outside the tubing and its temperature is now superheated above the saturation temperature. Steam condensing:The condenser condenses the steam from the exhaust of the turbine into liquid to allow it to be pumped. If the condenser can be made cooler, the pressure of the exhaust steam is reduced and efficiency of the cycle increases.

Re heater:Power plant furnaces may have a re-heater section containing tubes heated by hot flue gases outside the tubes.Exhaust steam from the high pressure turbine is re-routed to go inside the re-heater tubes to pickup more energy to go drive intermediate or lower pressure turbines.Air path:External fans are provided to give sufficient air for combustion.Steam turbine generator:High pressure-low pressure turbine in a series coupled with generator.Fly ash collection:Fly ash is captured and removed from the flue gas by electrostatic precipitators or fabric bag filters.

Wind turbine power plantWind is induced in the atmosphere due to uneven heating of earths crust by sunAbout 2% of the solar radiation reaching earths surface is converted in to KE as wind and out of this about 30% occurs in the lowest 1000m of the elevation.Windmill is converting the KE of wind to rotary mechanical energy.Horizontal axis and vertical axis.The power produced by the windmill depends on the diameter of the wheel and wind velocity.It is designed to produce rated power at less that maximum prevailing wind velocity at any place.Aluminium fiberglass and steel are the materials for the blades.Power produced= 0.5*density*area*velocity3

Schematic of a Wind turbine power plant

Solar power plantThe total quantity of solar energy incident upon earth is of low grade temperature due to atmospheric interference from the clouds.It is cyclic in nature due to earths rotation.Solar radiation is converted in to heat to produce fluid power.The fluid power is converted in to mechanical energy and then to electrical energy. Collection and concentration of solar radiation in an efficient manner to have reasonably high temperature heat source.Special devices like heliostats reflect solar radiation to fall on the central receiver.In a central receiver the concentrated high temperature solar heat energy is absorbed by the concentrated fluid.

Rankine cycle:If the circulated fluid is water, it gets converted in to steam and this high pressure steam operates a steam turbine, to which a generator is coupled. To produce electricity.Brayton cycle: If the circulated fluid is helium or air, it gets heated up in central receiver and its pressure increases with volume expansion. The high pressure gas operates a gas turbine to produce mechanical power which will be converted to electricity by a generator.

Layout of a Solar Thermal power plant operating in a combined cycle

Photovoltaic conversion is a direct electricity generation technology using solar cells.(made of silicon)They are connected in a series-parallel arrangement called a module to produce required current and voltage.Several modules makes up a panel.Finds applications in navigation aids, telecommunication systems, microwave relay stations etc..Coupled with batteries for storage, it becomes more dependable and economical for specific applications.Dc to AC conversions system is an essential part of the system.

Ocean thermal energy conversion (OTEC)Temperature gradient in the ocean can be used to run a thermal system to generate electricity.The wind generates large waves with lot of energy that can be converted to electricity.The other source that can be converted to electricity is tides.Ocean surface temperature is around 250C and at a depth of 100 m to 200m its temperature is around 100C.Low boiling point liquids like ammonia, propane or Freon oils boils in to high pressure vapour using heat of warm water supplied from the ocean surface in a boiler.The vapour is used to run a turbine coupled with a generator to produce electricity. after expansion, it is condensed in to liquid in a condenser using cold water from the deep ocean at a temperature of 100C.The condensed liquid is pumped back to the boiler.

Schematic of OTEC

Tidal power plant The tides can rise the level of water of the ocean and by constructing a dam on the seashore, water can be stored.A reversible turbine located at the bottom of the dam can generate mechanical power from both in and out flows of the water.A generator coupled to the turbine converts mechanical energy in to electrical energy. Its also a hydro electric power plant.The tidal range is the difference b/w water level at high tide and water level at low tide.Range is not constant and is maximum at new and full moon and minimum at first and third quarter noon.Ranges have to be significantly high to justify the cost of constructing dams and hydroelectric power plants.

COMPONENTS OF TIDAL POWER PLANTSThe following are the components of a tidal power plant:Dam or dyke: The function of dam or dyke is to form a barrier between the sea and the basin or between one basin and the other in case of multiple basins. Sluice ways: These are used to fill the basin during the high tide or empty the basin during the low tide, as per operational requirement. These devices are controlled through gates. Power house: A power house has turbines, electric generators and other auxiliary equipments. As far as possible the power house and sluice ways should be in alignment with the dam or dyke.

Nuclear power plantWorks similar to steam power plantsNuclear reactor replaces steam generator.Heat required to generate steam is from fission process of uranium atoms.Heavy unstable nucleus is split in to two or three lighter nuclei, associated with the release of large quantity of heat, which is used for steam generation.Types of reactorsFast breeder reactorBoiling water reactorPressurized water reactor

Working layout of a Nuclear power plant

Pressurized water reactorPressurized water reactor contains two loops:Coolant loopWorking fluid loopNuclear reactor is the housing inside which energy release due to nuclear fission takes place.This energy is transferred to coolant which circulates through the nuclear reactor.This coolant transfers this received energy to the working fluid inside the heat exchanger (exchanges).The working fluid (Water) absorbs this heat and gets converted in to steam which drives a turbine.The steam after doing work is re-circulated by a pump back to the heat exchanger, after condensation in a condenser and preheating in a feed water heater.

Pressurized water reactor (PWR)

Boiling water reactor

It consists of a reactor, turbo-alternator, a condenser, feed pump and other auxiliaries.The liquid coolant on entering the core receives sensible as well as latent heat and it is converted in to a mixture of liquid and vapour.The vapour gets separated from the liquid at the steam separator, flows to the turbine and does useful work and gets condensed in a condenserThe recirculation of the condensate by the feed pump.The saturated liquid separated from the vapour in the steam separator flows downwards through the down comers and mixes with the condensate from the feed pump, before entering the reactor.The flow of liquid downwards is natural due to the difference in density of the liquid in the down comer and that of the liquid vapour (Two phase) mixture in the reactor core.

Boiling water reactor

Breeder reactorsA breeder reactor is one in which more fissionable material is produced than consumed.Fertile U238 is converted in to fissionable Pu239.In a FBR, the core containing U235 is surrounded by a fertile material U238.No moderators are used.The fast moving neutrons produced by the fission of U235 are absorbed by the U238 and gets converted in to fissionable Pu239 which is a fissionable material capable of sustaining chain reaction.Advantages: (Nuclear Power Plant)A nuclear power plant occupies less space when compared with other conventional power plants of the same size.Fuel transportation cost and fuel storage facilities needed are less.They are not affected by adverse weather conditions.

DisadvantagesCost of establishing a nuclear power plant is more than that for a hydro or thermal power plant.Sufficient care must be taken to dispose off the radio active wastes which may otherwise cause a serious problem to the health of workers as well as the environment.Maintenance cost is high.It requires skilled personnel for its operation.Nuclear power plants in India:Tarapur nuclear power station.(Trombay)Rana pratap sagar (Rajasthan)Kalpakkam nuclear power station.(T.N)Narora nuclear power station (Uttar Pradesh)Kakrapar nuclear power station (Gujarat)Kaiga nuclear power station (Karnataka)heavy water plants at Kota, Baroda..etc..