The major limitations or disadvantages of a steam engine or external combustion engine are given below :
- A steam engine is huge and heavy. (That is an external combustion engine is huge and heavy).
- A steam engine does not start at once.
- A steam engine is unsafe to use.
- A steam engine has low efficiency.
Pollution. The advent of the steam locomotive and railroad also saw the start of major pollution caused by big business, which is all too often seen today. Polluted rivers and smoke-filled air began to dominate cities, which in turn created poor living and working conditions that gave rise to socialism.
The first useful steam engine was invented by Thomas Newcomen in 1712. The Newcomen engine was used to pump water out of mines. Steam power really took off with improvements made by James Watt in 1778. The Watt steam engine improved the efficiency of steam engines considerably.
Steam is used in a wide range of industries. Common applications for steam are, for example, steam heated processes in plants and factories and steam driven turbines in electric power plants, but the uses of steam in industry extend far beyond this.
Steam turbines use high-pressure steam to turn electricity generators at incredibly high speeds, so they rotate much faster than either wind or water turbines. That's one reason why steam turbines were quickly adopted for powering ships, where space was very limited.
WORKING PRINCIPLE OF STEAM TURBINE
A high-velocity steam is coming from the nozzles and it strikes the rotating blades which are fitted on a disc mounted on a shaft. This high-velocity steam produces dynamic pressure on the blades in which blades and shaft both start to rotate in the same direction.According to the designers, diesel engines could run faster and work longer than steam locomotives. They were more fuel-efficient; they didn't require frequent stops to replenish coal and water. Locomotives, in comparison, had a low thermal efficiency.
All thermal power plants convert heat energy into mechanical energy, and then into electricity. This is done by using heat to turn water into steam and then directing the steam at a turbine. The steam turns the turbine blades, converting heat into mechanical power.
Geothermal Energy Disadvantages
- Potential emissions – Greenhouse gas below Earth's surface can potentially migrate to the surface and into the atmosphere.
- Surface Instability – Construction of geothermal power plants can affect the stability of land.
Thermal power is revered by environmental activists because it is completely renewable, does not use fuel to produce power and has virtually no emissions. It also helps reduce global warming and pollution and requires far less land than a coal mine or oil field.
Disadvantages: It pollutes the atmosphere due to production of large amount of smoke and fumes. It is costlier in running cost as compared to Hydro electric plants. The heated water that comes from thermal power plant has an adverse effect on the lives in the water and disturbs the ecology.
Thermal energy can be dangerous. In humans high temperatures can cause heat boils, heat stroke, dehydration, heat cramps and even death. However if used in the right way it can benefit all living things. heat is used to keep our homes warm during winter and provide hot water.
Hydropower has the ability to generate electricity without emitting greenhouse gasses. However, it can also cause environmental and social threats, such as damaged wildlife habitat, harmed water quality, obstructed fish migration, and diminished recreational benefits of rivers.
Thermal energy removes a large amount of stress from the environment by using a renewable source. This renewable source uses no fossil fuels, creates no pollution, and emits no greenhouse gases. This lessens the impact on the environment and on the wallet. Ocean thermal energy is particularly positive.
The advantages of wind energy are more apparent than the disadvantages. The main advantages include an unlimited, free, renewable resource (the wind itself), economic value, maintenance cost, and placement of wind harvesting facilities. First and foremost, wind is an unlimited, free, renewable resource.
Thermal energy can be transferred from one object or system to another in the form of heat. Geothermal energy is thermal energy within the Earth due to the movement of the Earth's particles. Most of this geothermal energy is contained within the core of the Earth.
Making electricity from steam is generally a three step process, involving: 1) Converting water to high pressure steam 2) Using the high pressure steam in a steam turbine to rotate the turbine shaft 3) Using the rotating turbine shaft in an electric generator to generate electricity In most cases, the used steam is
A steam/thermal power station uses heat energy generated from burning coal to produce electrical energy. This power station uses the Rankine cycle. This is the cycle of the steam produced in the boiler, then taken to the Steam turbine (prime mover).
CLASSIFICATION OF STEAM POWER PLANTS The steam power plants may be classified as follows: 1. Central stations. 2. Industrial power stations or captive power stations Central stations : These stations is meant for general sale to the customers who wish to purchase it.
In the case of steam, sensible heat has kinetic energy and latent heat has potential energy. Steam is an invisible gas created by adding heat energy to water. It is liquid water changed to its gaseous state. Saturated steam - steam in immediate contact with the water from which it is being generated.
The major components of this power plant are boiler, steam turbine, condenser and water feed pump.
The
gas turbine is made up of the following
components: An air compressor. A combustor. A power
turbine, which produces the power to drive the air compressor and the output shaft.
Process
- Adiabatic compression.
- Constant pressure heating.
- Adiabatic expansion.
Natural gas is environmentally friendly because it burns cleaner than other fossil fuels. It's safer and easier to store when compared to other fossil fuels. Natural gas is extremely reliable, unlike electric power that can be knocked out during a storm. Natural gas is less expensive than other fossil fuels.
The path the air takes through the engine and how power is produced determines the type of engine. Four types of gas turbine engines are used to propel and power aircraft. They are the turbojet, turbofan, turboprop, and turboshaft.
How do they start jet engines on airplanes? Gas turbine engines come in many shapes and sizes. The electric motor spins the main shaft until there is enough air blowing through the compressor and the combustion chamber to light the engine. Fuel starts flowing and an igniter similar to a spark plug ignites the fuel.
The gas turbine is most efficient at maximum power output in the same way reciprocating engines are most efficient at maximum load. The difference is that at lower rotational speed the pressure of the compressed air drops and thus thermal and fuel efficiency drop dramatically.
Gas turbines are used to power aircraft, trains, ships, electrical generators, pumps, gas compressors, and tanks.
The gas turbine is used to make mechanical energy from a combustible fuel. In the gas turbines used to make industrial/electrical power the mechanical energy comes in the form of a rotating shaft (as opposed to pressurized thrust of a gas turbine jet engine). This shaft has an enormous amount of power and torque.
For stand-alone gas turbines, without any heat recovery system the efficiency will be as low as 35 to 40 per cent. This is attributed to the blade efficiency of the rotor, leakage through clearance spaces, friction, irreversible turbulence, etc.
