How efficient (or inefficient) are Thermal Power Plants?

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	How efficient (or inefficient) are Thermal Power Plants? Asked by : Sidhartha Singh, Sales/BD Manager, Tata Power Industry : Power Functional Area : Executive Education Activity: Question posted: 12 15 2008 13:18:16 +0000, 6 answers, 401 views, last activity 07 06 2010 20:18:08 +0000	Answer

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Electricity is a convenient form of energy. Thermal power plants convert the energy in coal to Electricity. how much is lost in the process of generating electricity? how efficiently the natural energy sources are converted???

Boiler Efficency in the range 75 % to 85 % depend up on design, while Turbine Efficiency we can get @ 40 45 %. Generator Efficiency may be considered 99.5%.

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by SSPatel , Head/VP/GM-Production/Manufacturing GSECL | 06 07 2009 13:03:38 +0000

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6 Answers for "How efficient (or inefficient) are Thermal Power Plants?"

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Answered by Amar Nath Mukherje, Top Management, Synergy Power | 08 29 2009 05:17:40 +0000

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This shows if you can save 1kw in house or in industry you save Power Plant input equivalent to more than 2 kw.,since thermal plant efficiency is less than 45%.

Energy saving by new method is welcome for future survival.and to reduce global warming.

Answer modified by Vineet Prakash, Sales/BD Manager, Tata Power | 08 25 2009 05:08:35 +0000

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The efficiency of a thermal power plant is typically between 30 and 50%. This means that only half or even less of the heat energy generated in the plant is available as electricity the remaining heat is dissipated to the environment. As a result, these power plants are judged inefficient and to be replaced as soon as possible by ’better ones’.

Their relatively low efficiency is mainly a consequence of the definitions used, and based on these definitions, it is governed by the laws of physics. Based on these different definitions, it is impossible to determine by that single value which is ’better’: a hydro power station with 85% efficiency, a coal-fired thermal power plant with 45% efficiency, or a solar power plant with 15% efficiency.

Answered by Amar Nath Mukherje, Top Management, Synergy Power | 08 24 2009 04:35:48 +0000

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In case your plant need any low pressure steam then Non condensing Thermal Plant will fetch right efficiency considering utilisation of steam from Turbine exhaust for your process apart from Power Generation.( Co Generation)

Answered by Rajender Sharma, Senior Consultant, Softwell | 12 15 2008 13:22:40 +0000

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The energy conversion is the combustion where the potential energy in coal is converted to heat energy. The efficiency of this conversion is around 90 %. Why?

    Due to practical limitations in heat transfer, all the heat produced by combustion is not transferred to the water; some is lost to the atmosphere as hot gases.
    The coal contains moisture. Also coal contains a small percent of Hydrogen, which also gets converted to moisture during combustion. In the furnace, moisture vaporises taking Latent heat from the combustion heat and exits the boiler along with the hot gases.
    Improper combustion of coal, hot ash discharged from the boiler and radiation are some of the other losses.
The second stage of conversion is the thermodynamic stage. The heat from combustion is transferred to the water to produce steam. The energy of the steam is converted to mechanical rotation of the turbine. The steam is then condensed to water and pumped back into the boiler for re-use. This stage works on the principle of the Rankine cycle. For plants operating with steam at subcritical pressures (less than 221 bar) and steam temperatures of 570 °C, the Rankine cycle efficiency is around 43 %. For the state of the art plants running at greater than supercritical pressure and steam temperatures near to 600 °C, the efficiency is around 47 %. Why is it so low?

    The steam is condensed for re-use. During this process the latent heat of condensation is lost to the cooling water. This is the major loss and is almost 40 % of the energy input.
    Losses in the turbine blades and exit losses at turbine end are some of the other losses.
    The Rankine cycle efficiency is dictated by the maximum temperature of steam that can be admitted into the turbine. Due to metallurgical constraints steam temperatures are at present limited to slightly more than 600 °C.
The third stage converts the mechanical rotation to Electricity in a generator. Copper, magnetic and mechanical losses account for 5 % loss in the Generator. Another 3 % is lost in the step-up transformer which makes the power ready for transmission to the consumer.

To operate the power plant it is required to run various auxiliary equipment like pulverisers, fans, pumps and precipitators. The power to operate these auxiliaries has to come from the power plant itself. For large power plants around 6 % of the generator output is used for internal consumption.

This brings the overall efficiency of the power plant to around 33.5 %. This means we get only 1.9 kwhr of electrical energy from one kg of coal instead of the 5.56 kwhr that is theoretically available in the coal.

The efficiency or inefficiency of power plants is something that we have to live with for the present till technology finds away out.

Answered by Gargi Sinha, Senior Consultant, Hewitt Associates | 12 15 2008 13:19:00 +0000

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