Misplaced Pages

#60939

88-571: The current station was built on the site of an earlier 128 MW coal-fired power station built in 1951, and an open cycle gas turbine plant commissioned in 1965 (see below). Both these stations were closed on 1 November 1982 and were subsequently demolished. The gas-fired station, near Hoddesdon , is about eighteen miles north of London , was built in the early 1990s and fully commissioned in November 1993 and officially opened in April 1994. Output from

176-467: A greenhouse gas which is a major contributor to global warming . The results of a recent study show that the net income available to shareholders of large companies could see a significant reduction from the greenhouse gas emissions liability related to only natural disasters in the United States from a single coal-fired power plant. However, as of 2015, no such cases have awarded damages in

264-645: A capacity of 1.3 million gallons per hour (1.64 m/s). A dock was built on the Lee Navigation adjacent to the power station for unloading coal in addition to the railway sidings. The station comprised four 30 MW Richardsons Westgarth-Parsons turbo-alternators, generating at 33 kV. These were supplied with steam from the Babcock pulverised coal boilers which produced a total of 1.4 million pounds per hour (176.4 kg/s) of steam at 600 psi (41.4 bar) and 454 °C. In 1965, an open cycle gas turbine power station

352-630: A cooler cooling system. However, it may be used in cogeneration plants to heat buildings, produce hot water, or to heat materials on an industrial scale, such as in some oil refineries , plants, and chemical synthesis plants. Typical thermal efficiency for utility-scale electrical generators is around 37% for coal and oil-fired plants, and 56 – 60% (LEV) for combined-cycle gas-fired plants. Plants designed to achieve peak efficiency while operating at capacity will be less efficient when operating off-design (i.e. temperatures too low.) Practical fossil fuels stations operating as heat engines cannot exceed

440-404: A cooler medium must be equal or larger than the ratio of absolute temperatures of the cooling system (environment) and the heat source (combustion furnace). Raising the furnace temperature improves the efficiency but complicates the design, primarily by the selection of alloys used for construction, making the furnace more expensive. The waste heat cannot be converted into mechanical energy without

528-413: A curve connecting an initial state (A) and a final state (B). The area under the curve is: which is the amount of heat transferred in the process. If the process moves the system to greater entropy, the area under the curve is the amount of heat absorbed by the system in that process; otherwise, it is the amount of heat removed from or leaving the system. For any cyclic process, there is an upper portion of

616-503: A factory or data center, or may also be operated in parallel with the local utility system to reduce peak power demand charge from the utility. Diesel engines can produce strong torque at relatively low rotational speeds, which is generally desirable when driving an alternator , but diesel fuel in long-term storage can be subject to problems resulting from water accumulation and chemical decomposition . Rarely used generator sets may correspondingly be installed as natural gas or LPG to minimize

704-491: A fine filter that collects the ash particles, electrostatic precipitators use an electric field to trap ash particles on high-voltage plates, and cyclone collectors use centrifugal force to trap particles to the walls. A recent study indicates that sulfur emissions from fossil fueled power stations in China may have caused a 10-year lull in global warming (1998-2008). Fossil-fuel power stations, particularly coal-fired plants, are

792-478: A fossil fuel power plant the chemical energy stored in fossil fuels such as coal , fuel oil , natural gas or oil shale and oxygen of the air is converted successively into thermal energy , mechanical energy and, finally, electrical energy . Each fossil fuel power plant is a complex, custom-designed system. Multiple generating units may be built at a single site for more efficient use of land , natural resources and labor . Most thermal power stations in

880-748: A given set of thermal reservoirs. Although Carnot's cycle is an idealization, Equation 3 as the expression of the Carnot efficiency is still useful. Consider the average temperatures, ⟨ T H ⟩ = 1 Δ S ∫ Q in T d S {\displaystyle \langle T_{H}\rangle ={\frac {1}{\Delta S}}\int _{Q_{\text{in}}}TdS} ⟨ T C ⟩ = 1 Δ S ∫ Q out T d S {\displaystyle \langle T_{C}\rangle ={\frac {1}{\Delta S}}\int _{Q_{\text{out}}}TdS} at which

968-636: A major source of industrial wastewater . Wastewater streams include flue-gas desulfurization, fly ash, bottom ash and flue gas mercury control. Plants with air pollution controls such as wet scrubbers typically transfer the captured pollutants to the wastewater stream. Ash ponds , a type of surface impoundment, are a widely used treatment technology at coal-fired plants. These ponds use gravity to settle out large particulates (measured as total suspended solids ) from power plant wastewater. This technology does not treat dissolved pollutants. Power stations use additional technologies to control pollutants, depending on

SECTION 10

#1732791999061

1056-426: A minus sign appears in the final expression for η {\displaystyle \eta } . This is the Carnot heat engine working efficiency definition as the fraction of the work done by the system to the thermal energy received by the system from the hot reservoir per cycle. This thermal energy is the cycle initiator. A Carnot heat-engine cycle described is a totally reversible cycle. That is, all

1144-408: A particular fuel. As an example, a new 1500 MW supercritical lignite-fueled power station running on average at half its capacity might have annual CO 2 emissions estimated as: = 1500MW x 0.5 x 100/40 x 101000 kg/TJ x 1year = 1500MJ/s x 0.5 x 2.5 x 0.101 kg/MJ x 365x24x60x60s = 1.5x10 x 5x10 x 2.5 x 1.01 x 3.1536x10 kg = 59.7 x10 kg = 5.97 Mt Thus the example power station

1232-433: A serious impact on public health. Power plants remove particulate from the flue gas with the use of a bag house or electrostatic precipitator . Several newer plants that burn coal use a different process, Integrated Gasification Combined Cycle in which synthesis gas is made out of a reaction between coal and water. The synthesis gas is processed to remove most pollutants and then used initially to power gas turbines. Then

1320-693: A single Siemens turbogenerator producing 250 MW at 15.75 kV. The combined outputs feed the National Grid at 400 kV. The station has the largest air-cooled condenser in Europe. The chimneys are 58 m high. The station employs thirty-seven people. The 128 MW coal-fired Rye House power station was built by the British Electricity Authority (later the Central Electricity Generating Board ) and

1408-487: Is a deceiving baseline for comparison: just the Chernobyl nuclear disaster released, in iodine-131 alone, an estimated 1.76 EBq. of radioactivity, a value one order of magnitude above this value for total emissions from all coal burned within a century, while the iodine-131, the major radioactive substance which comes out in accident situations, has a half life of just 8 days. Carnot efficiency A Carnot cycle

1496-429: Is a formal statement of this fact: No engine operating between two heat reservoirs can be more efficient than a Carnot engine operating between those same reservoirs. Thus, Equation 3 gives the maximum efficiency possible for any engine using the corresponding temperatures. A corollary to Carnot's theorem states that: All reversible engines operating between the same heat reservoirs are equally efficient. Rearranging

1584-424: Is a relatively cheap fuel. Coal is an impure fuel and produces more greenhouse gas and pollution than an equivalent amount of petroleum or natural gas. For instance, the operation of a 1000-MWe coal-fired power plant results in a nuclear radiation dose of 490 person-rem/year, compared to 136 person-rem/year for an equivalent nuclear power plant, including uranium mining, reactor operation and waste disposal. Coal

1672-507: Is absorbed from the hot temperature reservoir, resulting in an increase in the entropy S {\displaystyle S} of the gas by the amount Δ S H = Q H / T H {\displaystyle \Delta S_{H}=Q_{H}/T_{H}} . Isentropic ( reversible adiabatic ) expansion of the gas (isentropic work output). For this step (2 to 3 on Figure 1 , B to C in Figure 2 )

1760-421: Is an ideal thermodynamic cycle proposed by French physicist Sadi Carnot in 1824 and expanded upon by others in the 1830s and 1840s. By Carnot's theorem , it provides an upper limit on the efficiency of any classical thermodynamic engine during the conversion of heat into work , or conversely, the efficiency of a refrigeration system in creating a temperature difference through the application of work to

1848-411: Is best understood by using a temperature–entropy diagram ( T – S diagram), in which the thermodynamic state is specified by a point on a graph with entropy ( S ) as the horizontal axis and temperature ( T ) as the vertical axis ( Figure 2 ). For a simple closed system (control mass analysis), any point on the graph represents a particular state of the system. A thermodynamic process is represented by

SECTION 20

#1732791999061

1936-419: Is burned that significant amounts of these substances are released. A 1,000 MW coal-burning power plant could have an uncontrolled release of as much as 5.2 metric tons per year of uranium (containing 74 pounds (34 kg) of uranium-235 ) and 12.8 metric tons per year of thorium. In comparison, a 1,000 MW nuclear plant will generate about 30 metric tons of high-level radioactive solid packed waste per year. It

2024-553: Is caused by the emission of nitrogen oxides and sulfur dioxide . These gases may be only mildly acidic themselves, yet when they react with the atmosphere, they create acidic compounds such as sulfurous acid , nitric acid and sulfuric acid which fall as rain, hence the term acid rain. In Europe and the US, stricter emission laws and decline in heavy industries have reduced the environmental hazards associated with this problem, leading to lower emissions after their peak in 1960s. In 2008,

2112-428: Is converted to steam in the boiler; additional heating stages may be included to superheat the steam. The hot steam is sent through controlling valves to a turbine. As the steam expands and cools, its energy is transferred to the turbine blades which turn a generator. The spent steam has very low pressure and energy content; this water vapor is fed through a condenser, which removes heat from the steam. The condensed water

2200-469: Is cooled to a temperature that is infinitesimally higher than the cold reservoir temperature T C . The entropy remains unchanged as no heat Q transfers ( Q = 0) between the system (the gas) and its surroundings. It is an isentropic process . Isothermal compression. Heat is transferred reversibly to the low temperature reservoir at a constant temperature T C (isothermal heat rejection). In this step (3 to 4 on Figure 1 , C to D on Figure 2 ),

2288-403: Is delivered by highway truck , rail , barge , collier ship or coal slurry pipeline . Generating stations adjacent to a mine may receive coal by conveyor belt or massive diesel-electric -drive trucks . Coal is usually prepared for use by crushing the rough coal to pieces less than 2 inches (5 cm) in size. Gas is a very common fuel and has mostly replaced coal in countries where gas

2376-507: Is estimated that during 1982, US coal burning released 155 times as much uncontrolled radioactivity into the atmosphere as the Three Mile Island incident . The collective radioactivity resulting from all coal burning worldwide between 1937 and 2040 is estimated to be 2,700,000 curies or 0.101 EBq. During normal operation, the effective dose equivalent from coal plants is 100 times that from nuclear plants. Normal operation however,

2464-421: Is estimated to emit about 6 megatonnes of carbon dioxide each year. The results of similar estimations are mapped by organisations such as Global Energy Monitor , Carbon Tracker and ElectricityMap. Alternatively it may be possible to measure CO 2 emissions (perhaps indirectly via another gas) from satellite observations. Another problem related to coal combustion is the emission of particulates that have

2552-453: Is heat transferred from the hot reservoir to the system per cycle. A Carnot cycle as an idealized thermodynamic cycle performed by a Carnot heat engine , consisting of the following steps: Isothermal expansion. Heat (as an energy) is transferred reversibly from the hot temperature reservoir at constant temperature T H to the gas at a temperature infinitesimally less than T H . (The infinitesimal temperature difference allows

2640-440: Is not possible to build a thermodynamically reversible engine. So, real heat engines are even less efficient than indicated by Equation 3 . In addition, real engines that operate along the Carnot cycle style (isothermal expansion / isentropic expansion / isothermal compression / isentropic compression) are rare. Nevertheless, Equation 3 is extremely useful for determining the maximum efficiency that could ever be expected for

2728-660: Is referred to as a combined cycle power plant because it combines the Brayton cycle of the gas turbine with the Rankine cycle of the HRSG. The turbines are fueled either with natural gas or fuel oil. Diesel engine generator sets are often used for prime power in communities not connected to a widespread power grid. Emergency (standby) power systems may use reciprocating internal combustion engines operated by fuel oil or natural gas. Standby generators may serve as emergency power for

Rye House power station - Misplaced Pages Continue

2816-464: Is still important as the fuel source for diesel engine power plants used especially in isolated communities not interconnected to a grid. Liquid fuels may also be used by gas turbine power plants, especially for peaking or emergency service. Of the three fossil fuel sources, oil has the advantages of easier transportation and handling than solid coal, and easier on-site storage than natural gas. Combined heat and power (CHP), also known as cogeneration ,

2904-502: Is still unknown as to which kinds of particulate matter pose the most harm, which makes it difficult to come up with adequate legislation for regulating particulate matter. There are several methods of helping to reduce the particulate matter emissions from coal-fired plants. Roughly 80% of the ash falls into an ash hopper, but the rest of the ash then gets carried into the atmosphere to become coal-fly ash. Methods of reducing these emissions of particulate matter include: The baghouse has

2992-462: Is the " nameplate capacity " or the maximum allowed output of the plant, " capacity factor " or "load factor" is a measure of the amount of power that a plant produces compared with the amount it would produce if operated at its rated capacity nonstop, heat rate is thermal energy in/electrical energy out, emission intensity (also called emission factor ) is the CO 2 emitted per unit of heat generated for

3080-536: Is the use of a thermal power station to provide both electric power and heat (the latter being used, for example, for district heating purposes). This technology is practiced not only for domestic heating (low temperature) but also for industrial process heat, which is often high temperature heat. Calculations show that Combined Heat and Power District Heating (CHPDH) is the cheapest method in reducing (but not eliminating) carbon emissions, if conventional fossil fuels remain to be burned. Thermal power plants are one of

3168-433: Is then pumped into the boiler to repeat the cycle. Emissions from the boiler include carbon dioxide, oxides of sulfur, and in the case of coal fly ash from non-combustible substances in the fuel. Waste heat from the condenser is transferred either to the air, or sometimes to a cooling pond, lake or river. One type of fossil fuel power plant uses a gas turbine in conjunction with a heat recovery steam generator (HRSG). It

3256-413: Is true as Q C {\displaystyle Q_{C}} and T C {\displaystyle T_{C}} are both smaller in magnitude and in fact are in the same ratio as Q H / T H {\displaystyle Q_{H}/T_{H}} . When a Carnot cycle is plotted on a pressure–volume diagram ( Figure 1 ), the isothermal stages follow

3344-465: Is what remains after the coal has been combusted, so it consists of the incombustible materials that are found in the coal. The size and chemical composition of these particles affects the impacts on human health. Currently coarse (diameter greater than 2.5 μm) and fine (diameter between 0.1 μm and 2.5 μm) particles are regulated, but ultrafine particles (diameter less than 0.1 μm) are currently unregulated, yet they pose many dangers. Unfortunately much

3432-522: The Carnot cycle limit for conversion of heat energy into useful work. Fuel cells do not have the same thermodynamic limits as they are not heat engines. The efficiency of a fossil fuel plant may be expressed as its heat rate , expressed in BTU/kilowatthour or megajoules/kilowatthour. In a steam turbine power plant, fuel is burned in a furnace and the hot gasses flow through a boiler. Water

3520-621: The Carnot efficiency and therefore produce waste heat . Fossil fuel power stations provide most of the electrical energy used in the world. Some fossil-fired power stations are designed for continuous operation as baseload power plants , while others are used as peaker plants . However, starting from the 2010s, in many countries plants designed for baseload supply are being operated as dispatchable generation to balance increasing generation by variable renewable energy . By-products of fossil fuel power plant operation must be considered in their design and operation. Flue gas from combustion of

3608-828: The European Environment Agency (EEA) documented fuel-dependent emission factors based on actual emissions from power plants in the European Union . Electricity generation using carbon-based fuels is responsible for a large fraction of carbon dioxide (CO 2 ) emissions worldwide and for 34% of U.S. man-made carbon dioxide emissions in 2010. In the U.S. 70% of electricity is generated by combustion of fossil fuels. Coal contains more carbon than oil or natural gas fossil fuels, resulting in greater volumes of carbon dioxide emissions per unit of electricity generated. In 2010, coal contributed about 81% of CO 2 emissions from generation and contributed about 45% of

Rye House power station - Misplaced Pages Continue

3696-460: The fossil fuels contains carbon dioxide and water vapor, as well as pollutants such as nitrogen oxides (NO x ), sulfur oxides (SO x ), and, for coal-fired plants, mercury , traces of other metals, and fly ash . Usually all of the carbon dioxide and some of the other pollution is discharged to the air. Solid waste ash from coal-fired boilers must also be removed. Fossil fueled power stations are major emitters of carbon dioxide (CO 2 ),

3784-436: The greenhouse gas carbon dioxide within the atmosphere will "very likely" lead to higher average temperatures on a global scale ( global warming ). Concerns regarding the potential for such warming to change the global climate prompted IPCC recommendations calling for large cuts to CO 2 emissions worldwide. Emissions can be reduced with higher combustion temperatures, yielding more efficient production of electricity within

3872-450: The heat energy of combustion into mechanical energy , which then operates an electrical generator . The prime mover may be a steam turbine , a gas turbine or, in small plants, a reciprocating gas engine . All plants use the energy extracted from the expansion of a hot gas, either steam or combustion gases. Although different energy conversion methods exist, all thermal power station conversion methods have their efficiency limited by

3960-518: The United States. Per unit of electric energy, brown coal emits nearly twice as much CO 2 as natural gas, and black coal emits somewhat less than brown. As of 2019 , carbon capture and storage of emissions is not economically viable for fossil fuel power stations, and keeping global warming below 1.5 °C is still possible but only if no more fossil fuel power plants are built and some existing fossil fuel power plants are shut down early, together with other measures such as reforestation . In

4048-409: The amount of work done by the system per cycle. Referring to Figure 1 , mathematically, for a reversible process, we may write the amount of work done over a cyclic process as: Since dU is an exact differential , its integral over any closed loop is zero and it follows that the area inside the loop on a T – S diagram is (a) equal to the total work performed by the system on the surroundings if

4136-462: The ceiling efficiency of a heat engine than raising the temperature of the hot reservoir by the same amount. In the real world, this may be difficult to achieve since the cold reservoir is often an existing ambient temperature. In other words, the maximum efficiency is achieved if and only if entropy does not change per cycle. An entropy change per cycle is made, for example, if there is friction leading to dissipation of work into heat. In that case,

4224-472: The cycle and a lower portion. In T - S diagrams for a clockwise cycle, the area under the upper portion will be the energy absorbed by the system during the cycle, while the area under the lower portion will be the energy removed from the system during the cycle. The area inside the cycle is then the difference between the two (the absorbed net heat energy), but since the internal energy of the system must have returned to its initial value, this difference must be

4312-508: The cycle is not reversible and the Clausius theorem becomes an inequality rather than an equality. Otherwise, since entropy is a state function , the required dumping of heat into the environment to dispose of excess entropy leads to a (minimal) reduction in efficiency. So Equation 3 gives the efficiency of any reversible heat engine . In mesoscopic heat engines, work per cycle of operation in general fluctuates due to thermal noise. If

4400-453: The cycle is performed quasi-statically, the fluctuations vanish even on the mesoscale. However, if the cycle is performed faster than the relaxation time of the working medium, the fluctuations of work are inevitable. Nevertheless, when work and heat fluctuations are counted, an exact equality relates the exponential average of work performed by any heat engine to the heat transfer from the hotter heat bath. Carnot realized that, in reality, it

4488-423: The cycle. As of 2019 the price of emitting CO 2 to the atmosphere is much lower than the cost of adding carbon capture and storage (CCS) to fossil fuel power stations, so owners have not done so. The CO 2 emissions from a fossil fuel power station can be estimated with the following formula: CO 2 emissions = capacity x capacity factor x heat rate x emission intensity x time where "capacity"

SECTION 50

#1732791999061

4576-510: The electricity generated in the United States. In 2000, the carbon intensity (CO 2 emissions) of U.S. coal thermal combustion was 2249 lbs/MWh (1,029 kg/MWh) while the carbon intensity of U.S. oil thermal generation was 1672 lb/MWh (758 kg/MWh or 211 kg/ GJ ) and the carbon intensity of U.S. natural gas thermal production was 1135 lb/MWh (515 kg/MWh or 143 kg/GJ). The Intergovernmental Panel on Climate Change ( IPCC ) reports that increased quantities of

4664-753: The expressions above with the entropy: Q H = T H ( S B − S A ) = T H Δ S H {\displaystyle Q_{H}=T_{H}(S_{B}-S_{A})=T_{H}\Delta S_{H}} and Q C = T C ( S A − S B ) = T C Δ S C < 0 {\displaystyle Q_{C}=T_{C}(S_{A}-S_{B})=T_{C}\Delta S_{C}<0} . Since Δ S C = S A − S B = − Δ S H {\displaystyle \Delta S_{C}=S_{A}-S_{B}=-\Delta S_{H}} ,

4752-431: The first central stations used reciprocating steam engines to drive generators. As the size of the electrical load to be served grew, reciprocating units became too large and cumbersome to install economically. The steam turbine rapidly displaced all reciprocating engines in central station service. Coal is the most abundant fossil fuel on the planet, and widely used as the source of energy in thermal power stations and

4840-479: The first integral is over a part of a cycle where heat goes into the system and the second integral is over a cycle part where heat goes out from the system. Then, replace T H and T C in Equation 3 by ⟨ T H ⟩ and ⟨ T C ⟩, respectively, to estimate the efficiency a heat engine. For the Carnot cycle, or its equivalent, the average value ⟨ T H ⟩ will equal

4928-573: The fuel system maintenance requirements. Spark-ignition internal combustion engines operating on gasoline (petrol), propane , or LPG are commonly used as portable temporary power sources for construction work, emergency power, or recreational uses. Reciprocating external combustion engines such as the Stirling engine can be run on a variety of fossil fuels, as well as renewable fuels or industrial waste heat. Installations of Stirling engines for power production are relatively uncommon. Historically,

5016-501: The gas from this work exactly transfers as a heat energy Q C < 0 (negative as leaving from the system, according to the universal convention in thermodynamics ) to the cold reservoir so the entropy of the system decreases by the amount Δ S C = Q C / T C {\displaystyle \Delta S_{C}=Q_{C}/T_{C}} . Δ S C < 0 {\displaystyle \Delta S_{C}<0} because

5104-447: The gas in the engine is in thermal contact with the cold reservoir at temperature T C , and is thermally isolated from the hot reservoir. The gas temperature is infinitesimally higher than T C to allow heat transfer from the gas to the cold reservoir. There is no change in temperature, it is an isothermal process . The surroundings do work on the gas, pushing the piston down (Stage Three figure, right). An amount of energy earned by

5192-422: The gas in the engine is thermally insulated from both the hot and cold reservoirs, thus they neither gain nor lose heat. It is an adiabatic process . The gas continues to expand with reduction of its pressure, doing work on the surroundings (raising the piston; Stage Two figure, right), and losing an amount of internal energy equal to the work done. The loss of internal energy causes the gas to cool. In this step it

5280-415: The heat to transfer into the gas without a significant change in the gas temperature. This is called isothermal heat addition or absorption .) During this step (1 to 2 on Figure 1 , A to B in Figure 2 ), the gas is in thermal contact with the hot temperature reservoir, and is thermally isolated from the cold temperature reservoir. The gas is allowed to expand, doing work on the surroundings by pushing up

5368-409: The highest temperature available, namely T H , and ⟨ T C ⟩ the lowest, namely T C . For other less efficient thermodynamic cycles, ⟨ T H ⟩ will be lower than T H , and ⟨ T C ⟩ will be higher than T C . This can help illustrate, for example, why a reheater or a regenerator can improve the thermal efficiency of steam power plants and why

SECTION 60

#1732791999061

5456-460: The hot exhaust gases from the gas turbines are used to generate steam to power a steam turbine. The pollution levels of such plants are drastically lower than those of "classic" coal power plants. Particulate matter from coal-fired plants can be harmful and have negative health impacts. Studies have shown that exposure to particulate matter is related to an increase of respiratory and cardiac mortality. Particulate matter can irritate small airways in

5544-706: The hot reservoir to the system (in the isothermal expansion) will be Q H = T H ( S B − S A ) = T H Δ S H {\displaystyle Q_{H}=T_{H}(S_{B}-S_{A})=T_{H}\Delta S_{H}} and the total amount of heat transferred from the system to the cold reservoir (in the isothermal compression) will be Q C = T C ( S A − S B ) = T C Δ S C < 0 {\displaystyle Q_{C}=T_{C}(S_{A}-S_{B})=T_{C}\Delta S_{C}<0} Due to energy conservation,

5632-418: The isotherm lines for the working fluid, the adiabatic stages move between isotherms, and the area bounded by the complete cycle path represents the total work that can be done during one cycle. From point 1 to 2 and point 3 to 4 the temperature is constant (isothermal process). Heat transfer from point 4 to 1 and point 2 to 3 are equal to zero (adiabatic process). The behavior of a Carnot engine or refrigerator

5720-534: The isothermal compression decreases the multiplicity of the gas. Isentropic compression. (4 to 1 on Figure 1 , D to A on Figure 2 ) Once again the gas in the engine is thermally insulated from the hot and cold reservoirs, and the engine is assumed to be frictionless and the process is slow enough, hence reversible. During this step, the surroundings do work on the gas, pushing the piston down further (Stage Four figure, right), increasing its internal energy, compressing it, and causing its temperature to rise back to

5808-629: The loop is traversed in a clockwise direction, and (b) is equal to the total work done on the system by the surroundings as the loop is traversed in a counterclockwise direction. Evaluation of the above integral is particularly simple for a Carnot cycle. The amount of energy transferred as work is W = ∮ P d V = ∮ T d S = ( T H − T C ) ( S B − S A ) {\displaystyle W=\oint PdV=\oint TdS=(T_{H}-T_{C})(S_{B}-S_{A})} The total amount of heat transferred from

5896-428: The lungs, which can lead to increased problems with asthma, chronic bronchitis, airway obstruction, and gas exchange. There are different types of particulate matter, depending on the chemical composition and size. The dominant form of particulate matter from coal-fired plants is coal fly ash , but secondary sulfate and nitrate also comprise a major portion of the particulate matter from coal-fired plants. Coal fly ash

5984-479: The main artificial sources of producing toxic gases and particulate matter . Fossil fuel power plants cause the emission of pollutants such as NO x , SO x , CO 2 , CO, PM, organic gases and polycyclic aromatic hydrocarbons. World organizations and international agencies, like the IEA, are concerned about the environmental impact of burning fossil fuels , and coal in particular. The combustion of coal contributes

6072-488: The most to acid rain and air pollution , and has been connected with global warming . Due to the chemical composition of coal there are difficulties in removing impurities from the solid fuel prior to its combustion. Modern day coal power plants pollute less than older designs due to new " scrubber " technologies that filter the exhaust air in smoke stacks. However, emission levels of various pollutants are still on average several times greater than natural gas power plants and

6160-536: The net heat transferred, Q {\displaystyle Q} , is equal to the work performed W = Q = Q H − Q C {\displaystyle W=Q=Q_{H}-Q_{C}} The efficiency η {\displaystyle \eta } is defined to be: where The expression with the temperature η = 1 − T C T H {\displaystyle \eta =1-{\frac {T_{C}}{T_{H}}}} can be derived from

6248-614: The particular wastestream in the plant. These include dry ash handling, closed-loop ash recycling, chemical precipitation, biological treatment (such as an activated sludge process), membrane systems, and evaporation-crystallization systems. In 2015 EPA published a regulation pursuant to the Clean Water Act that requires US power plants to use one or more of these technologies. Technological advancements in ion exchange membranes and electrodialysis systems has enabled high efficiency treatment of flue-gas desulfurization wastewater to meet

6336-419: The piston (Stage One figure, right). Although the pressure drops from points 1 to 2 (figure 1) the temperature of the gas does not change during the process because the heat transferred from the hot temperature reservoir to the gas is exactly used to do work on the surroundings by the gas. There is no change in the gas internal energy, and no change in the gas temperature if it is an ideal gas. Heat Q H > 0

6424-419: The processes that compose it can be reversed, in which case it becomes the Carnot heat pump and refrigeration cycle . This time, the cycle remains exactly the same except that the directions of any heat and work interactions are reversed. Heat is absorbed from the low-temperature reservoir, heat is rejected to a high-temperature reservoir, and a work input is required to accomplish all this. The P – V diagram of

6512-423: The reversed Carnot cycle is the same as for the Carnot heat-engine cycle except that the directions of the processes are reversed. It can be seen from the above diagram that for any cycle operating between temperatures T H {\displaystyle T_{H}} and T C {\displaystyle T_{C}} , none can exceed the efficiency of a Carnot cycle. Carnot's theorem

6600-423: The right side of the equation gives what may be a more easily understood form of the equation, namely that the theoretical maximum efficiency of a heat engine equals the difference in temperature between the hot and cold reservoir divided by the absolute temperature of the hot reservoir. Looking at this formula an interesting fact becomes apparent: Lowering the temperature of the cold reservoir will have more effect on

6688-530: The scrubbers transfer the captured pollutants to wastewater, which still requires treatment in order to avoid pollution of receiving water bodies. In these modern designs, pollution from coal-fired power plants comes from the emission of gases such as carbon dioxide, nitrogen oxides , and sulfur dioxide into the air, as well a significant volume of wastewater which may contain lead , mercury , cadmium and chromium , as well as arsenic , selenium and nitrogen compounds ( nitrates and nitrites ). Acid rain

6776-518: The station is enough to meet the daily power needs of nearly a million people - almost the population of Hertfordshire. Rye House is owned and operated by VPI, part of the Vitol group. Rye House was built by Siemens AG . It has three Siemens V94.2 gas turbines rotating at 3000 rpm . Each drives a generator producing 150 MW at a terminal voltage of 11 kV and exhausts at 540 °C into a Babcock Energy steam generator. The three steam generators supply

6864-615: The system or engine to the environment per Carnot cycle depends on the temperatures of the thermal reservoirs and the entropy transferred from the hot reservoir to the system Δ S {\displaystyle \Delta S} per cycle such as W = ( T H − T C ) Δ S = ( T H − T C ) Q H T H {\displaystyle W=(T_{H}-T_{C})\Delta S=(T_{H}-T_{C}){\frac {Q_{H}}{T_{H}}}} , where Q H {\displaystyle Q_{H}}

6952-402: The system. In a Carnot cycle, a system or engine transfers energy in the form of heat between two thermal reservoirs at temperatures T H {\displaystyle T_{H}} and T C {\displaystyle T_{C}} (referred to as the hot and cold reservoirs, respectively), and a part of this transferred energy is converted to the work done by

7040-426: The system. The cycle is reversible , and entropy is conserved , merely transferred between the thermal reservoirs and the system without gain or loss. When work is applied to the system, heat moves from the cold to hot reservoir ( heat pump or refrigeration ). When heat moves from the hot to the cold reservoir, the system applies work to the environment. The work W {\displaystyle W} done by

7128-747: The temperature infinitesimally less than T H due solely to the work added to the system, but the entropy remains unchanged. At this point the gas is in the same state as at the start of step 1. In this case, since it is a reversible thermodynamic cycle (no net change in the system and its surroundings per cycle) Δ S H + Δ S C = Δ S cycle = 0 , {\displaystyle \Delta S_{H}+\Delta S_{C}=\Delta S_{\text{cycle}}=0,} or, Q H T H = − Q C T C . {\displaystyle {\frac {Q_{H}}{T_{H}}}=-{\frac {Q_{C}}{T_{C}}}.} This

7216-408: The thermal efficiency of combined-cycle power plants (which incorporate gas turbines operating at even higher temperatures) exceeds that of conventional steam plants. The first prototype of the diesel engine was based on the principles of the Carnot cycle. The Carnot heat engine is, ultimately, a theoretical construct based on an idealized thermodynamic system . On a practical human-scale level

7304-583: The updated EPA discharge limits. Coal is a sedimentary rock formed primarily from accumulated plant matter, and it includes many inorganic minerals and elements which were deposited along with organic material during its formation. As the rest of the Earth's crust , coal also contains low levels of uranium , thorium , and other naturally occurring radioactive isotopes whose release into the environment leads to radioactive contamination . While these substances are present as very small trace impurities, enough coal

7392-438: The world use fossil fuel, outnumbering nuclear , geothermal , biomass , or concentrated solar power plants. The second law of thermodynamics states that any closed-loop cycle can only convert a fraction of the heat produced during combustion into mechanical work . The rest of the heat, called waste heat , must be released into a cooler environment during the return portion of the cycle. The fraction of heat released into

7480-481: Was built adjacent to the steam station. This comprised two 70 MW oil-fired gas turbine/generator sets. This was a peak shaving plant designed to operate at times of maximum demand. The output from the steam plant and the gas turbine plant are shown in the following charts. Rye House (steam) power station output 1954–1982 in GWh. Rye House (gas turbine) power station output 1965–1982 in GWh. Rye House power station

7568-618: Was commissioned in 1951. The station was located between the London to Cambridge railway line and the Lee Navigation , providing access for the delivery of coal and a water supply for condensing steam in the plant. The building was designed by the architect Sir Giles Gilbert Scott in a steel-framed, brick-clad ‘cathedral of power’ style exemplified by Scott's Battersea and Bankside power stations . The station had single chimney and three reinforced concrete cooling towers. Each tower had

7656-498: Was decommissioned on 1 November 1982. It was subsequently demolished and then replaced by the CCGT station. Fossil fuel power plant 2021 world electricity generation by source. Total generation was 28 petawatt-hours . A fossil fuel power station is a thermal power station which burns a fossil fuel , such as coal , oil , or natural gas , to produce electricity . Fossil fuel power stations have machinery to convert

7744-455: Was found in the late 20th century or early 21st century, such as the US and UK. Sometimes coal-fired steam plants are refitted to use natural gas to reduce net carbon dioxide emissions. Oil-fuelled plants may be converted to natural gas to lower operating cost. Heavy fuel oil was once a significant source of energy for electric power generation. After oil price increases of the 1970s, oil was displaced by coal and later natural gas. Distillate oil

#60939