Talk:Combined cycle power plant

message: this page calls natural gas a relatively expensive fuel. I was under the impression that whilst true in the usa this is not true in europe where it is even sometimes used in thermal power plants when the price fluctuations make it attractive to do so. Plugwash 00:16, 15 September 2005 (UTC)
replies: text: Nat Gas is typically more expensive in Europe than it is in the United States for most European countries.  But it fluctuates quite a bit.  Typically, however, coal, nuke, and hydro power is cheaper to operate. --Ignignot 19:57, 23 February 2006 (UTC)
thread_title: US bias

message: Shouldn't this page be categorised? Maybe under thermodynamics and engineering? -- Pelle-Gnillot 04:08, 27 April 2007 (UTC)
thread_title: Categories?

message: Perhaps IGCC should have it's own article?  It is a major technology in its own right, and a IGCC plant is very different to a conventional combined cycle. -- PeterHewett 09:30, 9 July 2007 (UTC)
replies: text: Absolutely agree.  The average person looking up "combined cycle" isn't looking for detailed information on IGCC. KyuzoGator 20:24, 31 July 2007 (UTC)
thread_title: new page?

message: I don't think this article differentiates properly between CCPP and CCGT.  My understanding is that a CCGT is a single-shaft arrangement, with very high (hhp), high (hp) and low (lp) pressure steam turbines on the same shaft as the gas turbine.  The design diagram on this page shows a single GT and a single ST, the ST powered by heat recovery from the GT.  This isn't really a CCGT (although the term is often used), its a CCPP since the turbines are not on the one shaft.  In my experience there is usually more than one GT for each ST.shanvy 14:50, 24 August 2007 (UTC)
thread_title: Shafts

message: GE has developed H System with 60% efficiency, using 9H gas turbine. The first unit in commercial operation is at Baglan Bay in 2004. MHI (Mitsubisi Heavy Industry) has also finished verification of their H-series turbine in 2003, which also claimed 60% efficiency. These gas turbine manufacturers have been developing the new turbine series to achieve 60% efficiency under the Advance Turbine System (ATS) program, which was funded by US government.
--Nitchawan 17:38, 28 September 2007 (UTC)
thread_title:  CCGT Plant Efficiency 

message: I think the following sentence under Design principle should be changed to:
" In a combined cycle power plant, the heat of the gas turbine's exhaust is used to generate electricity by passing it through a heat recovery steam generator (HRSG)...."
from  " In a combined cycle power plant, the heat of the gas turbine's exhaust is used to generate steam by passing it through a heat recovery steam generator (HRSG)..."
Is this correct?  —Preceding unsigned comment added by 121.45.24.141 (talk) 14:52, 16 April 2008 (UTC)
thread_title:  Design principle 

message: The following statements have no citations and no clear explanation of why these statements are true/valid/complete
"High pressure steam requires strong, bulky components."
"For gas turbines the amount of metal that must withstand the high temperatures and pressures is small, and lower quantities of expensive materials can be used." Why is this? Is the power density of a gas turbine higher than a steam turbine?  —Preceding unsigned comment added by Metric america (talk • contribs) 04:29, 25 February 2010 (UTC)
replies: text: Steam cycles typically use pressures around 130 bar and above, while the highest pressures in gas turbine cycles is around 30 bar or so.  Greater wall thickness is required to provide the strength to contain the higher pressures used in the steam cycles. --Pakaraki (talk) 21:13, 11 March 2011 (UTC)
thread_title:  Clarification on why different materials are used in steam turbines vs gas turbines 

message: Article reads: "The primary disadvantage of multiple stage combined cycle power plant is that the number of steam turbines, condensers and condensate systems - and perhaps the cooling towers and circulating water systems - increases to match the number of gas turbines."
I think that instead of multiple shaft arrangement, this is the disadvantage of the single shaft design.
(Can't find the prior signature, so I may have stomped on it)
I agree, and had already changed the substantive page when I found this comment.
ArthurDent006.5 (talk) 07:05, 26 June 2013 (UTC)
thread_title:  Disadvantage of single shaft arrangement 

message: Any turbocharged engine is effecively a combined cycle with the turbo charger extracting extra energy from the exhaust gases, and which could be used to drive the wheels, however it is more convenient to use this extracted energy to force air into the engine which reduces the suction loss and thereby improves the efficiency overall.
It seems to me this is not correct at all. Turbocharged engine is not effectively a combined cycle. any engineers around to correct this? Kotika98 (talk) 16:01, 24 March 2011 (UTC)
thread_title:  Turbocharger 

message: I found this text in the article:
: However, global natural gas reserves are expected to be fully consumed by 2070.
...with a reference to a BP article. However, the BP article does not support the claim at all.
The BP article claims that the Reserves/Production ratio (R/P) is less than 60 years. However, this means almost nothing. The term reserves does not refer to the total amount of gas available in the ground to be extracted. Reserves means the proven amount we have already found which is economically recoverable using today's technology. However we discover new reserves every year; this is the norm. For example, reserves in the US have been increasing at more than 5%/year for more than a decade, and the rate of increase has also been increasing. Today, we have higher reserves than in 1971, despite considerable usage during that time. Thus, we cannot calculate the number of years remaining by looking at reserves, because it's not constant but is always growing.
What we need here is an estimate of the total recoverable resources (proved reserves plus probable future reserves) of natural gas. The term resources refers to the total amount of gas which is likely to be discovered altogether. Any figure for total resources is an estimate, of course, since nobody knows how much resource there is.
Estimates of resources are usually 5-6x higher than present reserves. This would provide enough gas for 300 years.
Of course, this does not take into account growth in consumption.
I don't think we should have any text in this article indicating how much gas is remaining. All we could say is: "depletion is not imminent." Other than that would require considerable explanations, alternative scenarios, multiple points of view and estimates, etc.
Twerges (talk) 22:03, 25 November 2011 (UTC)
thread_title:  Significant error 

message: The subject of whether or not turbocompound engines are a failure should be covered within the cited entry on turbocompounding.  The turbocompound DDC DD15 engine in the U.S. is one example of a recent, commercially successful turbocompound heavy-duty diesel engine.  — Preceding unsigned comment added by JoeM42 (talk • contribs) 20:34, 1 May 2013 (UTC)
thread_title:  Turbocompounding 

message: The fuel section contains discussions of peak gas, fracking, Brazilian economics and Chinese economics.  I think that each of these deserves a page in its own right, and some of them probably already have one.  There also seems to be a lack of citations.
ArthurDent006.5 (talk) 07:11, 26 June 2013 (UTC)
thread_title:  Fuel (but further to Significant Error above) 

message: In a couple of places the article suggests turbocharging (of automobile engines) and turbocompounding (of aero engines) are examples of combined cycle operation.  Strictly speaking I don't beleive this is true, since there is no transfer of heat energy between working fluids - the same hot gas is used in both the reciprocating and the turbine stage, which is analogous to a turbine with a high and low pressure section.
If turbocharging and turbocompounding are to be considered combined cycle I suggest they be in their own section, and the difference (i.e. the absense of heat transfer) be explained.  Otherwise reference to them should be removed (perhaps with a footnote explaining why they are not combined cycle).
Additionally, if turbocompounding is retained, mention should be made of modern hybrid systems where the turbine drives a generator to charge batteries which in turn power a motor to drive the wheels, as opposed to the turbine being mechanically connected to the drive train.  — Preceding unsigned comment added by 2601:3:4480:6E0:B944:24A5:AEDA:E200 (talk) 00:32, 16 February 2015 (UTC)
replies: text: I would tend to agree with you, I think of combined cycle as being two distinct heat engines, with the heat transferred in an exchanger between working fluids rather than simply piping the same fluid from one engine to the next. If we go down that road, where do we stop? Is a triple-expansion steam engine "combined cycle"? Wouldn't any turbine be combined cycle since each stage feeds the next? Although I could maybe see the argument for turbocompounding, since you have two types of heat engines, one recip and one turbine. Maybe. Kendall-K1 (talk) 00:53, 16 February 2015 (UTC)
thread_title:  Article needs clarity on turbochargers and turbocompounding 

message: In the sentence, "Many new gas power plants in North America and Europe are of this type", "this type" needs to be defined.  In the previous sentence the type just mentioned is a single-cycle steam generator.  Should this say they are of the Combined Cycle Gas Turbine type?Fconaway (talk) 19:24, 1 January 2016 (UTC)
thread_title: Clarification

message: This article is supposed to be information about Combined Cycle Systems, however it focuses almost exclusively on Gas Turbine units.  Many small modular systems distributed outside the USA/EU use Combined Cycle Combustion Engines CCCE usually with a large Diesel internal combustion engine as the primary cycle and a steam plant running off of the exhaust heat as the secondary cycle.  These systems are also very energy efficient rating just a few percentage points below CCGT (54%) with CCCE rating 51%.  CCCE have advantages and disadvantages compared to CCGT the primary advantage being they can run on a much broader spectrum of fuel inputs without excessive wear or higher maintenance cycle rates being required.
See http://www.wartsila.com/media/news/29-09-2006-wartsila-bio-engines-drive-italian-green-power for a biofuel modular plant in Italy.
See http://powerplants.man.eu/solutions/combined-cycle for MAN diesel combined cycle power plant examples in multiple countries.
See http://www.wartsila.com/energy/references/europe/aliaga-turkey For a Wartsila Diesel Combined Cycle power plant burning Natural Gas fuel.
Tanada (talk) 12:13, 8 May 2016 (UTC)
replies: text: It would be good to get some sources that are independent of the manufacturers. Kendall-K1 (talk) 12:23, 8 May 2016 (UTC)
thread_title:  Combined Cycle Combustion Engine 

message: Don't know enough about this to say if it is true, but Mitsubishi is claiming >63% LHV for the M501JAC certain others of their J-series turbines.. should this trigger an article update? 98.117.67.55 (talk) 04:32, 16 January 2017 (UTC)
replies: text: I stuck this in. We might want to remove some of the older efficiency claims, as this section is getting crowded. Kendall-K1 (talk) 05:11, 16 January 2017 (UTC)
thread_title:  Mitsubishi-Hitachi efficiency 

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thread_title:  External links modified (January 2018) 

message: The error is in the introduction that states as quoted below that the efficiency increases fifty percent. The actual increase, again as quoted, is 100% (meaning doubled). A fifty percent increase from 34% would be 34+17=51%. Either the fifty should become 100 or the 62.22 should be reduced. 
Secondly, the precision "62.22%" seems quite overly detailed and mathematically in error, and should be reduced to only sixty-two percent. 
By combining these multiple streams of work upon a single mechanical shaft turning an electric generator, the overall net efficiency of the system may be increased by 50–60%. That is, from an overall efficiency of say 34% (in a single cycle) to possibly an overall efficiency of 62.22% (in a mechanical combination of two cycles) in net Carnot thermodynamic efficiency.  — Preceding unsigned comment added by 23.249.100.250 (talk) 19:21, 21 September 2018 (UTC)
replies: text: That sentence in the article needs to be rewritten. I don't know anything about the subject so I can't really help. It now says "[...] to possibly an overall efficiency of 62% (combined cycle), 84% Theoretical efficiency (Carnot cycle)" and ends like that. I'm not even sure what it's supposed to mean. Aeluwas (talk) 15:33, 15 June 2019 (UTC)
thread_title:  math error 

message: The article includes a comparison to the Carnot cycle efficiency: 
"This is more than 84% of the theoretical efficiency of a Carnot cycle."
This statement requires context of the hot/cold reservoir temperature that is assumed to calculate the Carnot cycle efficiency otherwise it is meaningless. Ideally whichever specific power plant achieves this efficiency should be linked. 212.114.178.106 (talk) 15:50, 29 December 2023 (UTC)
thread_title:  Comparison to Carnot efficiency 

message: Ref 3 is not working for me but as far as I can tell it is not worth a separate article  Chidgk1 (talk) 17:37, 27 February 2024 (UTC)
replies: text: @Jusdafax@Clayoquot Thanks for commenting on another hydrogen merger proposal - if you have an opinion on this one please comment  Chidgk1 (talk) 07:26, 25 March 2024 (UTC)
thread_title:  Merge [[Combined cycle hydrogen power plant]] to here