Talk:Combined cycle power plant/Archive 1

Archive 1

US bias

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)

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)

Categories?

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

Shafts

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)

CCGT Plant Efficiency

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)

new page?

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)

Absolutely agree. The average person looking up "combined cycle" isn't looking for detailed information on IGCC. KyuzoGator 20:24, 31 July 2007 (UTC)

Exactly. Combined (or binary) power production cycles are generally a gas turbine passing its waste heat into a steam turbine system. The other is an INTEGRATED cycle. Donebythesecondlaw (talk) 16:37, 7 December 2007 (UTC)

I have done this. The IGCC now has its own page. I just cut and pasted. I also moved the link from syngas and linked back to here. Hope this is OK Donebythesecondlaw (talk) 14:48, 4 January 2008 (UTC)

Design principle

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)

Clarification on why different materials are used in steam turbines vs gas turbines

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)

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)

Significant error

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)

Turbocompounding

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)

Disadvantage of single shaft arrangement

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)

Fuel (but further to Significant Error above)

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)

Integrated solar combined cycle (ISCC)

Ok, let us try to resolve the misunderstandings. September 22 I find a description of what is an ISCC that is partially wrong and anyway unclear. This is what I found:

"An integrated solar combined cycle, or ISCC, is a power plant using solar thermal collectors. This is typically in the form of tower-mounted solar receivers surrounded by a mirror field or parabolic troughs."

First the existent most ISCC's use solar troughs, no towers, and anyway I don't understand what are "tower-mounted" solar receivers. And "a power plant using solar thermal collectors" is not a very helpfull description. I roll up my sleeves and write:

"An Integrated Solar Combined Cycle is a hybrid technology in which a solar field is integrated with a combined cycle plant (CCS). In ISCC plant, solar energy is used as an auxiliary energy supply, increasing the cycle efficiency and reducing associated CO2 emissions. The operation of a ISCC hybrid plant is similar to a conventional CCS plant. The auxiliary energy supply from the solar field supports the steam cycle, which results in increased generation capacity of the cycle. The solar resource partially replaces fossil fuel use. Thermodynamic benefits are that daily steam turbine startup losses are eliminated and efficiencies are higher than those of a SEGS plant." Up to this point, the text requires only a few tweaks. Follows: "Solar conversion efficiencies are higher than SEGS plant, but Brayton and Rankine cycle efficiencies remain the same. But annual solar contributions are limited to less than 7%."

and I admit that is incomplete/unclear (to have higher solar conversion efficiencies, the solar contributions *should* be limited to less than 7%). Follows: "Economic benefits are that power plant costs are 25% to 75% those of a SEGS plant." where I horrendously mis-quote the reference, as said by User talk:Ariadacapo which corrects my error. But also inserts some inaccuracies (I guess he did not read carefully the source I had given). He also asks for a citation. Ok. I correct the inaccuracies, expand about the startup losses and give a citation from Siemens. And change my edit about the solar costs. Here is the result:

"An Integrated Solar Combined Cycle is a hybrid technology in which a solar field is integrated within a combined cycle plant. In ISCC plants, solar energy is used as an auxiliary heat supply, supporting the steam cycle, which results in increased generation capacity or a reduction of fossil fuel use. Thermodynamic benefits are that daily steam turbine startup losses are eliminated. Major factors limiting the load output of a combined cycle power plant are the allowed pressure and temperature transients of the steam turbine and the heat recovery steam generator waiting times to establish required steam chemistry conditions and warm-up times for the balance of plant and the main piping system. Those limitations also influence the fast start-up capability of the gas turbine by requiring waiting times. And waiting gas turbines consume gas. The solar component, if the plant is started after sunshine, or before, if we have heat storage, allows us to preheat the steam to the required conditions. That is, the plant is started faster and we consume less gas before achieving operating conditions. Economic benefits are that the solar components costs are 25% to 75% those of a Solar Energy Generating Systems plant of the same collector surface."

But User talk:Ariadacapo is not satisfied and instead to open a talk page (as asked), asks again a citation about the startup losses, and reverts the part about solar costs, stating, this time, erroneously, that I have again horrendously mis-quoted the referenced source. About the citation, I guess he has not read che Siemens source. About the mis-quotation, the source exact wording is: "Incremental Rankine cycle power plant costs are 25 to 75 percent those of a SEGS plant." I find that such a wording is not suitable for Wikipedia, which has a general public. My paraphrase is: "the solar components costs are 25% to 75% those of a Solar Energy Generating Systems plant of the same collector surface." which is how I think would help to understand the solar field (the solar component present in a ISCC plant) cost relationship compared to a complete solar installation. But User talk:Ariadacapo does not agree without explaining why. So, now I will revert and wait. --Robertiki (talk) 22:29, 25 September 2013 (UTC)

Hi Robertiki, I am not so much concerned about the accuracy/correctness of the description (I am not an expert in CCPPs) as about reflecting what the quotes actually say (see WP:NOTTRUTH).

• When you write that "Startup losses are eliminated" you do not provide a source. In the Siemens document which you quote I read that these losses can be minimized, but I found no mention about bringing them to zero, which is not the same thing. Please do not remove the {citation needed} tag next to a bold statement without actually providing a source. If the statement can be found in the Siemens document please add another ref tag pointing out where exactly.
• The word incremental is crucial in the last quote and omitting it from the text is indeed horrendous. In essence what the source says is that costs of pouring solar (heat?) energy into a steam plant to make electricity are 25-75% those of making electricity with photovoltaics if you already have a steam plant at hand. If you remove the word "incremental" you completely change the meaning of the sentence.
• The NREL source that you provide is interesting but it is a series of bullet points used a support for an oral presentation. As such it is very stern, sometimes imprecise (incremental costs per electrical Watt? per electric Joule? under what startup/load profiles?) or almost deliberately vague ("25 to 75%" sounds much like "in my experience roughly half" to me). It’s a good introduction but it does not provide very strong references for bold statements.

So, please provide a reference for challenged statements instead of reverting addition of {citation needed} tags. Ariadacapo (talk) 11:35, 26 September 2013 (UTC)

That "Startup losses are eliminated" is stated in page 3 of [1]. You asked, and I have added the Siemens document which explains what happens in a CCS plant without solar integration: at start up the two gas turbines have to wait, idling, while che recovery boilers capture the gas turbine waste heat to heat the steam for the steam turbine (operation of standard CC). In the Siemens document they talk of minimizing, because the have no auxiliary heat source, and have to use a trick. But if you have a solar field, which also heats the steam boilers, you could heat the steam to operating temperature, with the gas turbines still shut. Once the steam has reached operating temperature, you can start rotating the steam turbine (idle, and you still don't have gas consumption) and only after, start the two gas turbines, full power, followed full power with the steam turbine. You ave so fully eliminated the idling losses. It could help to read [2] and [3], page 2, middle-section, where you have a schematic of a ISCC plant.

You have confirmed my fears :-) The source is cryptic. What the source says is that the "increment" of the "plant cost" (please note: "Rankine cycle power" is only a description of the *type* of plant) is 25% to 75% those of a full Solar THERMAL electricity generating system (SEGS ha nothing to do with photovoltaics !!!) and what is implied is: with the same solar capture capacity (i.e. same collector surface). It is easy to understand why: what are the savings if you get a SEGS and strip of: steam turbine, generator, power transformer, condenser cooler, facilities, buildings, etc. keeping only che solar trough field anche the heat exchanger ? Guess it: 25% to 75% of the costs (the solar field without storage is about 25% of a SEGS total cost, if there is storage, we have a larger field and the cost goes up to 50% of a SEGS total cost and giving a margin of at most 25% for the CCS modifications, we coome up with 25% to 75% where 25% is with a new CCS plant, no modification costs).

Another problem of solar fields is that they dramatically lose efficiency at begin and at end of day (insufficient water temperature). But when integrated with a thermal plant, the last joule of energy captured from the sun enters the steam turbine at optimal temperature, because the necessary missing energy is provided from the standard gas cycle.

To help understanding: in a ISCC the solar field adds NO POWER (a lot of descriptions are really wrong when they try to split the total power given beetwen solar and fuel!)! The steam turbine is only one, the same before and after solar field integration. The ISCC plant is in principle a Thermal Plant with a solar HEAT integration (no phovoltaics, non electricity in play, no solar-electricity conversion in the field, but only after the thermal plant powerful steam turbine plus "big" generator. Got it ? ;-)

After reading the sources given above of a real ISCC plant, I would suggest you to propose here how to modify the article and together edit with a better result.--Robertiki (talk) 02:48, 27 September 2013 (UTC)

References

Turbocharger

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)

A turbocharged engine is not an example of a combined cycle as it is using the same working fluid, and would be better considered as slightly modified version of the diesel or otto cycle. Furthermore, the gain in efficiency in turbocharging is from an increase in the cylinder mean effective pressure, not from some kind of "suction loss", whatever that is. — Preceding unsigned comment added by 79.136.117.226 (talk) 06:56, 2 May 2014 (UTC)

Article needs clarity on turbochargers and turbocompounding

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)

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)

Clarification

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)