Category Archives: Systems

In air conditioning for the LM6000

I decided to clean my office over the weekend, and came across the Power Magazine from June 2013. One of the feature articles is on the ARCTIC inlet conditioning system by Energy Concepts, Kiewit Power Engineers and Nooter/Erikson.

ARCTIC stands for Absorption Refrigeration Cycle Turbine Inlet Conditioning. And that’s precisely what it does.

Designed around the LM6000 (but also available for other engines), the ARCTIC uses heat from the gas turbine exhaust to power an absorption chiller which cools a heat transfer medium for use in the gas turbine inlet. The system can use existing inlet coils, and can also run in heating mode. This is of special interest to the aeroderivative engines, due to their multiple control limits, which cause them to have an optimum compressor inlet temperature (CIT) for best output performance.

The optimum CIT for the LM6000 is between 46F and 49F (and varies between individual units to a small extent). The ARCTIC system can be setup to control the CIT to that optimum temperature, no matter the outside ambients. According to the Power Magazine article, the system can also start and stop automatically with the gas turbine.

With a drop of only 120F in exhaust temperature (for the LM6000, this is from ~840F to ~720F), there is still energy available for other uses from the exhaust gases, including hot water exports or combined cycle operation (which is more likely on frame based units).

Overall, a very intriguing design concept, and if you’re in the market for a new or upgraded inlet chilling system for your gas turbine, definitely worth looking into.

To read more about ARCTIC, view the Power Mag article here: http://www.powermag.com/improving-warm-weather-performance-of-the-lm6000/

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Instrumentation Issues

Welcome back! It’s been a while since I’ve posted here. Been buried with client requests… there are worse problems to have, I suppose.

This summer’s focus is INSTRUMENTATION.

I’ll be digging into the instrumentation requirements for combined cycle facilities, looking at what instrumentation you’re likely to have on site, what accuracy and uncertainty you can expect for your key performance indicators (such as GT compressor efficiency, ST sectional efficiencies and overall plant net heat rate), and the cost to add instrumentation – especially those items you very likely don’t currently have (such as an accurate weather station or gas chromatograph).

So… please post any suggestions, comments or questions regarding instrumentation here on this blog entry, or jot me an email direct.

I’d love to hear from you about what your current issues are regarding instrumentation:
* How often do you calibrate devices not required by controls?
* What manual inputs do you make (or try to make) on a regular basis? (i.e. HHV)
* What roadblocks do you run into when trying to add instrumentation?

And check back here for updates. Hopefully more often than once a year!
I hope you all enjoy your summer.
-Tina

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SW Power Outage

I was surprised to hear of the large power outage across the Southwest last night.

Power was out from Yuma, AZ to San Diego, CA and into parts of Mexico. Approximately 5 million people were in a blackout – which started right around 4pm, in the heat of the afternoon and the start of rush-hour traffic.

According to the news reports and statements from APS, the outage was triggered by a worker who was removing some monitoring equipment at a sub-station in Yuma – the equipment had apparently not been working correctly. It must have been behaving very badly for the utility to send out a worker to remove it during the peak time of a hot summer day. The worst case scenario expected by APS was for a blackout in Yuma, AZ. That the outage spread to San Diego and Mexico was unexpected, and will be the focus of their outage investigation.

Back in 2009, there were talks about upgrading the US Transmission grid. An example of one plan is found at NPR.org. In the picture from NPR, if you click the Proposed Lines “off”, you can see that the San Diego area has only one medium sized transmission line feeding it – coming directly from Yuma, AZ.

Most of the power is back on this morning, and airports are beginning to recover from the disruption. But, maybe it’s time to revisit the idea of upgrading the US transmission grid?

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NFPA 56 Coming to a Site Near You

As reported by Combined Cycle Journal, presentations at this year’s spring CTOTF gathering included an outline of the new NFPA 56; regulations on safe handling of natural gas piping systems – including preparation for repairs, venting and purging.

From the article, regarding the new “Provisional Standard for the Commissioning and Maintenance of Fuel Gas Piping Systems”:

“NFPA 56 provides minimum safety requirements for the commissioning and maintenance of fuel gas piping—from the point of delivery to the equipment shutoff valve—found in power plants and industrial and commercial facilities. Activities impacted include the cleaning of new or repaired piping systems, placing piping systems into service, and removing piping from service. The term “system” applies to all system components—including valves, regulators, and other appurtenances—and any segment of the system that can be isolated from it.”

The standard, which is expected to be released later this year will require new operating procedures and inspections for most facilities.  To learn more about NFPA 56 from the CTOTF presentation, visit www.ctotf.org- there should be an item on the left-hand navigation bar for “NFPA 56″.  The link opens a PDF of the presentation made by John Puskar of CEC Combustion Services Group.  A full copy of the NFPA 56 draft is included at the end of the presentation for industry review (note, this is not the official release version – that is not expected to be available until later this year).

Natural gas is a powerful commodity.  Please be safe.

Thank you again to CCJ for another timely and important article.

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Improving GT Availability

This month’s Power Engineering magazine highlights one of the best papers of the 2010 Power Gen Conference.

See page 54 in Power Engineering, February 2011.

The whole paper can be found at PowerGenWorldwide in PDF form.

The paper gives details around MHI’s experience with increasing the availability of the M501F, but the information could be extrapolated to apply to all industrial gas turbines, and other equipment as well.

The highlights of the paper include planning for gas turbine performance from four difference angles of attack:

  1. Design
  2. Scheduled Maintenance
  3.  OEM Support
  4. Continuous Monitoring

Better designs, which include planning for maintenance, can lead to less downtime.  Especially when the designs lead to increased part longevity.  Time between repairs and/or replacements is on the rise as better coatings and materials are available.

Using experienced crews and well-tested procedures for your scheduled maintenance can lead to shorter outages overall, so your plant can get back on line – or at least available to be on line – faster.

OEM support, especially for newer designs, can improve troubleshooting efforts and may lead to upgrades in parts or services which further reduce down time in the future – especially if the upgrade means a part can operate longer between inspections.

Continuous monitoring – my personal favorite – can lead to finding problems when they’re small, and fixing small problems with a short outage – instead of waiting to find big problems later, requiring extensions on major outages if additional parts need to be ordered.

Monitoring technology is improving every year.  Neural net, or “smart” software can learn how a plant operates, then detect small abnormalities before alarm limits – or even warning limits – are reached.  Expertise is still needed to find the source of the abnormalities and solutions for getting back to ‘normal’ – but overall these new systems are effectively reducing downtime – leading to significant improvements in equipment availability.

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Heat Rate Improvement

Another good post on Heat Rate Improvement programs from EnergyPulse:

How to Build a Successful Heat Rate Improvement Program

Some of the comments after the article note that just watching heat rate is an ‘old paradigm’… but, sometimes the oldies are also goodies. In today’s world of automation, we are all susceptible to relying too much on technology and forgetting to think for ourselves.

In a world where many people will blindly follow whatever road their GPS takes them down, knowing how to read a map can still come in handy. Just recently, when asked to take us to the nearest Sonic Drive-in, our “Neverlost” system took us to the middle of an exclusive residential area where there were no restaurants for miles. We were lucky to get turned around and out of the neighborhood before the local sheriff showed up to escort us back to our hotel.

Had we known the general direction of the nearest strip mall, we might have questioned the GPS’s directions, and opted for the second Sonic on the list instead. But, we trusted the automation, and ended up on the wrong side of town. Luckily, not the wrong side of the tracks!

When controlling your equipment, knowledge of the process and expected trends in performance are essential to following the correct optimization recommendations. Automation and optimization systems for process control may work flawlessly 99% of the time, but that last 1%, when they take you in the opposite direction from intended they can potentially undo all the value of the other 99% – depending on the timing and source of the mis-calculation.

Automation systems are at the mercy of their incoming data. When a meter drifts or fails, the automation system may not recognize the error immediately. Recommendations for changes in control settings may go against the control room operator’s best judgment. If the operator blindly allows the plant to follow the automation signals, heat rate may be only one of the resulting casualties.

Continuous heat rate improvement programs need human involvement. This includes operators tracking real-time performance, maintenance and I&C personnel making sure data signals are accurate, and engineers supporting periodic detailed evaluations and capital improvement projects. Heat rate improvement is best accomplished as a team activity.

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Central performance monitoring makes the grade

I highly recommend reading this month’s Power Magazine – especially the article starting on page 66; Entergy’s ‘big catch”.  It’s a great example of how performance monitoring – with all the best tools and personnel – can make a huge impact on a plant’s performance and, more importantly for many, it’s reliability.

Most notably, the company in the article (Entergy) had setup a central performance monitoring and diagnostic center, where they had 24×7 support for equipment monitoring. The central staff was looking for performance losses, but also at reliability issues, such as increases in vibrations, temperatures, and other parameters which might indicate an imminent failure. The plant staff soon learned that this central group of professionals was there “not looking over their shoulder, but rater, watching their back.”

For a lot of plants, a central diagnostic center may be financially out of reach – although, when you consider the potential savings in forced outages and maintenance costs, it’s harder to make that argument. But, any additional observations you can make will support increased intelligence of plant operation which can lead to finding that abnormal condition before a catastrophic event occurs.

Just constantly trending your overall net heat rate in real time, where the control room operator can view it as time allows, will start the ball rolling. It’s not much – but it’s something. Small Steps. Kaizen. Once real time heat rate is being consistently monitored, you’ll start to see why a corrected heat rate can be helpful – changes in heat rate at full load become more apparent when corrected to a common baseline conditions.

Setting up a corrected heat rate trend does not need to be a large undertaking. Some information from the OEMs may be necessary, but again, taken in small steps, it can be fit into nearly any operating budget – and the time to payback is often very short. Errors in fuel metering are commonly found once heat rate is scrutinized relative to a set of reference conditions. Bad heat rate assumptions can lead to poor dispatch assumptions – which lead to operating in poor markets, or not operating in profitable ones.

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Reduce CO2 by Improving Performance

or… Improve Performance by Reducing CO2

As the framework for carbon cap-&-trade programs is developed, more people are starting to look for where we can reasonably hope to cut CO2 and other greenhouse gas (GHG) emissions – quickly.

The most obvious way to stop emitting GHG, is to stop burning carbon-based fuels, such as natural gas, coal and oil.   And, there are many, many demand-side conservation programs in place, which are making a significant impact on reducing the amount of energy required for many processes.  But, I think we could all agree, that very few of us, if any, are willing to turn off the lights completely to reduce GHG.  So, how else can we reduce fuel consumption? 

By reducing supply-side GHG generation.  Reduce the amount of fuel per kWh generated. 

Which is exactly what improving heat rate does for existing generation facilities.  It reduces the amount of fuel burned (and GHG produced) per kWh generated.  There is a wealth of CO2 reduction potential in our existing power generation assets in the US.

As Steve Stallard points out in his article at EnergyCentral, performance monitoring programs on one way to not only improve your plant economics – but also to reduce your CO2 emissions.

Performance monitoring programs can point out where you are losing efficiency in your power generation facility; how your operators can make small changes which improve efficiency; and what you can expect from capital improvements in terms of increased capacity, reduced heat rate and reduced GHG emissions.

Now, if we could only get the regulations adjusted, such that new capacity at existing facilities – at improved heat rates – are not “new sources”, just better sources. 

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Plant Dispatch

Is it really March already?

I must be having way to much fun, because time really seems to be flying these days.

One item which keeps coming up, is plant dispatch.  What is the best way to dispatch a plant?  I would vote for efficiency based dispatch, of course.  Which means you need to know what your current efficiency (heat rate) is, and how that will change when you go to a new load – or need to operate under different conditions.

To that end, I’m working with a number of clients on putting together dispatch tools – all spreadsheet based.  In some cases, these are day-ahead spreadsheets, where the user enters the weather forecast for tomorrow, and the spreadsheet will spit back the expected capacities and heat rates for various “units” of the plant (base load, steam augmentation, duct burners, chillers, etc.).  In other cases, the user provides a long-range forecast, with expectations for different months or seasons, to see how the plant will do over the next 1, 5, 10 or 20 years.  When you add in expected gas and electricity prices, a picture of the overall plant economics comes into play. 

While some might call these “just spreadsheets” (which is what they are), they also lean on the power of VBA (visual basic for applications, or macros).  By putting the expected plant performance curves into VBA functions, you gain a lot of flexibility in how you can use the information.  You can determine when the plant will beat the spark spread and be in the money – when you can expect to be dispatched – when the best time to plan a major outage would be (when you expect not to be dispatched) – the list could go on…

I mentioned using these spread-sheets for day-ahead expectations, but they can also be used for hour-ahead expectations, or even current hour expectations.  Where are you versus where you expected to be?  How much can you offer the dispatcher if they call on you to “max out” your available capacity? 

Maybe you know of another application for these spreadsheet models – is there anything you need that you haven’t been able to find out  there in industry?

Or, do you use something besides a spreadsheet tool for these kinds of questions?

I’d be interested to hear from you.  I’m always looking for a better, more efficient, way to do things!

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Plant Data Networks

I was reading through some past Power magazines over the weekend, and came across a couple that dealt with Plant Data Networks (PDN).

 

I’ve noticed how, over the years, the amount of data collected and archived at power plants, especially combined cycle plants, has grown significantly.  Ten years ago, a 1×1 combined cycle plant might have 800 points archived in their historian.  Today that number is easily doubled, and in some cases quintupled.  The ease of adding points to the historian, and the low cost of digital storage media have allowed plants to add just about every data point entering the control system to their archives.  And, for people like me who love data, this is a great thing!  But, not everyone has this luxury.

 

Historians can be expensive, from $50k for a base model, to millions for a fully configured system at a multiple train site.  These historians often offer all sorts of add-ons, too.  OSI-PI is famous for some of the wonderful modules that they have available, from the ProcessBook graphics display and trending package to the DataLink add-in for Excel. 

 

But, as I see it, this all has a single purpose:

 

    Get the right data to the right person at the right time.

 

OK, that sounds more like more than just one purpose.  And, its not such a simple thing to do, either. 

 

First, you have to know what you want the data to do (improve predictive maintenance, alert operators to hourly generation overruns, improve annual fuel burn forecasts, etc.), then which data is needed for that purpose, who needs to see it, and who needs to act on it – and then you need to configure the system to get that data to those people ON TIMEIf your plant data network is completely connected, things are a little easier.  Files, alerts and reports can all be placed in a central location.  Pop-ups can be sent electronically to stations when immediate action is needed, or information can be made available for month-end and year-end reporting on an as-needed basis. 

 

But, what about when you don’t have a connected network?  Can you still benefit from the data you do have?

Of Course!

 

The comment on my previous post points out that some facilities do not have historians, let alone complete data networks.  But even if you have limited digital access, you can still benefit from what you have available – it just might take more personnel time.  For peaking units with limited data connectivity, operators can maintain hourly data logs by manually noting the current load, pressures, temperatures, levels, valve positions, etc.  These logs can then be entered, manually, into digital form as a spreadsheet or database, where it would then be available for later use in trends, reports, and potentially, post-event root-cause analysis.  When operators find themselves too busy for manual log-taking, you might be able to setup printers to log certain events to hard copy; then, as time allows, the values can be typed into a data archive (spreadsheet or database).  Yes, it’s a lot more work than just pulling up a trend from the online historian, but for sites without that sophisticated option, it’s at least a start.  And, when that data is finally recognized as indispensible by the people who hold the purse strings, when they become addicted (like me) to more and more data… they just might be able to find a way to install a plant data network at sites where it was previously thought not to make ‘financial sense’.

 

If you have a site which is trying to justify a new historian, or other plant data network component, let me know (send an email, or post a comment here), and I’ll see if I can’t come up with some numbers to help you make that justification.  It doesn’t take much of an upset for heat rate and fuel costs to increase and easily surpass that $50k entry-level data archive value.

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