Combined Cycles: From Conception to Operation

Issue 7 and Volume 106.

By: Douglas J. Smith IEng, Senior Editor

Developing a power project from initial feasibility studies to construction and commercial operation can take many years and millions of dollars. A major challenge facing today’s generating companies is to find ways to reduce the time for the construction and commissioning of plants. In general there are four phases in developing a power generation project:

•Feasibility studies.
•Project development, permitting and design.
•Procurement and construction.
•Start-up and commissioning.

Utilizing advanced technologies, the time required to manufacture equipment, design the plant, and construct and commission a power plant can be substantially reduced. Although not directly related, the training of plant personnel to take over the operation and maintenance of the plant once the plant starts commercial operation is also very important. It is imperative that training is carried out in parallel with the construction and startup activities. Well-trained operators can save thousands of dollars during the lifetime of the plant.

Preparing gas turbine for installation. Photo courtesy of Bechtel.
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Prior to deregulation of the electric power industry, utility companies owned and operated the power plants and earned a fixed rate of return. At the same time the engineering, procurement and engineering companies designed and constructed the plants according to utility detailed specifications. Similarly, original equipment manufacturers generally furnished the equipment.

According to Ram Narula, principal vice president, Bechtel Power Corporation, the traditional roles of the utility, designer, construction and equipment supplier are not so well defined today. With deregulation, electric generating companies need the option of picking and choosing from a menu of plants that use different technologies and fuels, says Narula. They also are requesting features that meet site and permit requirements such as dry-cooling, selective catalytic reduction (SCR) or various switchyard configurations. Today, the goal is to limit customization to just satisfy the specific needs of the project.

Developers: What are They Doing?

With a need to be competitive, electric generating companies are all looking at ways to reduce costs and speed up the time from design through commercial operation of their new combined-cycle plants. Entergy, Duke Energy North America and Calpine all say that they are using standard designs and reference plants to reduce costs and the time to get plants into commercial operation.

Construction of HRSGs at Harrison County Power Project, Texas. Photo courtesy of Entergy.
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The goal is to be able to replicate the same plant design over and over where possible. Another power plant developer, Mirant, is reducing the time for developing a plant and putting it into commercial operation by coordinating the permitting and construction processes.

In developing a merchant power project Duke Energy North America chooses multiple sites for preliminary engineering, analysis and permitting. However, only one site may eventually be chosen.

According to Ron Barnes, senior vice president operations, Duke/Fluor Daniel, although preliminary engineering of multiple sites is expensive, in the end it pays dividends. Working together, Duke Energy North America and Duke/Fluor Daniel have reduced the time to develop, construct and put a plant into operation by at least 12 months.

According to Doug Kieta, senior vice president construction management, Calpine, the use of standard designs eliminates contractor contingencies and improves overall planning and scheduling. Using this approach Calpine is significantly speeding up the development and commercialization of new plants.

425 MW combine-cycle power plant nearing completion in Lake Charles, Louisiana. Photo courtesy of Entergy.
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Scheduling is a major issue for all power plant developers. Because of problems with the quality of scheduling done by sub-contractors, Calpine has taken over the scheduling task themselves. In Kieta’s opinion, time spent upfront in developing an integrated schedule is very important.

Unlike some developers Calpine hires the engineers and buys most of the equipment themselves. Although Calpine does use general contractors for some projects, in general this work is now performed in house.

Every month Calpine management receives an update from the project team and subcontractors on the status of all of the plants under construction. If there is a problem with the project falling behind schedule, management sits down with the project team and subcontractors. From this meeting they come up with a plan to return the project to schedule. The contractor is no longer responsible for determining if a project is on schedule. Today, this is the responsibility of Calpine’s management, says Kieta.

In recent years Entergy has optimized project management by instituting what they call “cold eyes reviews.” All power plant construction projects have regular cold eyes reviews, says Bob Malone, vice president engineering and construction. Under this program, at various stages of the project, Entergy brings in people from other parts of the company who are not involved with the project to review the project’s status. These teams conduct a review of the project and report back to management if the project is on schedule or not. Should the project be falling behind schedule they suggest ways to rectify the problem such as getting more manpower on-site or expediting of equipment delivery.

According to Malone the use of people not involved with the project allows them to complement the on-site project management team. These review teams focus on problem areas that the on-site project team might not have the time for or which they might miss. Malone says that over the years Entergy has improved project management and three recent combine-cycle power plants were completed on budget and on time.

Commissioning and Startup

A key issue for Calpine to reducing commissioning time is to make sure piping and equipment delivered to the site is kept clean before and after installation. For all projects Calpine has very disciplined quality assurance (QA) and quality control (QC) programs, says Kieta. Each month QA and QC audit teams visit all of the projects under construction.

The teams audit the projects to determine how materials are being stored and maintained prior to and after installation. The aim is to make sure that pipes are capped, and if required, that heaters and nitrogen blankets are being used. Kieta says these audits have paid dividends. When the startup times of their plants are compared to average industrial benchmark data, Calpine’s startup times are quicker.

Flushing and steam blowing of power plant equipment is time consuming and can increase the length of startups. According to Calpine, keeping piping and equipment clean and protected dramatically reduces the time taken for steam blowing and flushing.

Duke/Fluor Daniel is reducing the time for steam blowing by hydro lancing, a process where very high-pressure water is used to clean steam and feedwater piping prior to steam blowing. Not only has this saved money, it has also allowed the company to reduce startup times for major equipment by two to three weeks, says Barnes.

With improved scheduling, and the implementation of their “cold eyes revue” process, Entergy has reduced the time for start-up and commissioning of new plants. It now takes Entergy 90 days, from mechanical completion to commercial operation, to start-up a combined-cycle plant, says Malone. The startup of a coal-fired power plant, on the other hand, can take up to eight months.

Training Staff

Training of personnel to take over the operations and maintenance of a completed combined-cycle power plant is very important. Well-trained operators are essential for optimizing power plant operations. Invariably power plant developers use a combination of classroom and hands-on training. At Calpine all of their operators are trained on simulators at the Calpine University. Vendor engineers are also used if there is a need for specialized training.

Entergy involves the operation and maintenance staff that will eventually staff the plant at the design stage of the project. This allows the design engineers to get input on the operability and maintainability of the finished plant. The operating and maintenance staff is also used to work on punch lists and for operating equipment during construction and commissioning of the plant. However, the operators still receive classroom instruction in addition to getting hands-on experience.

Duke Energy North America’s senior vice president for asset management, Steve Gilliland, states that their policy is to hire the plant manger at least one year before commercial operation. The other plant staff is hired four to six months after hiring the manager.

Joint Ventures

Some power plant developers are now forming partnerships with engineering and construction companies to jointly develop new plants. Two of these partnerships are: Duke/Fluor Daniel, a partnership of Duke Energy and Fluor Corporation, and EntergyShaw LLC, a partnership of Entergy Corporation and the Shaw Group.

A big advantage of forming joint venture partnerships, says Gilliland, is it prevents litigation. Should a problem occur at a plant under construction either partner just picks up the telephone and the problem is resolved, Gilliland says. The telephone call is generally followed up with a contractual agreement that spells out what work was agreed to and who pays.

Since January 2000 the Duke/Fluor Daniel partnership has been responsible for bringing 27 greenfield merchant generation projects into commercial operation an average of 44 days early. The EntergyShaw partnership, a 50/50 joint venture, was formed in September 2000. All new power generating project are now developed and constructed by the partnership.

Looking Ahead

Although power plant developers are designing and constructing plants more efficiently than in the past there are still some concerns that need to be resolved. A big issue for Entergy on any new project is that the engineering and procurement be completed in time to order equipment to meet the construction and startup schedules. Until about one year ago a major concern of Duke Energy was the availability and cost of qualified craft labor. However, with the economy slowing down this is no longer an issue, says Gilliland.

According to Kieta, an on-going issue for Calpine is the concern about the ability of contractors to manage the on-site labor force. Calpine believes that when a contractor reaches a certain level of manpower they lose the ability to control them. Quality of workmanship is another worry. As with other plant developers Calpine is always worried that the contractor will not meet schedule.

According to David Payne, a spokesman for Mirant, his company is always concerned that the plant is designed to minimize operation and maintenance costs over the life of the plant. In addition, Mirant always worries if the design and permitting requirements will allow the plant meet the market requirements.

Reducing design time and costs

In the late 1990s Bechtel’s senior management challenged the company’s strategic product development group to develop and implement a program that would cut power generation costs by 30 percent and shorten construction schedules by 25 percent. In reviewing the options the group realized that the traditional approach of one-of-a-kind power plant design was not the answer.

Modeling combine-cycle power plants. Source: Bechtel.
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What was needed in their opinion was a plant that would be mostly pre-designed but would have the capability of customizing individual plant systems if the customer so desired. Under this scenario most of the design work would be completed before a particular application was identified. Using these pre-designed plants would also allow Bechtel to reduce the time and costs of responding to customer requests for proposals.

According to Ram Narula, principal vice president, the pre-designed approach achieves the economies of mass production while allowing enough flexibility to meet the special requirements of individual projects and customers. Using this system, which is called “mass customization,” 80 percent of the scope requirements of a new power plant can be met by selecting one of the pre-designed models, says Narula.

To meet the challenge Bechtel developed “PowerLine,” which is used to develop low cost standard power plant designs. Standard designed combined-cycle plants, from 260 MW to 770 MW, include a list of major equipment, predicted performance, site layout, general arrangement drawings, 3D models of critical components, intelligent piping and instrument diagrams, heat and water balances and single-line diagrams. They also include a capital cost model and a construction schedule.

A list of model-specific standard options is also available to allow for customization of the plant to meet specific site and operational needs. Some standard options available for combined-cycle plants include:

  • Alternate gas turbines
  • Water treatment systems
  • Switchyards
  • Selective catalytic reduction
  • Dual fuel capability
  • Wet cooling towers
  • Air-cooled condensers
  • Bypass stack and dampers
To achieve optimum overall design of the various PowerLine models, Bechtel formed cross-functional design teams, made up of people from engineering, construction, procurement, startup and estimating. For each model the design team selected a set of design criteria based on the foreseen market for that particular model. Once the design criteria were established the plant’s power cycle was optimized.

One of the combined-cycle power plants that Bechtel has developed using the PowerLine model is the Redbud Energy Project near Luther, Oklahoma. The plant, currently under construction, has four 300 MW power islands each comprising a single gas turbine generator, a heat recovery steam generator (HRSG) and a steam turbine generator.