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In today’s climate of advanced environmental regulations and greater public awareness (or sometimes fear) of energy issues, the evaluation, planning, and permitting of new power plants are critical issues.

For a developer today to be successful, they must select the best technology and site, receive the required permits and construct the plant in a timely and cost-effective manner.

This article examines the most important issues of this process, with a particular focus on the most popular installations in the U.S., combined-cycle power generation plants. However, many of the topics apply to other methods of power generation including coal, stand-alone combustion turbines, biomass plants and others.

Steps 1 and 2

– Site and Technology Selection

Many variables must be clarified/determined during this phase of project development. These items include:

• Targets for plant performance
• Fuel source and availability
• Fuel constituents and chemistry
• Technology assessment
• Project schedule
• Geotechnical conditions
• Makeup water source, chemistry, and treatment selection
• Exhaust steam cooling – Cooling tower – Air-cooled condenser
• Wastewater treatment selection
• Interconnection logistics
• Noise constraints

Some of these variables are easier to identify than others, but all need to be addressed very early in the project development cycle. The lack of timely decisions can significantly impact the overall project schedule. Owners today are being challenged with permitting and interconnection agreements that may take in excess of 12 months to complete. Lead times for major equipment acquisition are another schedule driver and will become a greater challenge as the global market for these products continues to grow. To help minimize the impact of equipment acquisition, a limited engineering release is necessary to begin procurement and preliminary design. Developers need a thorough understanding of the selected site prior to acquiring bids from engineering and construction firms, as this will greatly influence the final cost of the project. While much data exists in the public domain regarding subsurface conditions for many states and counties across the country, the data is often not specific enough to finalize costs and schedules. Often, a site investigation with only a handful of borings can give much insight, but a detailed study should be completed before design commencement or site activities.

With regard to equipment selection, a number of reputable and experienced vendors are available both nationally and globally to supply the major equipment plus the auxiliaries. Of course, the key selections include the combustion turbines, HRSGs, and steam turbine. However, auxiliary systems should not be overlooked by excessive focus on the major equipment. Important auxiliaries include transformers, makeup and cooling water equipment, auxiliary boilers, and instrumentation and control systems, to name several.

As the decision is made regarding the primary technology, thereupon comes development of heat and water balances. Modern programs incorporate specific data from the equipment chosen and will produce accurate calculations for many parameters including combustion turbine output, heat rate, steam production in the HRSGs, cooling tower performance and circulating water flow rate, among others. This data in turn allows refined calculations of water balances. Precision is paramount, as the water balance determines the required capacity of makeup water, and at times cooling water, treatment equipment. Undersizing of such equipment can lead to severe operating problems at and after startup, while oversizing adds significant cost to the system and may also result in poor performance. Another factor of importance is that a poor water balance can lead to installation of piping that is either too small or large for the application. Excel or a similar spreadsheet program is an excellent tool for preparing water balances, as water flow rates and usage can easily be calculated for any variety of conditions.

Once equipment selection has been finalized, the focus shifts to equipment layout. Some sites offer plenty of space for combustion turbine and auxiliary systems placement, but others may be very tightly constrained. One of the most significant factors for overall plant cost is quantities of commodities. Regardless of the space available, proper effort is needed to optimize the plant layout and in turn accurately calculate quantities and simplify construction. Factors that impact quantities include: piping and wiring locations and run lengths, steam turbine location, switchyard location, water treatment building placement, cooling tower location and many others.

It is important as a developer or utility to write the RFP in a manner that gives the EPC contractor flexibility regarding the plant layout. This is possible while still maintaining pre-established emission points included in air permit applications. As the equipment is being laid out two-dimensionally, designers also construct the model in 3D, which allows a much better analysis of pipe rack, cable tray and other overhead equipment locations. Development of the equipment arrangement expediently and with precision is also important for planning of of underground piping and electrical supplies. These need to be installed accurately upon the first attempt, as otherwise considerable time and effort may be expended in rerouting piping and cables after the fact.

All of these decisions factor into final technology selection. Besides power requirements, important aspects of combustion turbine selection include:

• Fast start requirements
• Planned startup/shutdown frequency
• Emissions control

  – SCR system

  – CO catalyst

• Possible water requirements

  – Compressor intercoolers

  – Water injection for NOx control

  These factors drive the choice of combustion turbine(s), including aeroderivative or frame units. The former offer very fast startups, but the heat rate is not as good as for frame units.

  Of course, for a combined-cycle plant the complexity increases. Additional equipment selection issues include:

  • HRSG details

    – Quantity

    – Width (2 bay vs. 3 bay)

    – Single- or multi-pressure

    • Steam turbine manufacturer
    • Makeup water treatment
    • Steam condensation technology

      – Cooling tower

      – Air-cooled condenser

      – Wet-surface air coolers

    • Wastewater discharge control

    The bulleted items above include reference to a critical aspect of power plant design, water/wastewater equipment selection and treatment. Author Buecker has covered many of these issues in recent issues of Power Engineering, but additional commentary regarding impending wastewater issues is provided in the section below.

     

    Step 3

    – Permitting

    As even many homeowners know, construction of simple buildings often requires one or more permits. The issue is vastly more complicated for power plant construction. Critical to the start of any project are air and water discharge permits, for if these are not requested early and contain very accurate information, the project will inevitably be delayed. As time passes, air permits continue to become more and more complex. In the past, permits were consistent regarding the pollutants to be regulated, and they were relatively specific and straightforward on reporting requirements. Permits today include strict limitations on startup and shutdown activities and may now include limitations on CO2 emissions. If permitting requirements are not clearly defined and matched to plant design, the owner could face operating limitations that significantly impact the profitability of the plant.

     

    Regarding water discharge, the guidelines are also becoming more complex. The EPA is preparing new National Pollutant Discharge Elimination System (NPDES) regulations. For many years, the primary impurities regulated by NPDES guidelines were pH, total suspended solids (TSS), oil & grease (O&G) and residual halogen (most typically chlorine or bromine). But now other items are appearing on the list, and not only from the USEPA but often from local or regional regulators. We are seeing limits for copper, zinc, ammonia, phosphate, sulfate and total dissolved solids (TDS). Undoubtedly, others will appear. This requires careful thought when it comes to deciding on selection of makeup and cooling water treatment, well ahead of equipment selection. Some experts now recommend zero liquid discharge installation for nearly every new project to avoid difficulties with additional regulations that most likely will occur in the future. But, ZLD is easier said than done. A final stream always remains from the primary process, and careful analysis, including additional permitting, is needed to determine whether the final product can be disposed in evaporation ponds, deep well injection, by off-site means, or by thermal evaporation. The upshot is that it is important to begin the permitting process very early on in a project, for final approval may take well over a year.

     

    Step 4

    – Construction

    Many projects we perform are of the engineer-procure-construct (EPC) type. Two critical items are important for starting a project correctly and taking it to a successful conclusion. These are:

    • Safety
    • Close contact with the owner throughout the project

    Bringing in the EPC contractor early in the development process helps with planning and constructability of the project. The engineering and construction team can identify potential safety risks related to construction or operations/maintainability of the plant.

     

    Step 5

    – Startup and Performance Testing

    As construction reaches completion, the startup and performance testing activities commence. These activities can be performed by the owner, the EPC contractor or a third party. In any event, it is critical to involve the startup and testing teams early such that coordination of the tests and testing equipment may be incorporated in the design and construction.

    Kiewit Power Engineers has been involved with countless project development and EPC projects. The time and effort owners put into making a project “shovel ready” is quite significant. By getting a jump on permitting and involving an EPC Contractor early, owners have a better chance of seeing the project up and running in the most expeditious amount of time.