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May 2013 · Energy-Tech Magazine
May 2011 Go to Page 1 2 3 4
Hot windbox and combined cycle repowering to improve heat rate
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Figure 1. Current configuration
Figure 1. Current configuration


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Indirect costs

  • Sales tax: A sales tax of 5 percent was included on the costs of the equipment and construction materials.
  • Engineering costs: A lump sum allowance for detail engineering was included. This allowance was derived from experience in similar projects and based on expected total man hours to complete the project.
  • Construction management costs: A lump sum allowance for construction management was included. This allowance included salaries and expenses for one site manager and discipline leads. The Construction Manager will be responsible for developing bid packages and managing the field effort through construction completion.
  • Spare parts: An allowance of 4 percent of the equipment cost was included for capital spare parts. This allowance includes cost of vendor recommended spare parts (on major equipment), as well as cost of other undefined spare parts.
  • Owner’s cost: An allowance of 3 percent was included to cover Owner’s costs for the project. This includes items such as training, job site costs, startup, etc.


Other costs:

  • Contingency: An allowance of 10 percent was added to the total direct and indirect costs for contingency.
  • Escalation: An escalation rate of 6 percent of total direct costs (to end of 2010) was assumed for this study.


Items not included in the estimate:
The following items were not included in this capital cost estimate:

  • Financing costs or capitalized interest costs
  • Land purchase, if required
  • SCR or SNCR if required
  • Results and discussions

To view a detailed table of this cost estimate summary, see Table 5.

Retrofitting existing power generation plants by repowering is becoming an attractive option to improve plant performance with less cost. “Hot Windbox Repowering” involves utilizing the hot exhaust gas from a combustion gas turbine and using it as combustion air for an existing fossil-fuel boiler. “Combined Cycle Repowering” or “Full Repowering” involves completely replacing the existing boiler with a combined cycle consisting of a gas turbine(s) and a heat recovery steam generator (HRSG). The existing steam turbine will be used in both repowering scenarios.


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