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Combined Cycles

Combined Cycles

Combined Cycle Performance

In today’s competitive generation market, being at the top of your combined cycle efficiency is crucial to make educated decisions. The combined cycle heat rate and combined cycle efficiency are among the parameters of major interests for power generators. However, from a total power plant performance analysis, TGPS also determine the individual equipment efficiency that impact your combined cycle heat rate and power output.

Combined Cycle Performance Test

TGPS evaluates the combined cycle performance of power plants around the world. TGPS’ performance engineers are ready to provide an un-biased combined cycle efficiency analysis anywhere in the world.

Either for conducting a contractual performance test or the diagnostic the combined cycle performance we comply with the international accepted protocols such as ASME PTC 46.

TGPS can help in conducting a combined cycle performance test for any of the following reasons:

  • Contractual Acceptance Performance Test to demonstrate the combined cycle performance guarantees.
  • Diagnostic Performance Test to identify the main areas of opportunity to increase your combined cycle efficiency and combined cycle power output.
  • Combined Cycle Performance Audit to determine the technical parameters required by the Grid Operators, Dispatch Center or Ministers of Energy in different countries. These technical parameters might include: Power Output, Heat Rate Vs Load, Minimum Load, Start-up and Shutdown costs, among others.

Combined Cycle Heat Rate

Probably the most important parameter in a combined cycle power plant is the combined cycle heat rate. The ratio of heat consumption Vs electricity production. In general terms, the plant heat rate is the inverse of the plant efficiency. The most efficient gas turbines at the moment are the H-technology. In a combined cycle application, the combined cycle efficiency can reach over 60% . Several factors can alter the combined cycle efficiency over time. Operational modes, equipment degradation, load cycling, etc.

TGPS helps you to identify the areas of opportunity to improve the combined cycle efficiency.


One of the most common internationally accepted performance testing protocols for combined cycle performance test is the ASME PTC 46. These protocols describes in detail the activities and preparations for a combined cycle performance test. Together with other testing protocols such as ASME PTC 22, ASME PTC 6, etc. they provide a guide to conduct an accurate and repeatable combined cycle performance test.


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Performance Test Procedure

These are some of the main points that a combined cycle performance test procedure should include.

  • Purpose of the Performance Test
  • Combined Cycle Isolation (thermal and electrical isolation)
  • Test Boundaries Definition
  • Combined Cycle Performance Guarantees
  • Testing Instrumentation
  • Calculation of final Combined Cycle Performance
  • Test Uncertainty

TGPS has a diverse range of experience, not only in the CC configuration, but also in complex evaluation of projects that occurs in a multi-stage testing program as defined in the ASME PTC 46.

Acceptance Test vs Diagnostic Test

Depending on the objective of testing certain parameters are more critical than others. Only an experience power plant performance engineer can guide the process through the most efficient path to achieve the specific objectives. For a contractual performance test topics such as test uncertainty, performance guarantees are more relevant. In a diagnostic test, not only these parameters are important, but also looking to historical trends, power plant upgrades, operation modes, load cycling, among others. Our team uses the latest tools to diagnostic the combined cycle performance in an accurate and practical way.

Overall Plant Assessment

In a combined cycle power plant, it is critical to look the overall plant performance and analyzing the individual equipment. For example, the combined cycle heat rate could be affected by some upgrade in the gas turbine efficiency. It is recommended that before making a decision on the upgrade of any major equipment at your plant; it is recommended to create  thermal performance mode to decide what would be the return on investment of the plant modification.

Why is Power Plant Efficiency Important?

Power Plant Efficiency is directly correlated to the business sustainability in terms of financial performance and long-term feasibility.

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