Non-linear least- squares is used to fit measured data to a mass and energy balance model of the power plant.  Data that is inconsistent with other measurements are identified and replacement values are supplied for the bad measurements.

Once the heat balance analysis data is available, the expected performance of plant equipment is predicted from new & clean models of the equipment. Detailed heat balance data (such as exhaust gas flow and composition) improves the accuracy of the expected performance prediction.


Dr. Rodney R. Gay


For combined-cycle power plants, MapEx has pre-configured heat balance analysis that is fast to set-up and easy to use. You can chose to use the MapEx heat balance analysis or link to GateCycle for the calculations. 

MapEx Combined-Cycle Heat Balance Analysis


Heat Balance

MapEx heat balance model of a combined-cycle power plant.

MapEx is a performance monitoring software system that performs first-principles-based thermodynamic analysis to derive thermal performance data from power plant measured data.

At the simplest level it is a virtual sensor that produces data and information that cannot be directly measured but can be derived from basic thermodynamic principles. This derived data becomes part of the plant historical database, which then can be used to improve and optimize plant operations. At a higher level, it is a tool that an engineer can use to implement sophisticated plant performance models and compare the model predictions to plant measured data.

MapEx retrieves measured data from a plant historical database, and then applies conservation of mass and energy (heat balance analysis), chemical balances, plus sensor validation to produce a set of derived data (thermal performance data) that contains more information and is more accurate than the raw measurements.

State-of-Art Thermal Performance


About Us

Data Validation


Figure shows compressor efficiency over a one year period, vertical lines indicate times of compressor washes.

MapEx Software:

Dr. Rodney R. Gay is president of MapEx Performance Monitoring.
Dr. Rodney Gay founded an engineering software company (Enter Software Inc.), built it to become the market leader in power plant design software, and then sold the company to General Electric.  The modeling methods developed by Dr. Gay (GateCycle, EfficiencyMap and Plant Payback) were adopted as GE core technology for power plant design, performance monitoring and economic optimization. GE installed EfficiencyMap throughout the GE fleet of gas turbines as part of General Electric’s “Smart Plant” program starting in 2002.
He has broad experience in many types of power generation including wind power, gas-fired combined cycles, coal-fired power plants, fluidized-bed combustion, compressed air energy storage, and nuclear power systems Dr. Gay has visited power plants and utility engineering offices worldwide, and worked directly with hundreds of plant managers and asset optimization engineers.

GateCycle Modeling 

GateCycle heat balance model of a combined-cycle power plant.

Reference book that gives the details of performance monitoring analysis for all types of thermal power plants (538 pages). Click on link above for more information.

The expected

equipment performance models are combined with mass and energy balances to predict the plant performance at user-input operating conditions.  

A model of the power plant is tuned to match selected  plant measured data. This model uses conservation of mass and energy to calculate values for all flow streams in the power pl;ant, including data that cannot be or is not measured.

Figure shows gas turbine measured (black), expected (blue) and corrected (red) power over a one-year period. Corrected power improves with each compressor wash and degrades between washes.

GateCycle heat balance model of a coal-fired power plant.

MapEx can optionally link to GateCycle models to perform any of the analysis tasks involved in plant performance monitoring and/or predictive analysis.