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The advent of climate change protocols and the Clean Air Act has put fossil fuels in the forefront of the political debate. Adhering to these standards while improving bottom-line performance has made heat rate a common term at all power plants.

Heat rate is a measurement used in the energy industry to calculate how efficiently a power plant uses heat energy and is expressed as the number of Btus of heat required to produce a kilowatt hour (kWh) of energy. There are several different calculations for heat rate. The following equations offer the basics of heat rate calculation; however, the most commonly used calculation is Net Unit Heat Rate.

Another variation on heat rate calculation is turbine cycle heat rate. Turbine cycle heat rate determines the combined performance of the turbine, condenser, feedwater heaters and feed pumps. Knowing the unit heat rate and the turbine cycle heat rate allows the plant to determine the boiler efficiency.

To run your plant at 100% efficiency, the heat rate would need to be 3,412 Btu/kWh. Although this target is not a practical expectation, it is important to note that any increase in heat rate will amplify the amount of fuel needed to generate a given number of kWh of energy.

Even a minor deviation from the target rate can cause a substantial change in the annual fuel cost for your plant. To illustrate this point, let’s calculate the increase in annual fuel cost for a plant with a target heat rate of 12,000 Btu/kWh and an actual heat rate of 12,011 Btu/kWh. We will use the following equation and assumptions to calculate the impact of a 1 Btu/kWh deviation.

Multiplying US$8,503.64 by any heat rate deviation will yield the annual cost or savings for the particular deviation. The increase in annual fuel cost in going from a heat rate of 12,000 Btu/kWh to 12,011 Btu/kWh results in a deviation of 11 (US$8,503.64 x 11) or a US$93,540.00/year increase in annual fuel cost.

This post is the first in our series on heat rate. In this series, you’ll learn about:

- The Impact of Feedwater Heater Operation on Fuel Costs
- Feedwater Heater Factors to Consider for Heat Rate Reduction
- How to Monitor Feedwater Heater Performance to Ensure Optimum Heat Rate
- The Impact of Instrument-Induced Errors on Heat Rate

To get the full series, watch for future posts here on our blog – or subscribe now to get the rest of the posts in this series delivered straight to your inbox.