In my experience, there is more to benchmarking than meets the eye. "Benchmarking" is a phrase used by the industry for many years and it can mean many different things to different people. Some people benchmark units based on similar unit designs for making comparisons, while others benchmark units to see if they're spending resources wisely. This paper focuses on tips to help you wisely select similar units for comparison.
Tip No. 1 - Talk the same language
Making sure everyone is talking the same language is one of the most fundamental issues when discussing benchmarking. I've learned we may not always be talking about exactly the same thing. For example, take the phrase "base-load units." What does base-load mean? When we speak of a unit being base-loaded, we often refer to the unit as being operated as much as possible to produce as much energy as possible. However, do base-load units have any reserve shutdown hours? Can only cycling units cycle on- and off-line periodically while base-load units do not? These questions can only
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I've performed several hundred benchmarking analyses for different utilities. A typical benchmarking request would be, "I would like you to benchmark my unit. Can you compare it to similar units?" My first question always is, "What are the unique characteristics of your unit?" There often is no response to this question because they've never thought about what makes one unit similar or different from another. It's important to have the answer to this question so you know if you have a good peer group or not. Let's take a look at some experiences in benchmarking so you can answer these questions and do some benchmarking on your own.
Tip No. 2 - Determine what's important
There are many different opinions about how to divide a set of units into peer groups. Some engineers or managers look for units based on design information such as the fuel being burned, the megawatt (MW) size, the manufacturer of the steam turbine, or other physical characteristics. Why are such characteristics used? Many times it is simply "gut feel" rather than statistical or widespread operating experiences. That's OK! But, it's also important to consider other attributes besides the typical ones that might not be all that important. Let's look at an example that we've experienced in the industry.
Many people feel that MW size of the unit is very important. In the North American Electric Reliability Corporation's (NERC) Generating Availability Data System (GADS) Generating Availability Report (GAR) we grouped fossil steam units into 100 MW increments. Why? Because it looks nice on paper and it has been the tradition for more than 30 years to show the units in these groupings. But is there a real difference between units that are 99 MW and those are 100 MW? It would be very hard to prove that these two sizes can be divided using statistical methods.
NERC produced a special report for the World Energy Council's (WEC) Performance of Generating Plant (PGP) Committee. We took fossil units in the U.S. from the database in 100 MW increments, just like in the GAR. We chose Equivalent Availability Factor (EAF) as our key indicator and located the EAF for each major percentile for each 100 MW group. We chose 2003-2007 as our time period, since all units were required to report for all 5 years. The results are illustrated in Figure 1.
As you can see, most of the percentile lines are straight across the board. What does this mean? It means that no matter what MW size you pick, you would get the same result by percentile. This proves that MW size is not as important as most people think. Yet many people considered it one of the primary divisions for power plants. There are times when MW size is very important and can be statistically used to divide units into groups. The same thing can be said about fuels. However, when we benchmark using the NERC method, more than 50 percent of the time neither MW size nor fuels are used to create peer groups.
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