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How Much Energy Can You Save?

Nov. 18, 2022
Pinch analysis and benchmarking offer reliable methods for determining energy savings.

I came into the energy efficiency arena through pinch analysis. The pinch methodology enables us to calculate a rigorous target for energy consumption, based on a simplified physical model of heat transfer in an industrial process, together with simplified economic assumptions (“Take the Heat Off Pinch Analysis,” July 2019, https://bit.ly/3ES2A3I). In its basic form, pinch analysis only considers savings through heat recovery, assuming a pre-determined plant configuration, in which only the heat exchangers can be changed. The genius of the pinch approach is that it allows us to calculate the energy target without knowing the design of the optimized heat exchanger network.

In practice, there is no guarantee an economical design will achieve the pinch target; the target is even more difficult to attain in revamp situations than in new plant designs, as the existing equipment and plot space restrictions often limit possible improvements. Over the years, many clever techniques have been developed to mitigate these challenges; advances in computing have helped, but, to some extent, challenges remain.

Other types of target-setting also are used, most notably, benchmarking. These often act as a basis for estimating potential energy savings, thus justifying energy management programs (“Quantify Your Energy Efficiency Program,” October 2022, https://bit.ly/3h06H6j). Several for-profit providers offer benchmarking services, including energy benchmarking, for different industries around the world.

Pinch targets and benchmarks are similar; both provide a quantitative measure of the potential for saving energy in a process and are useful in driving improvements in energy efficiency. However, the underlying methodologies and assumptions are inherently different. While pinch targets represent the amount of heat the process would consume with an optimized heat exchanger network, benchmarking, on the other hand, is based on performance comparison of different types of assets or practices to find the most effective or economical. Rigorous benchmarking of existing processes is based on the statistical comparison of actual operating data. In other words, pinch targets represent what might be achievable, whereas benchmarks represent what already has been achieved.

Due to anti-trust requirements, benchmarks are commonly developed by confidential side-by-side comparisons of validated operating data from at least four similar company plants. This practice avoids revealing any one company’s data points. Results usually are reported back to individual producers as a set of averages and statistical measures, which can be compared to that producer’s own data. These comparisons can show a producer’s overall standing versus competitors and indicate areas where further efforts will pay off. The benchmark results, together with monetary gap calculations, provide an economic justification for improvement efforts. This, in turn, can drive key business decisions, including the development of multi-year strategic improvement plans.

In some parts of the world, government mandates necessitate energy benchmarking to drive conservation and energy consumption improvement efforts, as well as decarbonization. The mandates typically set aggressive energy-reduction goals, which may go beyond those dictated by normal economic returns, to achieve national or regional energy objectives.

Energy benchmarking is well-established in the process industries. Global refineries have practiced it for many years, thus a large body of experience and a great deal of data exist. Nearly every refinery is unique, with different processes and facilities, so a factor-based approach, based on the fundamental crude distillation process, has become well-accepted.

More widely produced petrochemicals and plastics also have used benchmarking, and over the years have compiled reliable databases for the more-common products and processes. Products made in fewer locations or using widely varied technologies require more specialized analysis.

Many large-volume industrial chemicals and fertilizers also have access to dependable benchmarking databases. Like the situation with petrochemicals, some lower-volume materials require more specialized analysis.

(For more information, see: Mark Eggleston, “Energy Benchmarking” in Alan P. Rossiter & Beth P. Jones, Energy Management and Efficiency for the Process Industries, Wiley-AIChE, 2015, pp. 56–65.)

About the Author

Alan Rossiter | Energy Columnist

Alan Rossiter is a former contributor for Chemical Processing's Energy Saver column. He has more than 35 years of experience in process engineering and management, including eight years in plant technical support, design and research with Imperial Chemical Industries (ICI, United Kingdom) and nine years in energy efficiency and waste minimization consulting with Linnhoff March, before starting his own business. In 2019 he joined the University of Houston as Executive Director, External Relations for UH Energy. He is a chartered engineer (U.K.) and a registered professional engineer in the state of Texas. His latest book, Energy Management and Efficiency for the Process Industries, coauthored with Beth Jones, was published by John Wiley & Sons in 2015. He is a Fellow of the American Institute of Chemical Engineers and a Past Chair of the South Texas Section of the AIChE. 

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