Printed on paper containing at least 50% wastepaper, including 10% post consumer waste.iii PrefaceThis report has been produced by Intertek APTECH for the National Renewable Energy Laboratory (NREL) and Western Electricity Coordinating Council (WECC) to support their renewable integration studies.This report provides a detailed review of the most up to date data available on power plant cycling costs. Increasing variable renewable generation on the electric grid has resulted in increased cycling of conventional fossil generation. Previous studies by NREL and WECC have corroborated this fact and the purpose of Intertek APTECH's task was to provide generic lower bound power plant cycling costs to be used in production cost simulations. The inclusion of these costs in production cost simulations would result in accounting for some of the increased costs (system aggregate) and reduced reliability of conventional generation due to cycling.The results of this report are only indicative of generic lower bound costs of cycling conventional fossil generation power plants. The primary objective of this report is to increase awareness of power plant cycling cost, the use of these costs in renewable integration studies and to stimulate debate between policymakers, system dispatchers, plant personnel and power utilities. About Intertek APTECHIntertek APTECH is in Intertek's Industry and Assurance Division and is an internationallyknown engineering consulting firm specializing in performance optimization of equipment and the prediction and extension of the remaining useful life of piping, boilers, turbines, and associated utility equipment, structures, industrial equipment, and materials.Intertek APTECH has been examining the cycling damage to power plant components for over two decades and has pioneered the development of numerous condition assessment methods for power plant equipment. They have been working closely with several clients with increasing renewable resources to assess the integration cost impacts on conventional generation. iv Executive SummaryCompetition and increasing penetration of variable renewable generation are having a farreaching impact on the operation of conventional fossil generation. For many utilities and plant operators, plant operations and maintenance (O&M) expenditures are the one cost area that is currently rising at a rate faster than inflation. To stay competitive, utilities need to better understand the underlying nature of their plant O&M costs, and take measures to use this knowledge to their advantage. A major root cause of this increase in O&M cost for many fossil units is unit cycling. Power plant operators and utilities have been forced to cycle aging fossil units that were originally designed for base load operation.Cycling refers to the operation of electric generating units at varying load levels, including on/off, load following, and minimum load operation, in response to changes in system load requirements. Every time a power plant is turned off and on, the boiler, steam lines, ...

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This paper presents an evaluation of the failure probability and cost of high energy piping (HEP) failures. Using a conventional definition of risk as the product of failure probability and failure consequence, we propose in this paper a dollar value of consequence in order to develop a quantitative approach to risk-based inspection (RBI) methodology. A 16-year historical database of probability and consequence was evaluated as an RBI methodology for devising a life management strategy for welds in main steam and hot reheat piping systems. This evaluation provides us the raw data necessary for producing a concrete example of this new Richter-scale-like approach. Uncertainty in consequence and probability estimates is also provided in plotting (a) a static consequence vs. likelihood diagram at a specific time for comparing the relative severity of a variety of potential failures, and (b) a dynamic risk vs. time diagram for a specific hardware under continuous monitoring where the effect of life management decisions over a period of time is quantitatively displayed. Significance of this new approach to risk-based inspection strategy for advancing the state-of-the-art of managing aging structures is discussed.