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, ...
This report was prepared by General Electric International, Inc. (GE) as an account of work sponsored by NREL. Neither NREL, nor GE, nor any person acting on behalf of either: 1. Makes any warranty or representation, expressed or implied, with respect to the use of any information contained in this report, or that the use of any information, apparatus, method, or process disclosed in the report may not infringe upon privately owned rights 2. Assumes any liabilities with respect to the use of or for damage resulting from the use of any information, apparatus, method, or process disclosed in this report.
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Nuclear power plants are no longer immune to cycling operation. While certain nuclear power plants in Europe have been performing load following operation, this type of operation has largely been avoided in the United States. Due to increasing contribution of nuclear generation in the mix, European operators were forced to make modifications to increase the maneuverability of their nuclear generation assets. However, in the United States, nuclear generation is still a relatively smaller contributor (19%), but with rapid increase in renewable generation, some nuclear plans are being asked to operate at reduced power and cycle to lower power levels. These shutdowns are typically of a short-term duration on a weekend or in periods of high renewable megawatt generation. With most future renewable integration studies advocating for increased flexibility on the grid, nuclear generation maneuverability will allow system operators with another resource to mitigate and reduce system costs. This paper presents the results of a detailed study of a 1,150 MW boiling water reactor (BWR) nuclear plant when cycled to low loads. The authors present the relative damage of cycling to various reduced power levels 80% to 15% power levels compared to a cold startup and shutdown of a nuclear plant. An assessment was made of the systems that had fatigue damage and costs. We also discuss some of the limitations of cycling that a nuclear plant has and present and discuss recommendations to reduce damage and costs.
Recent work done by Aptech Engineering Services, Inc. (APTECH) has demonstrated that many hot section gas turbine components are not achieving their intended service lives and/or maintenance intervals, falling short by a factor of as much as ten. As summarized in (Makansi, 1996), this observation has been confirmed by numerous industry and literature reports of failures, degradation, reduced availability and increased maintenance for a wide variety of turbines and manufacturers. This paper focuses on hot corrosion damage as one common mechanism that is frequently the cause of failure to reach expected service intervals. In general, attempts are made to limit hot corrosion damage by specifying impurity limits for fuel oil, combustion air, NOx reduction injection water and compressor washing water. Strict adherence to manufacturers recommended impurity limits is often very difficult to achieve, particularly if the machine is frequently cycled through harsh (but not uncommon) operating transients. A discussion of various manufacturer specifications and their implications will be presented, followed by two case studies which demonstrate that extensive hot corrosion damage can result even when manufacturers specifications for fuel, air and water purity are (apparently) being met. A proposed modification of traditional impurity limit specifications is offered, which would include guidelines for acceptable corrosion rate limits. Practical recommendations for reducing the potential for hot corrosion are also offered.
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