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Twenty-first century power systems, with higher penetration levels of low-carbon energy, smart grids, and other emerging technologies, will favor resources that have low marginal costs and provide system flexibility (e.g., the ability to cycle on and off to follow changes in variable renewable energy plant output). Questions remain about both the fate of coal plants in this scenario and whether they can cost-effectively continue to operate if they cycle routinely. The experience from the CGS plant demonstrates that coal plants can become flexible resources. This flexibility-namely the ability to cycle on and off and run at lower output (below 40% of capacity)-requires limited hardware modifications but extensive modifications to operational practice. Cycling does damage the plant and impact its life expectancy compared to baseload operations. Nevertheless, strategic modifications, proactive inspections and training programs, among other operational changes to accommodate cycling, can minimize the extent of damage and optimize the cost of maintenance. CGS's cycling, but not necessarily the associated price tag, is replicable. Context-namely, power market opportunities and composition of the generation fleet-will help determine for other coal plants the optimal balance between the level of cycling-related forced outages and the level of capital investment required to minimize those outages. Replicating CGS's experience elsewhere will likely require a higher acceptance of forced outages than regulators and plant operators are accustomed to; however, an increase in strategic maintenance can minimize the impact on outage rates.

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Increased renewable generation on the grid along with market deregulation has resulted in a significant increase in the cycling of coal and gas-fired power plant. This increase in cycling will result in increased wear-and-tear costs for units that were not traditionally designed for cycling. Asset owners can make operational changes to mitigate the wear-and-tear impact or alternatively retrofit existing units for improved flexibility. With retrofits, these plants can provide increased operational flexibility, or in other words cycle more, but this comes at an initial cost. On the other hand, increased flexibility in terms of faster starts, better turndowns and ramp rates also provides opportunity for the asset owners to recover their costs in the market. This paper evaluates the operational, as well as cost-benefit of retrofitting power plants for flexibility using a portfolio of generation resources in North America.

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.

Wind based electric generation is one of the fastest growing energy sources in the world. With rapid development of wind farms, many challenges have emerged with respect to the reliability and availability of the in-service equipment. Additionally, with increasing size of wind turbine blades, both onshore and offshore, the serviceability and maintainability of the equipment poses its own unique challenge. There is also an inherent risk from the economics of energy production, which dictates that low-cost manufacturing methods are employed to produce cost-effective machines. In our experience, there are additional risks associated with supply chains and limited availability and understanding of damage mechanisms and reliability data of the myriad manufacturers and models of turbines, blade design and associated equipment. Failure of different components results in different outage times and therefore impact operational and maintenance (O&M) costs in different ways. Achieving high availability targets requires a robust O&M plan. The authors will highlight operational risks of large wind turbines and methodologies to improve reliability and availability for wind farms.