Impact of Generator Flexibility on Electric System Costs and Integration of Renewable Energy

Abstract

Flexibility of traditional generators plays an important role in accommodating the increased variability and uncertainty of wind and solar on the electric power system. Increased flexibility can be achieved with changes to operational practices or upgrades to existing generation. One challenge is in understanding the value of increasing flexibility, and how this value may change given higher levels of variable generation. This study uses a commercial production cost model to measure the impact of generator flexibility on the integration of wind and solar generators. We use a system that is based on two balancing areas in the Western United States with a range of wind and solar penetrations between 15% and 60%, where instantaneous penetration of wind and solar is limited to 80%. We evaluate the impact of reducing the minimum generation level of the coal generation fleet from 60% to 40% of nameplate capacity and observe the corresponding decrease in production costs. At low wind and solar penetration, this increased flexibility provides very little benefit. However, at higher levels of renewable penetration, increased flexibility results in decreased curtailments, which reduces fuel consumption and decreases the system production cost. We also examine the impact of relaxing the 80% penetration limit, assuming that active power controls and other new technologies allow wind and solar to provide system stability services. This further decreases production costs, particularly in very high penetration scenarios. In all scenarios, emissions of CO 2 decrease as flexibility is increased and more variable generation is accommodated.

Capturing the Impact of Storage and Other Flexible Technologies on Electric System Planning

“…In this example, we observe curtailment fractions of less than 5% through 2025, but significantly higher marginal curtailment rates in 2030 due to growing renewable penetrations. This nonlinear behavior is consistent with other studies (e.g., Palchak and Denholm 2014). The box-and-whiskers plots show quartiles including medians.…”

“…This regression is then tested against data from flexibility studies in California (Paul Denholm et al 2015) and the Colorado Test System (Palchak and Denholm 2014) in order to ensure the regressions yield realistic results for other systems. The validated effective min-gen regression is then used with data for each model year to predict the effective minimum generation level for that particular system.…”

“…The modeling methodologies of large-scale renewable integration studies have also been used to conduct more targeted system flexibility research. In these studies, the flexibility of a system is incrementally altered-for example, by changing thermal plant configurations (e.g., minimum generation points and ramp rates), or adding direct energy storage technologies, concentrating solar power with thermal energy storage, or demand response-and differences driven by these incremental changes are evaluated to discern the operational impact of flexibility (Black and Strbac 2006;Palchak and Denholm 2014;Zucker, Hinchliffe, and Spisto 2013;P. Denholm et al 2013;Jorgenson et al 2013;Hummon et al 2013).…”

Market Power Under Nodal and Zonal Congestion Management Techniques

“…Another essential source of flexibility is conventional generators' ability to change their output to follow varying load. The ability of changing production in a short interval depends on technological aspects such as minimum up/down times, ramp rates, minimum generation levels and start-up costs (Palchak and Denholm (2014)) whereby some additional costs will be enforced to generators as well as the system. Hentschel et al (2016) evaluate the monetary value of conventional power plant flexibility options through developing a valuation tool which relates a change in technical parameters to an economic effect and revenue.…”

Impact analysis of variable renewable energy integration on total system costs and electricity generation revenue and impact mitigation

“…While flexibility has always been a necessary component of electrical systems, given the uncertainty of demand and conventional generation outages, the growth in VRE increases the need for flexible resources. Research [35] evaluated the impact of reducing the minimum generation level of the coal generation fleet from 60% to 40% of nameplate capacity and observed the corresponding decrease in production costs. At low VRE penetration, this increased flexibility provides minimal benefit.…”