As the electric power sector transitions toward higher levels of variable renewable energy resources, electric company system planners face challenges to reliably integrate these resources into system operations and develop strategies to manage their intermittency. More specifically, integrating high levels of renewable resources into a power system requires managing i) curtailments during times of low net load, reducing the value of renewable generation; ii) ramping challenges, particularly in evening hours as solar output drops off; iii) fluctuations in output, due to real-time changes in weather conditions; and iv) long-duration output when renewable generation output is low over a prolonged period.
Load flexibility has emerged as a powerful but currently underused tool to mitigate the challenges created by growing levels of renewable resource deployment. In addition to the “peak clipping” benefits associated with conventional demand response (DR), load flexibility programs also can provide daily dispatchable load shifting. Therefore, it may be possible to shift flexible loads to periods of high renewable generation, thereby reducing potential curtailments, and load from periods of low renewable generation when more expensive generation is required. Advanced load flexibility programs can provide greater net system benefits than traditional DR programs at high renewable penetrations. These benefits may include reduced investment costs, reduced energy production costs, and reduced carbon dioxide (CO2) emissions.
This EPRI technical update analyzes the potential benefits of deploying a representative portfolio of load flexibility programs into an illustrative electric utility system with a high penetration of renewable generation (that is, 66% generation in 2040 before introducing the load flexibility portfolio). The project team used a capacity expansion model (GridSim) to explore the changes in renewables generation, deployment, and system operations after introducing a realistic portfolio of load flexibility programs into this system. The load flexibility portfolio analyzed in this study consists of four measures: i) time-of-use rates, ii) grid-interactive water heating, iii) utility-controlled charging of behind-the-meter (BTM) storage, and iv) utility-managed charging of electric vehicles. This analysis demonstrates that it is possible to reduce curtailments in a system with a high share of renewable generation, improve the economics of renewable generation, and reduce system costs by using daily load shifting enabled by the load flexibility portfolio. Moreover, improved utilization of renewable generation leads to a significant reduction in total system CO2 emissions. This analysis also shows that more ambitious load flexibility portfolios (up to 8% of the peak demand) lead to higher renewables integration benefits, scaling nonlinearly.