Western Wind and Solar Integration Study
Can we integrate large amounts of wind and solar energy into the electric power system of the West? That's the question explored by the Western Wind and Solar Integration Study, one of the largest such regional studies to date.
Phase 1 Research
During its first phase, the Western Wind and Solar Integration Study (WWSIS) investigated the benefits and challenges of integrating up to 35% wind and solar energy in the WestConnect subregion and, more broadly, the Western Interconnection, in 2017. The study showed that it is operationally possible to accommodate 30% wind and 5% solar energy if utilities substantially increase their coordination of operations over wider geographic areas and schedule their generation and interchanges on an intra-hour basis.
What We Learned
- The integration of 35% wind and solar energy into the electric power system will not require extensive infrastructure if changes are made to operational practices.
- Wind and solar energy displace fossil fuels. A 35% penetration of solar and wind power would reduce fuel costs by 40% and carbon emissions by 25%–45%—the rough equivalent of taking 22–36 million cars off the road—compared to today's system.
- Increasing the size of the geographic area over which the wind and solar resources are drawn substantially reduces variability.
- Scheduling generation and interchanges subhourly reduces the need for fast reserves.
- Using wind and solar forecasts in utility operations reduces operating costs by up to 14%.
- Existing transmission capacity can be better used. This will reduce new transmission needs.
- Demand response programs can provide flexibility that enables the electric power system to more easily integrate wind and solar and may be cheaper than alternatives.
Phase 1 Publications
Phase 2 Research
Phase 2 of WWSIS was initiated to determine the wear-and-tear costs and emissions impacts of cycling and to simulate grid operations to investigate the detailed impacts of wind and solar power on the fossil-fueled fleet in the West.
What We Learned
- The negative impact of cycling on overall plant emissions is relatively small. The increase in plant emissions from cycling to accommodate variable renewables is more than offset by the overall reduction in carbon dioxide (CO2), nitrogen oxide (NOx), and sulfur dioxide (SO2). In the high wind and solar scenario, net carbon emissions were reduced by one-third.
- Operating costs increase by 2%–5% on average for fossil-fueled plants when high penetrations of variable renewables are added to the electric grid.
- From a system perspective, these increased costs are relatively small compared to the fuel savings associated with wind and solar generation.
- Cycling costs vary based on penetration level and wind/solar mix.
Phase 2 Publications
Phase 3 Research
Phase 3 of WWSIS investigated the dynamic performance of the Western Interconnection in the fractions of 1 second to 1 minute following a large disturbance (e.g., loss of a large power plant or a major transmission line) with high penetrations of renewable energy. Conducted by NREL and GE Energy Consulting, the study focused on large-scale frequency response and transient stability. Both are critical to grid reliability, particularly for the Western Interconnection, which has a long history of dynamic performance constraints on its operation.
What We Learned
- With good system planning, sound engineering practices, and commercially available technologies, the Western Interconnection can withstand the crucial first minute after severe grid disturbances with high penetrations of wind and solar on the grid.
- Adequate frequency response in the Western Interconnection was maintained for the conditions studied.
- Selected nontraditional frequency-responsive controls on wind and solar power plants and energy storage were examined and could improve frequency response.
- The transient stability of the system is not fundamentally changed by high wind and solar generation. This does not mean that the system behaves identically. There is, however, nothing to indicate that the system dynamics have changed so fundamentally that radically different means to ensure stability are required.