Midcontinent Independent System Operator (MISO) has issued a report analyzing the effects of renewable energy growth in the MISO region and concluding that the system can reliably accommodate a significant percentage of variable renewable resources.
The report, MISO’s Renewable Integration Impact Assessment (RIIA), is the culmination of almost four years of stakeholder collaboration. The RIIA evaluates increasing amounts of wind and solar resources on the Eastern Interconnection bulk electric system, with a focus on the MISO footprint, examining renewable penetrations levels in 10% increments. The RIIA concludes that the MISO region can achieve renewable penetration of at least 50% through transformational change and coordinated action. The RIIA is a technically rigorous systematic analysis that provides valuable insight into the feasibility of renewable penetration and the operational and technical issues that need to be addressed.
While MISO recognized that grid operators have long managed uncertainty, MISO stated that it anticipates an unprecedented pace of change to the bulk electric system. MISO noted that these changes will be driven by member utilities, state regulators, and customers. The RIIA is policy and pace agnostic and assumes that the generation changes in the analysis will occur regardless of external drivers and timelines.
The RIIA demonstrates that the needs and risks to the reliability of the bulk electric system rise with increasing renewable integration in the MISO region. Five risks of increased renewable penetration are identified in the RIIA analysis:
- Stability – Maintaining stable operation will become more difficult, especially when renewable resources are clustered in one region of the transmission system. MISO stated that a combination of multiple transmission technologies and operating and market tools to incentivize availability of grid services are needed to provide support, along with operational and market changes to identify and react to this risk as it occurs.
- Shifting Periods of Grid Stress – The periods of highest stress on the transmission system will shift from peak power demand to times when renewables supply most of the energy and long-distance power transfers increase. MISO stated that both increased flexibility and innovation in transmission planning processes are needed.
- Shifting Periods of Energy Shortage Risk – As the periods of grid stress shift, there is a risk of not having enough generation to meet demand, specifically during hot summer evenings and cold winter mornings, when low availability of wind and solar resources is coincident with high power demand. MISO stated that new unit commitment tools and revised resource adequacy mechanisms are needed.
- Shifting Flexibility Risk – Due to the variable nature of renewables, the ability of resources to provide system flexibility will be challenged. MISO stated that market products to incentivize flexible resources are needed.
- Insufficient Transmission – Current transmission infrastructure is insufficient to deliver new renewable energy to load. MISO stated that proactive planning is necessary, especially given the time needed to build transmission infrastructure.
The findings of the RIIA are encouraging for the continued growth and integration of solar and wind power. However, MISO also makes clear that further work is needed to change the way MISO and the power system are planned and operated. This work will require the coordination and participation of all stakeholders to be successful.