A new report advises that peak load hour is no longer the default riskiest time for a power system. That’s especially true for systems that host a large amount of intermittent renewable energy resources.
Instead, every hour of the year should be studied given the uncertainty about whether renewable resources will be able to generate when needed.
The report said that most supply uncertainty used to come from thermal resource forced outages. That’s no longer the case as variable renewable energy now contribute “most of the uncertainty in supply.” The upshot is that today’s power supply uncertainty “cannot be accurately captured with legacy tools using average annual profiles” to represent renewable resources.
That shift in system planning mindset was laid out in by the National Regulatory Research Institute (NRRI), an arm of national regulatory group NARUC. Its report, “Resource Adequacy Modeling for a High Renewable Future,” said that power system reliability models need to be updated to include the impact of weather as a driver of energy generation. And models should address correlations in production output between different variable energy resources, storage state-of-charge limitations, and common mode failures such as the risk of coal pile and natural gas equipment freeze-ups during bad weather.
In addition, policy makers, regulators, and power system planners should anticipate climate-driven impacts to resource adequacy as a result of more frequent extreme weather events and natural disasters.
“In other words,” the report said, “climate change increasingly means one cannot simply look to the past to understand the ongoing impacts of extreme weather events.”
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Turning to the load side of the equation, the report said that building electrification, electric vehicle adoption, and expected growth in customer-sited solar and storage are likely to have pronounced effects on future electric consumption. But uncertain load growth and changing daily consumption patterns increase the challenge of making sure that future resources can serve load around the clock.
The report also outlined possible changes to reliability planning models and identified what it said were the “core components of the new energy paradigm:” meteorology, variable renewable energy generation, forced outages, and energy limited storage. Seen this way, weather (primarily in the form of temperature, but potentially including insolation, humidity, wind speed, and so on), drives simulations of renewable generation and customer load.
Generation outage simulations can be modeled as correlated with extreme heat or cold events. Once the simulations are in place, models can compute multiple future paths on an hour-by-hour basis to determine when load cannot be fully served with the available resources.
The report concluded that modeling tools should simulate key structural variables and allow for validation of the simulations by benchmarking against the historical data used to create the simulations.
It said that simulations should include load growth expectations along with changes in seasonal and daily load shapes. Generation-forced outage simulations should include the possibility of correlated outages from extreme weather.
Climate change, the report concluded, will “drive more weather events in the power system” and this risk “should be accounted for in the models.”
Read the NRRI report here.
