A reliable bulk power system requires system operators maintain a constant balance between electricity supply and demand. Historically, this has been accomplished by planning generation capacity around peak demand forecasts and including a reserve margin to account for random uncertainties, like unexpected generation unavailability (i.e., due to failure) or inaccurate load forecasts. As the generation fleet transitions from dispatchable resources that are available on demand to variable resources that are weather-dependent and not always available when needed, the availability of energy to meet demand is more uncertain and existing methods used to determine adequate energy are less valid.
The current capacity-based assessments for determining adequate generation supply were designed for a fleet of dispatchable resources with reliable fuel sources, such as coal and natural gas. In contrast, variable resources like wind and solar lack a guaranteed fuel supply due to their dependence on weather conditions. Moreover, dispatchable resources are being retired at a much faster rate than new, reliable replacements can be added to meet the same load requirements, rendering traditional capacity assumptions increasingly irrelevant in today’s complex energy landscape. Additionally, these assessments do not account for the effect of weather on both generation supply and load demand. For instance, extreme cold temperatures can strain the power grid, limiting electricity generation and delivery precisely when demand is at its peak. Distributed energy resources, like rooftop solar and customer-site battery installations, serve electricity demand but need to be carefully managed by system operators to maintain reliability.
Because of these factors, a new way of understanding what energy is available (from a variety of different resources) to meet demand at all times must be developed.
NERC established an industry-led Energy Reliability Assessment Working Group (ERAWG) to address this risk. The working group proposed development of standards that require energy reliability assessments be performed to determine sufficient energy availability. As a result, NERC is undertaking this as a standards project (Project 2022-03 Energy Assurance with Energy-Constrained Resources). The following standards are affected by this work: TPL-001-5.1, EOP, TOP, and BAL.