The rise of distributed energy resources poses challenges to the U.S. electric transmission system, according to the North American Electric Reliability Corp. (NERC). In a report – 2019 Long-Term Reliability Assessment – released Thursday (Dec. 19), the nation’s reliability watchdog said, “Distributed energy resources (DERs) and storage are increasingly offering electricity customers an option to reduce energy costs and create additional resilience.”
DERs, NERC said, “are increasingly being implemented at the electric distribution level, resulting in a possible net source of power injected into the BPS instead of being load. This change will require a strong transmission system with good links to the distribution system to maintain an appropriate balance between load, variable energy resources (VERs), and energy storage devices.”
NERC said it expects 8 GW of electric storage connected to the bulk power system by 2024, along with 35 GW of distributed solar photovoltaic. The report added, “Increasing installations of DERs modify how distribution and transmission systems interact with each other. Transmission planners and operators may not have complete visibility and control of DERs, but information and data is needed for system planning, forecasting, and modeling as growth becomes considerable.”
The increasing scale of wind and solar, says NERC, means that transmission planning and infrastructure development will “need to keep pace” with the rise of the intermittent resources. According to NERC, “Under 15,000 circuit miles of new transmission is expected over the next 6 years; this is considerably less than the nearly 40,000 circuit miles planned earlier this decade.”
A lot of the wind and solar will be “remote from demand centers and existing transmission infrastructure.” The report notes that in the Southwest Power Pool and the Electric Reliability Council of Texas “the level of VERs are reaching full subscription of the transmission network and exhaust current as well as planned transmission capacity.”
NERC says it defines reliability of the bulk power system through “two basic and functional aspects.” These are “adequacy,” or the “ability of the electric system to supply the aggregate electric power and energy of the electricity consumes at all times, taking into account scheduled and expected unscheduled outages of system components,” and “operating reliability,” or “the ability of the electric system to withstand sudden disturbances, such as electric short circuits or unanticipated loss of system components.”
NERC said it doesn’t see any areas of unreliability in this year’s current report, although it is concerned about SPP and ERCOT.
— Kennedy Maize