The California Duck Curve reveals a potential costly issue for utilities and their customers. The annual peak load appears to be continuing to grow -- because it occurs after dark when there is no solar power being generated -- yet energy sales may be declining with the growth of distributed solar generation during the day. This results in the need to continue to expand the grid, but without the sales revenue to support the added capital expense, presenting a Catch-22 that utilities are struggling to overcome.
Researchers at DNV-GL did a fine report for the New York Independent System Operator a few years ago. Titled A Review of Distributed Energy Resources, it offered this definition of the various distributed energy resources (DERs) examined in the report:
“… DER technologies are defined as ‘behind-the-meter’ power generation and storage resources typically located on an end-use customer’s premises and operated for the purpose of supplying all or a portion of the customer’s electric load. Such resources may also be capable of injecting power into the transmission and/or distribution system or into a non-utility local network in parallel with the utility grid. These DERs include such technologies as solar photovoltaic (PV), combined heat and power (CHP) or cogeneration systems, microgrids, wind turbines, micro turbines, back-up generators and energy storage.”
Granted, the research team did acknowledge that some sources – including the New York Public Service Commission – included customer load in its list of DERs, but load wasn’t one of the DERs covered in the report. That’s too bad because load can hold its own against other DERs for a variety of grid-supportive purposes.