Traditionally, utilities built and operated a portfolio of generation plants consisting of a few large base load units – typically nuclear or coal – some intermediate plants and a number of peakers – typically natural gas fired units with rapid ramping capability (visual below).
Base load units ran flat out year-round, 24/7; the intermediate units were used to fill the fluctuations in demand while the peakers were used sparingly to meet occasional surges in demand, say on hot summer afternoons when air conditioning load would spike for a few hours.
Fast forward to 2019 and beyond and one is likely to encounter a different paradigm where on many networks an increasing share of generation is provided by renewable resources, most likely wind and solar, neither of which is dispatchable nor totally predictable.
In this environment, what the grid operators crave the most is flexible generation, especially those with rapid ramping capability to fill in any unexpected shortfalls in renewable generation and to maintain the system’s reliability.
This much is old news. What is new is that recent advances in energy storage technology, especially batteries, coupled with dramatic cost declines is making storage increasingly attractive relative to gas- fired peaking plants, which are not particularly efficient, are highly polluting and are expensive to maintain. Moreover, since peakers are infrequently used and only for a limited number of hours, they tend to be poor investments, sitting idle most of the time.
A case in point was a decision by San Francisco-based Pacific Gas & Electric Company (PG&E) backed by the regulator, the California Public Utilities Commission (CPUC) in Nov 2018 to replace 3 gas peakers with large battery storage units that would be among the world’s largest when completed.
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