Integrating Variable Resources and Flexible Demand

7 Dec 2020

What is the best way to mix in growing levels of intermittent renewable resources in networks such as California’s, as it marches towards a 100% clean energy portfolio by 2045? Among the usual suspects are better interconnections, and more generation diversity, including more storage and price responsive demand, a resource traditionally neglected. A newly released book, Variable Generation, Flexible Demand, provides a broad lens on the subject.

The book showcases paradigm changes away from the traditional way in which demand was forecast and generation resources were dispatched to meet it.

It highlights the need for grid operators to predict the amount of fluctuating wind and solar resources and to schedule complimentary demand. It provides lessons and examples of integrating rising levels of carbon neutral resources into the grid.

“California is one of the few places in the world where this paradigm change is happening because so much new solar and wind is being added,” Fereidoon Sioshansi, the book’s editor, told Current.

He added that the 100-year old utility model of predicting load and then matching it with fossil fuel generation, and some hydropower supplies, is out of sync with a green grid where the bulk of generation is non-dispatchable renewables. “Given the variable nature of renewable generation, particularly solar, a major shift is needed to create a smooth, efficient, and low-cost transition to this new world order,” he said.

The book looks at several evolving markets including ones in California, ERCOT, Italy, Spain, and Australia, among others. They all face rising levels of renewable resources.

But renewable generation still plays a minor role in many parts of the world where it can be squeezed into the traditional dispatchable generation model. In these places, variable renewables are the small tail on the big dog, Sioshansi said. In contrast, in California and in some European countries, the big renewable tail is increasingly wagging the dog.

In Denmark, for example, on some windy days, the wind output exceeds total demand on the network. But because of Denmark’s strong interconnections with Germany and Scandinavia, the excess wind can be absorbed in Germany’s much larger market and/or it can be stored in hydropower reservoirs in Sweden and Norway–acting as big batteries.

In contrast, California’s huge market dwarfs those of the neighboring states. Consequently, the state’s excess solar generation cannot easily be exported to the neighboring states–nor can its deficits be covered by imports–resulting in renewable curtailment.

Contributors to the book examine the role of expanding flexible demand to balance supply, including with energy storage.

“Batteries are more versatile and can respond almost instantaneously, compared to a natural gas fired peaking plant, which takes time to respond to signals from the grid operator,” Sioshansi noted. Other flexible demand can respond to signals in the same way.

In addition to the practical ways demand flexibility can play a constructive role as more systems move towards higher levels of renewable generation, the book also explores the role of market design, business models, enabling technologies, policies, and regulation.

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