Energy storage can help flatten 'duck' curves

July 23, 2014

One of the biggest management challenges electric grid operators encounter when fossil fuels are replaced with renewable energy is the dreaded duck curve - the graphic depiction of how energy supply and demand moves throughout the day seems to form the back of a duck. The "duck curve" graph, as it's known, shows the gap between the total load a utility serves and what that load looks like after wind and solar generation serve some of that load. According to GreenTech Media, "the graphic interpretation of that scenario looks somewhat like a sitting duck. It represents an average day, rather than a peak demand day."

The utility or grid has two concerns with the first being the risk of over-generation in the afternoon and the second concern is an increased need for ramping as solar generation drops off in the late afternoon.

Some believe the duck concept is overblown. "We need to declare hunting season on the Cal ISO's duck chart," said Mark Ferron, retired California Public Utilities Commission chairman. But it's clear that utilities are facing some pretty serious changes to their traditional balance between load and demand.

"This duck curve challenge is causing some utilities to raise questions about the long-term suitability of variable energy resources," wrote Jim Lazar, senior advisor for the Regulatory Assistance Project, in a recent report, Teaching the "Duck" to Fly.

Power and performance
Ferron told Greentech Media that there's a need to reduce the misleading ideas that support the ongoing use of the duck curve. The myths are causing some companies to wonder if the duck curve should be called a Nessie curve, after the Loch Ness monster.

Grid management
Promoting consumption strategies to flatten out the duck curve so less ramping is needed from traditional generation could help the long term viability of renewable generation and the reliability of the grid.

One solution, instead of going through constant peaks and valleys of energy, is to create thermal storage programs that helps companies regulate how much power they use and when they have to pull it from the grid. Demand response programs and market based electricity pricing can provide customer cost saving incentives to install proven storage technologies quickly. The technology exists today to flatten out the curve.

The 24th Annual Energy Storage Conference recently announced one of its major focuses would be on how to handle the duck curve.

According to the source, there's a major need for corporate insight into ways to deal with peak demands and load management, as well as ways to isolate energy storage needs and determine what's best for business oversight. Knowing how to control power requirements and create more positive corporate utilities makes for more balanced energy usage.

Katherine Hamilton, policy director of the Energy Storage Association, says energy storage is like pizza.

"Say you want a pizza. You can make a pizza from scratch. You can order one on the phone to be delivered," Hamilton said to Phys Org Online. "Or you can pull a frozen pizza out of the freezer. Energy storage is kind of like pizza from the freezer. It's there when you want it, and you don't have to wait for it."