Massachusetts Is Staring Down a Duck Curve of Its Own. Storage Could Help
Get ready for solar capacity to double in the next few years.
After a barrage of wicked nor’easters this winter, Massachusetts residents probably aren’t worried about having too much sun. They should be.
Over in Hawaii, California and Arizona, middaysolargeneration has begun to cause major swings in the balance of supply and demand on the grid. The resulting “Duck Curve” has become emblematic of the logistical challenges involved in massive renewables adoption.
As it turns out, this duck infestation is migrating from the sunny, palm-lined enclaves of Venice Beach and Scottsdale to the Bay State.
“We are absolutely beginning to see a Duck Curve,” said Judith Judson, Commissioner of the Massachusetts Department of Energy Resources, in an interview at the Energy Storage Association conference in Boston last week. “It shows that we’re being very successful in increasing renewable energy generation, but we need to start thinking about…how do we match up that generation with demand?”
The tell-tale shape of the duck is appearing in the daily energy charts from ISO New England, the grid operator for Massachusetts and five neighboring states. The ISO has about 2,400 megawatts of cumulative solar capacity, most of which is small scale.
Massachusetts represents almost half of the load in the territory, and the bulk of the solar capacity too. The data covers more than just Massachusetts, but the state drives regional trends.
In a typical spring or fall day, load starts climbing in the early morning hours and crests by mid-morning. Total load dips through the midday hours, starts climbing again in the late afternoon, and reaches a peak around 8 P.M.
That’s fairly normal for the time of year when people aren’t cranking the air conditioning; load peaks when residents get up in the morning and when they get home from work. What’s changing is what happens in between.
Massachusetts’ 2,076 megawatts of solar capacity has already started to pull down the load in the middle of the day. That action displaces other sources of power during those hours and increases the ramp rate needed to meet demand when the sun goes down.
That’s just the beginning. Massachusetts aims to nearly double its installed solar capacity in the next few years. This duck is about to have a growth spurt.
The widening gap between low midday load and high evening peak requires fast responding capacity to keep the grid healthy. Gas can play that role, but geography and climate impose certain constraints.
The Duck Curve shows up in the winter months too. When cold snaps or polar vortices descend, much of the region’s natural gas supply goes toward heating. That drives up the prices for gas-fired electrical generation, sometimes forcing a shift to other fuels like coal and oil, said Judson.
“Storage has particular value as being a solution on peak winter days — when our electric system is stressed and our heating system has full demand — as a way to be able to reliably and cost effectively meet our energy needs,” she said.
The expected ramping needs, combined with a coming influx of wind and solar generation, lend an urgency to Massachusetts’ recent push to expand energy storage deployments. Storage offers an alternative to natural gas for peak capacity, and can absorb surplus renewable generation, as seen in the belly of the Duck Curve.