By - Jim Vess

New Englanders used more grid electricity while sleeping than at noon on a sunny, mild April day

Energize Weekly, June 6, 2018

In a regional first, on a mild, sunny April day, New Englanders used more electricity from the grid while they were sleeping than they did at midday, according to grid operator ISO New England (ISO-NE).

The game changer on April 21 was the 2,400 megawatts (MW) of solar capacity in the region, most of which is used in place. This is particularly true for “distributed generation,” such as rooftop solar, the regional independent system operator, or ISO, said.

On April 21, distributed solar was producing about 2,309 MW at 1:30 p.m. As a result, midday grid demand dipped below overnight demand for the first time ever in New England.

“New Englanders using distributed solar power use commensurately less electricity from the regional power system,” according to the grid operator. “As the grid operator, ISO New England experiences distributed solar power as a reduction in grid demand.”

While this was a first for the region, ISO-NE expects there will be more days like this in the future.

“We were expecting this to happen at some point as more behind-the-meter solar gets installed in New England and the weather conditions were just right,” ISO-NE’s forecast and scheduling supervisor Mike Knowland said in a statement. “While this kind of dip in demand is new for New England, it’s a common occurrence in California.”

With more than 5,800 MW of distributed solar power expected to be deployed in New England by 2027, the grid operator said it anticipates more occasions when the demand may dip extremely low, particularly during the spring and fall.

The growth in distributed solar comes with challenges, which the grid operator is preparing to address, such as large, unexpected dips in demand, which can leave excess energy on the system. That could cause high system voltages and frequencies, and unscheduled flows of power into neighboring regions.

In response, the ISO may have to issue emergency requests for power resources on the high-voltage system to reduce output or shutdown.

“To be able to more accurately anticipate solar output, the ISO is working with industry experts to build a day-ahead forecast of distributed solar generation that can be integrated into our existing load forecast models, for an improved forecast of system load,” ISO-NE said. “Additionally, negative pricing minimize times where there’s too much energy on the system, while 2017’s improved real-time fast-start pricing will help incentivize power resources that can respond quickly to ISO dispatch instructions.”

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