The unknown unknowns are what keep regional grid operators up at night. And right now the rapid growth of customer-sited microgrids, invisible to grid operators, count high among them.
That’s the message delivered last week by Jonathan Monken, PJM senior director, speaking on a plenary panel at the Virginia Clean Energy Summit in Richmond.
PJM operates one of the world’s largest grids, which through a complex orchestration of 180,000 MW, keeps electricity flowing to 65 million customers in 13 states and the District of Columbia.
But change has come to the system at a rapid clip with customers installing their own generation in the form of microgrids and other distributed energy resources (DERs). These assets are not part of the grid managed by PJM but they do influence it. For example, they can change consumption patterns — and in ways the grid operator cannot see.
“The hard part is that we don’t see down to the customer level. We don’t see below 67 kV. That is where the rub comes,” he told the audience of clean energy advocates.
Risk and reward of the new reality
Because they do not know what the distributed assets are doing, grid operators cannot incorporate them into their overall planning, which could ultimately weaken the grid, he said.
As an example, Monken described how PJM got tripped up in its forecast during the solar eclipse of 2017. It’s difficult for a grid operator to forecast how much power is likely to be used on the day of an eclipse because there is little historical precedent. PJM had assumed demand would rise because homes and businesses with solar panels would turn to grid power as the eclipse blocked the sun.
“Then something very weird happened,” Monken said. Rather than rising, demand for power fell by 4,000 to 5,000 MW.
Why? As is often the case, weather played a role. It was cooler than expected. But the unknown unknown emerged from a distributed asset. Without notifying PJM, the maker of the NEST thermostat had asked customers to conserve during the eclipse, which reduced demand by 900 MW.
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