Eastern U.S. can handle 30% clean power — report

Source: Christa Marshall, E&E reporter • Posted: Thursday, September 1, 2016

Wind and solar can supply 30 percent of the annual power for the nation’s Eastern grid without reliability concerns, new research from the National Renewable Energy Laboratory said.

The Eastern Interconnection, which stretches from Maine to New Mexico, currently gets less than 7 percent of its annual power from the two renewable sources.

Prior to the study, there was an assumption that 30 percent wind and solar penetration wasn’t possible in the region, said NREL researcher Aaron Bloom. Nobody had conducted a review like NREL’s, which modeled the year 2026 as a test.

“A lot of people thought we weren’t going to be able to serve the load,” Bloom said. Many analysts assumed, he added, that thermal generators like coal and gas wouldn’t be able “to move around fast enough” to accommodate the intermittent nature of wind and solar.

The lab set out to answer whether a 30 percent renewable scenario was technically feasible and how it would affect grid operators. Researchers did not look into whether such an amount of renewable power was desirable.

Under a model scenario, coal and gas plants would have to stop and start much more often, even though their overall generation would decline.

Bloom compared it to moving from highway to “city traffic” for fossil fuel plants. Coal units, for example, had start about 20 percent more often under the model.

The study also documented major shifts in peak demand mode for generators not using wind and solar, which is typically between about 1 p.m. and 5 p.m. With higher power production from those renewables during the day, demand shifts.

“After sunset, when there is no solar on the grid, the net load rises substantially as people turn on lights,” Bloom said. “So the result is that, instead of having to dispatch thermals and hydro units to meet the peak load in the afternoon, they are dispatched to meet the net load, which is highest after sunset. ”

That kind of shift could have dramatic implications for power production factors like managing a workforce, which currently ties it hours to high power demand for non-wind and non-solar generators in the middle of the day.

‘System still worked’

NREL modeled what the power grid would look like on a daily basis in five-minute intervals over a year with 30 percent annual renewable power.

It considered unusual conditions, such as a six-hour hypothetical event in November when there was suddenly a major change in the wind forecast, a setting sun and high energy demand.

“The system still worked,” Bloom said.

Under the modeled scenarios, renewables provided closer to 50 percent during some periods and less than 30 percent at other times, depending on conditions.

The lab didn’t consider all the required capital costs of building new renewable energy infrastructure and transmission lines. It also didn’t consider policy incentives.

“The ability of the real system to realize these futures may depend more on regulatory policy and market design to incentivize the needed operating procedures,” said the report.

For example, NREL said it assumed hydroelectric energy, pumped storage and fossil fuel plants are willing to offer their generation at any time.

“If adequate short term opportunities and regulatory structures are not in place to incentivize this flexibility, resources may exit the market or prefer not to make their full flexibility available to the system operator,” said the document.

More coordination among regions, so that more renewable power could be bought and sold, would make higher levels of renewables easier, Bloom explained.

The study also signaled opportunities for technologies such as energy storage and demand response that can streamline the flow of power on the grid, according to NREL.

While the research did not consider many capital and construction costs, it did find that operating costs for the grid would decline about 30 percent once needed infrastructure was built.

The researchers analyzed much of the Canadian grid stretching east of Saskatchewan. They did not factor in other renewables such as geothermal.