Report: Regional power grid able to shift toward gas

More renewable sources won’t hurt reliability

The electric grid operator for Pennsylvania and 12 other states said in a report Thursday that it can accommodate massive shifts toward natural gas-fired generation and can incorporate significantly more renewable sources like wind and solar without sacrificing reliability.

Valley Forge-based PJM Interconnection found no upper limit to the amount of natural gas generation that could be reliably introduced into the grid mix, finding that electricity portfolios relying on up to 86 percent natural gas capacity would remain reliable.

But the study cautioned that the risks of over-reliance on natural gas may have less to do with power plants’ physical capability to provide reliable service and more to do with factors not considered in the analysis, like economic, policy, infrastructure and weather uncertainties.

“When you look at a penetration of 86 percent natural gas, while we don’t see — based on our metrics — any day-to-day issues with reliability, have we now hit the point where we’re putting too much reliance on one fuel type?” asked Michael Bryson, vice president for operations, who led the study.

The analysis found that PJM could remain reliable “with unprecedented levels of wind and solar resources” as long as they are mixed with other types of power generation, like natural gas or nuclear, that can balance their reliability weaknesses.

The study found a marked decrease in reliability for generation portfolios heaviest in wind and solar, suggesting that there are limits — probably around 20 percent of operational capacity — to how much of those types of intermittent renewables could be integrated

into the grid without sacrificing reliability. The analysis did not try to measure the effects of potential advances in battery storage or distributed energy.

The regional grid operator tackled reliability issues because the recent growth in natural gas and renewables generation, coupled with coal-fired and, potentially, nuclear plant retirements, have raised thorny questions about a secure energy mix.

“Stakeholders have questioned whether the system is losing too many resources which historically have been referred to as ‘base load’ generation capability and whether the system is — or could become — so dependent on natural gas or renewable resources that operational reliability is adversely impacted,” the study said.

In short, the answer is, it depends.

The analysts developed 360 variations of potential electric generation portfolios and identified those that are best able to meet reliability measures during normal conditions and periods of extreme hot and cold weather.

The portfolios with the best reliability scores tended to be those dominated by natural gas, nuclear and coal.

Portfolios with the largest shares of wind and solar tended to have the lowest reliability scores.

The study found that a reliable energy mix is not necessarily the most diverse one, even though diversity does help ensure the grid’s resilience when it is tested by rare extreme disturbances.

When 98 of the ideal portfolios were tested to see how they would perform in a simulated cold weather event, like the polar vortex in January 2014, only 34 were found to be resilient. Natural gas generation would be particularly sensitive to such a high-demand, cold-weather shock.

Those sorts of resiliency issues, which are not incorporated into conventional grid reliability studies, will become the focus of future PJM investigations, Mr. Bryson said.