As the US transitions to an increased reliance on renewable energy, most of the action has been on the West Coast, where both Hawaii and California have set targets of 50 percent renewable energy by 2030. But, in an effort to keep the pace, New York recently announced that it, too, would be aiming to get to 50 percent renewables by that date.

As in California, that level of intermittent renewable energy can pose a challenge for the grid. While New York has its own grid and is able to regulate the power there, the state is heavily integrated into the surrounding grids (including in Canada) and the Eastern Interconnection, which extends as far west as Kansas and Saskatchewan. This means New York's grid management challenge will probably create strains that extend well beyond its borders. A new study from the National Renewable Energy Lab (NREL), however, indicates that the Eastern Interconnection is probably up to the task, but may require new incentives and regulations in order to function efficiently.

NREL didn't look at New York's case specifically; rather, it focused on getting the entire Eastern Interconnection at 30 percent wind and solar power. But that turns out to be in keeping with New York's goals. Unlike California, the Empire State counts hydropower toward its 50 percent goal, and it currently gets a bit under 20 percent of its power from hydro. So, 30 percent wind and solar is about what New York plans to do; NREL simply applied it to the entire Eastern Interconnection.

To analyze the impact, NREL produced a computer model of the entire Eastern Interconnection that's able to balance supply and demand at five minute intervals. NREL ran the models under multiple scenarios. Two were controls that represented either freezing wind and solar at 2012 levels, or allowing them to grow until they met the current renewable standards of all the states in the Interconnection. There were also two 30-percent wind/solar scenarios. One of these met the requirements by putting all the wind and solar sources inside the same regional grid within the interconnection. The second allowed electricity to be shuffled among the regional grids in order to meet demand.

The most obvious change is that fossil fuel use goes down. The capacity factor of a coal plant (how much the plant produces compared to how much it could potentially produce) in the baseline scenario is about 75 percent. It drops to about 50 percent in the high-renewable scenarios. These plants also spend about half their time generating the minimum possible power. Natural gas plants, which can ramp up and down quickly, currently have a capacity factor of about 50 percent; that drops in half with high renewables. For both coal and gas, the amount of stopping, starting, and changes in output increases considerably.

The other thing that changes is when these plants are active. Currently, these plants tend to boost production of electricity during daylight hours to meet peak demand. Under the high-renewables scenarios, that peak is largely met by solar. As a result, fossil fuel plants tend to be used heavily during the morning and evening hours; in periods of high wind, they may not cycle up at all, as solar and wind could peak at over 60 percent of demand.

Another change was specific to the scenario in which we build enhanced connections among the regional grids, allowing renewable power to flow more readily across the Interconnection. Currently, a large amount of this capacity is used to bring electricity from Hydro Quebec south into the US. But, if interconnects are strengthened, then photovoltaic sites can be built in the US South, where they're more productive. At this point, the southern grid (SERC) starts sending a lot of electricity north, and Hydro Quebec exports less.

And, in general, it works: "We show that the system can be committed and dispatched to balance the system in a variety of conditions, including high load, high [variable generation], and during extreme ramping conditions." Or at least it could work. That optimistic assessment is followed by a significant caution: "We did not investigate whether transmission and generation operators will have sufficient incentives to provide the necessary ramping, energy, and capacity services for futures like the ones we studied."

In other words, it has to be in the energy producers' financial interests to operate their plants to meet the needs identified here. Otherwise, the whole system could come up short. And right now, those producers often base their plans on past history, older technology that hasn't reached end-of-life, and a regulatory environment that was built to ensure reliable power from non-intermittent sources.

Unless the financial and regulatory incentives are changed, producers have no reason to necessarily provide the flexibility they're capable of. The NREL report also mentions that, in the worst case, producers could leave the market entirely.

Of course, right now, New York has one of the most aggressive renewable energy plans on the East Coast. But, as wind and photovoltaic energy are continuing to see price drops, economics may drive things more aggressively than some states have planned for.