Thu. Mar 23rd, 2023
New analysis shows the eastern US can handle 30 percent renewable electricity

As the US moves toward greater reliance on renewable energy, most of the action has been on the West Coast, where both Hawaii and California have set goals of 50 percent renewable energy by 2030. But to keep up the pace, New York recently announced that it too aims to reach 50 percent renewable energy sources by that date.

As in California, that level of intermittent renewable energy can pose a challenge to the power grid. While New York has its own power grid and can control power there, the state is highly integrated into surrounding networks (including Canada) and the Eastern Interconnection, which extends into western Kansas and Saskatchewan. This means that the grid management challenge in New York is likely to cause tensions that extend far beyond its borders. However, a new study from the National Renewable Energy Lab (NREL) indicates that the Eastern Interconnection is likely up to the task, but may need new incentives and regulations to function efficiently.

NREL did not specifically look at the New York case; rather, it focused on getting the entire eastern interconnection on 30 percent wind and solar energy. But that seems to fit New York’s goals. Unlike California, the Empire State counts hydropower toward its 50 percent goal, and it currently derives just under 20 percent of its power from hydropower. So 30 percent wind and sun is about what New York plans to do; NREL just applied it to the entire Eastern Interconnection.

To analyze the impact, NREL produced a computer model of the entire Eastern Interconnection capable of balancing supply and demand at five-minute intervals. NREL ran the models under multiple scenarios. Two were controls that either freeze wind and solar at 2012 levels, or allow them to grow until they meet current renewable energy standards of all states in the interconnection. There were also two 30 percent wind/sun scenarios. One of these met the requirements by placing all wind and solar sources within the interconnection within the same regional grid. The second allowed electricity to be shuffled across the regional grids to meet demand.

The most obvious change is that the use of fossil fuels is decreasing. The capacity factor of a coal-fired power station (how much the power station produces compared to how much it could potentially produce) is about 75 percent in the base case. It drops to about 50 percent in the high renewable energy scenarios. These plants also spend about half of their time generating the minimum possible power. Natural gas plants, which can go up and down quickly, currently have a capacity factor of about 50 percent; that drops by half with high renewables. For both coal and gas, the number of stops, starts and changes in output increases significantly.

The other thing that changes is when these plants are active. Currently, these plants tend to ramp up electricity production during the day to meet peak demand. In the scenarios with a high degree of renewable energy, that peak is largely achieved by solar energy. As a result, fossil fuel power plants are often used intensively in the morning and evening; in windy periods they may not rise at all, as solar and wind can peak at more than 60 percent of demand.

Another change was specific to the scenario in which we build reinforced connections between the regional grids, making it easier for sustainable electricity to flow over the Interconnection. Currently, much of this capacity is used to bring electricity from Hydro Quebec to the southern US. But if interconnections are strengthened, photovoltaic sites could be built in the southern US, where they are more productive. At this point, the Southern Grid (SERC) is starting to send a lot of electricity north, and Hydro Quebec is exporting less.

And overall it works: “We show that the system can be deployed and shipped to balance the system in a variety of conditions, including high load, high [variable generation]and during extreme ramping conditions.” Or at least could be work. That optimistic assessment is followed by an important caveat: “We have not examined whether transmission and generation operators will have sufficient incentives to provide the necessary ramping, energy and capacity services for futures such as those we have studied.”

In other words, it must be in the financial interests of power producers to operate their power stations in a way that meets the needs identified here. Otherwise the entire system could fail. And right now, those producers often base their plans on the past, older technology that hasn’t reached end-of-life, and a regulatory environment built to ensure reliable power from non-intermittent sources.

Unless financial and regulatory incentives change, producers have no incentive to necessarily provide the flexibility they are capable of. The NREL report also notes that in a worst-case scenario, producers could exit the market completely.

Of course, New York has one of the most aggressive renewable energy plans on the East Coast right now. But as wind and photovoltaics continue to see price declines, the economy may steer things more aggressively than some states had planned.

By akfire1

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