USA: Planning for resilience in a renewable-dominated world

By Kathryne Cleary and Karen Palmer

In the United States, 29 states plus the District of Columbia have Renewable Portfolio Standards (RPS) that require a growing percentage of electricity sales to come from renewable resources over time. Some of these states, including California, New York, and Hawaii, require that 100 percent of electricity sales come from clean energy (mostly from renewables) within the next two to three decades. These ambitious laws are promising when it comes to achieving state climate goals, but considering related impacts on the electricity system will be imperative for successful attainment of these targets.

Renewables depend on variable weather conditions; therefore, their electricity generation is intermittent and often uncontrollable. Consequently, much research has been conducted on how to continue to provide reliable electric service to customers with a renewable-dominated resource mix. Proposed solutions typically include a significant expansion of energy storage capacity, a build-out of more transmission lines to transport renewable power from resource-rich geographic areas (e.g., solar from the southwest, wind from the north), and an expanded role for demand-side resources that adjust electricity usage patterns in response to the availability of renewable power (such as electric vehicles that charge during times of high renewables production). Several studies have looked at how to reliably operate a renewable-dominated grid using these solutions and found it to be possible (see Papaefthymiou and Dragoon 2016, Esteban and Portugal-Pereira 2014, and Kroposki 2017).

Another potential issue that receives far less attention, however, is how to keep the grid resilient, given a high penetration of renewable resources. In this context, resilience refers to the ability of the grid to resist and quickly recover from low-probability, high-impact events. The body of research surrounding grid resilience today finds that these low-probability, high-impact events are typically natural hazards, such as extreme weather, strong storms, and flooding (see Grid Strategies Report).

Studying and planning for resilience within the context of a renewable-dominated electric grid is important for a few reasons:

• Increased Physical Vulnerability: While renewable energy systems may have some resilience advantages due to their wide geographic distribution (see Union of Concerned Scientists), they can be more physically vulnerable to extreme weather, relative to traditional fossil fuel power plants, due to their exposure. Offshore wind, for example, is particularly vulnerable to hurricanes and high wind speeds (see DOE), and these events could potentially permanently damage generating capacity.
• Increased Reliance on Transmission and Distribution: Extreme events that cause prolonged outages normally impact distribution and transmission lines. An increased reliance on renewable energy resources may create an increased dependence on distribution lines, since most small renewables produce power locally on these power lines rather than at centralized power plants. Transmission lines may also grow in importance, given the need to transmit renewables over long distances for reliability purposes, as mentioned above. An increased reliance on both distribution and transmission infrastructure in a renewable-dominated grid could therefore exacerbate the consequences of extreme weather events on the grid.
• Expanded Definition of “Extreme” Event: A renewable-dominated grid will also be susceptible to more types of weather events, since these energy sources, by definition, depend on the weather. For example, an “extreme” weather event may no longer just refer to phenomena like extreme storms but also apply to unusually prolonged periods of no sunlight or excessive wind that might cause a large portion of the generating fleet to be out of operation for a period of time. Consequently, grid operators and local utilities would need to be prepared for more types of extreme events in order to keep the lights on.
• Other Decarbonization Goals: In addition to pursuing renewable energy goals, several states are also beginning to push for the electrification of vehicles and buildings (e.g., heating, cooling, water heating) as a way to decarbonize other sectors of the economy. Doing so will make society even more dependent on electricity, and therefore even more vulnerable to potential power disruptions.
• Climate Change: Climate change is expected to exacerbate all of the above-mentioned risks, thus making the study of resilience even more imperative.

RFF recently worked with the New York State Energy Research and Development Authority (NYSERDA) to identify research opportunities with respect to resilience, particularly in light of New York’s emergent energy policy, which will drive the state’s electricity sector to reach 70 percent renewable energy by 2030 and 100 percent clean energy by 2040.

RFF’s efforts found that, while several existing studies address how to improve the resilience of the grid of today, which contains a mix of fossil and non-fossil power generation, little research exists on the resilience of a decarbonized grid in light of many state policy goals. With these opportunities in mind, we identified several areas of research that could be useful for the future.

These research areas include (a) characterizing how risks to resilience will change as the penetration of renewables grows, particularly with respect to the physical vulnerability of renewables; (b) determining the role that distributed resources will play in both contributing to and weakening grid resilience; and (c) identifying which preventative measures should be taken to improve system resilience, while considering the costs involved and the societal benefits of avoiding an outage.

States face different types of climatic risks in the future. California, for example, may face increased drought, which could impact hydroelectric generation, while New York could face increased risk from hurricanes that could impact new offshore wind plants. States with high renewable goals could therefore likely benefit from increased resilience research that is tailored to their specific risks, along with efforts to improve grid resilience in the long term.