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Energy Resilience in San Francisco and New York City

This has been the year of the disaster. Hurricanes, earthquakes, and wildfires have ravaged North America.

In addition to the terrible loss of life and property, impacted communities have struggled with the loss of energy. Electricity is the vital life force of a modern economy, and without it, everything grinds to a halt—communication systems fail, hospitals are evacuated, and people can even die.

While power outages can sometimes be quickly remedied, they can also last for weeks. Three weeks after Hurricane Maria decimated Puerto Rico only 16 percent of the island had power. Crews struggled to replace power lines, transformers, and substations.

Those facilities and residents that relied on diesel and gasoline generators as a source of back-up power faced interruption of fuel supply chains, making it hard to get enough fuel to last more than a few days.

Incidents like these have spurred cities to look more closely at how they plan for energy resilience in their emergency management preparations. Many turn to new approaches that use solar and battery storage technologies to provide greater reliability and economics than diesel generators.

A traditional grid-connected solar installation shuts off during outages, to avoid putting power onto downed lines. When systems combine solar with new inverters and battery technologies, they are able to “island” themselves, providing power to a facility during extended grid outages.

This resilient solar system avoids the fuel risk of gas or diesel generators, with the added benefit of providing services every day. It generates electricity when the sun shines and uses the battery to cut peak demand charges, creating an emergency backup system that helps pay for itself.

While there is enormous potential for this technology to meet a critical need, getting beyond the early adopters and into the mainstream for these projects can be challenging. Local governments first need to inventory and evaluate their emergency facilities with an eye toward resilient solar deployment. The best prospects must then be prioritized based on an analysis of the specific features and uses of a facility. However, these novel technologies can be difficult to finance since they may not be eligible for existing support programs.

Ideally, energy resilience planning should be done at both individual sites and at the community level. Macro-level planning allows solar+storage systems to be integrated at scale into emergency management plans. It can also enable the city to identify and address barriers to deployment, such as permitting and financing.

With funding from the U.S. Department of Energy Solar Energy Technologies Office and support from the Institute for Sustainable Communities, the City and County of San Francisco and Sustainable CUNY at the City University of New York have completed in-depth feasibility studies on how to provide electricity to critical facilities like police and fire stations, hospitals, and shelters. Other communities now have the opportunity to learn from these leading cities and to use the practical tools, educational materials, and software they have developed.


San Francisco’s Department of the Environment (SFE) examined the use of solar+storage systems at facilities throughout the city that would serve critical loads in times of emergencies. The research produced a mapping tool, a roadmap, and a best practices guide.

“Neighborhood resources like fire stations, community centers, and schools often become a place of operation for emergency response,” said Peter Gallotta, Department of the Environment spokesperson. “It’s critical to have backup power at these sites in the event of the next large-scale grid outage.”

Batteries are expensive and take up space in a facility, therefore they are rarely sized to power an entire building. Rather, for each facility, the team in San Francisco identified the “critical loads”—the lights, appliances, phone charging stations, and other absolutely necessary items that would require power in the case of an outage.

The project is intended to serve as a national model, so that other cities and counties can more easily integrate solar+storage into their emergency response plans. SFE has released a Resilient Solar and Storage Roadmap and the Best Practices Guide, with lessons learned geared toward other municipalities interested in energy resilience.

The project also developed, a free web-based tool that estimates both the solar and battery energy storage system size and physical space needed to meet the critical load of a facility. The tool is designed for building owners, energy professionals, and city departments to develop equipment sizing and get an idea of the physical space necessary before embarking on more detailed studies. It does not require solar expertise, and can be used for any building or facility type anywhere in the country.

“For many resource-strapped cities, it can be an expensive and time-consuming process of reviews, approvals, and requests for information just to get an idea whether such systems are suitable. This tool eliminates that step,” said Jessica Tse, Distributed Energy Resource Coordinator for SFE.

While San Francisco has backup generators at some critical facilities, Tse pointed out some major drawbacks with diesel and gas. “Diesel generators don’t provide any benefits during normal operation—they can be noisy and polluting, and of course they don’t work without fuel, and fuel supplies are often interrupted during a disaster,” she said. “Plus, they are so seldom used that they often don’t get maintained and then they don’t start up when needed.” On-site solar paired with batteries can provide power over an extended period in the event of an emergency and can also help meet daily power needs.

Many buildings in San Francisco have solar, but there are very few able to operate during grid outages using battery storage. By studying how to integrate both solar and storage as a package, San Francisco is creating greater energy resilience.

City University of New York (CUNY)

New York City is also rapidly advancing solar use, with over 100 megawatts deployed in the five boroughs and more under development. Both the city and state of New York have aggressive clean energy and climate reduction goals.

Much like San Francisco, most of the current solar installations are not equipped with smart inverters and storage capacity, leaving the city unable to harness this power during emergencies and blackouts. When Hurricane Sandy hit five years ago, the 672 solar arrays in New York City at that time were unable to provide power during the outage.

CUNY’s own facilities were used as emergency shelters for almost a third of the city’s 9,000 evacuees, but like other facilities in the city, they faced fuel shortages that affected vehicles, backup generators, and buildings.

“Solar could have been used to help power critical loads across the five boroughs on the sunny days during the blackout – and storage could have helped around the clock,” said Tria Case, University Director of Sustainability and Energy Conservation for CUNY.

Now with more than 12,000 solar installations in the city, attention is shifting to storage. “We are working on a streamlined path for storage as well, so New Yorkers have more resilient energy options,” Case said.

Hurricane Sandy showed the importance of integrating distributed generation and storage into emergency and resiliency planning, spurring Sustainable CUNY to convene a “Smart DG Hub” for local, regional, and federal agencies and stakeholders.

The collaborative worked to streamline costs and create scalable, replicable models for communities across the country. CUNY created a set of reports and factsheets for installers, utilities, policymakers, and consumers about resilient hardware and design and the economics of solar+storage systems.

In 2017, Sustainable CUNY released the New York City Resilient Solar Roadmap, a five to seven year strategic plan addressing issues around hardware, software, economics, and policy. In NYC, the most significant barrier to solar+storage projects has been permitting. Because batteries are a new technology, it was unclear which agencies needed to issue permits and what the permit requirements would be. To help clarify the process, CUNY produced a permitting and interconnection guide for storage systems.

“We see the guide as a vital first step, however our work is ongoing,” Case said. “Permitting agencies, fire departments, and the industry needed a framework to be able to understand this continually evolving technology field, and that’s why CUNY, as an objective and trusted third party, leads these efforts.”

CUNY is working with local officials to implement streamlined permitting under a grant from the New York State Energy Research & Development.

nysolarmapThey are also expanding an online software tool, the NY Solar Map and Portal, to show current solar+storage installations in the city, and ideal locations for new systems to maximize the resilience benefits. An additional online calculator will analyze critical loads for residential consumers and provide a “first-floor” estimate of project size and cost.

In both New York and San Francisco, creating detailed strategies has led to a clearer roadmap on the opportunities, costs and benefits, and the policy and program changes that will lead to deployment.

“We found out, yes, solar plus energy storage at these facilities is feasible,” says Jessie Denver of the San Francisco Department of Environment. “So now we need to figure how do we actually pay for the projects and get them built.”

Written by Bentham Paulos, on behalf of the Institute for Sustainable Communities

Photo courtesy of Sustainable CUNY

About the Solar Energy Technologies Office
The U.S. Department of Energy Solar Energy Technologies Office (SETO) is a collaborative national effort that aggressively drives innovation to make solar energy fully cost-competitive with traditional energy sources before the end of the decade. Through SETO, the Energy Department supports efforts by private companies, universities, and national laboratories to drive down the cost of solar electricity to $0.06 per kilowatt-hour. Learn more.