The National Renewable Energy Laboratory published a report in June 2016 that examines the resiliency value of pairing solar and storage. The report, New York Solar Smart DG Hub-Resilient Solar Project: Economic and Resiliency Impact of PV and Storage on New York Critical Infrastructure (Resilient PV and Storage Report), is based on a study jointly conducted by NREL and the City University of New York (CUNY). It is part of a larger initiative run by Sustainable CUNY, the NY Solar Smart Distributed Generation (DG) Hub - Resilient Solar Project. The Resilient PV and Storage Report makes the case for using solar combined with storage to provide resiliency in addition to reducing greenhouse gases and lowering energy costs.
The New York Solar Smart DG Hub-Resilient Solar Project
Sustainable CUNY is responsible for a number of different initiatives in New York City and State to support the adoption of solar. Most recently, Sustainable CUNY launched the NY Solar Map and Portal that provides resources for using solar technology. Sustainable CUNY is also coordinating efforts in New York City to design a more resilient distributed energy system.
The backup generation capacity for New York City’s critical infrastructure is insufficient to fulfill the city’s needs during a grid outage. In addition to the current size of the city’s backup capacity being insufficient, what exists needs to be updated. During Hurricane Sandy, many of the city’s backup generators, such as generators located at some area hospitals, failed to operate.
Sustainable CUNY’s work to design a more resilient New York City distributed energy system includes helping stakeholders determine how solar technology may be used effectively during a grid outage. Although most of New York City’s solar arrays suffered little to no damage after Hurricane Sandy, they weren’t designed to work independently of the grid to provide the power during the outage. Sustainable CUNY’s NY Solar Smart DG Hub - Resilient Solar Project is working with stakeholders on strategies, such as combining solar with storage, that will enable the use of solar power to build a resilient energy supply that could function separately from the grid.
Overview of the Report on the Economic and Resiliency Impact of PV and Storage on New York Critical Infrastructure
The goal of the PV and Storage Report is to help stakeholders, such as building owners and managers, the solar industry, and policy makers, understand the economic and resiliency benefits of combining solar and storage. Diesel powered generators currently provide much of New York City’s emergency power. However, adding solar and storage can reduce the amount of fuel consumed and extend the system’s ability to operate for a longer duration.
Also, solar without storage can only function when an electric grid is available. However, solar combined with storage is able to operate with the grid or independently of the grid in the event of a power outage. Although there have been other studies analyzing the benefits of combining solar and storage, they do not examine the economic value of resiliency. By attempting to place a monetary value on resiliency, the avoided cost of a power outage, there is support for the added cost of combining solar with storage.
The study underlying the PV and Storage Report looked at three specific New York City critical infrastructure sites to evaluate the economic and resiliency benefits of solar and battery systems. Each of the sites represented one of three categories of facilities that are essential during a storm: fire stations, cooling centers, and coastal storm shelters. The study sites included a school that functions as a coastal storm shelter, a Brooklyn fire station, and a senior center that serves as a cooling center. Both the school and cooling center are located on a network grid, while the fire station is on a radial grid which is less reliable than the network grid. For each site, the PV and Storage Report evaluated the utility rate structure, load data from equipment needed to operate during an outage, existing backup power, and solar suitability.
The study considered different methodologies for valuing resiliency and decided to use the U.S. Department of Energy’s Interruption Cost Estimator (ICE) calculator. The ICE incorporates information such as the customer type, location, industry category, the average frequency of interruptions (SAIFI) and average duration of interruptions (CAIDI). Much of the necessary data was made available by Con Edison, the area electric utility. The PV and Storage Report also considered the costs of solar and storage in New York City.
For each site, the PV and Storage Report examined four different scenarios:
Scenario 1: solar and storage only sized for cost savings when grid-connected
Scenario 2: solar and storage system sized to sustain critical loads during outages
Scenario 3: solar, storage, and diesel generator to sustain critical loads during outages
Scenario 4: diesel generator to sustain critical loads during outages
Report Conclusions
The PV and Storage Report’s study found that solar and storage can provide resiliency and cost-savings at each of the three sites. However, given that a radial grid is more likely to suffer outages than a network grid, the greatest cost-savings would be achieved placing solar and storage at the fire station, the site on the radial grid.
The study showed that both solar combined with storage and a hybrid system (combining solar, storage and a diesel generator) can provide the same resiliency benefits as a stand-alone diesel generator while resulting in a better life-cycle cost. However, the hybrid system is the most cost-effective solution for responding to outages.
The study demonstrated that in addition to improving resiliency, storage can also be used for on-going cost savings, for example, during peak load times when there are higher rates for electricity from the grid. Yet, if the system is only sized to achieve cost savings, it will have limited resiliency benefits. The report showed that a system with solar and storage sufficiently sized to support critical electrical loads during an outage may cost more than one just designed for cost saving. However, the larger system becomes a good investment once the resiliency value is factored in.
The report notes that regulatory changes may be necessary to allow for solar paired with storage to work as emergency power. Hopefully, the PV and Storage Report’s findings will convince policy makers and other stakeholders that combining solar and storage is a good investment and can help New York City achieve greater resiliency as well as reach its goals for solar adoption.
Efforts to incorporate energy storage are beginning to happen. Just last week, New York City Mayor de Blasio set the city's first ever target for energy storage at 100 megawatt-hours by 2020.
