Microgrids can be a building block to more resilient communities

Insights from two microgrid feasibility studies
July 28, 2022 by Zack Mast

Cities have created climate action plans to reduce carbon emissions and make their communities more resilient in the face of a growing climate crisis. Any plan to boost community resilience must ensure the continuity of public services so that people can access the resources they value most in a crisis. 

Microgrids can help cities achieve their clean energy goals while maintaining critical services when the greater electric grid goes out. Beyond keeping services running, microgrids can provide additional benefits that make for more resilient communities—but only if a city fully understands the needs of its residents.

A tale of two microgrids: Our feasibility studies in Wisconsin

Slipstream recently completed feasibility studies on existing sites in two Wisconsin cities, Madison and Sun Prairie. Each city had its own reasons for exploring how a microgrid might help it meet its climate and resiliency goals.

Madison: A microgrid to support critical city services

Wisconsin's capital wants to run its city operations on 100% renewable energy by 2030. The city plans to convert two of its adjacent facilities into an interconnected microgrid. Each location houses critical city functions—including snow removal, road maintenance, and sewer maintenance—plus office support for medical, firefighting, and GIS services.

The site already has several distributed energy resources (DERs), giving it a head start on its conversion to a microgrid. The city also plans to convert its fleet of over 230 vehicles to 100% electric within the next 15 years, so the microgrid will have to account for the added EV charging capacity.

Sun Prairie: A microgrid to power a Community Resilience Center (CRC)

Last year Sun Prairie approved a conceptual design to expand and renovate the Sun Prairie Public Library, with a ribbon-cutting slated for 2024. Sun Prairie officials plan to expand the library's current emergency and community capabilities to meet the city's needs well into the future.

The proposed Community Resilience Center (CRC) would integrate solar and storage with microgrid controls to serve critical loads such as HVAC, lighting, and the Sun Prairie Media Center. With these improvements, the library could stand as a beacon of sustainability while providing benefits to residents, including refrigeration and emergency heating and cooling.

The benefits of a microgrid are even greater when you include societal and health factors in the analysis.

You can read the full slate of recommendations to each city in our reports at the links below.

We came away from these studies with insights on what all municipalities need to consider when evaluating a microgrid to build resiliency into a climate action plan.

What to consider in an evaluation of a municipal microgrid

Make sure officials and community members understand the larger climate and resilience plan. 

City officials should understand the reasons for installing a microgrid, including how the proposed site is important to climate resilience. A community climate and resilience plan should incorporate input from everyone, especially the members of the community. 

Anticipate the full scope of critical needs in an emergency.

Imagine this scenario:

A blizzard dumps snow and fells trees all over a city, wiping out power for at least a day. Emergency services stay online thanks to a savvy climate action plan that included a microgrid. In response to the outage, the site diverts all EV charging capacity to the city's plows and fire trucks. After all, it's not going to need the garbage trucks for a while. 

"But wait!" says the disposal fleet manager. "How else are we gonna pick up all these downed trees?"

Such a potential oversight came up in a discussion among Madison officials, who might never have considered it without the right collaboration. Cities should communicate across departments to understand the full scope of responsibilities and usage patterns.

In general, there are more variables than you think. 

You can very easily do the cost/benefit analysis of installing a microgrid under normal operations. But any evaluation must account for when things go wrong. In a crisis, the variables become more unpredictable. 

Our microgrid feasibility checklist

For cities/municipalities considering a microgrid, the following checklist should help you cover most of the analysis. Use this as a starting point to discuss the needs of your city/site—and add new variables as you think of them.

Identify all community stakeholders and engage them in the plan.

  • Prioritize community member input upfront. Build a plan that adequately addresses the needs of citizens and fully quantifies all the benefits of community resilience—not just a site's energy needs. 

Design with a microgrid in mind during renovations and construction

  • You don't have to convert everything to a microgrid all at once. Consider installing microgrid components piece by piece based on the individual value they bring—with the goal of leaving the financial and physical space for a battery when you are fully prepared.

Consider energy efficiency and demand management to decrease solar and storage capacity needs

  • As part of an evaluation of the microgrid installation, consider ways to improve efficiency in the building, such as HVAC system upgrades, or ways to manage demand through advanced lighting controls.

Consider the battery replacement strategy in the bidding process

  • We've identified three strategies that depend on your specific needs and budget:
    • Replacement: Plan to replace the battery after its lifespan (approximately 10 years). Highest future cost.
    • Augmentation: Add new cells periodically to offset the degradation of older cells (augmentation). This should keep replacement costs steadier over time.
    • Oversizing: Install an oversized battery at the outset to account for degraded capacity over time. Higher upfront cost, but lower cost over time.

When sizing DER components, determine the critical loads at the facility

  • People familiar with the building and its critical loads are key players in the success of a microgrid. 

Include resiliency benefits in calculations of cost-effectiveness

  • These benefits may vary depending on a city's priorities—and they can often be intangible. We recommend more research on how to incorporate community-driven values of resiliency into cost analyses.

Future considerations: What we still want to know

Our scope of work in these studies did not cover every aspect of a microgrid, especially when we evaluate how it benefits community resilience. We recommend more research to answer the following questions:

How do we quantify community-driven values of resiliency?

In these studies, we applied an assumed dollar value to many of the social benefits that come from added resiliency. However, we probably underestimated the direct health benefits from access to refrigeration, electricity, and a conditioned space. Future studies might also want to quantify the quality-of-life benefits of a Community Resilience Center—such as working phone chargers.

Without engaging community members directly, we miss critical information to evaluate how a microgrid can build a city's climate resilience.

The original scope of our studies didn't include community engagement, so we weren't able to talk to members of the community to ask what they would value during emergency situations—or to give them an opportunity to ask questions or share concerns during and after implementation. The input of city staff was very valuable, but without engaging community members directly, we were missing critical information to evaluate how a microgrid can build a city's climate resilience.

The scope of any future study should include an equity lens at the very beginning. We would include time and resources for meaningful community engagement to strengthen our findings.

How much charging capacity does a city need to maintain its EV fleet during power outages—and for how long?

How much charging capacity do we need to keep the city's fleet moving when the power goes out? As far as we're aware, there's no research on this specific question. We recommend more studies to analyze the capacity needed for a microgrid to fully support an all-electric fleet in emergency scenarios.

Are sites with existing backup generators an opportunity to scale microgrids more quickly?

A lot of municipal facilities across the country currently have backup (diesel) generators. But a generator is only useful during power outages, whereas converting a generator to a BESS with a PV array also provides benefits the rest of the year.

We could come up with a feasibility framework for any given municipal site with a diesel generator. That would help us create a roadmap for cities that already value resilience to explore microgrids at scale.

Reports and other resources

Download the full reports on these studies for more on the tool selection process and the results of our analysis:

Read more about our work with building Resilient Communities.

See our work on grid-interactive efficient buildings (GEBs) that enhance grid reliability and resilience.