Microgrids + mass transit = resilient mobility in a future clouded by climate change

Transit agencies can use microgrids to cleanly power electric buses and other systems during blackouts, but they’ll likely need help building them.
By Gordon Feller

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The bipartisan infrastructure package unveiled by senators this week includes $7.5 billion to build a new national electric vehicle charging network, $39 billion to upgrade public transit systems and $7.5 billion for zero- and low-emissions buses and ferries.

One major challenge unites these multibillion-dollar transportation electrification plans: energizing those assets with clean electricity.

Microgrids — combinations of solar PV, batteries, on-site generation and the technologies to integrate their operations with EV charging and the larger grid — could play a key role in transitioning public transit to clean power. The infrastructure package specifically mentions microgrids and would provide significant funding for microgrid components. The Biden administration has also expressed support for microgrids.

Well-designed microgrids can significantly cut the upfront and ongoing costs of switching from fossil fuel to electric vehicles for bus depots, airports and other public transit hubs. They can also optimize the value of on-site renewables, energy storage and backup generation.

A small number of public transportation agencies have developed microgrids for their systems. The numbers are growing, with the Massachusetts Bay Transportation Authority and Montgomery County Department of Transportation in Maryland among the new entrants.

Eight microgrids for use by public transit agencies are planned or operational in the U.S. today, according to Isaac Maze-Rothstein, an analyst with research firm Wood Mackenzie. Most have received state funding to support the additional infrastructure and technical expertise involved in solving the challenges of charging a fully electric bus fleet and providing resilient operations during a power outage,” he said.

Microgrids are costly and complicated endeavors that rely on coordination with multiple actors, including EV makers, regulators, utilities and technology vendors. Without such orchestration, they are doomed to fail to launch on time and on budget.

What makes up a successful public transit microgrid?

The next wave of microgrids needs to be designed and operated in ways that maximize value to both investors and the environment.

Eventually, standardization could turn these bespoke efforts into models that could be replicated across the country. That’s the view of Ruby Heard, director of Alinga Energy Consulting and principal author of Microgrids and Their Application for Airports and Public Transit, a report commissioned and published by the U.S. Transportation Research Board in 2018.

According to Heard, there are four key advantages of such projects:

  • Increased power system resiliency and reliability. The ability to island the power system in the event of a utility power outage or disturbance and continue to supply load from on-site power systems.
  • Energy cost savings. Reduced energy costs through increased self-consumption of renewable energy by utilizing on-site storage assets.
  • Increased renewable energy penetration. Increased self-consumption of renewable energy by utilizing on-site storage assets.
  • Flexible and modular energy systems. Microgrids can be designed and built out in stages and can be flexible for future expansion, while utility connections can be costly and slow to upgrade.

Most microgrid installations to date are focused on increasing transit system resiliency during times of grid instability. Transit agencies traditionally store emergency fuel on-site in case of supply disruptions. Microgrids provide the equivalent of emergency fuel for an all-electric fleet, Maze-Rothstein said: Batteries, solar and a possible backup generator can support operations at a bus depot during a power outage.

Heard highlighted the fact that microgrids are working all the time to reduce energy costs. Diesel generators, by contrast, are more of an insurance policy”; they entail installation and maintenance costs and only provide benefits in the event of an outage. They also tend to be smaller, localized units that support limited loads, and they require a constant supply of fuel, which may not be available during a disaster.

Utilities can benefit from customer microgrids if they can delay or eliminate the need for costly upgrades to utility infrastructure, for example, due to capacity shortages or constraints in the network,” said Heard. Transit agencies switching to electric buses can face multiple megawatts of new load that can bring significant infrastructure upgrade bills. By using a microgrid to reduce those costs, agencies could then make a case to share a portion of the development costs with their utility, she said.

Additional revenue streams could be garnered by providing grid services, such as frequency regulation and voltage support, she added, although these opportunities aren’t available to all customers.

But transit agencies aren’t utilities or energy market experts, and they are likely to turn to experts in microgrid design and operations to manage the technical, financial, regulatory and organizational challenges involved, Heard said.

It can be difficult to determine the value proposition for resilience and reliability in many industries, and Heard thinks that there’s a clear lack of this type of analysis in the public transportation sector.”

One example of a quantified economic loss due to a power outage occurred in 2017 at Hartsfield–Jackson Atlanta International Airport. An 11-hour blackout resulted in more than 1,000 canceled flights, 30,000 affected travelers and a cost to Delta Airlines of approximately $40 million — a loss the airline planned to recoup from either utility Georgia Power or the airport.

Microgrid developers weigh in on the public transit opportunity

Deploying a microgrid as part of a public transport system’s electrification is a complex and expensive undertaking that many public transportation agencies can’t afford to carry out on their own. But a host of firms providing key services in this arena are stepping in.

One of them is Siemens, the German industrial giant with a sprawling microgrid services business. While its executives are busy pursuing opportunities in the U.S., the company’s success stories are mainly in the European Union and Asia. Beyond charging solutions for e-buses, Siemens also provides Smart Infrastructure” solutions, such as the systems for a microgrid to power the e-bus fleet in the city of Ostrava in the Czech Republic. The purchase order includes software to automatically adapt the charging processes to the bus schedules and to optimize energy consumption, with operations scheduled to start in mid-2022.

As the devastating impacts of climate change continue to mount, transit agencies are increasingly concerned about natural disasters, rolling blackouts from storms, heat waves, wildfire risk and the variability of energy supply, said John DeBoer III, head of Siemens’ Future Grid and Global eMobility Solutions business. Microgrids are a natural way to address these concerns, especially those grids that include on-premise renewable generation and storage solutions.”

Bus and fleet operations have never required deep know-how in energy and electricity, however, and buying electric vehicles and chargers carries a capital burden that’s universally challenging, especially when presented in the context of Covid’s impacts on budget and operations,” he said. With the rapid transition to electrified transport, these new competencies must be developed or outsourced.

Engineering firm Black & Veatch has designed and built microgrids around the world, including one powering its global headquarters in the Kansas City metro region. It’s also worked with transit agencies in Stockton, Calif. to assess solar and battery solutions to support its growing electric bus fleet, and in Vail, Colo. to redesign the city’s electrical infrastructure to support its conversion to electric buses.

Randal Kaufman, sales executive for Black & Veatch’s transformative technologies business, agreed that there’s definitely an opportunity for partnerships” in the public transit microgrid space. Transit agencies may have the upfront capital, but Kaufman asks: What about the operations and maintenance to ensure those systems operate properly?”

Arup, a global engineering and design firm active in the microgrid space, is seeing the demand for electric buses in North America starting to pick up speed with improvements in vehicle performance and range, and an increased focus on carbon emission reduction,” said Geoff Gunn, the company’s lead for energy systems and zero-emissions vehicles in the Americas. But while an electric bus may drive its routes much as a diesel-fueled bus does, it faces a much lengthier refueling cycle when it returns to the depot.

A microgrid can use complex algorithms and forecasts to balance and optimize these charging demands while also ensuring that buses are charged in time to roll out as scheduled in the morning, incorporate maintenance needs and ensure electrical infrastructure is operating safely,” Gunn said. For example, a microgrid might generate on-site solar during the day and store this energy in a battery for use in the evening when the buses have returned from their routes, easing grid demand with carbon-free power.

In the event that utility power is lost, the microgrid might start on-site natural gas generators to provide resilient power to charge the fleet overnight, when solar is not available, thereby ensuring that all buses are at full capacity as scheduled the next morning. In this way, the microgrid can optimize the goals of energy cost reduction, carbon reduction and energy resilience, all without user intervention, Gunn said.

Alongside PXiSE and Vermont Energy Investment Corp., Arup designed the Martha’s Vineyard Transit Authority’s new microgrid for its electric bus fleet. The network will also include induction charging stations that recharge the buses while they are on their routes, allowing them to remain in service for their circuits of 200 to 300 miles per day without detouring to recharge.

As for managing the costs, microgrid or energy-as-a-service firms design, build, operate and maintain microgrids and sell their energy back to the owner, removing the complexity and risks for the transit operator. That helps reduce the burdens of upfront and ongoing costs to switch to electric buses, which cut air pollution, noise and ongoing maintenance costs compared to diesel buses.

State mandates such as those seen in California, federal and state incentives, and the growing push for decarbonization will lead to more agencies considering electric buses. The next step in the evolution of these systems is to build in standardization.

Currently, microgrids are bespoke, one-off solutions, with different pieces from different vendors all put together in different configurations. Standardization of communication protocols, equipment specifications, and operations will simplify the design and operation of microgrids, thereby reducing the costs. Given the sustainability, cost and resilience benefits of microgrids to support vehicle electrification, adoption will likely soon increase, with standardization to follow.

(Lead image courtesy of Valley Transportation Authority) 

With 40 years in Silicon Valley, reporting from more than 40 countries, Gordon Feller ’s 300+ published articles cover the full spectrum of energy/environment/technology issues.