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The Power of Microgrids


The aftermath of Superstorm Sandy reminds us of the fragile nature of the U.S. power infrastructure and its inability to withstand high levels of stress. Moreover, once infrastructure is broken, the time required to repair it greatly compounds a lack of safety, comfort, and efficiency. Even considering highly evolved processes—utility crews from around the nation converging on affected areas—the days and weeks that follow are very costly to cities and communities.

The widespread destruction to the grid caused by Sandy is reinforcing creative thinking about resilience. Now that power has been restored, rebuilding can accelerate in the hard hit areas, especially New York and New Jersey. Governors Andrew Cuomo and Chris Christie say that we need to do it smarter; and they couldn’t be more correct. Leveraging this opportunity to deploy even smarter grid technologies that increase energy security, improve efficiency, and often improve air quality, too, is essential. There are cost-effective solutions that can deliver multiple benefits at scale.

Microgrids are essentially miniature versions of the electric grid that include localized generation and storage. They offer the capabilities to “island” and run parallel to the macrogrid or sustain energy delivery from local generation if the grid is not available. Offering reliability and stability as well as renewable integration, microgrids command a harder look.

The concept of the microgrid goes back to 1882 when Thomas Edison developed the first power plant—the Manhattan Pearl Street Station—as the first source of power before the electric grid as we know it was even established. The technology has certainly evolved since then, but the fundamental concept remains the same.

Safety and prosperity depend on the modern grid more than ever, but it is routinely rocked by natural disasters. Volatile weather may cause power outages of up to two weeks. These outages cost millions of dollars and put lives at risk. In fact, the Department of Energy (DOE) estimates that the U.S. spends more than $26 billion annually on outages of more than five minutes. While the U.S. grid is good, its reliability does not compare well to other industrialized nations in Europe and Asia. Backup generation helps, but too often the emergency fuel is exhausted before the grid is restored.

For reliability, a compelling feature of microgrids is their ability to island, or separate from the grid. Localized and increasingly clean generation allows the microgrid to provide power to campuses and small communities independent of a macrogrid. These stability islands can keep whole communities of rate payers warm, fed, and safe. Importantly, microgrids allow first responders to start their work sooner. Of course, emergency services, communications, shelters, fuel movement, and supermarkets cannot tolerate weeks without the grid. Community microgrids can be a super set of emergency power systems that use and ration this distributed generation through pre-arranged plans and automated controls.

After Sandy, universities such as New York University and Princeton demonstrated how well-managed cogeneration systems kept campuses running for nearly two days. Other innovators are demonstrating the power of microgrids, too. Jose Marotta, senior engineer at Tampa General Hospital, has been to school on hurricanes. After all, Florida experienced more than four hurricanes in 2004. Responsible for the large Level 1 trauma center and an 11 MW campus, Mr. Marotta, routinely watches the weather and grid conditions, islanding intentionally to protect the facility’s mission. Mr. Marotta’s team is not only improving the trauma center’s capacity, but also its fault tolerance from external and internal events. Application of modern power management and automatic controls makes his team’s work consistent and the system dependable.

A microgrid can be improved by fuel diversification. Tampa General’s microgrid may draw from grid power, diesel-fueled generators, and perhaps in the future clean, natural gas-fired cogeneration.

Cogeneration and emergency generation are increasingly used to anchor local renewable generation sources as well. Renewables that are always “on” are grid-tied, meaning they must go offline when the electrical grid is disrupted. When the microgrid islands, the anchor resource provides a stable source of voltage and frequency, which makes these grid-tied resources transition to microgrids. This happens regardless of macrogrid availability.

Other features of microgrids are sophisticated switching between diverse sources and “black start” capability. If power is disrupted, restoration of the ancillary systems providing lubrication, cooling, and starting current are necessary to restart generation or cogeneration.

By bringing generation closer to the loads, we can achieve a higher penetration of renewables, mitigating costly grid modifications to manage the intermittent nature of renewable energy. Diverse energy sources or energy storage can fill supply gaps due to a lack of sun or wind. Further, the storage element and its high-speed power electronics can make the microgrid more fault-tolerant.

Energy efficiency and project economics are being improved by gas-fired cogeneration, combined heat and power (CHP), and renewable energy:

  • Natural gas prices are less than one-third of recent peaks.
  • When a facility needs heat, the heat from local generation is far easier to deploy in the form of hot water or process heat.
  • Absorption chillers can be paired with CHP to cool data centers and buildings.
  • Localized generation mitigates the up to 7 percent electrical transmission and distribution losses reported by the Energy Information Administration.

Recent projects seek to further monetize microgrids through participation in the ancillary services market. By providing local power for peak demand and regulation services, microgrid owners are capturing credits and reducing rates.

But there is more to do. Permitting, codes, and standards must continue to evolve to enable the new generation technologies. Special rate structures for “certain power” must be approved by public utility commissions. The important work on IEEE 1547 Standard for Interconnecting Distributed Resources with Electric Power Systems must continue. It is important for more utilities to adapt to and embrace the microgrid momentum.

While upfront costs, pricing, and regulation are being managed, increased collaboration with utilities, public utility commissions, and public-private partnership will help the technology reach its wide-scale potential. Pike Research predicts that more than 3.1 GW of microgrid capacity will be available by 2015. Some states are piloting initiatives alongside DOE, but we need to continue to build awareness around the technology.

Next | Energy Reliability with Microgrids