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First of all, what is a microgrid? It’s a localized electrical network that includes both generators and loads — for example, a college campus that has its own sources that can power some or all of the buildings.

Microgrids come in two main flavors: those that run completely independent of any external power sources (permanently islanded) and those that can run either independently (islanded) or connected to the main power grid.

A microgrid needs to have a steady, reliable source of power. Cogeneration, also known as combined heat and power (CHP), is a commonly used technology. It either uses waste steam from industrial processes to run an electrical turbine or waste steam from the turbine as a source of heat, which can be used by nearby buildings.

I think that microgrids are going to be an increasingly important piece of our electrical infrastructure because they serve a number of important functions — resiliency and the integration of renewables being two of the most important.

Resiliency

Resiliency becomes an issue when the main power grid goes down. Hospitals, for example, need to keep the power going as a matter of life and death. For that reason, most hospitals have backup generators. But, during Hurricane Sandy, several New York City hospitals had to evacuate hundreds of patients because their backup generators failed. According to the white paper The Rise of Clean Energy Microgrids  , backup generators fail 20 to 30 percent of the time. One reason is that a backup generator sits unused most of the time waiting to be activated during an emergency. A microgrid, on the other hand is in continuous operation.

During Sandy they proved their worth. Co-op City, a massive residential and commercial development in the Bronx was able to keep the lights on and residents warm throughout Sandy by relying on its microgrid, which has a 40-MW CHP plant.

In Manhattan, New York University’s microgrid kept parts of the campus up and running due to its CHP plant. And in New Jersey, Princeton University’s microgrid did the same, relying on a 40-MW CHP plant kept thousands of apartments and dozens of businesses and schools running for nearly two days.

Microgrids provide resiliency in a couple of different ways. If there’s a failure of the main grid, a connected microgrid can automatically disconnect and continue generating power. If there is a failure of the microgrid it can disconnect so that the failure will not cause problems for the main grid.

During periods of peak demand on the utility, the microgrid can disconnect and function in islanded mode, thereby removing its load from the grid. And the control system of the microgrid could shed non-essential loads in order to lower peak demand.

Integration of Renewables

Microgrids are an ideal way of integrating renewables. They can combine different types, like solar and wind, or even multiple installations of the same type, say a solar panel on each building. There could be a single storage unit, generally made up of batteries, that serves the entire complex. And importantly, the CHP generator will keep the batteries charged and balance and equalize the outputs of the various renewable sources.

Government Support

Because of these advantages, the U.S. Department of Energy is supporting the growth of the microgrid infrastructure in a variety of ways. The Pacific Northwest National Laboratory (PNNL), for example, has developed modeling methods that “can help decision makers weigh tradeoffs and ultimately design microgrids that are more likely to keep the lights on during an emergency, or power areas without access to a main grid.”

They feel this is vital because “The aging energy grid is being pushed to the breaking point. Power outages from extreme weather alone cost anywhere from $2 billion to $77 billion per year.”

The Future of Microgrids

By 2035, microgrids are envisioned to be essential building blocks of the future electricity delivery system to support resilience, decarbonization, and affordability. Microgrids will be increasingly important for integration and aggregation of high penetration distributed energy resources. Microgrids will accelerate the transformation toward a more distributed and flexible architecture in a socially equitable and secure manner.

“ Microgrids as a Building Block for Future Grids  ” — Lawrence Livermore National Laboratory

To achieve this goal, work will have to be done to understand how to integrate large numbers of microgrids. A team of researchers from Oak Ridge National Laboratory is implementing an important step in that direction. They have developed an “orchestrator,” which they installed in a remote community in central Puerto Rico to coordinate the operation of two separate microgrids.

Final Thoughts

Microgrid technology is here to stay — it has been proven in a large number of existing installations. To my mind, there is no doubt about their importance for the future of the national electricity supply. It will make that supply much more flexible and reliable and will be vital for the integration of renewable energy sources. It will enable a mixture of existing and future sources and storage systems to be readily integrated because it can be done in local microgrids and gradually expanded.

But, of course, there are huge problems — the devil is in the details. The analysis tools PNNL is working on to optimize the microgrids for each unique location are critically important. Devising a strategy for actually how to go about modifying the national grids is a major undertaking, but the technology is just one part of the challenge. Even more daunting will be the financing, the political will, and the coordination across the 48 contiguous states.

But to my mind, it’s a challenge well worth the struggle.

Topics:
Power Management Renewable Energy Smart Grid

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