Lessons for Cities Considering Community Microgrids

Lessons for Cities Considering Community Microgrids

We cant always count on electrical grids as recent events like Superstorm Sandy have made painfully clear. Electrical power distribution systems do fail, and sometimes for long periods of time. Thats why community microgrids with energy storage are vital to keep power flowing to critical services, those that provide health care, energy and security, such as hospitals, shelters, gas stations and police and fire departments.

More and more communities are considering installing community microgrids as a protective measure. But it isnt a simple matter for a community. Threshold questions must be answered in advance. Which services are critical? How much distributed generation is necessary to support the microgrid? Should it include energy storage? And is a microgrid really the right solution?

Microgrid versus diesel back-up

For some communities, back-up generators, fueled by diesel, can be helpful for a limited duration following a storm. But there is risk in relying on these fuels and advantages to microgrids with storage instead.

Diesel and other liquid fuels can become scarce after a natural disaster. In fact, the military has become increasingly aware of this problem, which is why it is working to reduce its dependence on fossil fuels. The Department of Defense, wisely, is trying to instead incorporate new technologies, such as microgrids and other clean energy technologies. As Navigant Research pointed out: Microgrids can shrink the amount of fossil fuels consumed to create electricity by networking generators as a system to maximize efficiency.

Why choose microgrids with storage

Energy storage can be a valuable component in a community microgrid. Storage offers back-up power when the grid is down or when a community lacks a reliable grid connection. A microgrid with storage also can help a community reduce its diesel use, carbon emissions and water pollution, as is the case with the U.S. National Park Services microgrid on Alcatraz Island in San Francisco Bay.

The island was at one time linked to the mainland grid. But a ships anchor ruptured the underwater power lines in 1950. Alcatraz was forced to turn to diesel fuel and coal as its source of power.

Today, a microgrid on the island offers much cleaner, independent generation. The microgrid system is comprised of Princeton Power System inverters, a solar array, advanced batteries, a Princeton Power Systems Site Controller, and back-up generators.

Designing and building the system required careful consideration, given that Alcatraz is one of the most well-known historic landmarks in California and the United States. This was especially the case when it came to component replacement and commissioning:

Component Placement: Preserving the island in pristine condition while completing the installation was the greatest challenge. Given that a system of this size requires a large construction effort, component placement was key. To prevent the solar array from being visible from San Francisco, it was placed on the roof of the prison in a flat configuration rather than a traditional angled configuration. The inverters, battery rack, and generators were placed in the old generator room, as this space is isolated and not accessible for tourists. The room was also protected from the harsh salt water environment.

Commissioning: The fragile natural environment and wildlife, particularly the birds (Alcatraz is an old Spanish word for pelican), added to the challenge. Extra attention was given to the solar panels after being damaged by rocks and shells dropped from overhead birds. Despite the coarse condition of the generator room, engineers were able to insulate the room to prevent future problems and ensure reliable long-term operation.

We hope the approach, design and technology used at Alcatraz Islands offers a model for communities as they install microgrids. It offers valuable lessons for those that must into account historic or environmental preservation, but also can serve as an example for other communities as well, as they seek to reduce outage time, lower emissions, and become more energy efficient.

Source: Microgrid Knowledge

Smart Grid Bulletin April 2018

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