Off to Summer at my Remote Microgrid

Credit: Sean D Elliot

Contributing writer Cara Miale Goman takes us on a trip to Star Island, a New England getaway made energy-smart with a remote microgrid.

Star Island, one of the nine Isles of Shoals off the coast of New Hampshire near Maine, has everything one might expect from a remote island getaway: beautiful views of the Atlantic, boating, kayaking, 43 acres for hiking and family activities – even programs to pursue personal and spiritual growth.

It also has something one might not expect: its own 130-kW solar array microgrid.

“Just being on an island in general, you are more tuned-in to conservation,” said Joe Watts, CEO of Star Island Corp., the nonprofit that manages the island resort.

Energy costs are naturally higher than on the mainland, and resource management, from electricity to water, is more challenging.

During peak season, Star Island is home to some 100 staff members, hosts up to 150 day-visitors, and has capacity for up to 400 overnight guests. To support peak season demand, Star Island used on average 20,000 gallons of diesel fuel each summer to power generators and boilers (now extinct on the island) – the cost of which was often unpredictable.

They were interested in exploring alternatives and finding a way to “convert problems into solutions,” said Watts.

Enter, the microgrid.

Unlike diesel, solar power offers Star Island fixed-price energy; they have signed a 13-year solar power purchase agreement, facilitating budgeting and looking toward Star’s long-term goal to achieve fixed-price economics.

Theirs is a remote microgrid—not connected to any larger grid—and therefore cannot earn revenue by selling energy back to the central grid; it has to be totally self-sufficient. Not a problem for Star Island, which has a thriving environmental stewardship mission, according to Watts. The microgrid is one piece of a multifaceted sustainability program known as the Green Gosport Initiative which includes measures like water conservation and waste-treatment, upgrading to more energy efficient dishwashers and water heaters, and a “death to boilers” campaign.

Installed in November 2014, the Star Island microgrid comprises 130-kW ground mounted array with Schneider Electric charge controllers and inverters; 420 Solar World panels, and a 600-kWh glass mat battery bank which will operate in conjunction with two Kohler 80-kW 120/208 V, 3 phase generators with John Deere engines. Each generator can independently carry the entire load, and features an attached heat recovery system designed and built in-house by Star Island. Ayer Electric was centrally involved in all aspects of this project, and a lot of work and procurement went through the supplier AltE.

The new system is projected to provide up to 60 percent of the island’s anticipated total summer demand, and 100 percent of demand in the off-season.

Combined with Star’s additional conservation efforts, Star expects their solar microgrid will reduce summer diesel fuel use from 20,000 to 5,000 gallons – a number they aim to cut to 2,000 gallons in the future.

Said Watts, “One of the goals in our strategic plan is environmental stewardship. We want to do right by the environment.”

2015, Star Island’s centennial year, marks the first season the new microgrid system will be in use. While the initial investment for the microgrid system is more expensive than diesel, even a short-term cost analysis is difficult, said Watts, because of the other benefits of the system. For example, Star Island has seen a recent uptick in donations. Could it be the solar microgrid?

“People really like that we are moving in this direction,” said Watts. “And we want to get the word out.”

With up to 14,000 guests each year, many who come for the day, Star Island is poised to become a model for others to learn about solar microgrids. Thanks to their comprehensive energy conservation efforts, the island is leading the way into the next hundred years of energy “as it ideally might be”.

Star Island celebrates its centennial with a ribbon cutting for its solar array on Saturday, June 27, 2015. For more information on Star Island and its sustainability practices, visit starisland.org.

Star Island’s solar system at-a-glance

13-year solar power purchase agreement
130-kW ground mounted array, 20 degree tilt for maximum summer season output
420 Solar World panels, 305 W each, 7 strings, 60 each string
- Thanks to volunteers, the ground in between solar panels has been seeded for both grass and milkweed to create more habitats for monarch butterflies on island.
600-kWh fully sealed glass mat battery bank, Exide Absolyte GP 2 volt, 4200 Ah AGM. Battery bank and controls are in an old generator room.
Schneider Electric/Xantrex XW6048 inverter/chargers in three banks each capable of providing 36-kW, 3 phase 120/208
Six inverters per bank, total 18 inverters
Schneider Electric XW-MPPT 80-600 charge controllers; 30 controllers, each controlling 30 strings of solar panels
Two Kohler 80-kW 120/208 V, 3 phase generators with John Deere engine; each can independently carry entire load. Features an attached heat recovery system designed and built in-house by Star Island.
System controls allow for addition of more solar panels and batteries.