For decades the fuel came in by barge, and the island turned it into electricity itself.
A hall of diesel engines ran around the clock because there was no alternative.
On a morning in May the engines stopped, and this time they stayed stopped.
The turbines out on the water get the credit for that.
What actually did it was a cable.
The turbines were the reason anybody paid for one, which is not the same thing.
Why an island pays fifty cents for a kilowatt hour
An electrical island has to match generation to demand second by second using only machines standing on it.
No borrowing from a neighbor at four in the morning. No selling a surplus at noon.
Diesel is the technology that does that at small scale, which is why almost every unconnected island runs on it.
The cost follows from the isolation rather than from the fuel. You pay for the fuel, the barge that brings it, and generators sized for a summer peak that lasts a few weeks.
Rates here ran up to about fifty cents a kilowatt hour in summer against roughly fourteen on the mainland.
Lay a cable and that whole structure collapses. The island stops being an island electrically, and the diesel plant becomes a backup.
What is actually out there
Five machines stand about 3.8 miles off the southeast shore, spaced roughly half a mile apart in a line about two miles long.
Each one is around 593 feet to the blade tip, and they sit on twisted jacket foundations rather than monopiles.
That choice was costed. The jackets came in near 20.9 million dollars against about 26.1 million for monopiles at this site.
The whole project ran to roughly 290 million dollars for 30 megawatts, which is expensive per megawatt and was never the point.
Every offshore wind project since has been cheaper per megawatt, and every one of them started from this sequence.
A separate submarine cable, laid by the regional utility, links the farm to a substation on the island and then runs on to the mainland grid.
The island’s diesel plant went quiet on the first of May in the year after the turbines were finished.
The numbers, and which way they run
Annual output is about 18,400 megawatt hours, which is a real number rather than a nameplate one.
The island holds roughly a thousand year round residents, swelling to somewhere between 15,000 and 20,000 in high summer.
Its load is about 1 megawatt off season and 4 at the summer peak, so the farm is several times larger than the place it was built beside.
The remainder covers something like 12,500 mainland households, which is where the ninety percent figure comes from.
On diesel displaced, two numbers circulate. The island’s historic burn was put at around a million gallons a year, while a later performance study calculated displacement of up to 456,900.
Both are defensible and they measure different things, which is worth saying before either gets quoted alone.
What the small numbers cannot carry
The marine findings rest on a survey of 25 fishermen. Forty four percent reported additional species, thirty six percent reported mussels on the structures.
Self reported, small sample, one site. Real, but not a study anybody should scale up.
Noise on the island fell by about 14 decibels on average once the engines stopped, which is more than halving what a person actually hears.
Summer occupancy rose around 19 percent in July and August, and the 300 construction jobs were temporary by definition.
None of it tells you much about a farm 20 times the size, like the 704 megawatt project that now feeds Rhode Island and Connecticut from 15 miles out.
The detailed accounting for this site is public in a case study that lists its own methods.
What 30 megawatts was actually for
It was never a power plant in any meaningful sense. It was a permit, a supply chain and a construction sequence run once, in American water, to see whether they worked.
Everything since has been built on the answer, including the projects that later found their own faults, as one blade adhesive did when a bond never reached full strength.
The island got something more specific and more valuable than clean power.
It got interconnection, and with it the ordinary condition every mainland town has taken for granted for a century.
Take the turbines away and leave the cable and the engines would still be off, which is the sentence the anniversary coverage rarely reaches.
Take the cable away and leave the turbines and the island is back on barges by the first calm week.
