Most sailing yacht owners harbour a sly smugness that their pastime and their mode of seagoing transportation approaches carbon-neutral. But once tied to the dock, many good intentions fade in the power-hungry reality of luxury living ashore. Enter Dr. Ed Bosarge and Marie, his wife, owners of the sailing yachts Tenacious and Marie, and now an entire Bahamian island that runs on its own grid of renewable energy.
To date, the system has offset more than 600 tons of CO2 and should avoid the production of more than 950 tons annually, double the annual emissions from the Bosarge’s two yachts. Over Yonder Cay, which was completed in March 2012, is approximately 70 acres and encompasses four villas, a boathouse and seaplane base, a deep-water marina, pools, and numerous support buildings entirely powered by wind and sun. Located in the Exuma chain near Sampson Cay and Bell Island, the island sits on the edge of North Cut.
When the Bosarge Family Office purchased the island, the idea was to develop it to be independent of diesel fuel.
‘My first thought was to set up the island to run on ammonia gas,’ says Bosarge. Converting large diesel generators, vehicle engines and outboards to burn liquid ammonia, however, proved a bit more difficult than powering the island with wind, sun and storage batteries. More than 1,200 Evergreen cells are arrayed in the solar field, putting out 260 kilowatts per hour of DC power at peak output, which is sent to the inverter room for conversion to 480V AC power. The three permanent magnet wind turbines each pump out a maximum of 100 kilowatts of AC power. The island is set up on a 13,200V grid with all utilities buried well underground.
A computer-controlled system either pulls the AC power directly or triggers stored DC power from the batteries to flow through an inverter for use. All unused power is fed to the storage batteries, and Bosarge says the entire island could run for several days on the battery power alone. By comparison, a neighbouring resort island burns through $1.8 million in diesel annually to power the island. Bosarge says he will recoup his alternative energy investment at Over Yonder in about four years.