A small island in American Samoa is making the switch from diesel generators to 100 per cent renewable energy.

Ta'u, the easternmost of the Samoan islands, has just been equipped with a new microgrid, with 1.4 megawatts of solar generation capacity and 6 megawatt-hours of battery storage. It's enough to power the entire island - both night and day.

With an area of just 44sq km, Ta'u has a population of fewer than 1000 people, and until now, they have relied almost entirely on diesel generators for their electricity.

About a year ago, the American Samoa Power Authority began soliciting help with a project that would save the island the inconvenience, costs and greenhouse gas emissions associated with relying on diesel.


"[They] basically just put out a solicitation to see if anybody could provide an alternative to diesel, and that's something that we responded to," said Peter Rive, co-founder and chief technology officer of solar provider SolarCity, which was recently acquired by Tesla.

The result is a system composed of more than 5000 SolarCity solar panels and 60 Tesla Powerpack battery storage systems. The new microgrid could save the island nearly 416,395 litres of diesel fuel each year, which amounts to about 2.5 million pounds of carbon dioxide emissions.

The microgrid is covering about 99 per cent of the island's power needs. The battery system can provide three full days of power to the island without sun, he added. And it can fully recharge in seven hours of sunlight.

Last year the Nature Conservancy completed a US$1.2 million ($1.7m) solar and wind project on Palmyra Atoll, located about 1600km south of Hawaii. Although there's no permanent population on the atoll, it serves as a scientific outpost and temporary residence for researchers. According to The Nature Conservancy, the island now runs almost entirely on renewable energy.

Since 2008, the Galapagos island of San Cristobal - the second largest in the archipelago - has sourced about 30 per cent of its power from wind and solar. SolarCity and Tesla are involved in another project on the Hawaiian island of Kaua'i, which will finish up with 17 megawatts of solar generation capacity and 52 megawatt-hours of battery storage, Rive said.

Rive says the future of solar power lies in these types of battery-coupled systems, which allow energy to be stored and dispatched even when the sun isn't shining.

One of the biggest hurdles for renewable energy sources like wind and solar is that they can only generate power intermittently - when the sun is out or the wind is blowing. The continued development of more effective, fast-responding energy storage solutions is key to the continued expansion of renewables.