Saddled with the highest electricity rates in the world (and threatened by climate change more than almost any other communities), many islands and isolated grids have opted to integrate wind and solar to replace expensive, imported diesel fuel. One challenge for these systems is that they do not have the benefit of calling upon neighboring systems to balance their wind and solar against load–leading to instability and insecurity of supply.
As a result, many remote grids are adjusting their technical requirements for connecting intermittent resources like wind or solar to the grid, requiring that these resources be firmed. In late 2013, for instance, Puerto Rico adjusted its technical requirements for connecting wind and solar assets to the Puerto Rican grid. This isn’t a direct requirement for energy storage specifically, but is a good fit for storage.
The Flywheel Option
Other island markets are betting on storage more directly. Aruba has committed to an aggressive plan to become 100% renewable by 2020 and has signed agreements with BYD and Temporal Power, as well as a power purchase agreement with Hydrostor in order to achieve its energy goals.
The typical applications in these markets are wind, solar, and diesel hybrids. In previous years, the most common technology for remote, isolated grid storage was advanced batteries. This was partly a function of availability and technology fit. Very few other storage technologies are modular–underground compressed air and traditional pumped storage require specific geologies–and few vendors were targeting the space. Moreover, the working assumption in terms of technology fit has been that a longer-duration storage system is more valuable than a short-duration storage system. Several flywheel vendors are disproving this assumption, however.
ABB’s Powercorp, for example, uses flywheel technology in remote microgrids, such as the BHP Billiton nickel mine in Western Australia and the Coral Bay community in Northwestern Australia. These are remote diesel-led systems.
Way Up North
Beacon Power has commissioned a demonstration project in St. Paul, Alaska, combining an existing plant, which includes a 225-kW wind turbine and 300 kW of diesel generators, with a 160-kW flywheel system. In this scenario, the flywheel system will enable the host utility to further improve wind utilization and deliver fuel savings of up to 30% over existing (pre-flywheel) consumption levels.
While it is still the case that some amount of long-duration storage is necessary in order to achieve very high renewables penetration on an isolated grid, flywheels are demonstrating that significant diesel savings can be achieved with as little as 30 minutes or less of storage.