Kodiak AK Utility Powered by 98% Hydro & Windpower
Wind turbines in Kodiak, Alaska. Photo by Science in HD on Unsplash
Kodiak, Alaska is an of-the-grid community. The location is Kodiak Island, separated from the mainland. Kodiak Electric Association (KEA) is not connected to other utilities by high-voltage transmissson lines. Alaska is too big for electric utilities to share power from generating stations.
KEA must generate all of its customers' electric power needs locally. Hydropower installed in the 1970s was adequate for a few decades, until growth required adding diesel-fueled generators. PBS Newshour reports from Kodiak, describing why and how Kodiak Electric reduced diesel fuel consumption for generating electricity, added wind turbine generators, and installed big batteries to store windpower.
This year, through September 28, 98% of KEA's power supply has been generated by non-fossil-fuel sources, according to data at KEA's website. Hydroelectric supplies most of the power requirements, followed by windpower and diesel engines (see chart at bottom.)
Pillar Mountain Wind consists of six turbines rated 1.5 MW each. Terror Lake Hydroelectric has three turbines with a combined capacity of 30 MW. The combined system has two forms of energy storage: batteries, and water behind a dam.
When the wind stops blowing, a 3 MW battery bank automatically switches-online until the the hydroelectric power generators adjust to increase their power output.
PBS Newshour describes a potential electric power problem arose when a shipping facility at Kodiak's port planned to replace an old engine-driven crane with a new electric crane. As the crane lifts a heavy container from dock up to a cargo ship deck, the crane's electric motor draws a large amount of electric power. When the crane lowers, the descending weight provides mechanical energy to the motor, causing the motor to generate power which could flow back onto the local powerline. This cycling would disturb the power quality of the electric line supplying service to other customers by causing voltage swings.
To smooth the power variations before they happen, KEA and the shipping customer installed and connected a flywheel to the powerline. The flywheel spins continuously when a ship is loaded so that its rotational momentum will supply energy when needed. When the crane lifts cargo, some of the flywheel energy is converted to electric power. During crane descent, the flywheel absorbs electric energy from the motor by converting the excess electric power to mechanical rotating energy. KEA told LineCurrents that the crane and flywheel controls communicate via fiberoptic cable, assuring that the flywheel reacts quickly to inject or absorb electric power.
Links
PBS Newshour - Kodiak video (same as text link above)
KEA 2017 Electric Power Supply - megaWatthors
MW-hrs: megaWatt-hours
One megaWatt-hour equals 1,000 kiloWatt-hours