Hawaiian Electric Co. is adding a flywheel system to Oahu’s electric grid.

The utility said Monday it had teamed up with Union City, Calif.-based Amber Kinetics Inc. to test a flywheel system at Campbell Industrial Park.

Flywheels use the energy from the motion of a rotor that spins in a nearly frictionless tank with a vacuum pump attached to it. When HECO needs backup power, the inertia from the spinning rotor can be converted to electricity. The flywheel is connected to a motor-generator that sends the energy to HECO’s grid. The Amber Kinetics flywheel can provide backup energy to the utility for up to 4 hours at a time.

Hawaii law requires HECO to get nearly 100 percent of its energy from renewable energy resources by 2045. Shelee Kimura, vice president for corporate planning and business development at HECO, said the flywheel will help the electric utility achieve the goal.

“Energy storage is essential to reach a 100 percent renewable energy future, optimizing the use of Hawaii’s abundant but variable solar and wind energy,” Kimura said in a statement. “We are collaborating with a variety of partners to test a range of energy storage technologies and we are very excited to work with Amber Kinetics to evaluate this very promising flywheel energy storage system.”

Amber Kinetics will build and install an Amber Gen2 Model 25 steel flywheel system and HECO will evaluate its operation.

HECO said the storage system can help renewable solar energy — which changes its output according to the weather — be more consistent. HECO said the system also will support the reliability of the utility’s operations by shifting peak energy, providing flexible capacity and smoothing voltage.

Peter Rosegg, HECO spokesman, said the typical cost for a flywheel is approximately $200,000 for equipment, engineering, shipping, training and ongoing testing.

The project is funded by HECO and the Energy Excelerator, a program that provides resources to support energy startups. Amber Kinetics is one of the startup companies working with the Energy Excelerator.

“Hawaiian Electric Co. is a leader among U.S. utilities for adopting and integrating renewable energy to create a sustainable energy future,” said Ed Chiao, Amber Kinetics’ co-founder and CEO. “Now it is continuing that leadership by exploring the potential of flywheel energy storage.”

HECO said the Amber Kinetics system can support unlimited cycling with zero capacity loss over a more than 20-year service life and is readily deployed outdoors. Other advantages of the Amber Kinetics energy storage system include safety, sustainability, full recyclability and cost competitiveness over electrochemical batteries.

Former HECO President and CEO Dick Rosenblum is on Amber Kinetic’s board of directors.

This is the second energy storage system to be added to HECO’s grid within a month.

In September, HECO added the first utility-scale battery system to Oahu’s electric grid. The $1.6 million system from Wyoming-based Altairnano has the capacity to provide 1 megawatt of power. The Hawaii Natural Energy Institute, a renewable energy research unit at the University of Hawaii, paid for the battery, which will be studied over a two-year demonstration period.