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Technology Allows More Solar on Molokai

A technology collaboration between University of Hawaii’s Hawaii Natural Energy Institute (HNEI) and Maui Electric will allow more rooftop solar systems to be added on Molokai’s electric grid.

At the end of 2018, a 750-kilowatt (kW) “load bank” was connected to the island’s electrical grid at Maui Electric’s Pala‘au power plant. The load bank acts as a “safety valve” designed to rapidly absorb excess energy that might occur during periods of high photovoltaic (PV) generation during the day or unplanned system disruptions, such as a sudden loss of electricity usage on the grid, according to Maui Electric.
“A small island power system like Molokai is very dynamic, and the high PV penetration adds another level of complexity to managing those dynamics,” said Rick Rocheleau, HNEI director. “This makes Molokai the perfect location to demonstrate advanced solutions for reliable operations of grids, in a state with some of the highest penetration levels of distributed solar generation in the world.”

Maui Electric officials say since 2015, the high amount of solar electricity being generated on Molokai’s grid has raised reliability issues. Set up to be operated both autonomously or by a Maui Electric operator, the load bank provides the ability for the utility to accept up to an additional 725 kW of rooftop PV.
“The load bank is one of the technical solutions we have installed on the island’s electrical system that enabled customers who had previously been waiting with [Net Energy Metering program] applications to move forward,” said Maui Electric’s Shayna Decker.

Because the size of private rooftop solar systems can differ, Decker couldn’t give a number of additional customers the load bank might be able to accommodate under currently open solar programs.

“As more intermittent renewable energy, like PV, comes on to the Molokai system, less and less generation is needed from the traditional generators that must run at minimum operating levels to maintain reliable electrical service to the island,” said Chris Reynolds, director of operational technology at Maui Electric. “The load bank helps to prevent the generators from going below these minimum must-run levels and keeps them running in a stable manner.”
The load bank project is funded by the U.S. Office of Naval Research, and complements the HNEI/Maui Electric two-megawatt battery energy storage system commissioned at the utility’s power plant in 2016.

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