As Hawaii develops policy responses to climate change and expands renewable energy sources, dependability under all scenarios is critical. Legislators have repeated the need for “24/7/365” renewable sources over and over, but have never put any meat on those bones. For Oahu, 100% renewable energy is likely to be mostly solar, with a smaller wind component. But when the sun doesn’t shine and the wind doesn’t blow, they produce less electricity, or shut down completely. The increased potential for destructive storms because of climate change increases the risk of future renewable supply. Dependability is not a problem today, because any renewable disruption is immediately made up by fossil fuel generation.
Our existing system, about 60% fossil-fueled on Oahu, keeps the lights on no matter what. But by 2045, all HECO’s existing fossil fuel generators are scheduled to be decommissioned, and we hope to be 100% renewable. Without sufficient storage or backup, that will be an unreliable system. HECO’s current formula for firm renewable power provides only hours of battery storage and not for all sources. Hawaii will continue to have extended days of rain and overcast, days of calm, as well as hurricanes and tropical storms. We cannot leave Oahu dependent on intermittent solar and wind, backed up by battery storage of only a few hours.
Hoping for more and better batteries to cover these inevitable outages is not the answer. The additional batteries to keep Oahu powered up during an extended weather event would be astronomically expensive, cover thousands of additional acres, and have to be replaced periodically (typically, every 10-15 years). HECO’s 2021 “Integrated Grid Planning” report estimates that we will need about 9,700,000 megawatt hours of renewable electricity in 2045, averaging 26 gigawatt hours a day. By comparison, the new Kapolei Energy Storage project cost $220 million and provides 565 megawatt hours of storage (.565 GWh). To cover a one-week weather outage, Oahu would need about 330 times the batteries of the Kapolei project, costing tens of billions of dollars, and mostly just sitting there. That investment in standby battery capacity would have to be recovered through what you and I pay for electricity.
There is a lot more to battery storage than the one in your car. Large, industrial batteries have a life cycle, just like solar panels, and a typical one produces about 300 lbs of CO2 per kilowatt hour of capacity during manufacturing. Plus, batteries are not 100% efficient, and large industrial ones are 60-80% efficient. So, if Oahu is to run off battery power for any significant period of time, we need even more batteries and renewable sources to cover that loss.
We certainly need some basic battery storage for solar and wind to match the daily production variability of renewables with demand. But there will be weather events with the potential to limit or shut down solar and wind beyond the capacity of the batteries currently being installed (not to mention storms and hurricanes that can destroy them). Because of these infrequent, but significant, events there has to be something that will keep the lights on. It is simply not an option to build billions of dollars of battery farms for such events, which would just sit idle most of the time. Some claim advances in battery technology will make massive battery storage feasible, but we cannot rely on that or put any numbers to it. As HECO’s scheduled decommissioning of its power plants proceeds, Oahu will become more and more vulnerable. Yet neither our Legislature, the Energy Office, HEI, nor the PUC have presented a dependability plan that addresses these infrequent, but inevitable risks extended periods of rain, calm, and tropical storms pose to our renewable electricity future.
Brian Barbata is a former energy executive, a founding director of the Kauai Island Utility Co-op, and the former manager of Hawaii Photovoltaics, LLC.
