Will the 2023 Legislature take steps to ensure that our renewable energy transition will dependably keep our lights on? It’s not as simple as announcing that a new solar farm in Waiawa has begun operations, as reported in a Jan. 16 article (“New solar farm in Waiawa now operational,” Star-Advertiser). The implication that batteries are going to be the source of backup for lack of sunlight on Oahu is simply wrong. That is not the purpose of battery storage, and more batteries are not a backup solution.

Hawaiian Electric has said as much, and is soliciting proposals for “spinning machines” — generators — to provide dependable renewable backup to solar. That’s a technical requirement to overcome issues with the grid when power is supplied by variable sources like solar or batteries.

The “spinning machine” renewable fuels most prominently mentioned are biofuels. Hydrogen — next on the list, and despite support for it — would require transition on a scale of production as yet unconceived. Though elegant, it’s also not so simple.

For a utility, biofuel means biodiesel — and engines don’t run on 100% biodiesel. It is blended 20% biodiesel plus 80% regular diesel fuel. There is no known technology for utilities to reliably use 100% biodiesel to back up peak demand. It is produced locally by collecting and refining waste cooking oils, but the amount is inconsequential compared to Oahu’s requirements.

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Hawaiian Electric estimates that in 2045 — when Hawaii is to be 100% renewable, by law — Oahu demand will require 1,450 megawatts of capacity. Since weather disruptions of solar power are inevitable, that’s probably what we need to back up Oahu. How long “spinning machines” might need to run depends on weather and fuel storage.

There is yet no estimate of the backup of spinning megawatt-hours Oahu might need, regardless of the fuel. We need a scientific assessment of the worst-case number of days, and the backup hours needed, when solar is diminished or not working at all. These need to be determined meteorologically, taking into account projected climate change impacts on Hawaii. It is a wide range — from a hurricane hitting Oahu, potentially destroying the millions of panels we will rely on by 2045, to a week of rain. But such an assessment will determine generation, storage and supply requirements. And if biodiesel is to be the “spinning machine” generator’s fuel, that product comes with sourcing, transport and storage constraints very different from fossil fuels.

Where will we get these yet undetermined quantities of renewable biofuels? Whatever it is, the rest of the world will also want it. Can Hawaii expect to have dependable electricity, competing against the rest of the world for continuous supplies of various fuels? For biodiesel, vast energy farms will have to seamlessly grow and process fast-growing plants on a massive scale, each compatible with other biodiesels to become a common commodity fuel.

There has been intense controversy over the conversion of farmland from food to ethanol. Food versus biodiesel will be an even bigger concern. It’s hard to imagine the trillions of acres, fertilizer, pesticides, herbicides, water, machinery, soil management, seasonality, processing, storage and transportation to keep up with a biofueled electricity demand, even as a backup. And then there’s the question of how to burn 100% biofuel of any kind, and its production of carbon dioxide from creation to combustion.

The assumption that Oahu can keep the lights on with spinning-machine biofuels when solar power is down, is simply unrealistic. The 22 years, from now to 2045 for the 100% renewable energy mandate, will go fast. Fuels like hydrogen and fusion are even further from reality for this purpose. Our legislators need to require the development of criteria and forecast solutions to fill this gaping hole — of some form of dependable, continuous non-fossil fuel backup generation — in Hawaii’s renewable energy future.

Brian Barbata is a former energy executive, a founding director of the Kauai Island Utility Co-op, and former owner of Hawaii Photovoltaics, LLC.