If the state intends to wean itself from fossil fuels by 2045 — and that’s the plan — it will take a lot more than good intentions.

House Bill 623, signed into law on Monday by Gov. David Ige, proposes that the state will get 100 percent of its energy from renewable sources by 2045. Going from 90 to 0 percent dependency on fossil fuels in 30 years, with no clear plan for getting there, is ambitious by any measure.

Now comes a project to match that ambition. AW Hawaii Wind (AHW), a subsidiary of Alpha Wind Energy, proposes to build two massive offshore wind projects, with 102 wind turbines, each one taller than the Washington Monument, spinning within sight of Waikiki and possibly the North Shore.

The turbines would be attached to a platform called WindFloat, a tri-legged floating structure anchored to the ocean floor. Undersea cables would carry the energy to onshore power plants. The Danish company promoting the project says it would supply 30 percent of Oahu’s electricity needs.

That would certainly be a significant step toward energy self-sufficiency, assuming it’s possible. However, a project of this size using Alpha Wind’s proposed technology has never been attempted. Pilot projects using WindFloat are underway in Portugal and Coos Bay, Ore., and other offshore wind projects are in development in Atlantic City, N.J., and Virginia Beach, Va. But it’s likely that if approved, Hawaii would serve as Alpha Wind’s utility-scale proving ground. An abundance of caution and a tight grip on the taxpayers’ wallet are warranted.

The public version of a proposal by Alpha Wind notes that the project’s technology will evolve, possibly altering fundamental features such as the electrical cable specifications and the layout of the giant turbines.

There are a host of other unresolved issues as well: the project’s effect on whales and other marine life, military exercises, fisheries and Native Hawaiian culture.

Will the spinning blades kill seabirds, as land-based wind turbines do? Will the sound of the blades, imperceptible from shore, disturb marine mammals?

It’s also not clear what would happen in a major hurricane: “Further studies, design improvements and tests are required prior to manufacturing and installation,” AWH says.

Because the project is at such an early stage, its impact on the state, from the overall economy to the individual ratepayer, remains an unknown. Much will depend on AWH’s ability to negotiate terms with its anticipated primary customer, Hawaiian Electric Co., on the cost of its energy and connecting to the grid.

“AWH … cannot emphasize enough the importance of close, in-depth and positive cooperation between the Project and HECO in order to optimize the benefits of the Project,” AWH said.

Even that remains uncertain, as HECO soon could be under new management. Shareholders on Wednesday approved the sale of Hawaiian Electric Industries to NextEra Energy, a Florida-based power company that develops its own renewable energy projects. The state Public Utilities Commission will hold public hearings on the deal proposal in the fall.

Furthermore, developing wind power offshore is not cheap; AWH estimates the cost to build Hawaii’s project at $1.6 billion. There’s no telling how much of that cost, plus operations, could be passed on to taxpayers in the form of industry tax credits, or to ratepayers in the form of higher electricity bills. Officials need to make sure that the private companies promoting these projects carry their full share of both the costs and the risks.

Proponents of renewable energy argue that renewables are a safe long-term economic bet: As the technology improves, the price will come down, whereas the cost of extracting fossil fuels will inevitably increase. There’s also the obvious benefit to using clean, home-grown energy in a state especially vulnerable to the effects of fossil-fuel generated climate change.

There is little doubt that Hawaii needs to head toward energy independence. Our geographic isolation, abundance of renewable resources and highest-in-the-nation electricity costs demand an evolution toward clean energy.

Offshore wind turbines for Oahu could prove a practical alternative to building them on Lanai, Molokai or in Kahuku, where land is scarce and public opposition strong. And ambitious goals like a 30-year deadline can prod Hawaii policymakers to act when they otherwise would dawdle.

Nonetheless, AWH’s request for lengthy offshore lease rights to develop its project raises legitimate concerns that must be thoroughly vetted.

We want clean energy, but at the right price.