Waiting for a wave of offshore wind

A long-awaited bill has been introduced to lay the regulatory groundwork for allowing offshore wind farms to be built in Australian waters. Will this spark a tsunami of projects?

Offshore wind is more expensive to build and maintain, but more efficient than “conventional”  onshore wind. While the size of onshore wind turbines average around 3MW, offshore turbines are huge, averaging around 7.5MW per turbine. The largest offshore turbine available today, the 12MW Haliade-X has three carbon fibre turbine blades each 107m long, making them larger than the wing of a jumbo jet. The blades (which rotate at over 300km/h at the tips), generator and associated equipment weigh over 900 tonnes. They are enormous renewable beasts.

There are, self-evidently,  several challenges with installing giant wind turbines in the sea. In shallow waters, the logistics of anchoring the turbines are possible, but more challenging than onshore. A platform is required to hold the pylon and turbine in place, and special ships are required for construction and maintenance. The transmission connection needs to be laid underwater.

As the sea gets deeper (where the best winds often are), construction has to flip to a floating platform, and the supply chains from port get longer, the further out the wind farm is. For this reason, floating wind farms are only just moving past the pilot project stage. Oil rigs float and are anchored in deep seas, so it is technically possible. But the energy produced by an oil rig is much greater than the energy produced by each floating wind turbine.

The flip side is that with access to stronger winds and the larger turbines, offshore wind farms have higher capacity factors – up to 60 per cent in the best situations. This slightly offsets the increased costs on a levelized cost basis, but there’s still a big gap. IRENA estimates the average LCOE of onshore wind at US$39/MWh versus offshore at US$84/MWh.

So why would anyone build offshore wind if it’s twice as expensive as onshore? To answer this question, look at the places that are building offshore wind: UK, western Europe, northeast USA, Japan, Taiwan. They all have high population densities. So, there is not enough land to power their economics purely on land-based renewables. They have no option but to look offshore. The UK in particular has plans for around half its power to come from offshore wind by 2050.

Australia does have options. We have lots of land. We also have better solar resources to complement wind power than the countries listed above. There are grandiose plans for 30-50GW projects based around onshore wind, solar and battery storage. It’s true that there are some excellent offshore wind resources that could deliver much better capacity factors than anything on land. But these prime resources are off the coast of Southern Tasmania, which is not very near any major loads. It seems unlikely that locals would welcome the industrialisation of that part of the world, either.

Where offshore wind is a central part of a country’s plans for decarbonising its power system there has been a key focus on ways to drive down costs. Economies of scale from large and multiple projects are critical, allowing for shared construction equipment (such as the “jack-up” ships that can anchor themselves to the seabed while craning parts up to the top of the pylon) and maintenance facilities and supporting local manufacturing. In other words, there’s not much point in building one offshore wind farm, you need to build a dozen – in roughly the same area. Extensive R&D has also played a key role.

But if Australia doesn’t really need one offshore wind farm, we definitely don’t need a dozen. Some optimists think that’s what we’ll get though, with 18 prospective wind farms for a total of 29GW apparently under consideration. Look a little closer and it turns out they are almost all in the “pre-feasibility” stage. Some of the proponents are struggling to build a functioning website, let alone a wind farm.

It may be that Commonwealth government foot-dragging on implementing the regulatory framework for developing offshore wind is a key reason these projects are all in their infancy. But outside of a benevolent government, it’s not clear who would pay the inevitable premium to underwrite any of them. It’s a classic chicken and egg situation – offshore wind is too expensive right now, but to make it more competitive we’d need to build a lot of it – but there’s no sign it’s one we need to resolve to decarbonise Australia.