Offshore wind power: the answer may in fact be blowin’ in the wind
People have been talking about offshore wind power for almost 20 years (remember Cape Wind?¹). But only 48 GW has been installed worldwide, as of the end of 2021 — compared to 790 GW of onshore wind and over 1000 GW of PV solar.
And 90% of those 48 GW installed are in three countries alone: China, the United Kingdom and Germany.
In 2021, President Biden announced a 30-GW-by-2030 national offshore wind energy goal for the United States — but to date (2022), only two pilot projects composed of a mere 42 MW (0.15% of the objective) have been installed in the country.
Why are so many countries vying for a technology that has barely seen the light of day?
The pros of offshore wind power
Offshore wind power, like nuclear energy and other renewables, is an important low-carbon source of energy and alternative to replace fossil fuels.
But let’s look closer at the specific advantages of offshore wind as compared to onshore wind power:
The efficiency of offshore wind power
The amount of power generated by a wind turbine is mainly correlated to:
- Wind speed: the wind speed/power output relationship is not linear but cubic: if the wind speed doubles, the power output is multiplied by 8.
- Blade length: the power output of a wind turbine is a function of the square of the blade length: if the blade length doubles, the power output is multiplied by 4.
Wind speed: winds are stronger and more consistent at sea than on land leading to capacity factors that are much higher for offshore wind (40–50%) than onshore wind (~30%). The International Energy Agency (IEA) designates offshore wind in a “category of its own, as the only variable baseload power generation technology” — meaning that unlike the intermittency of onshore wind or solar power, offshore wind provides a baseload of steady power output due to consistent winds, but beyond this baseload, there is also variability due to differing wind conditions.
Blade length: wind turbine manufacturers aim to continuously scale up the size of wind turbine blades. However, because of logistical, transport and acceptability constraints, onshore wind farms face more limitations than offshore wind farms when scaling up the size of turbines.
For instance, bigger towers and blades can be transported by boat than by road, making it easier to increase the size of wind turbines offshore.
While the average onshore wind turbine has a capacity of 2.5-3MW with a blade length of about 60m, today’s offshore wind turbine is double the size and has a much greater potential to scale up than onshore turbines in the future.
For these two reasons (stronger, more consistent winds at sea and the potential to build bigger and higher turbines), offshore wind farms have an enormous power output capacity.
Location: less visual impact & less competition for on-land use
The other major advantage of offshore wind power is that it is simply not on land. Thus it does not face the same NIMBY*-ism that onshore wind faces (*Not In My Backyard) and countries have identified huge potential for offshore projects accumulating to a pipeline of 429GW in 2022.
If offshore wind power is a low-carbon energy source with the potential to generate huge amounts of power in unpopulated and uncontentious zones, why has it been so slow to develop in certain countries?
The cons of offshore wind power
The major downsides of offshore wind power over the past decade have been technical complexity, cost and long administrative and approval processes.
Technical complexity and maturity
Offshore wind farms are more technically complex than onshore wind farms due to their massive size, the fact that they are mounted in bodies of water, their complex maintenance, and the difficult infrastructure needed to send electricity back to land.
To date, almost all existing offshore wind farms are “fixed-bottom” installations which are designed for shallow waters (depth of < 50m).
In Europe, 80% of existing offshore (fixed-bottom) wind farms are located in the North Sea, which is no coincidence because the North Sea provides a vast space of relatively shallow waters.
However, shallow waters that are not visible from shorelines (since people prefer not to see the wind farms) are not easy to come by: 80% of offshore wind resource potential is in deeper waters which require floating technology. Floating technology exists but it is still in its early stages, being used in only a handful of offshore wind farms worldwide — and the technology is even more complex and costly than fixed-bottom options.
Costs & administrative processes
The technical complexity and early-stage maturity of offshore wind technology mean higher costs. But since 2014, the cost of offshore wind has significantly declined due to the growing maturity of the industry, advances in technology, economies of scale, and growing competitiveness of the market.
And while floating technologies are more costly than fixed-bottom structures, their costs are expected to go down as well, creating vast opportunities for the offshore wind market.
The complexity of offshore wind farms has also meant long administrative processes. France’s first offshore wind farm at Saint-Nazaire is scheduled to go online at the end of 2022, 10 years after its initial call for tender.
Countries are working to streamline these processes to facilitate the deployment of offshore wind power as a key part of decarbonization strategies to combat climate change.
What about marine biodiversity and rare earth metals?
The effects of offshore wind farms on biodiversity are still not well known, and while our first thought may be the impact on migrating birds (which is being addressed with radars on the turbines), experts agree that the construction of an offshore wind farm is the phase that most negatively affects species, namely underwater species. High noise levels underwater will cause marine mammals to escape these sound levels and in effect, lose their habitat. Though techniques to lower the impact are being tested, it is difficult to track what happens to affected mammal populations afterward.
One potential positive effect of offshore wind farms is the “artificial reef effect” which has been well-documented in Belgian wind farms. New species like mussels, crabs and fish will begin to settle around the wind turbine, and then attract new species, creating a new habitat rich in animal and plant marine biodiversity.
With respect to rare earth metals: in contrast to photovoltaics and onshore wind farms, offshore wind turbines do in fact use rare earth metals to limit technical problems and thus minimize maintenance which is particularly complex and costly for offshore wind farms. This material dependence creates geopolitical issues as these resources and industry are dominated by China in addition to environmental problems due to complex extraction. However, the risk is limited as the volume required of these materials is quite small.
While these two issues are ongoing reason for concern, and we must continue to mitigate their impact and risks, the benefits of offshore wind as a powerful resource of abundant low carbon-emitting energy are significant, especially at at this critical moment where we need to reduce our carbon emissions drastically and avoid building/restarting fossil fuel plants.
Let the wind carry us
As the technology matures and costs go down, offshore wind presents a competitive renewable power solution, especially as countries search critically for alternatives to fossil fuel energy sources not only to reduce CO2 emissions but also to reduce dependence on foreign oil and gas.
On a personal side note, I actually prefer smaller, more distributed energy solutions like onshore wind and solar which are easier and faster to implement and can be managed by local actors.
Energy technologies with massive centralized infrastructure, like nuclear and offshore wind, require high upfront costs and national coordination and political acceptance. Given that these technologies have been so slow to develop in the past decade, it is in some respect hard to be hopeful that offshore and nuclear will develop with the necessary urgency in the next decades.
And if they do develop and replace fossil fuels, will wind turbine manufacturers become the future energy giants with massive power and influence (that they then use in vested instead of general interest)— for instance, replacing Shell with wind manufacturer Vestas? I hope not.
But as the latest IPCC report affirms, we need to act urgently to fight climate change and thus stop all new fossil fuel projects and invest abundantly in all low-carbon energy sources — including offshore wind power.
¹ Cape Wind was an offshore wind project in Massachusetts proposed in 2001 that over the course of 16 years, faced countless licensing and legislative setbacks and was eventually terminated in 2017.
This article is also published on the author's blog. illuminem Voices is a democratic space presenting the thoughts and opinions of leading Sustainability & Energy writers, their opinions do not necessarily represent those of illuminem.