Interest in an article offshore wind and hydrogen encouraged me to once more reach for the virtual ‘pen’ and delve into the area of offshore wind floating wind.
In some respects, floating wind is the ‘new kid on the block’ of the wind industry although one with which I’ve been involved with for years floating-offshore-wind-revisited. The first operational site ‘Hywind’ is situated off the coast of Aberdeen in Scotland and after the first few years of operation, is generating with capacity factors approaching 60%, something deemed impossible not so long ago.
There are both advantages and disadvantages to floating wind and added complexity when considering hybrid schemes with technologies involving hydrogen production and electrolysis onshore, offshore, or even within the turbine.
Currently, floating offshore wind is much more expensive than its fixed-bottom counterpart, but as with its predecessor, as the industry scales it may be that cost reductions occur, and the industry can become price competitive.
Obviously, there is a reduced expense for the steel needed in the foundations as they do not go right down to the seabed but are instead anchored by cables and weights. Because of this there is a flexibility on siting, releasing floating offshore wind arrays free from these constraints relating to the ground conditions; sea-depth become less critical and deep-water conditions open up most of the global seabed.
Wind farms usually require cabling from the foundation down to the seabed. The cable is then trenched a metre deep through the seabed back to the ‘beach’ and onwards to the substation. This method is so routine that it was still used by the otherwise hugely innovative Hywind at Buchan deeps.
As the industry innovates, we can anticipate more dynamic cabling – perhaps using buoys under the surface to get to shore. This will greatly reduce both the amount of cable required and the environmental impact on the seabed. This form of moving cabling is not without controversy; stakeholders such as the fishing community and those involved in protecting diving birds will have plenty to say, but this kind of cabling may de-commissioning easier and is something upon which we can expect development.
Floating machines can be made at remotely at what Shell – a floating wind and hydrogen market re-entrant – terms, slightly oddly, ‘the beach’. The machines can be manufactured and assembled at the quayside enabling industrial scale mass production and the associated cost reductions. Once assembled they are simply towed out to sea ‘plugged in and planted on site.
The streamlined mass production envisaged for floating offshore wind means scaling is possible and the industry can realistically build sites much further out to sea where harsher conditions prevail. This process also avoids challenges around expensive specialist jack-up and installation vessels, an industry chokepoint to date and greatly reduces the cost.
Fixed foundations require favourable seabed conditions and work up to around 30 metres; deeper than that and the amount of steel becomes prohibitive. Floating machines, anchored with cables are, in theory at least, freed from these geographical constraints.
This does not necessarily mean that floating wind farms will immediately go further out to sea as the cable will still need to reach the shore which will need to be factored into a project. However, deeper waters, close to major population centres and sites previously ruled out as being too deep, are now very much back and there is a new technology namely hydrogen which may mean that schemes much further out can be viable.
As reflected in offshore wind and hydrogen, combining floating wind and hydrogen to make gas from air represents a significant global opportunity.
One of the problems faced by the offshore wind sector has been finding suitable commitment from the grid bodies often involving shareholders who may baulk at the costs involved in providing connections in unfamiliar terrain, hundreds of miles at sea on projects that may or may not come to fruition.
It is difficult for grid planners to work on that basis; if, however, hydrogen production rather than electrical generation was the main reason for the new sites, then a game-changing situation exists. The relatively constraint-free floating wind and associated electrolysis and infrastructure could be sited near existing oil and gas assets and a pipeline network which may be suitable for distributing the finished hydrogen to shore. This is not fanciful the dolphyn off Aberdeen is already in the public domain and oil and gas majors BP, Total and Shell engaged, and sites are being assessed. One to watch with interest is Scotland’s ScotWind leasing round where around four gigawatts of floating wind development is being scoped. Sites off California, Wales, Holland, Germany, Norway, and Ireland are all being actively considered
Source: energycentral
