Can floating wind turbine fleets succeed the scale-up ?

Floa­ting wind tur­bines show much pro­mise for ener­gy pro­duc­tion world­wide : 330,000 TWh per year, or 79% of the total theo­re­ti­cal poten­tial of off­shore wind power¹. Floa­ting devices are used beyond a depth of 50 metres, the limit at which it becomes too expen­sive to deploy land-based tur­bines. The first semi-com­mer­cial sites have star­ted pro­duc­tion. Part of the Float­gen pro­ject, the SEM-REV² off­shore test site, sup­por­ted by École Cen­trale de Nantes, is the first to pro­duce elec­tri­ci­ty in France using an off­shore wind tur­bine. The wind tur­bine deployed by the com­pa­ny Ideol has been gene­ra­ting over 6 GWh of elec­tri­ci­ty a year since 2018. Hydro­dy­na­mics research engi­neer Yves Per­ignon is res­pon­sible for the test site.

While many land-based wind farms have been in ope­ra­tion since the 1990s, off­shore wind power is only just begin­ning to emerge. How do you explain this ?

Off­shore wind tur­bine tech­no­lo­gy is indeed less mature. The first pro­to­type was deployed in Nor­way by the oil com­pa­ny Equi­nor in 2009. Por­tu­gal fol­lo­wed with ano­ther pro­to­type from the floa­ter Prin­ciple Power in 2011. Fur­ther deve­lop­ments then ensued, and there are now around ten pro­to­types world­wide. Seve­ral coun­tries are star­ting the com­mer­cial phase : for example, in Scot­land, two wind farms with ins­tal­led capa­ci­ties of 30 and 50 MW are in ope­ra­tion. In France, four pilot farms will be built over the next few years.

There are a num­ber of rea­sons for this delay. Nor­thern Euro­pean coun­tries – Ger­ma­ny, the Uni­ted King­dom, the Nether­lands, Den­mark, Nor­way, and Bel­gium – have been pio­neers in wind power. After tes­ting onshore tur­bines on islands, many of them have inves­ted in off­shore wind power. The know­ledge gai­ned thus far has allo­wed them to resolve many issues, such as cost reduc­tion, pro­duc­tion capa­ci­ty, connec­tion to elec­tri­ci­ty grids, etc. Land-based wind power has shown that off­shore wind power could also be of inter­est for a coun­try’s ener­gy balance. Off­shore wind power tech­no­lo­gy, which is less tech­no­lo­gi­cal­ly mature, is the next logi­cal step. The pro­jects and deve­lop­ments are being car­ried out by inter­na­tio­nal consor­tia, often inclu­ding players from the off­shore oil indus­try, who alrea­dy have many of the skills requi­red to deve­lop floa­ting wind power.

What are the tech­no­lo­gi­cal bar­riers to the com­mer­cia­li­sa­tion of off­shore wind ?

The main issue concerns the struc­ture – com­pri­sing a float and an ancho­ring sys­tem – that sup­ports the wind tur­bine. A varie­ty of advan­ced tech­no­lo­gies exist, but various obs­tacles still need to be over­come. For example, regar­ding their relia­bi­li­ty, mate­rial fatigue and resis­tance to extreme condi­tions during storms must be tes­ted throu­ghout the life of a wind farm. Ano­ther chal­lenge is up-sca­ling from the pro­to­type stage to a wind farm, which will also involve repla­cing dete­rio­ra­ted anchor lines.

Other chal­lenges involve the elec­tri­cal connec­tion : manu­fac­tu­rers are wor­king to improve the strength and relia­bi­li­ty of connec­ting cables. What is more, today, indi­vi­dual wind farms are connec­ted to each other in a series, which means that seve­ral wind tur­bines have to be shut down in the event of a fai­lure. Alter­na­tive solu­tions could help limit downtime.

Does sca­ling up pose other challenges ?

Yes, and more gene­ral­ly, it means that we need to think about the upkeep of these farms, which are loca­ted far out at sea. The obs­tacle is not only tech­ni­cal, but also eco­no­mic : these farms will require more under­wa­ter ins­pec­tion around cables, anchors or the float. Main­te­nance must be made more rou­tine and adap­table to cope with this. Opti­mi­sing the means of ins­pec­tion, for example, may have impor­tant eco­no­mic impli­ca­tions. Final­ly, port infra­struc­tures, and the sui­ta­bi­li­ty of the construc­tion or sto­rage areas for floats and other com­po­nents, will be crucial.

Manu­fac­tu­rers are now capable of buil­ding floa­ting wind tur­bines, but the chal­lenge is to scale up to low-cost, low-car­bon power generation.

Why is the eco­no­mic equa­tion a pro­blem ? How might it be solved ?

To date, only one ten­der has been laun­ched in France for the crea­tion of a floa­ting wind farm – in Sou­thern Brit­ta­ny by 2029. The costs of floa­ting wind power are 1.5 to 4 times higher than those of land-based wind power³. This can be explai­ned by the fact the off­shore sec­tor is not as mature. Pros­pec­tive stu­dies⁴ show, howe­ver, that the cost of floa­ting wind tech­no­lo­gy will decrease and ali­gn with mar­ket price in less than 15 years.

The eco­no­mic model of floa­ting wind ener­gy is based on inno­va­tive tech­ni­cal and ope­ra­tio­nal choices, but also on a bet­ter exploi­ta­tion of tur­bine capa­bi­li­ty. As with land-based wind ener­gy, increa­sing the unit power of wind tur­bines will improve the yield of wind farms.

Why deve­lop off­shore wind turbines ?

Floa­ting wind power repre­sents a very impor­tant source of ener­gy pro­duc­tion that land-based wind power can­not cover. But it also offers other advan­tages : floa­ting wind tur­bines have higher load fac­tors, for example, than those of land-based wind ones, and thus suf­fer less from inter­mit­tent ener­gy pro­duc­tion. Deployed fur­ther from the coast, floa­ting wind tur­bines are expo­sed to stron­ger winds and the­re­fore have a higher pro­duc­tion capa­ci­ty. The visual impact of these struc­tures is also redu­ced – because they are built far out at sea. More broad­ly, we are begin­ning to bet­ter unders­tand the socio-eco­no­mic and bio­di­ver­si­ty impact of off­shore ins­tal­la­tions. We can the­re­fore eva­luate the advan­tages and limi­ta­tions of floa­ting wind tur­bines in the context of ener­gy poli­cies and when plan­ning future wind power installations.