π Energy
Offshore wind: drop in the ocean or energy tsunami?

Offshore wind turbines: “cheap, green energy with great potential”

Anaïs Marechal, science journalist
On January 19th, 2022 |
4 min reading time
Daniel Averbuch
Daniel Averbuch
Engineer at IFP Énergies nouvelles
Key takeaways
  • In France, le Réseau de Transport d’Électricité (RTE) forecasts an offshore wind capacity of 22 to 62 GW by 2050. By then, the existing nuclear fleet will see its capacity fall from around 60 GW to 16 GW as older plants close.
  • More specifically, the International Energy Agency (IEA) estimates that offshore wind power could produce 420,000 TWh of electricity each year, or 11 times the global electricity demand in 2040.
  • Thanks to these advantages, the offshore wind sector is expanding rapidly. The global installed capacity has increased from 3 GW in 2010 to 23 GW in 2018. Europe dominates the market, accounting for 80% of installed capacity.
  • The call for tenders for the Dunkirk wind farm in 2019 revealed that production costs are falling faster than expected: the price per MWh is €44, compared with around €65 for onshore wind power and €40-70 for ground-based solar photovoltaic power.

Since the Paris Agree­ments were adopt­ed in 2015, the inter­na­tion­al objec­tives in the fight against cli­mate change have been clear: to aim for car­bon neu­tral­i­ty by mid-cen­tu­ry. It is impos­si­ble to achieve this ener­gy tran­si­tion goal with­out the mas­sive devel­op­ment of renew­able ener­gies. Off­shore wind pow­er is at the fore­front: all pro­jec­tions show that the sec­tor, which cur­rent­ly accounts for only 0.3% of glob­al elec­tric­i­ty pro­duc­tion, will dra­mat­i­cal­ly evolve. In France, the RTE describes the sec­tor as “one of the most promis­ing for long-term low-car­bon elec­tric­i­ty pro­duc­tion”1. The UK is the cham­pi­on to date: installed off­shore wind capac­i­ty is 10.4 GW (com­pared to 14 GW onshore), and the coun­try is tar­get­ing 40 GW by 20302. Even though no wind farms are cur­rent­ly oper­a­tional in France, RTE fore­casts off­shore wind capac­i­ty of 22 to 62 GW by 2050. By then, the his­tor­i­cal nuclear fleet (exist­ing infra­struc­ture) will see its capac­i­ty decrease, due to the clo­sure of age­ing plants – i.e. sec­ond gen­er­a­tion reac­tors built in the 1980s. It will reduce from about 60 GW of cur­rent pro­duc­tion to 24 GW, or even 16 GW, depend­ing on the sce­nar­ios in which nuclear pow­er still has a place in the ener­gy mix.

Huge potential for offshore wind

Wind tur­bines can be fixed to the seabed at depths of up to 50 metres or beyond that on a moored float­ing base. “For eco­nom­ic rea­sons, off­shore wind tur­bines are best installed in areas in which the aver­age annu­al wind speed is at least 8 metres per sec­ond,” explains Daniel Aver­buch. “This lim­i­ta­tion, togeth­er with the min­i­mum depth require­ment, results in an enor­mous tech­ni­cal poten­tial.” More pre­cise­ly, the IEA esti­mates3 the poten­tial of off­shore wind pow­er at 420,000 TWh of elec­tric­i­ty per year, that is, 11 times the glob­al demand for elec­tric­i­ty in 2040.

“The unit pow­er of off­shore wind tur­bines is cur­rent­ly 10 MW, and the indus­try is aim­ing for 15 MW or more by the end of the decade,” explains Daniel Aver­buch. “This is much more than onshore wind tur­bines, which are small­er so as to lim­it visu­al impact for near­by res­i­dents and which have a unit pow­er of around 3 MW”. Anoth­er advan­tage of off­shore wind pow­er is the load fac­tor. This para­me­ter rep­re­sents the ratio between the elec­tric­i­ty actu­al­ly pro­duced and the the­o­ret­i­cal pow­er of the tur­bine. It is often a prob­lem for renew­able ener­gies that rely on inter­mit­tent sources such as sun­shine or wind.

But off­shore wind tur­bines out­per­form all oth­er forms of elec­tric­i­ty gen­er­a­tion except nuclear ener­gy: new wind farms have an aver­age load fac­tor of 40–50%, com­pared to 25% for onshore wind tur­bines in France and 14% for solar pho­to­volta­ic pan­els4. The Hywind Scot­land wind farm has even set a new record with an annu­al aver­age of 57%!5 “This can be explained by the nature of the winds, which are stronger and more reg­u­lar at sea, but also by the design choic­es made for off­shore wind tur­bines,” explains Daniel Aver­buch. Europe has a prime loca­tion: in the North Sea, the Baltic Sea, the Bay of Bis­cay, the Irish Sea and the Nor­we­gian Sea, winds reach load fac­tors of 45 to 65%, com­pared to 35 to 45% for Chi­na or Japan and 40 to 55% for the Unit­ed States.

This greater pro­duc­tion sta­bil­i­ty makes off­shore wind an inter­est­ing choice for the bal­ance of the ener­gy mix. More­over, pro­duc­tion is com­ple­men­tary to that of oth­er renew­able ener­gies: in Europe, Chi­na and the Unit­ed States, it is more impor­tant in win­ter, unlike that pro­duced by pho­to­volta­ic panels.

Towards mature technology

Thanks to these advan­tages, off­shore wind is rapid­ly expand­ing. Glob­al installed capac­i­ty has grown from 3 GW in 2010 to 23 GW in 2018, out­pac­ing all oth­er sources of elec­tric­i­ty except pho­to­voltaics. Europe, led by the UK, dom­i­nates the mar­ket, account­ing for 80% of installed capac­i­ty in 2018. Chi­na could take the lead by 2030, how­ev­er, increas­ing its installed capac­i­ty from 5 to 36 GW. In France, Ademe esti­mates the eco­nom­ic poten­tial of off­shore wind pow­er at 924 mil­lion euros a year in added val­ue by 2030, with 11,300 direct jobs being cre­at­ed each year.

For years, the cost of off­shore wind pow­er has been an obsta­cle: the aver­age pro­duc­tion costs of onshore wind pow­er in France are esti­mat­ed at around €100/MWh, com­pared to €79–149/MWh for hydro, €50–70/MWh for onshore wind, €45–81/MWh for ground-based solar pho­to­volta­ic or €43.8–64.8/MWh for nuclear (depend­ing on the method of cal­cu­la­tion used). How­ev­er, the ten­der for the Dunkerque wind farm in 2019 shows a faster than expect­ed decrease in costs 6: the price per MWh for this ten­der is €44. 7Pro­duc­tion costs could even fall to €25–30 per MWh by 2030. For Daniel Aver­buch, this sig­nif­i­cant decrease is explained by “the greater matu­ri­ty of the indus­try, which reduces the cost of bank loans. The increase in the size of off­shore wind tur­bines also makes it pos­si­ble to pro­duce more with few­er tur­bines,” he adds, “and there­fore to reduce invest­ment and main­te­nance costs.”

Obstacles to overcome

It will not be all plain sail­ing though: the suc­cess of off­shore wind pow­er will depend will depend on over­com­ing cer­tain dif­fi­cul­ties. “The increase in elec­tric­i­ty pro­duc­tion will require stronger elec­tric­i­ty trans­port net­works,” explains Daniel Aver­buch. “Off­shore wind pow­er con­cen­trates elec­tric­i­ty pro­duc­tion in cer­tain geo­graph­i­cal regions: it requires the dis­si­pa­tion of large quan­ti­ty of ener­gy, unlike onshore wind pow­er or pho­to­voltaics, which are more dis­trib­uted.” Anoth­er impor­tant point: the mate­ri­als need­ed to build wind tur­bines. Daniel Aver­buch adds: “The resources of crit­i­cal met­als and rare earths required for the ener­gy tran­si­tion are the sub­ject of prospec­tive work, par­tic­u­lar­ly with­in the IFPEN8. How­ev­er, wind ener­gy, which requires rare earths for per­ma­nent mag­nets, only rep­re­sents a small share of the glob­al market.”

Final­ly, float­ing off­shore wind – installed in areas deep­er than 50 metres – is sub­ject to greater uncer­tain­ty. About 70% of the world’s pro­duc­tion poten­tial is based on this type of wind tur­bine. The tech­nol­o­gy is less mature and no float­ing farms have yet reached the com­mer­cial stage. But even if no float­ing wind farms were to be built, this would not her­ald the death knell of off­shore wind farms. The poten­tial of installed wind tur­bines alone sur­pass­es the pro­ject­ed glob­al demand for elec­tric­i­ty by 2040.

The envi­ron­men­tal impact of off­shore wind tur­bines is weak, accord­ing to a Life Cycle Assess­ment (LCA). The LCA takes into account trans­port, man­u­fac­tur­ing, instal­la­tion, use and the tur­bines’ end of life. In 2015, Ademe esti­mat­ed the emis­sion rate of French wind farms at 14.8 grams of CO2 equiv­a­lent per kWh9 over a life­time of 20 years. A recent study on float­ing wind tur­bines eval­u­ates their LCA at 19.5 g CO2 equivalent/kWh for a 25-year life span10. These val­ues are com­pa­ra­ble to onshore wind (14.1 g CO2 equivalent/kWh), low­er than Chi­nese-made pho­to­voltaics (56 g CO2 equivalent/kWh) and much low­er than emis­sions from a gas-fired pow­er plant (418 g CO2 equivalent/kWh) but still high­er than nuclear (less than 6 g CO2 equivalent/kWh)1112.

1RTE, Futurs énergé­tiques 2050, octo­bre 2021
3Agence Inter­na­tionale de l’Énergie, Off­shore Wind Out­look 2019, World ener­gy out­look spe­cial report
4https://​www​.equinor​.com/​e​n​/​n​e​w​s​/​2​0​2​1​0​3​2​3​-​h​y​w​i​n​d​-​s​c​o​t​l​a​n​d​-​u​k​-​b​e​s​t​-​p​e​r​f​o​r​m​i​n​g​-​o​f​f​s​h​o​r​e​-​w​i​n​d​-​f​a​r​m​.html, con­sulté le 7 jan­vi­er 2021
5Ademe, Éolien off­shore : analyse des poten­tiels indus­triels et économiques en France, décem­bre 2019
6Ademe, Éolien off­shore : analyse des poten­tiels indus­triels et économiques en France, décem­bre 2019
7www​.eoli​en​nesen​mer​.fr, con­sulté le 7 jan­vi­er 2021
9Ademe, Impacts envi­ron­nemen­taux de l’éolien français, 2015
10Com­mis­sion nationale du débat pub­lic, BL Évo­lu­tion, Analyse bib­li­ographique des bilans car­bones de l’éolien flot­tant, décem­bre 2021

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