Energy boom on the sea

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All over the world, huge wind farms are grow­ing out of the water; in the North Sea alone, they already pro­duce around 30 gigawatts of elec­tric­i­ty. But there are even far greater plans. In April 2023 in Ostend, Bel­gium, gov­ern­ment rep­re­sen­ta­tives from nine coun­tries, includ­ing Den­mark, Ger­many and the Nether­lands, decid­ed that the North Sea should be devel­oped into Europe’s pow­er plant: 300 gigawatts of envi­ron­men­tal­ly friend­ly elec­tric­i­ty for around 300 mil­lion house­holds are planned by 2050. To illus­trate the dimen­sions: today there are about 1,000 wind tur­bines in the North Sea, but ten times as many are need­ed to ful­fill the ambi­tious plan.

It is thanks to peo­ple like Tor­ben Glar Nielsen that a gigan­tic project like this is even pos­si­ble. He already had the idea of installing wind tur­bines on the sea when hard­ly any­one even thought of such a pos­si­bil­i­ty. “When I once pre­sent­ed the idea to the Euro­pean Par­lia­ment at the begin­ning of my career, I was still laughed at.” In his home coun­try of Den­mark, wind pow­er is now ubiq­ui­tous, cov­er­ing about 55 per­cent of the country’s elec­tric­i­ty needs from wind pow­er alone. In the 45 years of his pro­fes­sion­al life, Nielsen him­self has set up many of the plants which make this pos­si­ble. Most recent­ly in his role as CTO at the Dan­ish trans­mis­sion sys­tem oper­a­tor Energinet, where he worked until 2021. Today, he sup­ports var­i­ous com­pa­nies in renew­able ener­gy projects with his own con­sult­ing com­pa­ny. Nielsen says: “I want to con­tribute to the fact that we will soon be able to live in a CO2-neu­tral way.”

Artificial energy islands

The project in the North Sea brings mankind a lit­tle clos­er to this goal. One of the cen­tral ques­tions, how­ev­er, is how these enor­mous amounts of elec­tric­i­ty will reach con­sumers on land in the future. Espe­cial­ly since the plants have to move fur­ther and fur­ther out to sea, as there is not enough space near the coast. The vision: a net­work of arti­fi­cial islands that col­lect the elec­tric­i­ty from sur­round­ing wind farms as part of a transna­tion­al pow­er grid, dis­trib­ute it fur­ther or con­vert it into hydro­gen on site. The idea was born in 2017 at a meet­ing between the two trans­mis­sion sys­tem oper­a­tors Energinet and Ten­neT to real­ize the COBRAcables—a high-volt­age direct cur­rent trans­mis­sion line between Den­mark and the Nether­lands. Nielsen, then still CTO at Energinet, chat­ted with his man­ag­ing direc­tor col­league at the time at Ten­neT, Wil­fried Breuer, dur­ing a break.

“The cable also cross­es wind tur­bines on its way through the North Sea, and that’s when we got the idea that ener­gy islands might be a good solu­tion to bet­ter con­nect off­shore wind pow­er,” Nielsen recalls. Breuer, who is now man­ag­ing direc­tor of Maschi­nen­fab­rik Rein­hausen, says, “The North Sea is quite shal­low and there­fore actu­al­ly pre­des­tined for arti­fi­cial islands that could dis­trib­ute elec­tric­i­ty to sev­er­al coun­tries at once.” As crazy as the idea may sound, it’s not at all. Pil­ing land on top of the sea is tech­ni­cal­ly noth­ing new. The air­ports of Hong Kong and Osa­ka, for exam­ple, are built on arti­fi­cial islands. This form of land recla­ma­tion also has a long tra­di­tion in the Nether­lands: Huge areas were wrest­ed from the sea by build­ing dikes for agri­cul­ture, but also for large parts of the port of Rot­ter­dam.

The idea nev­er left the two engi­neers. Only six months lat­er and after sev­er­al dis­cus­sions with represen­tatives from pol­i­tics and indus­try, they ini­ti­at­ed the North Sea Wind Pow­er Hub Pro­gram (NSWPH). The con­sor­tium of Ten­neT, Energinet, Gasunie and the Port of Rot­ter­dam is to pre­pare tech­ni­cal and eco­nom­ic fea­si­bil­i­ty stud­ies to devel­op the North Sea into Europe’s ener­gy hub.

The North Sea as a power plant

Until now, off­shore wind pow­er has been col­lect­ed on steel plat­forms known as jack­ets, which are also used by the oil and gas indus­try for pro­duc­tion. They house the rec­ti­fi­er sta­tions that con­vert the wind pow­er into direct cur­rent for onshore trans­port. The prin­ci­ple is tried and test­ed, but it also has its dis­ad­van­tages: space is lim­it­ed, main­te­nance work is not pos­si­ble at all times of the year, and the ser­vice life of the plat­form is also lim­it­ed in view of the harsh con­di­tions. An island would be more sus­tain­able here, and it would also offer much more space for build­ing the infra­struc­ture. The jack­et solu­tion cur­rent­ly man­ages to han­dle a max­i­mum of 2 gigawatts of pow­er. With the ener­gy islands, about 10 gigawatts would be pos­si­ble in a first expan­sion stage and up to 30 gigawatts with each addi­tion­al island.

In addi­tion, it opens up fur­ther poten­tial uses that would not even be eco­nom­i­cal­ly pos­si­ble on a plat­form, explains Breuer: “Some of the elec­tric­i­ty could be used direct­ly on site for the pro­duc­tion of hydro­gen, which would then be brought ashore via pipelines.” Elec­tric­i­ty has the dis­ad­van­tage that it has to be com­plete­ly dis­si­pat­ed every frac­tion of a sec­ond. The gen­er­a­tion peaks can there­fore be used for hydro­gen pro­duc­tion. This also offers the advan­tage that the elec­tric­i­ty infra­struc­ture would not have to be designed for the peaks, but only for the con­tin­u­ous load, and thus about 30 per­cent small­er. Main­te­nance work is also eas­i­er because the island offers enough space to store spare parts and build accom­mo­da­tions for tech­ni­cal per­son­nel. This means that repairs can be car­ried out quick­ly with­out any­one hav­ing to trav­el out by heli­copter or ship.

A power grid at sea

Think­ing a lit­tle fur­ther, the ener­gy islands could also become part of an inter­na­tion­al pow­er grid at sea, link­ing coun­tries and off­shore wind farms. Until now, wind farms have been con­nect­ed radi­al­ly, like a one-way street, to the inter­con­nect­ed grid of the coun­try in whose ter­ri­to­r­i­al waters they are locat­ed. In order to exchange the elec­tric­i­ty between dif­fer­ent coun­tries, the oper­a­tors then lay new sub­ma­rine cables, some of which run right past the wind farms from which the elec­tric­i­ty orig­i­nal­ly came. Incon­ve­nient, actu­al­ly. “The ener­gy islands could col­lect the pow­er from sev­er­al off­shore wind farms and distri­bute it via sub­ma­rine cables to sev­er­al neigh­bor­ing states at once,” Nielsen says.

With this so-called hub-and-spoke con­cept (see box) and by inter­con­nect­ing the ener­gy islands with each oth­er, sig­nif­i­cant­ly more elec­tric­i­ty from renew­ables can be inte­grat­ed into the pan-Euro­pean sys­tem. In this way, Nor­way with its large hydropow­er reserves which are avail­able regard­less of wind, could also be includ­ed. “Of course, the tech­ni­cal pre­req­ui­sites for this still have to be cre­at­ed in order to link the var­i­ous DC sys­tems, but stud­ies are already under­way for this as well,” says Breuer. In the future, much more sta­ble renew­able ener­gy gen­er­a­tion will then be pos­si­ble, and exchanges between inter­na­tion­al elec­tric­i­ty mar­kets will also be much eas­i­er.

When will the vision come true?

At the moment, there is advanced plan­ning for two islands. The Bel­gian trans­mis­sion sys­tem oper­a­tor Elia is already plan­ning to build Princess Elis­a­bet Island in 2024, and anoth­er is being con­sid­ered off Thors­minde in Den­mark. How­ev­er, the arti­fi­cial ener­gy islands are not cheap. For the Dan­ish project, plan­ners cal­cu­late costs of 28 bil­lion euros, five per­cent of which is for build­ing the island. “Up to a capac­i­ty of 2 gigawatts, con­ven­tion­al jack­ets are cer­tain­ly the cheap­er solu­tion. But at the pow­er lev­els envis­aged, our ener­gy islands have an advan­tage,” says Nielsen. Breuer is also con­vinced that the more eco­nom­i­cal solu­tion is bundling via islands. “Every­thing close to the coast is done fur­ther radi­al­ly, which affects about 100 gigawatts, but for the oth­er 200 gigawatts, ener­gy islands are the bet­ter option.” Depend­ing on the con­cept, a total of about eight ener­gy islands would be nec­es­sary for the plans in the North Sea. The Dog­ger Bank, a huge sand­bank about 300 to 350 kilo­me­ters long and up to 120 kilo­me­ters wide that lies under the sea, is suit­able for addi­tion­al islands. “It is also geo­graph­i­cal­ly very con­ve­nient because the British, Euro­pean and Scan­di­na­vian coasts are about the same dis­tance away,” adds Nielsen.

In any case, the North Sea Wind Pow­er Hub pro­gram has sub­mit­ted the tech­ni­cal and eco­nom­ic fea­si­bil­i­ty stud­ies. Now it is the politi­cians’ turn to cre­ate the frame­work con­di­tions so that the plans can also be turned into real­i­ty. “As the Rein­hausen Group, we offer the tech­nol­o­gy and ser­vices to ensure that the grid at sea func­tions just as reli­ably as it does on land. We also already have many years of expe­ri­ence with mar­itime solu­tions,” Breuer empha­sizes.  Nielsen is also already think­ing beyond the North Sea. Because the mod­el could also be a blue­print for oth­er regions of the world: “In Asia, wind pow­er expan­sion is still in its infan­cy; there, too, there are ambi­tious cli­mate tar­gets.” With his con­sult­ing com­pa­ny, he wants to help make that hap­pen.