Within days of each other, two projects have been announced which will, if completed, represent a transformation for offshore wind and renewable energy in general. Denmark has committed to building a world-first artificial island to act as a base for hundreds of gigantic wind turbines, while South Korea has given the go-ahead for an offshore farm dwarfing the largest currently in existence.

Offshore wind offers some major advantages over land-based wind turbines. Some very rare exceptions aside, the wind is more constant out to sea with nothing to obstruct it. Delivering towers, blades, and turbines by ship avoids restrictions and neighbors’ objections that keep some onshore wind farms from reaching their ideal height. Consequently, offshore wind farms are usually bigger and can catch the more consistent winds at altitude, leaving far smaller gaps to be filled from polluting sources than onshore wind, let alone solar power.

The lack of shallow-water sites in some parts of the world is one obstruction to offshore wind's growth, but a much bigger one has been the cost. Until recently, offshore wind has been so expensive to build that it accounts for roughly 0.5 percent of global electricity production. These two developments indicate that this is about to change.

Denmark leads the world in the proportion of energy it draws from the wind. In recent years an increasing proportion of that has come from offshore, and now the Danish Government has announced its intention to go further, building a 120,000 square meter (30 acre) artificial island to service an expansion. The island will be bordered on three sides by a sea wall, while the fourth will provide a safe harbor for vessels that will service the turbines located around it. The project will be shared 51/49 between the Danish government and private companies.

“The energy hub in the North Sea will be the largest construction project in Danish history. It will make a big contribution to the realization of the enormous potential for European offshore wind.” Denmark’s climate minister, Dan Jørgensen, said in a statement.

Along with a smaller hub to be built to Denmark’s east, the island is expected to support 5 gigawatts of new offshore wind in its first phase – four times the current largest offshore wind farm and equal to total world capacity nine years ago

Combined with existing wind farms, both on and offshore, the project will turn Denmark into a net exporter of clean energy to its neighbors. Construction is to start in 2026, although there are warnings it may not be completed by 2030, the date by which initial Paris Commitments are meant to be achieved.

Innovative as the construction of an artificial island may be, by the time it’s finished the farm it will serve is unlikely to be the world’s largest. For a start, it will probably be beaten by the 8.2 GW behemoth just approved by South Korean President Moon Jae-in. "The wind farm to be built on the waters off Sinan will be as much as seven times the size of the world’s current largest wind power complex," Moon said in a statement.

Moon has a goal of abolition of coal, currently his nation’s largest source of power, by 2030. As a densely populated country, South Korea has struggled to find space for solar farms, but the Yellow Sea to its south is if a good depth for wind farms, although wind speeds are slower than off Denmark. The project will cost 48.5 trillion won ($43 billion), mostly from companies that have already signed on.

Plunging costs have made these projects feasible, not through any one technological breakthrough, but from a series of small improvements that have combined to make an enormous difference.