Swedish technology paves the way for offshore wind power

Mikael Dahlgren, who has been working at Hitachi Energy for the past six months, says this. Hitachi Energy is one of the world's leading technology providers of offshore wind power solutions.

This concerns a previously untapped opportunity in the use of so-called HVDC technology, which was developed as early as the 1950s at ASEA, which later became part of ABB, where Mikael Dahlgren previously worked as a research director. HVDC, which stands for High Voltage Direct Current, was originally developed as a more efficient alternative for transmitting large amounts of electric power over long distances. Instead of using alternating current, as in the regular power grid, the electricity is converted to high-voltage direct current during the transmission. Initially, the technology was used in land-based lines or in underwater cables between countries. However, in recent years, direct current cables have also proven to be an effective solution for bringing electricity from offshore wind farms.

"The advantage of using direct current cables instead of alternating current is that they have lower energy losses along the way and we can transmit more power over long distances. We can also have better control over how much electricity we transmit and increase the flexibility and stability of the power grid," says Mikael Dahlgren.

Offshore Wind Power Must Increase Faster 

In recent years, the expansion of wind power has increased rapidly. Last year, 116 GW of new wind power was installed globally, equivalent to approximately 100 Swedish nuclear reactors. Nevertheless, many experts believe that progress is too slow if the world is to achieve the goal of limiting global warming to 1.5 degrees. This is particularly true for the expansion of offshore wind power, which in 2022 accounted for only seven percent of of the world's total wind power capacity. This is despite the fact that offshore wind power is considered to have significantly greater development potential than on land, as it is often more windy at sea and there are larger available areas to utilise. However, to be able to expand offshore wind power on a large scale, new technical solutions are required to make it both practically and economically feasible. One of the keys is to find more efficient ways to bring the produced electricity to land.

New Piece of the Puzzle could Enable Large-Scale Expansion

Today, high-voltage direct current (HVDC) underwater cables are already used to transmit electricity from offshore wind farms in several parts of the world. New projects are underway in both the Baltic Sea and the North Sea. The largest is the Dogger Bank Wind Farm off the coast of England, which is expected to produce electricity for 6 million households when completed in 2026. However, the technology has so far been used on a much smaller scale than what is possible. Mikael Dahlgren believes this could soon change, thanks in part to a previously untapped technical solution he has helped develop. It involves a type of electrical switch that makes it possible to connect entire networks of direct current cables. This solution has the potential to take offshore wind power to entirely new levels.

"What we are now facing is the transition from having distributed hubs where each offshore wind farm has its own cable to land, to being able to build international mega-grids with these stable direct current links offshore, where many different wind farms can be interconnected and create common connections to land, or to several different countries," says Mikael Dahlgren.

Increased Opportunities for Swedish Expansion

Today, Sweden lags behind many other countries in the development of offshore wind power. Currently, there are four wind farms off the Swedish coast. The government has plans for an additional 16 new wind farms, but only three have been granted permission to start construction, and several previous projects have been scrapped. In public debate, the explanations have often revoöved around high investment costs, complicated legislation, and complaints from local politicians and the public who are concerned that the new wind turbines will disturb important natural values and obscure the horizon. However, Mikael Dahlgren believes that connections with direct current cables, instead of with alternating current, could also be a solution here.

"With the help of this technology, it would be possible, among other things, to place the wind farms further out at sea where they are not visible from the coast. Especially now that it is becoming possible to build floating wind turbines that do not need to stand on the seabed."

About Off Shore Wind Power

From a global perspective, China and Europe are leading the expansion of offshore wind power. In 2022, China accounted for 49 percent of the total installed offshore wind power. Europe was in second place with 43 percent (Source: GWEC Global Wind Report 2023).

The EU has set the goal of achieving net-zero greenhouse gas emissions by 2050. To succeed, the European Commission estimates that offshore wind power capacity in Europe must increase twentyfold compared to today (Source: European Commission).

In May 2023, the government in Sweden appointed a special investigator to analyse how the approval and permitting processes for the construction of new offshore wind power in Sweden could be streamlined. The results are to be presented no later than 30 November 2024. 

Sweden's largest offshore wind farm is located at Lillgrund, just south of the Öresund Bridge. It consists of 48 wind turbines with a combined capacity of 110 MW, enough to supply 60,000 households with electricity. The world's largest offshore wind farm currently under construction, Dogger Bank Wind Farm in the North Sea off the coast of England, is planned to generate just over thirty times the capacity (3.6 GW) of Lillgrund, sufficient to supply up to 6 million British households with electricity.

About Mikael Dahlgren

Mikael Dahlgren is a Senior Principal Project Lead Engineer at Hitachi Energy. He previously worked as a research director at ABB, where he drove innovation efforts in new green power technology. He studied engineering physics at Chalmers University of Technology and holds a doctorate from the Vienna University of Technology.

Mikael Dahlgren is a Fellow of the Royal Swedish Academy of Engineering Sciences' Division of Electrical Engineering since 2021.