In 2020, the country's 4333 wind turbines produced 16% of our energy in Sweden (Energi myndigheten 2020, Ny statistik över installerad vindkraft 2020 (energimyndigheten.se). That's a lot of power plants and more are expected in the coming years. They produce renewable energy, but also contribute to greenhouse gas emissions. In general, today's wind turbines are built with materials such as steel and concrete. Strong materials that can withstand the forces a wind turbine is subjected to, but the traditional choice of materials contributes to high greenhouse gas emissions. The largest contributor to the climate impact of wind power comes from the raw materials used in the manufacture of the turbines.

The wind power industry has a need to reduce the climate impact when manufacturing new power plants. The Gothenburg-based company Modvion is helping to reduce the climate impact of the wind power industry by replacing the tower, which is usually made of steel, with a wooden tower of the same height. In 2020, the first 30-metre-high wooden wind power tower was erected on Björkö in the Gothenburg archipelago. Another tower was recently erected in Skara, reaching 105 metres. Subsequently, even higher towers are planned to support turbines with even greater production capacity.

Advantages of wooden wind towers
Wood is a renewable material that also sequesters carbon over the life of the wind turbine. Steel is strong - stronger than wood - but it is also heavy. When comparing the strength of materials in relation to their weight, wood outperforms steel. In increasingly tall towers, the weight of the tower means that the steel tower needs to be reinforced to support its own weight. Wooden towers, which are lighter, do not have the same problem with their own weight and so it is possible to build tall and slender with wood. To cope with the extreme forces of the massive rotor blades at the top of the tower and the strong winds to which a wind turbine is exposed, Modvion has developed and now manufactures wooden frames for wind towers. The construction consists of thin wood laminates that are glued and pressed together into curved 15 metre long wooden modules. The modules are erected, joined and then stacked on top of each other to erect the tower. The relatively small size of the modules allows them to be transported to the construction site by smaller lorries compared to today's steel towers where specialised vehicles are used to transport larger components.

Development work
One challenge has been to develop strong joints for joining the modules that can be efficiently assembled on site and withstand the extreme forces on the tower. The solution used is inspired by a relatively new technique where a steel plate with holes is glued between the wooden elements to be joined. This differs from traditional jointing solutions where steel plates are used in combination with, for example, screws, bolts or dowels. Using glue instead of metal connectors results in very strong and rigid joints. The manufacture of glued wood structures is usually done in a factory in a controlled environment and under controlled conditions. On the construction site, temperature, humidity and working conditions vary and thus it can be difficult to control the quality of the gluing. In the project Stuck in the middle with you (SIMWY), funded by Vinnova, Modvion, Henkel and RISE are collaborating to develop Modvion's method for construction gluing on the construction site. You can read more about the project on the project website, (Link).

Developing new technology means that it needs to be tested and evaluated. RISE has experts in various subject areas and laboratories for testing and evaluating materials and structures, both on a small and large scale. Together with Modvion, RISE has tested the the new hybrid joint for different types of loads that mimic those it needs to withstand in reality in a completed wind turbine tower. The joint has also been subjected to fatigue through cyclic tests where it has been loaded and unloaded thousands of times over a long period of time to failure. Fatigue is rarely relevant in ordinary wooden buildings, but in structures such as bridges and nowadays tall towers that are loaded with high varying loads during their lifetime, the phenomenon becomes relevant. 

This is an article from our magazine Trävärden, it is available in full here! (Link)

Offshore wind power is one of the most promising options for renewable electricity generation, and Sweden has great resource potential. As wind turbines become larger, the cost per kilowatt hour (KWh) produced decreases significantly.

According to the Swedish Energy Agency, Sweden’s total electricity consumption amounted to 140 terawatt hours (TWh) in 2022.

“The offshore wind power sites currently planned along the Swedish coast amount to 90 gigawatts (GW) of installed power,” says Nermina Saracevic, Senior Project Manager for Renewable Offshore Energy at RISE. “Most of these projects are in the application stage. If just half of them are implemented, it can cover all of Sweden’s current electricity needs.”

Overlapping interests create potential risks

The growing need for fossil free energy and the increasing establishment of offshore wind farms highlight the conflicting interests that exist between shipping, commercial fishing, environmental protection, and the production of renewable energy.

The permit process when developing new wind farms is complex and involves several state and regional authorities. On behalf of various project developers, RISE analyses potential nautical risks in the establishment and operation of wind farms. These are presented together with proposals for risk mitigation measures, which are then reviewed by the Swedish Maritime Administration, the Swedish Transport Agency, and other relevant stakeholders.

“When wind turbines are planned in areas with established shipping and fishing, new risks are created, and these need to be identified and minimised,” says Christian Schell, Head of Strategic Development – Maritime Environment, Risk and Operation at RISE. “RISE is an independent partner that supports a growing industry.”

 “A lot revolves around ensuring that there are sufficient margins between shipping lanes and the wind farm, while at the same time considering both the marine environment in general and national, commercial fishing. We have well-established methodology for investigating maritime traffic patterns, as well as proven calculation programs for calculating the probability of allisions, collisions and groundings. The current increase in applications requires an overview of the cumulative effects of the establishment of new offshore wind farms, along with their impact on ship traffic and the marine environment.”

Upgrading of Nordic ports

The permit process for offshore wind farms can take between 7 and 10 years and requires several different stakeholders to approve the project for it to become a reality. In addition, port infrastructure and supply chains need to be adapted, as their role in a future offshore wind establishment will be significant both in the short and long terms.

RISE, via the cluster platform OffshoreVäst, is leading the Swedish part of the NOW PORTS project. It aims to support Nordic ports in ensuring adequate surfaces and quays, and that expertise is in place to create an optimal supply chain when establishing and operating offshore wind power.

The project is a joint initiative where Sweden, Norway, and Denmark collaborate on issues related to future ports and offshore wind industry.

“In addition to infrastructure issues, Swedish wind power stakeholders have indicated a need for a national coordinator who can facilitate the development of offshore wind power between different authorities, as well as regional and local politicians who have an impact on the permit process,” says Nermina Saracevic, Project Manager of NOW PORTS at RISE. “As a neutral party, RISE can assume that role.”

Risk analyses, consultation, and testing

RISE offers expertise throughout the life cycle – from pre-analyses of a proposed establishment site to decommissioning and recycling of end-of-life turbines. We possess a significant pool of expertise in the area to support this, as well as test facilities for floating wind turbines, CFD analysis for wind, and hydrodynamic design and verification.

“Today, RISE is entrusted by the majority of project developers in Sweden, where various services, such as nautical risk analyses, consultation, and testing and verification constitute some of the largest service areas,” says Christian Schell. “RISE’s experts have delivered to all major projects that have received permits from the government. Commercial offers in combination with scientific research position RISE as a strong and valuable partner to the operators who are actively pushing for the establishment of offshore wind power in Scandinavia.”

It may sound strange to produce less electricity from our wind turbines when it is windiest. Electricity prices have skyrocketed, and the solution ought to be to produce as much electricity as possible, right?

“Technology is a limit; we cannot produce more electricity than the electricity grid can handle. To cope with the few days every year when the conditions for electricity production are most favorable and consumption is minimal, we would have to expand the capacity of the electricity grid enormously”, says Emil Hillberg, project manager of a recently completed project that has developed solutions and models for flexible control of electricity production.

Able to build more facilities

Before new production facilities for solar and wind power can be put into use, the electricity grid needs to be expanded to cope with the high peaks in electricity transfer, peaks that may only occur a few times a year. The rest of the time the grid has free capacity for increased production. The construction of new power lines has a negative impact on the climate and the environment and is often associated with long permit processes and construction times.

“The solutions that we have developed in the project can be used to control the electricity production based on the capacity of the electricity grid. By reducing the production when it is most windy, we can start production using the existing electricity grid instead of waiting for ten years for new power lines to be built. This means that more facilities can be built, which creates the conditions for more electricity production even when there is less wind. The result is more renewable electricity produced overall”, says Emil Hillberg.

Tested in Hungary and on Öland

The project has tested the solutions on a smaller scale in Hungary and in northern Öland.

“There are many wind parks on Öland already, but the electricity grid cannot cope when new facilities produce at max capacity. The flexibility solutions we have developed could enable new facilities to be established using the existing electricity grid”, says Emil Hillberg.

Interest in flexibility has increased

Flexibility in the production of electricity is important, but there is also room for more flexibility in the consumption of electricity which can help us make smarter use of our electricity grids.

“We have seen a large increase in the interest for flexible electricity consumption since the project started in 2019, such as heating the house or charging the car when prices are lower. Although the focus of our project was on the production side, these solutions and models can also be applied to the consumption side. We have a large capacity in our electricity grids today, but it is important that we smoothen the utilisation so that we can manage that capacity more efficiently”, says Emil Hillberg.