Wind power plays an important role in the energy transition, but as increasing numbers of wind turbines reach the end of their service life, the volume of decommissioned turbine blades is also growing. The blades consist largely of glass-fibre composite, a durable material that is technically challenging to recycle and for which established circular value chains are still lacking.

In Sweden, the volume of end-of-life wind turbine blades is expected to increase significantly over the coming decades. This creates a need for solutions that are not only technically feasible, but also economically viable and supported by stakeholders across the entire value chain.

From individual solutions to a shared commitment

ReBladeNet addresses this challenge by bringing together wind farm owners, industry associations, recycling companies, and businesses developing new applications for the material.

The project aims to lay the foundation for a Plastics Contract for end-of-life wind turbine blades – a voluntary joint commitment that defines ambitions, responsibilities, and targets for a more circular approach to managing glass-fibre composites.

The work includes, among other things:

• develop shared goals and commitments for stakeholders across the value chain,
• identify and strengthen circular solutions for reuse and recycling,
• test and validate the Plastics Contract together with industry stakeholders,
• create the conditions for the approach to continue and scale up beyond the end of the project.

In this way, ReBladeNet aims to help move from individual initiatives towards a more integrated market, where end-of-life wind turbine blades can increasingly be viewed as a resource for new products and value chains.

The project builds on knowledge gained from the Solar and Wind Policy Innovation Lab (SVPI-Lab), where technical, economic, organisational, and policy-related barriers to circular material flows in the wind energy sector have been analysed.
 

Till de utmaningar som svenska hamnar ställs inför hör osäkra planer för vindkraftsprojekt, oklar lönsamhet för hamnen, utvecklingsrisker samt konkurrens med den affärsverksamhet som redan bedrivs i hamnen. 

Projektets syfte är att utveckla en innovativ metodik och identifiera hur en affärsmodell kan sättas upp utifrån de nya behov som vindkraftsindustrin som kundsegment har. Potentiella styrmedel och finansiella instrument kommer också att utvärderas och föreslås. 

Projektet ska hjälpa att etablera  samarbete mellan hamnar, rederier och vindkraftsindustrin med fokus på kunskapsutbyte och fördelning av risktagande utifrån potentiella affärsmöjligheter.

Projektpartner hamnar är Trelleborg hamn, Göteborgs hamn, Gävle hamn, Smålandshamnar, Stockholms hamnar, Söderhamns Stuveri & Hamn, Wallhamn, Ystad hamn, Kålvik hamn, Falkenbergs terminal & hamn, Hallands Hamnar samt Grenå hamn.

Vindindustrins deltagare inkluderar Vattenfall, Zephyr, Eolus Vind, RWE, OX2, Freja Offshore, Siemens Gamesa Renewable Energy, Northern Offshore Services och Jan de Nul. Ytterligare några tillkommer. Sveriges Hamnar (Transportföretagen) och nordiska partners (Norwegian Offshore Wind och Energy Cluster Denmark) ingår i en referensgrupp för att stötta projektet med expertis och industrinätverk. 

Projektet drivs av RISE i samarbete med  Göteborgs Universitet.

Background

Wind power has good opportunities to promote the transition towards a sustainable energy system by contributing to all the grid services that SVK needs, to ensure a robust electricity system with security of supply. Future wind power needs to support the electricity grid when needed. Wind power's ability and incentives to provide system services are related to its economics. With new regulations, which the Swedish TSO Svenska kraftnät (SVK) introduced in 2025, it is even more important to produce in accordance to the bids that have been set. Otherwise, there is a risk of high imbalance costs.

Purpose

The purpose of this project is to:

• increase wind power's contribution to the various ancillary services that SVK procures.
• demonstrate the potential and costs for a wind farm to provide support services
• demonstrate how different turbines in the farm can and should interact to deliver a stable and predictable combination of electricity production and ancillary services.

Wind power reserve

To provide sustainable flexibility, similar to base load production, some form of power curtailment is required. However, the compensation for support services must exceed the value of the energy spilled. A crucial quantity is “Available power” and “Reserve power”. The latter forms the basis for compensation from SVK when the power is curtailed or turned off. These quantities can be calculated in different ways. A first idea could be to use the anemometer on the nacelle roof to measure wind speed and based on that calculate the available power. However, this signal contains several systematic errors, especially during operation. The project has developed and validated an algorithm for how “Available power” can be calculated more accurately, see document “Calculation and analysis of available power signal” below.

Tests and validations on Chalmers’ research turbine

Within the project, several tests and validations have been carried out on Chalmers research turbine in Sweden. It is a turbine with a diameter of 17 meters and approximately 30 kW of power. It has been curtailed during operation to create a “Reserve power”. The turbine has then been controlled to follow a synthetic grid frequency, where the frequency has been changed both stepwise and in sine waves. The turbine has also been connected to the actual grid frequency and counteracted actual deviations from 50 Hz. See more about these exciting experiments in the document “Results from Björkö field tests” below.

Loads and noise

Other important aspects are loads, lifetime and noise related to the delivery of ancillary services to the grid. When wind power deliberately limits its power and leaves the maximum Cp, it can be implemented in different ways, which has consequences for loads on different systems and noise. One can increase or decrease the Tip Speed ​​Ratio (TSR, dimensionless speed) and thereby reduce Cp by moving vertically in the graph below. Another way is to stay at a constant TSR and reduce power by pitching. These two extremes can also be combined arbitrarily.

The project has analyzed how a wind farm can be curtailed in three different ways and how it affects the turbine loads, see document “Wind Farm Service dispatching” below. There is certainly more to explore. 

Further analyses, simulations and tests have been carried out to see, at turbine level, how loads and noise are affected by two different power curtailment methods “Constant TSR” vs “Variable TSR” operation. More information in below presentation “Structural loads and noise”.

Wind power has a good ability and capacity to contribute to rapid frequency control to the electricity grid. Part 1 of this project focused on investigating wind power's possible and cost-effective contribution to the Fast Frequency Reserve (FFR) system service. It means maintaining a power reserve to quickly support the grid with, if the frequency drops below a certain level (around 49.7 Hz).

By increasing the rotor speed in wind speeds below rated wind, an additional rotational energy is generated, which quickly can be converted into additional power (FFR) to the grid, if the frequency should drop for any reason. With a coordinated and active control of the wind turbines, it is theoretically possible to handle the worst possible failure case (an FFR capacity of 280 MW) with wind power alone. The cost in lost energy production would then be approximately one percent (1%), as a result of operating at a higher rotor speed than optimal speed in low winds.

This part 2 of the project, funded by the Swedish Energy Agency, deepens the study and focuses on the economic consequences. A loss of production costs different depending on when the loss occurs. Therefore, it is important to go a step further and calculate whether or not it is financially beneficial to offer FFR for the hours to come. Therefore, the operation of wind turbines at different locations has been studied and compared hour by hour based on which product (energy or FFR) gives the best revenue.

To carry out the study, the wind speed has been estimated, hour by hour. First aactual wind measurements from 2016 and 2017 have been downloaded from twelve (12) locations around Sweden, three (3) in each SE area. Second, the wind speed has been calculated based on actual production data in each SE area. The result of a comparison can be seen in the graph below, which shows October 2017, where the wind speed has been measured at a height of 150 meters.

By this method, the wind speed for recent years has been calculated, when price information is available for both energy and purchased FFR.

T0 and T1 are two generic wind turbines IEA-3.4-130-RWT. By simulating different ways of running the turbines, the compensation for producing energy alone has been compared to the compensation for producing both energy and FFR. T0 runs in the traditional way to deliver maximum energy production. T1 runs at increased RPM in low winds, provided FFR is requested. T1 can thereby also receive income from FFR.

An example of how the revenue is distributed between the different operating modes is shown below, during two summer weeks in 2021. In this period, the FFR compensation far exceeds the compensation from the energy production, thereby compensating for the lower production.

By summing up the total revenues from the respective turbines T0 and T1 over the entire year, it can be shown whether FFR can generate additional revenues. Delivered FFR is a standby service, i.e. the turbine is ready to support the grid if the frequency would drop below 49.5 Hz. This does not mean that the extra power is actually executed, as such frequency drops are very rare.

The results show that FFR would generate an extra income of between 300 and 500 kSEK per year in 2021 and 2022, even though energy production decreased by approximately 1 percent. During 2023, however, SVK has procured significantly smaller volumes of FFR, also at lower marginal prices. Therefore, the corresponding earnings are significantly lower for this year.

Conclusion: If a wind turbine were to offer FFR, the income from FFR compensates for the loss of production that the higher speed entails.