The FEDRE project (Fondations d’Eoliennes Durables et REpowering - Sustainable Wind Farm Foundations with Repowering) aims to improve the competitiveness of wind farms by optimising the construction of their foundations (reinforced concrete slabs).
repowering: MODERNISING WINd FARMS
Onshore wind turbines are designed to have a lifespan of around 20 years. After this time, they need to be replaced in order to maintain their installed power. This phase is called wind farm repowering.
Wind farms were first developed in France some twenty years ago, which means that the first farms are now reaching their repowering phase.
Replacing wind turbines and towers also involves replacing wind turbine foundations. They comprise a heavy slab of heavily reinforced concrete to withstand the overturning moment. What currently happens is that the old slab is demolished and a new, wider and more solid one is put in its place. This approach is very unsatisfactory from an environmental standpoint.
The FUI25 FEDRE project has two objectives:
- 1/ to seek technical solutions so that existing slabs can be re-used as concrete ballast for new slabs, which would reduce the volume of concrete and steel needed,
- 2/ to design a new foundation slab which can be adapted for several successive generations of wind turbines by simply increasing the mechanical ballast.
FEDRE brings together the INSA Lyon [engineering school] and 5 private partners. Two doctoral theses are in progress and support the development of the project. They are set to be presented in early autumn 2022..
The project in detail
The project started in September 2018 and is structured as follows:
- The instrumentation of 3 new foundation slabs in 3 separate wind farms has been carried out. This instrumentation allows a better understanding of the distribution of stresses in the tower slab through to the foundation, including in the rigid inclusions put in place under one of the three slabs to improve the characteristics of the soil there.
- Digital analysis of results to assess the distribution of stresses within the instrumented slabs.
- Digital modelling of the soil for the foundations reinforced by rigid inclusions.
- Production of a first model to a scale of 1:10 based on digital modelling to identify the best rules of similarity with the life-size slab.
- Launch of a test programme on the scale model to assess the stresses in the slab and confirm the performance of the scale model and the digital model.
- Discussion and consideration about new slabs with a view to re-using old slabs. One solution, called the mushroom, in which a new slab covers the old one appears to meet the needs of the majority of wind farms.
- Studies of repowering solutions are continuing.
- The production of an instrumented model to a scale of 1:10 for the repowering solution to assess the stresses in the new mushroom slab and the stresses on the connection with the old slab.
- Analytical study of the life cycle of the repowering solution to identify environmental gains.
The theses of Janet Modu and Adnan Sahyouni will be presented in autumn 2022
The FEDRE project is scheduled to end on 30/06/2023.
To see the webinar presenting the project, click here
a WORD FROM A PROJECT MEMBER
« Adapting and strengthening existing slabs, rather than demolishing them and then building new ones, is an environmentally attractive approach as it reduces the carbon footprint of the foundations and the volume of waste produced.
The FEDRE project, which brings together experimental approaches, physical models in INSA Lyon’s laboratories and digital models, aims to develop solutions for slab re-use. This raises many diverse technical challenges. The enormous commitment of all the partners makes the project even more motivating.»
Eric Antoinet, Technical Director of Infrastructures at the AnteaGroup