CTE Wind R&D and Consulting services are the first choice when it comes to foundation design regardless of the WTG-manufacturer, model, size, power or soil conditions. Thanks to internal R&D-Team with senior engineers, holding over 100 years of cumulated experience in the design of wind turbine foundations, nothing is impossible.

La Richardais (FRA) – In 2019 Developers worldwide have globally commissioned a little over 45GW of onshore wind turbines. According to Bloomberg New Energy Finance, the Danish firm Vestas remained this way the world’s leading wind turbine supplier, with Spanish-German wind engineering company Siemens Gamesa a strong second. Chinas manufacturer number one Goldwind was third in the rankings, while US-Leader GE Renewable Energy’s secured its fourth place. Together the top four manufacturers accounted for 55 percent of the market share.

100 years of cumulated experience

This statement applies more or less also to CTE Wind, which calculated, designed and evaluated about 5000 WTG-foundations in 2019 around the globe. Thanks to CTE Wind’s internal R&D, with senior engineers holding over 100 years of cumulated experience in the design of wind turbine foundations worldwide, new turbine models from the top manufacturers as well as less common WTG-models from smaller or local manufacturers are only a little challenge. CTE Wind engineering services lead to state-of-the-art foundation solutions for wind turbines. Regardless of whether it is a prototype, such as GE’s giant 12 MW Haliade X or smaller 1 MW machine, from German ENO or Dutch EWT.

Wooden tower

Also worth mentioning: the different types of towers for wind turbines. Concrete (hollow foundation) and steel towers are well known to CTE Wind. Both tower systems are suitable to be used alone or in combination. Even foundations with wooden towers were calculated and designed by CTE Wind in the past. The sum of all experiences made during the projects since 2003 is the reason why their engineering services in foundation design are the first choice for wind turbine manufacturers, wind park developers and EPC contractors worldwide.

«To work with CTE Wind as designer was nice. The speed of response and reliability of the planning has been a winning experience for us.»

Arjan Louwerse from H4a Windenergie B.V.

Coöperatie Zuidenwind has poured the concrete for the foundation in Heibloem in the Netherlands and created the basis for the installation of their wind turbines. The foundation design and calculation for this project was done by CTE Wind Civil Engineering. The expert in foundation design WTG suggested their Soft-Spot® instead of a typical pile foundation.

Heibloem (NL) / La Richardais (FR) – The Netherlands soil consistsof unconsolidated, very young sediments. Due to the proximity of the low-lying part of the European continent, the basin of the North Sea, the bottom rarely rises higher than 30 m above sea level. In the areas along the coast (provinces of Groningen, Friesland, Noord-Holland, Zuid-Holland, Zeeland) the surface soil layers consist mainly of clay deposits. In the west of the Netherlands the clays are replaced by lowland moors (peat). To sum up: in the Netherlands, pile foundations are mandatory for wind turbines because of the concentrated forces occurring on little surface area. Except in Heibloem, where the ground is exceptionally stable. So good, in fact, that CTE Wind offered its resource-saving Soft-Spot® instead of the usual foundation.

Soft-Spot® in the Netherlands

The Soft-Spot® was developed by CTE Wind’s engineering team and is implemented in various countries around the world. «It was simply the most economical foundation we could choose », Arjan Louwerse from H4a Windenergie B.V. says. He is the project manager for Coöperatie Zuidenwind wind turbines. This foundation design optimizes the use of resources and helps to save up to 15 % of concrete and 2 to 5 % of reinforcement steel. In some cases what is even more important than the costs is the available space : with Soft-Spot® you need less surface for the foundation. This reduces the time and excavation costs. «The philosophy to reduce the costs of the Soft-Spot® was also a good point of discussion with our client. From the beginning we had a good feeling with the design», he explains.

In fact thanks to the new design the outer diameter of the foundation was 1.1m smaller compared to a typical foundation design. This resulted in a reduction of 11 % of concrete and 3 % of steel – or more precisely about 100m3 of reinforced concrete. «To work with CTE Wind as designer was nice. The speed of response and reliability of the planning has been a winning experience for us», Louwerse added. In spring 2020 the wind turbine will arrive together with the largest blades ever installed onshore in the Netherlands. (ctewind)

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Two simply but effective foundation solutions are the rock anchor, designed for a wind park in Mexico and the high plinth solution for a wind farm in Chile. They are highly cost efficient, feasible and have proven to be very reliable in many projects.

Bilbao (ESP) – Special requests often demand tailormade solutions. But tailormade needs an high specialization and a lot of knowhow from the engineers in the specific field. In foundation design for wind turbine generator (WTG), this specific knowledge is not that common, except for CTE Wind International. Their senior engineers are often asked to find new design solutions. For this purpose, they resort to tried and tested instead of reinventing the wheel. Two simply but effective solutions are the rock anchor and the high plinth solution. They aren’t NEW solutions but are highly cost efficient, feasible and their reliability has been proved in many projects. This article features two project cases, among many others, where CTE Wind International designed rock-anchored foundations for a wind park in Mexico and a high plinth foundation for a wind farm in Chile.

Cost savings thanks to rock anchors

In Mexico, CTE Wind Ibérica was selected as WTG foundation designer by the EPC company. The project consisted of more than 20 concrete tower WTGs. The project analysis conducted by the foundation design expert has led to the recommendation to deploy two different solutions in order to optimize the costs of project. In fact, the soil conditions showed that over a third of the wind turbines were planned on rocky ground. Rather than equipping all wind turbine with standard slab foundations, CTE Wind’s engineering team decided together with the customer to implement rock anchors. This solution uses the rock mass as a WTG foundation. In that way the construction company is able take advantage of the earth crust instead of building a slab foundation. The costs for the reinforced concrete and the construction work can be saved. But this solution is specially challenging as the engineers have to adapt the foundation, with an interface, between the concrete towers and the rock anchors. Not to forget the special design work of these anchors that needs to be done. Finally, the client was impressed and satisfied about the result. But more important: the project costs were below the initial budget.

High plinth for extra height

In another case, CTE Wind was approached by a global construction company and explained the challenge for its project in Chile, with over 35 WTGs. The customer needed an hub height of 4 meters more to increase the energy production and ensure the yield and so its income. They weren’t totally satisfied with a complex solution by one of CTE Wind’s competitors. That is why the construction company asked CTE Wind to find a simple, reliable, feasible and cost-effective solution. That is how the high plinth foundation was chosen: a solution already tested and implemented in multiple projects in Europe. The idea of this foundation is to reach higher hub height with a high pedestal. The tower stands 3 to 6 meters above the «ground level», keeping the gravity foundation independent from the tower system. Ideally, the solution provides a longer anchor cage. CTE Wind’s engineering team designed the anchor cage for this project and determined the bolt length and steel quality. If needed, CTE Wind can also prepare detailed anchor cage drawings. After comparing the results of CTE Wind’s predesigns to the competitor’s solutions, the customer decided to go ahead with CTE Wind’s high plinth foundation. No difficulties in regards the construction have been reported. On the contrary, the Spanish expert of WTG foundation design was congratulated.

CTE Wind Asia has been awarded with its 3^rd nearshore project. To this day, the Asiaese expert in foundation design has calculated 27 nearshore wind turbine foundations.

Hanoi (VNM) /La Richardais (FRA) – CTE Wind International branch office in Asia (CTV) captures the spirit of the times with its new design for nearshore foundation for wind turbine generator. With its 3^rd project in the intertidal zone in Mekong delta of Asia CTV won again the customers’ trust. This is already the 3^rd  project since 2019. With 18 wind turbines and a total power 75MW this project has increased the total of final designs made by CTV to 27. The other two nearshore projects are located in theThanh Hai and in Vung Tau provinces.

New design allows up to 30 % savings

All CTE Wind’s nearshore foundation designs allow to save 30 percent of the construction costs compared to similar projects due to the astonishing design. For the 4.1 MW machines CTE Wind Asia has designed a foundation with 550m3 of concrete, 120 tons of steel and 44 piles. The piles have an average length of 60 meters and are hammered into the muddy nearshore underground. In fact, the geotechnics were very challenging and the piles were also designed in-house to withstand tides, waves and ship movements close to the platforms.

If you want to learn more about CTE Wind International you can read more articles about projects and news in OUR-PROJECTS & OUR-NEWS – sections. For more Information about OUR-SERVICES please CONTACT US.

Since 2019 CTE Wind provides geotechnical engineering services to their clients. Over the last six months, Ana Bielza, Senior Engineer at CTE Wind Iberica has taken part in over 45 projects. We have asked her what she actually does and why her role is crucial for the foundation design of wind turbine generators (WTG).

Can you briefly explain to us what a specialist in geotechnical engineering like you does?
Ana Bielza: Geotechnicians apply scientific methods and engineering principles to predict the response of the ground to the foundation requirements. They then deliver this information to the civil engineers so they can design foundations accordingly.

What is the difference between common geotechnical engineering for bridges or building compared to the WTG-geotechnics?
Ana Bielza: There are not many differences. The ground has to be investigated with similar methods (drillings, geophysics, lab tests, etc.) and the same kind of parameters are needed. But the ground capacity is usually not what determines the foundation size, because most of the time the soil strength transmitted by a turbine foundation is not high. Besides, settlements in general are not important in this type of structures. But rotational stiffness can rather be the main ground parameter to manage and sometimes it can even set the foundation size.

CTE Wind offers his services worldwide

You worked on over 45 projects in six months, which is quite a lot. In which countries did you take a look at the ground?
Ana Bielza: Yes, there were many. It looks like our services are very appreciated by the customers (She smiles delighted). I worked for projects in Argentina, Australia, Belgium, Brazil, Chile, India, Indonesia, Israel, Lithuania, Mexico, Netherlands, Peru, Russia, Spain, Tanzania, Tonga, Turkey, and Ukraine. Of course, every country has its peculiarities. And I not only mean the different ground types you can find but also how the different investigations that are conducted and how the results are delivered.

Looking back on these last months, what were the challenges? Can you maybe share one or two projects with us?
Ana Bielza: Challenging projects are usually the ones located on recent soils in seismic areas and near to the shore (high water table). For example, we have done several basic designs for a huge project in India with 1000 wind turbines, located on a saline desertic zone most of the year. But during the monsoon season the landscape becomes a swamp, with water at ground level. It is a region with an extreme seismic risks, on a recent granular soil (potentially liquefiable) and very aggressive to the concrete. We had to analyze the ground with just four boreholes in an area for 1000 turbines!

Sounds like fun. As far as we know, there are no known cases of significant damage from liquefaction in wind farms. So, how did you solve this problem?
Ana Bielza: Well, with only four drillings for such a huge area, it was mandatory to be conservative, therefore, and according to the client, we worked with two possible scenarios. We hope they were representative for the situation in most of the future turbine positions. The civil engineer then follows our specifications and designs the foundations accordingly with piles.

Trust is an important key factor

Could you tell us about another project?
Ana Bielza: Another challenging project has been the one in a country in South America, a wind farm with over 40 turbines. This was a constructive design where we had also drafted the geotechnical study from a factual report given by the customer, with 45 boreholes, 80 trial pits and 46 geophysical tests as well as an important amount of laboratory tests. The ground was good, a consolidated gravely soil -a conglomerate-, but seemed to be prone to suffer some dissolution because it had salt in its matrix.

What does it mean exactly?
Ana Bielza: The matrix describes the different layers a soil can have. The salt in the matrix can be dissolved by heavy rain or ground water. But even if the ground suffers an hypothetical dissolution, the remaining gravely soil would show enough strength and rigidity to carry the WTG. Besides, there was no water at all in the area, it was in a desert area.

Good conditions. What was the problem then?
Ana Bielza: Yes, but the client was pressuring us to set down categorically that there was no risk of dissolution, and there was no possibility at all for buoyancy. The geotechnics of the project showed good conditions for our SOFT-SPOT® foundation, but the wind farm owner seemed to have unfounded fears and wanted us to affirm that there was zero risk in this area. But zero risk does not exist. It was tricky to explain why there are no risk but we had to write about an hypothetical dissolution. Luckily, we finally came to an understanding. (ctewind)