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With the Soft-Spot® CTE Wind Civil Engineering captures the spirit of the times. The success is not only due to the new design solution. It is more a result of the developers increasing projects requirements and the size of the turbines. CTE Wind masters both easily.

La Richardais (FRA) – CTE Wind International, expert in foundation design for wind turbine generators, has his finger on the pulse of time with the Soft-spot® solution. Trademarked and patented in France (patent pending worldwide), 750 wind turbines use the resource saving solution worldwide. Over the half of the 50 realized projects related to the Soft-Spot® are located in France.

Cost savings

The success of the civil engineering company CTE Wind is not only due to the Soft-Spot®. It mainly relies on the fact that CTE Wind can master the increasing requirements of the wind energy developers. Wind farms have to be designed in a way that saves resources and allows fast set-up times; two important factors which determine the construction costs of WTG foundations.

A further driver and important point why developers choose CTE Wind is the increasing size of the turbines. Four to five years ago, the hub height of wind turbines ranged between 80 and 90 meters. Today the average hub heights of CTE Winds projects are between 110 and 120 meters. Some of the final designs even had a hub height far above average. The highest hub height ever calculated by CTE Wind stands in Salzgitter Germany with 166 meters.

Adapting the design to soil conditions

CTE Wind adapts its foundations designs to the local soil conditions and in accordance with applicable national and international standards. To avoid extremely large foundations CTE Wind’s engineering team has found with the Soft-Spot® a good and reliable solution to meet the mentioned resource-saving requirements. The construction is very easy and it allows savings in concrete volume up to 15% and a total weight reduction of reinforcement bars of 7 to 9%. Thanks to the reduction of the foundation diameter the earthwork to be handled is also reduced. This leads to less surface use for the foundation.

Experts in Foundation Design

From 1 to 12 MW wind turbines

According to Bloomberg New Energy Finance in 2019 developers worldwide have globally
commissioned a little over 45GW of onshore wind turbines. CTE Wind designed, valueengineered
or peer-reviewed foundations close to 1,500 WTG-foundations around the globe,
which represents around 5 GW of the installed onshore wind energy in 2019. A good result
for the 30 engineers working together worldwide. CTE Wind is an international engineering
consulting firm, headquartered in France, and specialized in the analysis and design of
onshore wind turbine foundations. Its engineering services lead to inventive foundation
solutions for wind turbines. In Rotterdam, they have designed the foundation for GE’s giant
12 MW Haliade X. But they are also with familiar with smaller 1 MW machines carried by
wooden towers. «Thanks to our experienced civil, structural and geotechnical senior
engineers the design of those wind turbine foundations worldwide are only a little challenge
to us», said Alexander MARTIN, CEO of CTE Wind International, «regardless if it is for new
turbine models from the top manufacturers or less common WTG-models from smaller or
local manufacturers», he added.

Biggest wind park in France, Poland and Spain

The sum of all experiences made since 2003 is the reason why CTE Wind’s engineering
team with offices in Brazil, Poland, Portugal, Spain, USA and Asia are often the first
choice for OEMS, wind park developers and EPC/BoP contractors. «That is how we
achieved to do over 17,500 wind turbines in 67 countries and without any failures», continues
MARTIN. One of CTE Winds main goals is to deliver foundation designs that optimizes the
use of resources and help to save concrete and reinforcement steel. Such a solution is the
patented SOFT-SPOT®, a gravity foundation with a soft layer under the anchor cage. Each
project receives an adapted design solution to the specific soil conditions. In Finland CTE
Wind designed a rock anchor solution when its engineers also designed a near-shore
foundation in Asias Mekong-Delta. «The trust of our customers leads us not only to
design special and new solutions but also the foundations for the biggest wind parks in
France, Spain and Poland. We are thrilled when we can play an important role in a wind farm
project. This shows the confidence of our customers in our designs and is also an
encouragement for us to continue to perform well», he ends.

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)

CTE Wind Ibérica, experts in wind turbine foundation design, in Spain and Latin America, celebrates this year the 5^th anniversary of the company.

CTE Wind Ibérica’s journey began back in June 2017 in Bilbao (Basque Country) and focused its design and calculation work for the Spanish market and Spain based customers operating worldwide. Since then, many customers entrusted the Spanish experts in WTG foundation design with over 225 contracts. Foundations for 4900 WTGs (or close to 20 GW energy output) have been designed, value-engineered or peer-reviewed in 181 wind farms across 22 different countries.

«CTE Wind Ibérica has experienced phenomenal growth in its few years of existence», said Alexander MARTIN, CEO of CTE Wind International. «In the advancement of this growth, we will continue to bring cost-effective foundation design, geotechnical consulting services and exceptional customer service to EPC, CBoP, Developers and OEMs.»

All major turbine manufacturers

In five years of market presence, CTE Wind Ibérica has designed foundation for ten different OEMs: Enercon, Envision, GE, Goldwind, Nordex, NRG Patagonia, Senvion, Siemens-Gamesa, Vestas and WEG. Regardless if the wind turbine had a tubular steel or concrete tower. Noteworthy are the rock anchored foundation design in Mexico or the star foundation (ribbed foundation) in the Gecama wind park project in Spain (see picture).

CTE Wind Ibérica also implemented successfully CTE Wind’s patented Soft-Spot® solution, with most of the above-mentioned manufacturers. Particularly in Spain and Latin America is the low resource foundation a big success.

Active in Wind since 2003

CTE Wind Ibérica, as part of CTE Wind International, is an international engineering consulting firm specialized in the analysis and design of onshore wind turbine foundations. CTE Wind has been active in the wind energy sector since 2003. As of 2022, CTE Wind International has designed, value-engineered or peer-reviewed foundations for over 23,500 turbines in 74 countries. CTE Wind is headquartered in France and has offices in Brazil, Poland, Portugal, Spain, USA and Asia.

The company is a subsidiary of the CTE Group, a consulting firm, specialized in building and civil engineering. The CTE Group was founded in 1965 and today is one of the leaders in the structural engineering sector in France.