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In the last 2 years over 50 project developers trusted CTE Wind’s Soft-spot^® solution. Recently in Spain the expert of wind turbine foundations has won their third project, where the Soft-spot^® solution was implemented.

Bilbao (Esp) / La Richardais (FRA) – CTE Wind Ibérica has won again a contract in Spain to calculate and design foundations with its Soft-spot^® solution. This is an important milestone for CTE Wind International as now three wind farms on the Iberian Peninsula will take advantage of its cost saving design. In addition to these projects, CTE Wind’s clients are also adopting this solution in many other wind farms worldwide. Argentina, Brazil, Chile, France, Lithuania, Indonesia, Mexico, the Netherlands, Russia, Serbia, Sweden and Thailand to name a few. Over 50 wind farms around the globe, 750 wind turbines are using this resource saving solution which was introduced a while ago by CTE Wind.

« CTE Wind is proud of the confidence shown by its clients, and especially of the interest on applying the Soft-spot^® solution», Chief executive Alexander MARTIN said and added « Our design provides interesting advantages and cost saving in material consumption and civil works while being easy to be built. »

Simply the most economical foundation

The Soft-spot^® was developed by CTE Wind’s engineering team and is implemented in various countries around the world. As a result of his astonishing design this solution allows savings in concrete volume up to 15%, reduction of foundation diameter and total weight reduction of reinforcement bars of 7 to 9%. The earthwork to be handled is reduced too. In some cases, what is also important is the available space : with Soft-spot^® you need less surface for the foundation. The construction is very easy and the material for the soft layer can be easily purchased for a low price all over the world.

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)

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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 a rock anchor for a wind park in Mexico and a high plinth foundation for a wind farm in Chile.

Cost savings thanks to rock anchor

In Mexico CTE Wind Ibérica was selected as WTG foundation designer by a Spanish EPC company. The project has more than 20 WTGs with concrete towers. The project analysis conducted by the Spanish expert in foundation design 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 masses 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 the detailed anchor cage drawing. 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.

.

.

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 a rock anchor for a wind park in Mexico and a high plinth foundation for a wind farm in Chile.

Cost savings thanks to rock anchor

In Mexico CTE Wind Ibérica was selected as WTG foundation designer by a Spanish EPC company. The project has more than 20 WTGs with concrete towers. The project analysis conducted by the Spanish expert in foundation design 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 masses 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 the detailed anchor cage drawing. 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.