Monthly Archives: November 2018

Readers' questions: may I use an anchor cage somewhere else?

Posted on by
Reply

I’ve just received this question from a reader. As I believe it’s an interesting topic I’ve decided to answer with a post instead of an email or in the comment section.

“I'm custom broker and I have to classify under HS Code an anchor cage. I have consulted to Classification Office of Argentine Customs Service and they ask me if the anchor cages are designed to be used exclusively in the construction of wind generators, or if they could be used in other constructions, for instance an antenna tower.
I would appreciate if you could help me on this matter.
Kind regards.”

The answer is no – they can’t  be used somewhere else.

There are several applications for foundation cages: power transmission pylons, light poles, mobile phone antennas and other type of towers.

However, anchor cage are dimensioned to fit a specific type of tower. For instance, different wind turbine models have different anchor cages (both the number of bolts and their diameter might vary). You can’t take a generic anchor cage and put it below another tower: the number of bolts, diameter of the tower and size of the bolt would not match.

Some years ago there has been a famous mistake in a wind farm in Brazil – the wrong anchor cages have been shipped (and embedded in the concrete of the foundations). The mismatch between tower bottom and anchor cage was millimetric, so the installation crew tried to install the towers for hours before discovering the mistake. It was the anchor cage for a different model of tower for that specific wind turbine model.

It’s interesting to note that at least a wind turbine manufacturer offer a range of anchor cages with different bolt lengths compatible with a specific wind turbine model. This allow for a greater customization of the foundation and savings in material.

Peikko rock adaptor foundation

Posted on by
1

I've been asked by a reader of this website why there are no references to the various technical solutions available for wind turbines on rock.

The truth is that I’m not a specialist on this topic. However I’m learning, due to the fact that I’m currently working at several projects in northern Europe where it can be applicable.

To solve the problem I’ve decided to start with a video, that can be better than a 1000 words.

It’s an example of foundation on rock without anchor cage – one of several possible technical alternatives when the turbines are above shallow, unfractured rock.

Basically the tower rest on a steel “adapter” plate on top of a reinforced concrete block, and the turbine is fastened to the ground with dozens of post-tensioned anchors several methers long (figures above 9 or 10 meters are not unusual).

There are some very clear benefits with this solution if the geology is favourable: for instance less excavation, almost no blasting and lesser use of materials.

This video has been done by Peikko, a Finnish company specialized in steel elements. They have an interesting, unusual business model, as they do the engineering for the foundation and provide the steel but not the concrete or the manpower – therefore the foundation has to be built by another company.

Here a screenshot with the main elements of this solution:

One more video (possibly more detailed) on this technical solution here:

There is always a second time: wind farm repowering

Posted on by
Reply

At the beginning of the year I’ve had the pleasure to work at my first repowering EPC – Vergao, in Portugal, together with Generg (a big local player).

This is supposed to be one of the many projects that should materialize during the next years. My former manager Luis Miguel thinks that repowering is “the next big thing” in wind energy.

I agree with him that sooner or later it will kick off. In theory, wind turbines are designed for a life of 20-25 years. Through heavy maintenance and substitution of the main components (e.g. gearbox) it can be probably extended a bit more. This practice is called life extension or retrofitting.

However, at the end of the day the question is: does it make sense to keep running old turbines? Or it’s more cost effective to install new WTGs?

Older wind farms are usually in incredibly windy site (class I, according to the IEC classification) and are probably using turbines of less than 1 MW.

Therefore it will be possible to reduce the number of installed turbines (a ratio of 3 old for 1 new would not surprise me) and even so increase the total production.

What can sometime hinder the repowering is not the availability of a better technical solution – and it’s often not even a problem of financing. What can complicate the picture are difficult legal frameworks, low social acceptance, environmental constraints , etc.

In theory, there are scenarios where the best solution will be to dismantle the wind turbines and scrap them (or sell them to third world countries).

Coming back to my personal experience, working at a repowering has been a very interesting professional experience.

There are quite a lot of unusual challenges, as the existing WTGs have to be dismantled while in parallel new ones are erected. This makes the time schedule more complicate than usual, and bring new health and safety challenges due to the many teams working at the same time.

I’ve also had the opportunity to look into new topics, like the possibility to “recycle” the existing foundation incorporating it in the new one (yes, you can do it), the market price of used turbines or the environmental requirements linked to the dismantling and scrapping of wind turbines.