There are several recurring questions that I normally hear at least 3 or 4 time each year.
Some are variants of things like “How much does it cost 1 Km of road in Brazil?” - this was asked by my ex colleague Pau many, many years ago but it’s still a classic for me, and a reminder of the fact that in the wind industry BoP is something ancillary to the core business and not really understood by the majority of the colleagues.

Other questions are more interesting (or at least, it is possible to try to answer them in a more elaborate and complete way).
This is the case of the question “What is more expensive, EBoP or CBoP?”
If you are reading this blog you will probably know the meaning of the acronyms:

EBoP: Electrical Balance of Plant – that is substation, medium voltage cables, step up transformers (if any) and in some cases overhead line.

CBoP: Civil Balance of Plant that is roads, WTGs foundations, crane pads, trenches and other fancy stuff that could be requested by the specific customer/project.

And the answer is… it depends.

In some project, you are requested to build 2 or more substations: one or more windfarm substation to collect the energy plus a substation to evacuate the energy to the grid. This type of layout will also need several Km of overhead line, in single or double circuit.
In situations like this, EBoP is usually more expensive – above all if you don’t need special foundations and earthworks are not particularly complicated (e.g. a flat country, like Uruguay).

The opposite case would be a situation where the EBoP is easy (maybe because there is an existing overhead line crossing the wind farm, or an even more lucky situation where you simply have to connect to an existing substation).
In this cases, if you also have expensive civil works CBoP will be clearly more expensive. This happened for instance in some project I’ve the pleasure to work at in Chile and Honduras.

You can see 2 examples in the pie chart at the beginning of the post.

By the way, if you really need to answer the question of Pau (“How much does it cost 1 Km of road in the country XYZ?”) the best answer that you can give is 100.000 euros.
If it’s a road in an expensive country, remote location, in the mountain, etc. increase the figure (150K – 200K euros), while if it’s in a cheap place it would cost around 80K.

Some days ago I’ve had the opportunity to spend an afternoon at the EWEA summit, the European Wind Energy Association main event.
It was held in Hamburg, city where I have the pleasure to live since December 2015, and it was simply HUGE.

This year, both onshore and offshore were held together, resulting in an impressive amount of stands.
Unfortunately, I wasn’t able to meet too many new company specialized in onshore EPC (my main business).

However, I was able to enlarge the list of contact in engineering companies – coming from several years in Madrid I know fairly well who is who in southern Europe, while I still have to familiarize more with northern Europe consultancies (mainly Danish, but also German or French).

All in all, it was a very interesting experience and a great occasion to meet a couple of old friends.

I know that I’m probably biased on this subject but I want to spend a few words on a recurrent subject that pop up often in my discussion about wind energy with people from different sectors and way of life.

Basically, a standard argument about wind energy is that it’s unreliable and unpredictable.

In my opinion the reality is different (or at least, much more complex that that).

Obviously wind power fluctuate over time, basically under the influence of meteorological conditions.

Variations occurs at several scales: seconds (e.g. gusts), hours (e.g. day and night), months (e.g. summer and winder) and so on.

The electricity demand as well is highly variable, changing not only with well-known seasonal and night/day patterns but also incorporating several other variables such as the economic cycles.

Basically, the grid operator tries to match constantly demand and offer.

They will also need to have a reserve capacity in case of errors in the prediction of the demand or unexpected problem like power plants disconnecting from the grid for whatever problem.

The key point here is that wind energy is variable, not intermittent.

Even during severe storms, the turbines will need several hours to shout down – they will not disconnect all together.

Also, the failure of a turbine has usually no effect on the system as they are modular and diffused. This is usually not the case in other type if power plants.

It is also predictable within a reasonable margin of error – is not a random event like the number you get when you throw dices.

From the point of view of the grid, variations within the seconds or minutes are not felt.

Variation within the hours are felt by the system only when wind has a great penetration level (at least 5%-10%). This currently happen in very few countries, for instance in Denmark.


Note: the main source for this post was an interesting (at least for me) chapter of the book “Powering Europe: wind energy and the electrical grid”.

One of the first point that I try to spot when I receive an offer for a wind farm is an unusual dispersion in prices among subcontractors.

Usually, it means that there has been a misunderstanding regarding the actual scope of works.

Several items have usually very stable, predictable prices. This is the case for instance with the main transformer, which usually will have a similar price between the various offers (unless someone is proposing a Chinese transformer assembled in North Korea, or something similar).

However, other prices may vary wildly. In my opinion, the most unpredictable item is “the works included in the Road Survey”.

If you are reading this post you probably know what a Road Survey (or Route Survey) is.

Basically, it’s a document explaining how the various wind turbine components will reach the wind farm area. Depending on several factors the logistic can be very easy or extremely complicated.

For instance, it’s not strange for a project to use 2 different harbours, maybe one for the blades and another for towers and nacelles.

Also, the road from the harbour to the project area can be flat and easy or full of bends and critical points where works are necessary.

All this point are normally discussed in the road survey. If you are working at a wind farm development, you should have a similar study. Otherwise, you could discover at a later stage that there is a critical point somewhere in the access roads.

The most critical points are usually houses and land plots with owners reluctant to concede right of way, but you can find a lot of obstacles on your ways (e.g. overhead lines, rivers, huge earthworks, etc.).

So, what is the problem with Road Survey?

Basically, it’s a non-standard document. Each company is doing it in its own way. It can be redacted by a transport company or by some external consultancy more or less experienced in wind farm.

The result is usually similar – something that it’s very difficult to understand and to quote for the company that is going to do the works in the real word.

Often your only alternative will be to ask for a lump sum quote, making comparisons and considerations about price fairness of different bids impossible.

Also, it could be difficult even for someone knowledgeable about the business to understand what is really necessary. Is the necessary “bend widening” a quick, 10m3 work or is it an extensive (and expensive) intervention?

Sometimes you have some kind of control on this document, for instance if you are requesting (and paying) it.

If this is the case, you should be sure that some key points are included in the report:

  1. UTM coordinates of the points where works are necessary
  2. Pictures of the area (including orientation of the photo - looking North, East, etc)
  3. Exhaustive work description, with at least a tentative bill of quantities (m3 of cut/fill, number of trees to cut, meters of New Jersey barrier to remove,  etc.)

A good job would also include some kind of topography, but this is probably asking too much.

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A wind farm development is usually a complex, collective effort where several different companies are involved – the developer, the financing institutions,  the WTGs manufacturer, the companies doing the BoP and installation and several other.

As many tasks are performed in parallel, often is not very clear to people who are not in the wind industry who is doing what and where.

Luckily, my friend Alberto from ACWA sent me this enlightening step by step guide. It has been developed by K2, a management company active in the business.

As you might imagine sometime the borders between activities are sometime blurry and some task might be shuffled. For instance, the environmental impact study in some countries is done very late (you will probably have to work only with some preliminary document), or the land lease agreement can be closed very late in time. We’ve been forced to relocate quite a few turbines in projects ready for construction where landowners where very reluctant to close a deal.

Also, as I’m obsessed with engineering and construction, I do disagree with the construction line, where  the “Balance of Plant Completed” comes in parallel (and terminates before) with the “Detailed Design Complete”. The implication of this structure is that you could start construction without having construction drawings, which is usually not a good idea )although is something that I see recurrently).

However the scheme is very instructive – I hope you will find it useful for your business.

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For the second time in 2 years I’m working at a wind farm with a potential karst problem.

If you’re reading this post you are probably aware of what is karst – basically, the result of dissolution of rocks such as limestone and gypsum, that can produce beautiful landscaping results (such as caves, sinkholes and dolines) but also several problems for the foundations of structures.

If the size of the cavities is reduced (a couple of centimetres) the will not be a problem because the foundation will not notice them. However in unlucky cases, you can dig and open the foundation and discover a huge hole that can be several cubic meters big.

I’ve heard stories of civil subcontractors who pumped the load of several concrete mixers in the holes without filling them (in some cases you can find a network of connected cavities).

Relocation of the WTG is a solution, but is usually not the best due to several reasons (maybe the adjacent land plot is not available, or you have a tight layout with very close turbines, or there are environmental constraints).

Also, it’s usually not free: depending on your contract, the civil subcontractor could be entitled to ask for a variation order.

Which are the available technical solution?

As far I’m aware of, MASW, electrical tomography and ground penetrating radar (GPR). I’ve used the last one successfully in a project in Jamaica and it worked well.

Basically, the GPR investigation is a non-invasive technique that can detect anomalies (locations, depth and approximate size of cavities) and spot  any inconsistency or variation in the expect soil profile across each site.

Resuming shortly how it works, GPR generate and send electromagnetic waves into the surface with an antenna, moving along the inspected surface.

Whenever a radar pulse strikes a boundary interface of contrasting dielectric (basically, between different materials), a portion of the pulse is reflected back to the surface to a receiving antenna.

The contrast in properties between clay (the weathered material which usually fills the holes) and limestone help to identify zones of subsidence. Conversely, a lack of contrast indicates relatively uniform stratigraphy.

Subsurface profiles will be generated displaying the resulting echoes of individual pulses.

Integrating this technique with standard boreholes will decrease the geotechnical risk of your project.

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This week I've had the pleasure to meet (virtually) Tom, an electrical engineer specialized in SCADA.

Tom developed an interesting software called "SCADA miner".

Basically, the software automatically dig the available data from various sensors and cross check the information to spot actual or potential problems that might go unnoticed, "lost in the sea of other alarms and event codes" to use his words.

When something goes wrong the software automatically send an email to the people included in a distribution mail list, alerting them.

One of the advantage of the system is that no new, dedicated hardware is needed: the calculations are made by remote servers.

In his blog you can find several real word examples, such as high main bearing temperature, met mast failure, wind vane misalignment and several others.

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I’ve just received a short technical summary of the works performed in Raki (Chile) from Terratest, the company who has made the gravel columns.

Unfortunately it’s in Spanish, but the pictures are beautiful ;-)

About 9000 meters of gravel columns have been put in place. The diameter is 80 cm, while the length changed depending on the position (from 9 to 13 meters).

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A couple of months ago I’ve been invited by Esteyco to the erection of a prototype auto lifting precast wind tower.

Although I was unable to attend due to other meetings I want to describe shortly their invention, which looks interesting.

Basically, the idea is to create a tower that can “lift itself” without the use of a main crane.

The first step is the assembly all the pieces of a precast concrete tower at ground level (such as an onion, or a matryoshka doll).

Assembly is done from the inside out, with the most internal section being the top one holding the nacelle.

When assembly is completed lifting can begin – starting from the center (the top tower section with nacelle and blades) and moving toward the exterior.

The tower “self-lift” itself using heavy lift strand jacks. These are commercially available equipment, currently used in several industries such as heavy construction or offshore.

The strand jacks will be positioned on an auxiliary platform at the first level.

This solution save you the main crane: only a smaller, 350t to 500t crane will be needed to assembly all the components.

To give you an order of magnitude, to reach 120 m you will need 4 concrete levels that in fold position will have a height of approximately 40 meters.

The expected time for assembly and lifting of all components would be around 3 days.

As an added bonus, due to the increased weight of the tower (acting as a stabilizing load) the WTG foundation would be somehow smaller compared to a steel tower of the same height.


A spectacular video of Raki wind farm, a beautiful project I’ve worked at.

Owned by Rame Energy (formerly Seawind) It is a 15 MW wind farm in the Bio Bio region (more or less in the middle of Chile).

WTGs are 5x V112 3MW turbines, and civil works have been developed by CJR.

The earthworks were not especially complicated, while the geotechnical study for the foundation required a more detailed, in depth study.

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