I trust you, but… Professional Indemnity insurance

The Professional Indemnity insurance, also known as Professional Liability or “PI” here in Europe and “Errors & Omissions” at the other side of the ocean is an insurance who protect individuals (engineers, geologist, topographer…) and companies in case they made gross mistakes, negligence and similar errors causing losses to the counterpart who purchased their service.

In the majority of the projects I’ve worked at I have had the pleasure to know very good professional working for external subcontractors - people who helped us develop wind farms in faraway countries providing a variety of services.

Even if many work for “big names” in the business and I know many of them personally, it’s always a good idea to have a PI insurance in place when you purchase a professional service (in my case, something related to civil or electrical engineering).

The amount of the insurance should be related to the potential damage – in my case, the bigger the wind farm, the bigger the insurance that will let me feel comfortable.

However,  this type of insurance is not cheap – the more onerous the request, the more expensive the service will become because the consultant will (obviously) ask you to pay for the policy extension.

As far as I know, PI is not mandatory (at least, not for all professions and not in all countries). However the vast majority of companies and individuals I’ve worked with had it in place.

It’s also worth mentioning that such insurance will also need to stay in place quite a lot of time – some design errors are not self-evident and are usually discovered after a few years.

Lastly, I want to highlight that every now and then I see a new technical solution in the market (for instance, I’m currently studying at least 3 alternative foundation types).

As this are new, unproved technologies the need for a strong Professional Insurance insurance in place becomes even greater.

Types of cranes

Even if I’m not a specialist I would like to dedicate a post to a relevant element in a wind farm construction – the crane.

Crane procurement and wind turbines installation is normally organized by a specialized department, staffed with experts who knows what are the cranes available in the market and the implication of having a specific model instead of another on site.

In some countries, when the economy is thriving or if wind farms installations are booming, it can be really hard to find a free crane in the correct time slot - the few months when turbines are installed. In some case it might be necessary to import it from a different country.

Generally speaking, cranes can be categorized considering different technical characteristics:

  • Crawler vs wheels: cranes on wheel can use public roads and travel at a reasonable speed, while cranes with crawlers can go everywhere and they are often moved off road.
  • Standard vs narrow track: cranes on crawlers come in 2 version, with the crawlers at a “standard” distance (somewhere around 10 meters) and very near (below 6 meters). Obviously with a narrow track you will need less earthworks and the roads will be less expensive.
  • Telescopic vs lattice boom: 2 different solutions for the boom. “Hybrid” intermediate solutions are available

Cranes on wheels have a variable number of axles, usually somewhere between 6 and 9. As they are designed to be used on public roads the standard load per axle is 12 tons, even if partially rigged cranes can have a load per axle of 16 tons, 20 tons or even more.

The same crane can have different configurations, meaning that  the owner can purchase different tools and components to increase the maximum load and lifting height.

The configuration is indicated by hard to read manufacturers codes such as “T7YVENZF”. For instance, the code of the example means that the crane has a 100 meters telescopic boon, a Y- shaped guying system, an extension and a lattice jib.

Cranes can be moved from one wind turbine position to the following one fully rigged (not a frequent choice nowadays, given the increasing hub height of the turbines), partially dismantled or fully dismantled.

When a crane is dismantled the components are loaded on a truck and unloaded in the following wind turbine location. The number of trucks (and back and forth trips needed) depends on the crane model configuration but can be quite relevant: dozens of trips may be needed to move all components.

With a fair wind – something interesting to read this summer (if you like wind farms)

If you are reading this blog,  chances are that you are somehow interested in wind energy.

And if you are looking for a good, interesting book on this topic I would suggest you to start from here: With a fair wind (full disclosure – I’ve written the chapter on Civil Works).

It is a book edited by the Esteyco Foundation, who was established more than 25 years ago with the aim of contributing to the progress of engineering and architecture.

There are quite a lot of contributors including Manfred Petersen, a very experienced wind farm foundations designer who is working at several interesting new technical concepts. They are coordinated by Ramón López, who in addition to his career as an Engineer is also very active as Triathlete.

Download it here

Time is never enough: Early Works

Early Works, sometime also called Preliminary Works, Limited Notice To Proceed or something similar, are a common project strategy that is currently more frequent than ever before.

Basically, it means that some field works, engineering tasks and/or procurement activities are done before that the EPC contract enter into force.

EPC contracts have usually a long list of condition precedents to be fulfilled – basically things that should happen to give validity to the contract.

However, due to demanding planning and “hard” deadlines such as changes in the regulatory framework or a variety of other issues, it’s often difficult to wait for that point in time.

Additionally, negotiations can be longer than expected or problem with project finance closure are a reality in the majority of the developments.

Therefore Early Works are often the only chance to keep the project alive. Basically is a separate agreement between the customer and the contractor where both party acknowledge the situation and recognize that some tasks need to be performed immediately to keep the time schedule of the wind farm feasible.

It’s usually a “light” contract, a few pages highlighting the main terms and conditions. The content of the early works is obviously project specific.

Some activities that are frequently performed upfront are:

  • Geotechnical investigations
  • Foundation design
  • Finalization of the internal layout
  • Engineering and procurement of the main transformer

However, in the past I’ve seen a variety of tasks included in the Early Works, from the engineering of the substation to support to permitting for wind turbine transportation (in some countries authorities can be VERY slow).

I’ve also read of a wind farm in a very remote area with an Early Works package including an air runways, so as mentioned before the type of early works are dependent on the specific wind farm planning.

Piled foundation for wind turbines

I’ve noticed last week that the blog has no post on piled foundation and decided to write a couple of words on the topic on a flight back to Hamburg.

Piled foundations is a broad term that include several technical solution aimed at increasing the bearing capacity of the soil when design requirements such as bearing capacity, limited differential settlement and/or necessary rotational stiffness can’t be met designing a standard shallow foundation.

Piled foundation are a type of “deep foundation”, a concept opposed to the standard “shallow foundation” solution - other type of deep foundation solutions are for instance soil substitution and soil injections.

They are relatively frequent. The number of piled foundation that you will see are very dependent on the countries you are working in – probably almost 100% of the new WTGs in the Nederland are piled, while turbines installed in Portugal on the top of a mountain ridge are usually on a shallow foundation.

Piled foundation are usually expensive – as a rule of thumb, they can cost between 1.5 and 2.5 times the cost of a standard shallow foundation for the same turbine type.

The selection of a solution will  usually depend on 2 main criteria:

  1. Cost: unsurprisingly, the main concern is usually to limit the impact of special foundations on the project budget.
  2. Constructability: sometimes the “best” solution can’t be selected due for instance to a shortage of machinery (a problem more frequent that you might think, above all in good times of strong economic growth), environmental constraints or other potential impacts (for instance, some piles are hammered and they can induce vibration on other building and structures nearby).

The main categories of piles are

Precast piles: this solution use concrete (or more infrequently, steel) piles fabricated somewhere else. Piles are driven into the ground by a hammering machine that measure the resistance of the soil to each blow. They say that “a driven pile is a tested pile” – and if you are not reaching the needed capacity you can keep hammering the pile to a greater depth as they are modular. Precast piles are usually more expensive and as mentioned they generate noise and vibrations.

In situ piles: this type of piles are fabricated on the spot. Augercast piles, also known as continuous flight auger piles, are drilled by a machinery that first drill the hole to the requested depth and after, while retracting the auger, inject cement ground in the ground. After concrete reinforcement bars are inserted in the pile. Drilled piles are similar – first the hole is drilled, after the walls of the excavation are kept into place using a fluid like bentonite or a steel casing. After, as in the previous case, concrete is pumped and concrete bars are inserted in the hole. The last type are rammed aggregate piles (also called impact piers), where instead of concrete gravel is inserted in the hole and after hammered by the machine. By doing so a higher density is achieved for the  gravel and for the soil around it. This solution is specially effective in seismic areas, were concrete piles can be broken by earthquake.


Where do I go from here? Careers path in the renewable industry.

This post is about my personal experience with possible careers path in the onshore wind industry - what are the easy and the not so easy movements. I believe that the main concepts would be applicable to similar industries, such as Solar or Offshore.

It’s applicable to medium and big size companies organized in a classic way (Engineering design the product - in my case a wind turbine, Sales & Tender Management sell it, Project Management build it).

I focused on the departments that are near to my professional experience – therefore I’m not keeping into consideration Service and all auxiliary departments (e.g. HHRR).

The most “natural” career path is upward: you start for instance as a (Junior) Project Manager, you become a Project Manager, Senior Project manager, maybe a Project Director (if this position exist in your company) and finally you land in a Head of Project management position.

What makes fun (and broaden your view of the company) is to have also “lateral” movements.

I believe that some are easier than other. For instance I know many Project Managers that become Tender Manager and vice versa, or engineers becoming Tender Manager. Somehow more rare is to see a Sales Manager becoming a Project Manager, or a Tender Manager becoming a Sales Manager.

It’s not impossible, I know a bunch of cases. However, Sales guy are usually a different class.

For instance I’ve never met an Engineer with a Sales background: I’m not saying that it’s impossible, but for sure is a less frequent (and more complicate) career move.

I tried to summarize visually the idea in the picture.

I also beleive that  moving “lateral and up” would make the change even more complicate.

For instance it would be complicate for Tender Manager to become a Senior Project Manager (or Project Director), but it would be much more complicate for a Project Manager to step into a Senior Sales Manager (or Sales Director) position.

Google: powered by wind

One interesting fact that you might not know is that the Big G (that is, Google) decided several years ago to power 100% of its activities using renewable energy.

They reached their objective in 2017: what is surprising is that they started only in 2010, with a wind farm in the USA. Basically the strategy is to close Power Purchase Agreements with developers, aiming at investing in “additional” production.

“Additional” means that they don’t want only to buy renewable energy: they want to add this MW to the grid, building new plants and lowering the carbon footprint.

Another interesting fact is that they buy renewable plants connected to the same grid were the data centres are.

For instance their very first PPA was for a 114 MW windfarm in Iowa, one of the states with a data centre, while their 72 MW wind project in Sweden (2013) was intended to  “feed” the data centre in Finland.

The next step is to sell power to the grid at the spot price. Here is where the magic happen: Google is willing to sell it at a loss in case the spot price is lower than the price indicated in the PPA. The idea is that they wanted to use their financial power to give developers a steady cash flow, assuming the risk of fluctuations in prices.

They also get the famous “renewable energy credits”, and they use them to offset  the carbon footprints of the data centres.

A legitimate question would be “Why don’t you buy directly the renewable energy credits?”. The position of Google, as mentioned before, is that they want to help developers to create more and more renewable energy plants. They believe that the best way to do it is to  use their deep pockets to make more projects reality - "bankability", the possibility to get the money to finance a project from a panel of bank, is usually one of the critical point that kills many developments.

The good news, at least for people like me in the wind business, is that the vast majority of the investments (>95%) are in wind farms. The same apply to other business giants following Google on the renewable path, such as Amazon, Microsoft and Facebook.

Serrations: how to reduce those noisy vortexes

Every now and then a new technical solution appears in the wind energy business and it’s slowly implemented in the new wind turbines.

A good example is the use of trailing edge serrations – not really a new idea (it has been around for several years) but a simple solution that it’s spreading and gaining acceptance in the industry.

Basically they are a method that help reducing the noise of the blade and they look like small triangles. You can see them in the picture at the beginning of the post, which I ironically stolen from an anti-wind energy website.

This solution is particularly beautiful because it can be retro fitted – meaning that it can be applied also to existing, working wind turbines.

They work reducing the turbulent boundary layer on the trailing edge of the blade, which is the source of a relevant amount of the noise. This is a complicate subject and I’m not an expert in acoustic, but in general what happen is that the turbulences and the vortices created by the  layer of air that separate from the edge of the blades are creating the majority of the noise that we hear.

It’s interesting to observe that the length of the triangles has an impact on the reduced frequencies (the longer the serrations, the bigger the reduction at the low frequencies). This help reducing the frequencies that are more annoying for humans.

Also, it is worth mentioning that the amount of dB reduction is function of the serrations flap angle.

Obviously they don’t do miracles, but a reduction of 1 or 2 dB(A) for their price is a good trade off.

It’s also worth to notice that they do not affect substantially the performance (that is, the production) of the wind turbine.

Everything fine? Defects Notification Period

The Defects Notification Period (DNP) is a certain number of day counted from the date of completion of works that allow the customer to notify defects to the Contractor. In the Wind Energy business is usually 12 months, but in principle can be longer (2 years, 5 years, etc.) or shorter.

There are also situations where there are different type of DNP, shorter for not critical items and longer for critical items.

It is usually start from the certified completion of works (the day the Taking Over Certificate is issue). It is interesting to consider that the majority of contract also include a “deemed taking over” – basically a set of circumstances that constitute a “de facto” taking over.

During the Defects Notification Period the subcontractor will probably need to do some minor works to solve the problem listed in the Defects Punch List. If new problems are discovered by the customer, that the contractor is obliged to fix them.

Finally, a point worth mentioning is that the subcontractor is usually obliged to repair also defects not attributable to him (in this case he is obviously entitled to payment via Variation Order).

Nabrawind Technologies self erecting tower

Image copyright of Nabrawind

Some years ago I posted an article about a self-lifting wind turbine tower.

The idea was to use using heavy lift strand jacks already available in the market to lift the concrete sections of a wind turbine tower. It's a project developed by Esteyco, a Spanish engineering company.

Well, I just discovered that it’s not the only idea currently under development on this topic – another company (curiously from Spain as well) is studying a somehow different concept with the same objective: avoid using big cranes, above all in areas of difficult access.

The product is called Nabralift - you can read more on the company webpage.

Basically it's a tower with a mixed technology "standard" tubular steel + lattice where the steel section is erected by a standard auxiliary crane (like in the pre-erection of the first section) while the lattice elements are "pushed" little by little from the bottom by hydraulic jacks (this is a similarity with the solution discussed in the other post).

Apparently the solution doesn't use an anchor cage - instead what I see from the pictures look like an adapter between the steel and the lattice section.

The company stated that they are undergoing a 6 months long fatigue test on a full scale model already erected in northern Spain.

Theoretically, there are 3 possible sources of saving here:

  1. Installation cost (no main crane)
  2. Tower cost (the lattice segment is proportionally cheaper than a standard steel one of the same height
  3. Foundation cost (apparently this solution will need a smaller foundation).

Last but not least, the increased stiffness of the lower part could lower the self resonance risk due to the passing blades, frequent in the very high towers currently in the market.