Blades installation: more options than you might think

How are the blades of the wind turbines installed?

Although in general each wind turbine model has only one installation procedure, several technical alternatives have been developed through the years.

The quicker and easier method is probably to assembly the rotor on the ground. The three blades are connected to the hub and then lifted together in what is called “rotor installation” or more colloquially “the cross” (I guess because during the lift it vaguely remember a crucifix).

The main problem is that this solution need a lot of space. Additionally, as the blades are becoming bigger and bigger, it would be impossible to lift the weight of three blades at a height of more than 100 meters with the cranes currently available.

Another solution, very uncommon (actually I have never seen it in the real world) is the “bunny ears” method. Nacelle and two blades are lifted together, resembling (if you have a vivid imagination) the face of a bunny with two long ears.

The solution used more frequently nowadays is the single blade installation. The blades are lifted one by one and connected to the hub, usually horizontally although some turbine models are designed for an inclined or even vertical blade position.

Liftra, a company active in the wind industry, developed a tool called “blade dragon” that allow blade installation in every position.

The concept can be interesting in several situations – for instance if you want to disassembly a blade for repairing, you could use a smaller crane disassembly a blade in vertical position (that is, with the tip pointing downwards).

Liftra Blade Dragon inclined installation. Image Copright Liftra.

The single blade installation need a specific “blade lifting tool”. Such tools usually provided by the turbine manufacturer and are designed to fit a specific blade model.

Often there aren’t so many tools available (they are expensive, so their number is kept to a minimum) they can be a source of problems (for instance if the tool breaks or arrives late).

You will also need a second tool to turn the rotor, called "rotor turning tool" or "turning gear".

As the blades have to be installed horizontally, you will need to rotate the hub after the first blade is installed to have an empty socket in the right position, and repeat the procedure after the second blade is installed.

Those turning tools are hydro-mechanical. A power source is connected to a pump generating the pressure needed to rotate the gears.

The standard solution is to connect the tool to the disk brake used to stop the turbine in case of emergency. The brake disc wheel is toothed, allowing efficient coupling with the tool.

Liftra Blade Dragon vertical installation. Image Copyright Liftra

The single blade lift is generally more time consuming, as you will need 4 different lifts (one for the hub and three for the blades) compared to the rotor lift.

Do not trust me: reliance of data in EPCs

EPC contracts frequently include a clause on the reliance of data. It has several formulations, but it usually looks something like this:

“Employer-Provided Information has been made available for reference only.

The Employer makes no warranty as to the accuracy, completeness and reliability of any information, data, statement in the Employer-Provided Information.”

The objective is clear – avoiding claims during construction if the data is wrong. In the most extreme cases even information critical to price a project (like for instance a geotechnical survey) should be considered as a “not rely upon” data.

How did we get to this point?

To give some context, the theory is that standard EPC contracts like the Silver FIDIC explicitly request to the subcontractor to study the Employer’s Requirements to find errors and omissions.

This is usually written in this way (you can find an example with the full text for instance in chapter 5 of the standard Silver FIDIC contact):

"The Contractor shall be deemed to have scrutinised, prior to the Base Date, the Employer’s Requirements (including design criteria and calculations, if any)."

But there are exceptions - in an effort to create a reasonable contract, although not as balances as the FIDIC Red or Yellow, the authors of the clause add:

"However, the Employer shall be responsible for the correctness of the following portions of the Employer’s Requirements and of the following data and information provided by (or on behalf of) the Employer:

(a) portions, data and information which are stated in the Contract as being immutable or the responsibility of the Employer;


(d) portions, data and information which cannot be verified by the Contractor, except as otherwise stated in the Contract."

In an effort to unload risks and responsibilities, Employers try to avoid being accountable for ALL information provided during the tender. Basically, the bidder cannot trust the tender documentation and should double check.

Unfortunately, in many situations bidders cannot verify independently the information provided. For instance to confirm the results of a geotechnical survey for a wind farm a bidder would have to invest thousands of dollars and one or two months of time to make a new set of boreholes and trial pits.

This is clearly unrealistic and unreasonable. Such clause, if stretched to the extreme, can have as a result extremely high prices (as the bidder will have to foresee the worst case scenario) or few bidders (as they will simply decline to bid).

I also suspect that in some situation the Employer decide not to circulate available information, probably following some twisted logic.

All in all I strongly believe that it would be in the interest of the Employer to avoid using the “not to be relied upon” clause on information like wind data, geotechnical survey, grid connection info, topographical survey, etc.

BoP strikes back: the increasing relevance of Balance of Plant

A key difference between combined cycle plants and wind or solar plants is the CAPEX / OPEX distribution. According on recent data of the American Department of Energy, for a combined cycle plant the CAPEX will be only around 25%, being the overwhelming majority of the investment in operational costs (that is, fuel) and maintenance.

The picture is different for wind farms and photovoltaic plants, were the fuel is free (still no taxes on wind and sun) and the majority of investment is needed upfront, with over 80% of CAPEX.

An interesting trend I am observing is the shift in the weight of Balance of Plant (BoP, more usually called Balance of Systems in the PV industry).

It is well known that the costs of photovoltaic modules and turbines are following a downwards trend. I do not see the same trend for BoP, with costs per MW decreasing at a slower pace.

In the figure above, you can see how the BoP share can be more than half of the CAPEX for rooftop solar. The numbers are coming from the Fraunhofer Institute, which include in BoP also land acquisition costs, permitting and legal cost, taxes, etc. Even if I disagree with this “broad” definition of BoP, the result is unchanged - the relative weigh of BoP in renewable is increasing.

What are the consequences?

In my opinion, the most relevant is that now BoP can really make of kill a deal. When it was approximately the 20% of the CAPEX even a big movement in the BoP budget was not really moving the numbers that much. However now the relative weight increased to over 40% in some project, and an expensive BoP can make a project economically inviable.

Is there something that we can do about it?

For several items probably not. For instance, wind farms on top of mountains will need expensive access roads, complicate earthworks with rock blasting, etc. While there is probably still some room to decrease the price of wind turbines (e.g. with a better supply chain) I do not see why civil works should be cheaper in the future.

The same apply to some electrical works items such as medium voltage cables, which are basically a commodity linked to the price of aluminium, steel, etc.

In conclusion, I think that in the next years we will see an increasing effort in engineering and optimization to lower the cost of BoP and insure the economic sustainability of projects.