Circular economy: use of wind turbines blades as combustible and mix material for cement production

One of the future challenges of wind energy is to find a solution to recycle old blades from decommissioned wind turbines. In this post I will try to summarize several possible alternatives and to describe in detail what I think is currently the best option: to use them as a component for the production of cement.

The development of this interesting technical solution started in 2005 when one of the largest wind turbine manufacturer asked LafargeHolcim (a global cement producer) to use the decommissioned blades in cement production plants.

In 2008 Geocycle (the business unit of LafargeHolcim specialized in use of waste to produce cement) launched the full scale development of the solution in the Lägerdorf cement plant, in Northern Germany.

The recycling start in the wind farm, where the blades are cut in 10 meters long pieces using a mobile cutting technique that reduce the generation of fine dust humidifying the area. The resulting water is collected and brought to the recycling plant together with the other materials.

The pieces are then transported by train or truck to a pre-processing plant.

Here the blades are cut before in segments with a length around 1 meter and subsequently shredded in smaller pieces, with a final length of some millimetres.

Metals, both ferrous and not ferrous, are separated automatically from the material flow by magnet and eddy current magnet devices.

Finally, the crushed blade dust is mixed with a humid substrate material made of other residues such as plastic labels and miscellaneous packaging materials. The purpose of this substrate is to homogenize and bind together the blade dust. The material composing the substrate are wastes from other processes such as paper recycling.

All process steps in the pre-treatment plant are fully automated and performed in a controlled atmosphere. This guarantee maximum levels of occupational health and safety.

The end product is put in the cement plant.

In the pre-calciner (an element of the cement plant that optimize fuel consumption) the resin matrix is used as an alternative fuel, substituting coal, petroleum coke, heavy fuel oil or natural gas.

At a temperature around 900 °C the resin burn transforming the blade fibers into ashes. These ashes are then going together with the rest of the calcinated raw materials - usually a mixture of limestone and clay - in the sintering zone of the cement kiln to produce the clinker.

Finally the clinker is ground into a fine powder together with a small amount of gypsum creating the final product, cement.

The cement produced using wind turbine blades is indistinguishable in terms of quality from the standard product obtained without using the blades. It can be sold in the market or used again in wind farms, for instance in wind turbines foundations, closing the loop.

This solution provide alternative raw materials for cement production, reducing the need for quarrying, stone crushing and transportation. The ash of a wind turbine blade consists mainly of silica (SiO2) and calcium oxide (CaO) and due to this substantial amounts of natural resources like carbonate rock (limestone) and clay (usually in the form of sand) can be saved.

Additionally, it has to be noted that this solution contribute to savings of fossil fuel: the resin of the blade provide energy (around 12 MJ/Kg). This value is approximately the half of hard coal:  therefore each tonne of rotor blade substitute around half a tonne of hard coal.

It’s important to note that this solution has been indicated in 2011 as the best option available in a Position Paper subscribed by the European Composites Industry Association and other relevant category associations.

The test phase was successfully concluded in 2009 and the solution has been made commercially available since 2010.

I see several interesting benefits associated with this technique:

  1. It is capable of dealing with large amounts of materials, since the cement plants can handle thousands of tons of material.
  2. It address as much as possible geographically local opportunities, because it’s operated by LafargeHolcim, a multinational company active worldwide with over 2000 operation sites.
  3. It is feasible right now, because it is a commercially mature solution currently used in Germany and neighbouring countries. Hundreds of blades have already been recycled.
  4. It is cost-effective, because is the second cheapest alternative after landfilling.
  5. It address the totality of the materials of the blades, because the resin matrix is used as combustible, the fibres become part of the cement and other elements (e.g. metallic components) are separated upfront in the pre-processing unit.
  6. It follow strict environmental and safety standards. This solution has been developed in Germany (one of the first country to ban the landfill of wind turbines blades) and it has been certified by third party bodies.

The final cost is function of several parameters, such as the number of blades to be recycled, the distance of the wind farm from the nearest cement plant and the need to adapt the pre-processing facility.

Therefore, final cost will depend on scale factors, logistic costs and pre-treatment costs.

There are several other alternative. I will try to summarize them in the next paragraphs.

Landfill: Blades are sectioned into pieces of suitable dimensions and placed in a landfill. Transportation and preliminary shredding is needed.

Here no material recovery is possible and some national and local legislation impose high landfill taxes or complete bans on composites material with high organic percentage such as the blades.

Additionally, legislation worldwide is expected to become stricter acting as a driver for the development of alternative solutions and the creation of a recycling market, either with an extended ban or with a sharp price increase for landfill of blades.

Mechanical processes: Blades are reduced in size and separate into powder and fibrous fractions via cutting, crushing, shredding, grinding, or milling processes.

Finer pieces are sorted and used as fillers or reinforcements or as fuel for thermal waste processes.

This is currently done on a limited commercial scale and theoretically it has a wide range of potential applications for material recovery.

However, from an economical point of view it is competing with the lower market cost of alternative virgin fillers (calcium carbonate, silica).

Additionally, it has been observed a reduction of the mechanical properties of the resulting material (lower stiffness and strength). For instance, concrete made using shredded blades instead of crushed stones has unsatisfactory mechanical properties.

The only viable mechanical process currently operating in the market, presented as the competitor solution, is the one offered by Global Fiberglass Solutions, detailed in the following paragraph.

Mechanical processes - Global Fiberglass Solutions (GFS) pellets: The blades are transformed into small pellets that are sold under the brand name of “EcoPoly Pellets”. They are usable in injection mold and extrusion manufacturing processes and they are made from a customized blend of wind turbine blade materials.

EcoPoly Pellets are made to order for final customers based on the requirements of the customer’s own manufacturing process. GFS has initiated distribution options for pellet and has already found several wind farmers owner willing to provide decommissioned blades as input material for pellet production.

I believe that this technique it is currently available only in the USA.

Thermal processes - incineration: Blade sections are incinerated at high temperatures – usually over 800 °C.

Organic substances are combusted and converted into non-combustible material (ash), flue gas and energy. This process is usually combined with energy production and heat recovery.

The ash could also be used as a substitute for aggregate in other applications recovering the material or landfilled. However, no economically viable uses have been found for the ashes (beside the proposed use as input for cement production).

The advantage is that there are already numerous incineration plants available and that it can be done at attractive prices.

The disadvantage is that no large parts can be incinerated, making necessary a preliminary shredding.

Additionally, blades have a high ash content (around 50% to 65%) that needs to be landfilled afterwards with the associated transport and landfill tax costs.

Finally, burning blades create residues that can cause problems in the gas filtering systems.

For all these reasons this solution has been discarded.

Thermal processes – Pyrolysis: Blades are sectioned into suitable dimensions and decomposed using heating ovens in an inert atmosphere (450-700 °C).

Material is recovered in the form of fibres which can be reused in other industries. For instance, in pilot tests they have been used for glues, paints and concrete. Other products of this process include syngas (that can later be combusted for electricity and heat recovery) and char (recycled as fertilizer)

Under certain boundary conditions the resin matrix can be transformed in an oil “Pyrolysis Oil”.

The problem with this technique is that significant amount of energy are needed to activate the pyrolysis, impacting the overall environmental value of the solution.

Furthermore, available laboratory tests show a degradation of the properties of the glass fibers and no secondary market has been found.

Additionally, test have been performed only at laboratory scale so it is considered a solution with a low technological maturity.

Thermochemical processes – Solvolysis: Chemical solvents (water, alcohol, acid) are used to break the resin matrix bonds at elevated temperatures (300-650 °C) and pressures conditions.

Among all the solvents currently tested, water appears as the most commonly used. In this case the process is called hydrolysis.

Fibre materials recovered have a similar strength and could be reused in other applications. The resins as well can be separated and combusted for energy recovery

As far as I am aware test have been performed only at laboratory scale, mainly with focus on carbon fibres composites.

Moreover, due to the low market price of glass fiber, no secondary market is existing.

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

Looking for a tender manager BoP

Looking for a Tender Manager specialized in Turnkey (EPC) wind farms.

Ideally expert in wind farm Balance of Plant (roads, foundations, MV cables, substation) and technical and commercial negotiations for all BoP scope of supply.

Apply on Linkedin or here:

https://nordex-jobs.dvinci.de/cgi-bin/appl/selfservice.pl?action=jobdetail;sid=2ctve7ap88m7y3oy;job_pub_nr=06A416E2-A75E-454C-AB00-5062D288C634;p=homepage;job_pub_type=extern;

5 strange things that you might find in a wind farm

Working on a variety of projects worldwide I sometimes see unusual requests from customers that want to complement their new wind farm with some nonstandard feature.
I’m collecting here my personal top 5 of “...are you REALLY sure you want it?”. Even if often this type of requirements can lift considerably the price (and make the project less attractive) customers are often irremovable in their request.

#5 – Reserve main transformer. Sometime also poetically called “cold transformer” this is basically a very expensive spare parts to keep parked somewhere in the substation. With a price tag around 1 million it looks like a very expensive price to pay to have a backup in case something goes wrong with the main transformer.

#4 – Residences for the Service technician. In very big wind farm sometimes it’s a good idea to have someone on site 24/7. If the wind farm is in the middle of nowhere it can be also a good idea to provide fully furnished houses.

#3 – Gym. The same Service technician living in the middle of nowhere will presumably need something to do while they are off duty. A properly equipped gym can provide a good use for their spare time.

#2 – Mosque. With a mosque we are becoming very near to the concept of “wind farm town”. It was also a good opportunity to learn something more about the various requirements of this type of religious building.

#1 – Watchtowers. By far the most unusual requirement ever. Basically, a place where an armed guard can watch from a vantage point who is approaching the wind farm, with electricity (you will need to connect it to the substation somehow) and septic tank.

Environmental impacts of wind farms

When I talk about my job with people coming from different businesses I receive often question linked to the “environmental impact” of wind turbines.

This term include various effect related to the construction of a wind farm. They can be summarized in the following categories:

Visual impact

Are wind turbines ugly or not? This is a difficult question. Probably I’m biased, but I think they are beautiful – or at least, better than a nuclear plant, unless you like concrete cooling towers. Some nacelles shape have been designed by artist (like the first Acciona models) or architects, like Enercon’s egg shaped solution. It has been designed by Sir Norman Foster and has been awarded with the Design Council Millennium Products Award, the same prize given to beautiful stuff like the Lotus Elise.

However in several countries a specific study is done to evaluate the visual impact of the turbines. There are several indicator and methodologies, however this is usually done considering the “weighted” average height of the horizon before and after the construction of the wind farms.

Noise generation

New generation turbines use a lot of tricks to keep noise low. Noise is coming above all from the tip of the blade, being the rotating equipment in the nacelle only a secondary source. The “easy” way to limit noise is limit the tip speed of the blade. Other strategies involve special profiles for the blade and software control of the machine to limit noise emission when needed (usually during the night, and/or when the wind is blowing from specific directions).

Electromagnetic interferences

This is easy to measure. In general electricity is generated at a low voltage (around 700 Volt) and MV cables are buried, so this impact is negligible.

Shadow flickering

This is the risk that someone living near the wind farm could experience, for a prolonged length of time, the intermittent shadow of the blades passing in front of the sun. This impact is relatively easy to simulate: there are software that, given the position of the turbines and the meteorological parameters (wind direction, percentage of sunny days) calculate the amount of time an observer located somewhere near the turbine would experience the flickering.

Bird strikes

One of the most discussed issues. You will find quite a lot of studies online, done in countries were wind energy and environmental sensibility is well developed (US, Germany, Spain, etc.). In general my impression is that, compared with other causes of bird death (hunt, high buildings, traffic, etc.), impact with turbine is accountable for a very small percentage.

Additionally modern wind turbines can be equipped with a lot of technology that minimize this risk (bat detectors, LIDAR systems, artificial vision, etc.). I had the pleasure of working at projects were the space between machine was large enough to lower the risk of impact, and additionally the turbines were stopped when migrating birds approaching the wind farms were detected.

 

Wind farms: top 5 of myths & urban legends

A curious consequence of writing a blog about wind farms is that every now and then I’m contacted by someone hating wind energy.

In the majority of the cases, the writer also ask for help to stop or boycott a wind farm somewhere in the word, apparently ignoring the fact that wind turbines help me to bring food on the table every night.

To add insult to injury, in the emails they often ask me support to confirm some pseudoscientific “facts” about wind turbines.

I’ve collected some of them in this post – other are coming from anti-wind energy propaganda websites that I read on the subway when I’m bored to discover new, unexpected effect of windmills.

Some of them are similar to the urban legend of the albino alligator in the sewers of New York.

Feel free to contribute!

5. Wind farms causes bush fires. Well, it’s true that (very, very infrequently) a wind turbine burns somewhere. But to say that they are burning woods and bushes it’s a bit too much.

4. The foundations are poisoning the water. Unless you pump 1 million cubic meters of bentonite to do a piled foundation nothing will happen to the water – a foundation is basically only a big stone.

3. The turbine is scaring the fishes – I’m not fishing as much as before. This is courtesy of a fisherman in Juchitan de Zaragoza (Oaxaca, Mexico). I doubt that a fish 10 meters underwater can really hear a WTG.

2. You need more energy to build a wind farm than the energy produced by the turbines. I’ve seen several (serious, scientific) papers on the subject. The energetic payback is usually only a few months.

And the winner is...

1. Wind farms change the weather locally. I love this one. The theory is that, slowing the wind, wind farms modify somehow the climate in the area – some urban legends say that they warm it, some others that they make it more foggy. Well, at least here in norther Germany where I’m living they are not making it any warmer.

Acronyms in wind farms construction

I’ve been informed by one of my most affectionate reader that some acronyms that I’m using in the blog are not immediately clear.

Therefore I’ve started a first list of the most used ones - special thanks to Janos for helping expanding the list:

AEPAnnual energy production.
BoPBalance of plant. All civil (roads, foundations, crane pads) and electrical works (cables, substation, etc.) in the wind farm.
CapExCapital Expenditures
CODCommercial operation date
COECost of energy
EISEnvironmental impact sudy
EPCEngineering procurement and construction. A type of contract (also known as "turnkey")
FIDICInternational Federation of Consulting Engineers  (Fédération Internationale Des Ingénieurs-Conseils)
HSHealth and safety
HVHigh voltage
IPPIndependent power producer
IRRInternal Return Rate
LDLiquidates damages
MLAMechanical Load Assessment
MVMedium voltage
MWMegawatt
O&MOperation and maintenance
OEMOriginal equipment manufacturer. Here, the company producing the wind turbine.
OMAOperation and Maintenance Agreement (sames as SMA)
OpExOperation expenditures
PCCPoint of common coupling
PPAPower purchase agreement
RoWRight of way. The legal right to use a certain route.
S&ISupply and installation
S/SSubstation
SCADASupervisory control and data acquisition
SMAService and Maintenance Agreement (same as OMA)
SoWScope of work
TSATurbine supply agreement. The contract between the wind turbine manufacturer and the wind farm developer.
W&SWind and site. Usually, either the assessment of the wind farm (W&S study) or the department doing it.
WFWind farm
WTGWind turbine generator

Technical due diligence of a wind farm

It is a hard task to compress in a blog post the reasons behind the technical due diligence of a wind farm and the several points that must be evaluated.
In a nutshell, in the clear majority of the wind farms developments are built using borrowed money.
The equity (cash at risk) is put by the developer, while the debt (money given against some form of security) is provided by a financial institution, or more commonly by a pool of institutions.
There are obviously exceptions to this rule, that is wind farms developed only with cash coming from the books of the company investing in the project. Nevertheless, these are exception and what is common is to have most the budget (up to 70%) provided by a financial institution such as a bank.
The lenders will be obviously interested in being sure that the financial model behind the project is solid.
Therefore, they will ask for a due diligence to identify, quantify and (if possible) mitigate technical risks.
In general, the lender will check what he considers appropriate.
Normally 3 macro categories are checked:

Financial due diligence, including for instance

  • Hypothesis
  • Budgets
  • Financial models

Legal due diligence, including items such as

  • Land lease
  • PPA
  • Contracts (e.g. TSA) & subcontracts

Technical due diligence

There is obviously an overlap between the various categories – for instance, some items are not purely “technical” or “legal”.
The technical due diligence should investigate in detail several key points.
A short, non-exhaustive list would include at least the following items:

  • Site suitability (wind resources, turbulence, data solidity)
  • Choice of WTG model (track record and match with the wind resource, power curve, certification, etc.)
  • Archeological y environmental constrains (impact on flora and fauna, such as birds and bats)
  • Access to the area (road survey and works outside the wind farm)
  • Geotechnical survey (ground risk)
  • Noise study (a big problem in inhabited areas)
  • Shadow flickering & visual impact
  • Grid connection
  • Electrical losses (are they calculated correctly?)
  • Projects for the BoP (foundations, MV, substation, etc.)
  • Congruence of the time schedule of the project
  • Interface between subcontractors
  • Allocation of risk

EWEA 2016

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.