About Francesco Miceli

I’m a civil engineer specialized in wind farms civil works (usually called BoP, that is Balance of Plant). I’m currently based in Madrid, Spain and I’m developing several interesting project all around the world – southern Europe, North Africa and above all central and south America.

Guy-wire supported mast for a permanent met mast

Here you have some interesting pictures that we’ve received trying to define the meteorological tower (also known as “met mast”) foundation for one of our wind farms.

Strangely, our customer is going to use a wired met mast for both towers (the permanent mast of the wind farm and the temporary mast used to calibrate the power curve).

As you can see from the pictures the mast has an interesting hinged base joined to the foundation of the WTG with 4 screws - looks like an effective technique.

The mast is tower model is KT470 from Kintech engineering.

Geotechnical parameters for WTG foundations design

This is the first post after a long silence (more than 6 months), fortunately due to good news (the birth of my first son, who reduced dramatically my free time).

I want to thank José Ramon, one of our experienced Project Manager, who pushed me to start again 😉

This post is about geotechnical parameters relevant for wind foundation. I’m in debt with Ana from Esteyco, a very good geologist who explained me how this work.

She explained me that the most important parameters that we need define in a geotechnical survey for wind turbines foundation design are 2: bearing capacity and deformability.

 

Bearing capacity is defined by c (cohesion), ϕ (friction angle) and qu (unconfined compressive strength) and it is used in Ultimate Limit State (ULS) design.

In this type of verifications, loads such as extreme wind, abnormal loads or earthquake are used to check the foundation for overturn, slide and collapse (soil failure).

If we are working with soils, we normally define these parameters using in situ tests such as SPT (in sands), CPT, Pressuremeter test and Vane test, or with laboratory tests  such as triaxial (CD, CU, UU) , direct shear test or CBR.

In rock, we could use a compressive strength test, rock quality designation (RQD) or triaxial, although the bearing capacity of rock (even heavily fractured and weathered) is normally so high that these tests are normally not necessary.

Deformability is defined by E (Young's modulus) and G (Shear modulus).

These parameters are used to check if the foundation is compliant with vertical settlement, differential settlement and, above all, rotational stiffness.

These verifications are done with a Serviceability Limit State (SLS) design.

In case of soils, these parameters are defined with in situ test like SPT, CPT, down hole, cross hole (normally not used because we don’t have boreholes nearby normally) and pressuremeter. If we define them with laboratory test, we would use triaxial or oedometer test.

In both case, we prefer field tests to laboratory tests, mainly because it can be difficult to have undisturbed samples with their in situ characteristics.

It is important to highlight that in some cases, we could meet the bearing capacity requirements but not the deformability minimum conditions and vice versa. For instance, soft sandy soils with some combination of WTG and tower can offer a reasonable bearing capacity but an excessive deformability.

Wind energy in 2012: key figures and market evolution

In this post I want to show some figures about the evolution of the wind sector worldwide, both on the demand and supply side, and what happened in 2012.

From my point of view as Vestas employees the biggest new has been that GE is now the biggest wind turbine manufacturer. They now have a market share around 15% percent, with Vestas slightly below (14%) still winning the battle of the installed capacity.

The market is fragmented, with 10 more or less big companies and several smaller ones. It’s peculiar that the “small” manufacturers together have sold more than 20% of the installed turbines: apparently, they are not so small.

The Chinese manufacturers (Goldwind, Sinovel, Mingyang, etc.) felt the pain of a slowing internal market, falling down in the market share fight. Basically, they install only “at home”, in a closed, protectionist Brazilian style environment.

About 45 GW have been installed in our planet last year (2012), with an increase of 19% of the installed capacity. Right now there are about 286 GW of installed turbines.

Installed GWCumulative
20072094
200828122
200938160
201039199
201142241
201245286

Apparently in 2013 the installation of new turbines is slowing down, although figures are only preliminary.

The country with the biggest number of wind turbines is China, with around 54.000 WTGs, followed by the USA with 51.000. Of course they are the biggest markets in the planet.

If you wonder how many turbines are installed in the whole planet, the cumulative figure is around 222.000 machines.

In Europe, Germany is leading the sector with around 23 thousand machines, followed closely by Spain with over 20.000. Looking the distribution of installed capacity by continent Europe is still ahead:

Installed capacity (2012, GW)
Americas72
Europe110
Asia95
Pacific7
Africa1
Others1
Total286

Offshore is developing quickly in Europe, thanks to the Mega-projects in Germany and in the UK. Global installed offshore capacity is above 5.000 MW, usually concentrated in very big wind farms. Preferred foundation technology has been monopile (if you are interested in the subject, you can read more here about offshore WTG foundations).

As you will probably know the market is moving towards biggest turbines, being the average size of the newly installed generators around 2 MW.

Regarding owners, Iberdrola is the company with the most installed MW (13K), followed by 2 companies that I don’t know, Chinese Longyuan (10K) and NextEra Energy Resources, from the States (about 10 GW as well).

To close the post, the answer to a typical question regarding wind energy:

What is the contribution of wind power to the global electricity generation?

About 3%.

Wind Turbines Precast Foundations

I’ve recently discovered the existence of precast foundation for wind turbines. Strangely enough, this solution isn’t having a big success, at least as far as I know.

By the way, there are several clear advantages: first of all, an important time saving.

According to the developer brochure, only 2 days are needed to complete the foundation: the first to install the pieces and the second to connect the tower tensioning the bolts.

Then, as with all serial products, there is the advantage of tighter controls on the quality of the materials and the production

The manufacturer also suggest that the excavation volume is reduced, although I don’t understand why (in the end, it is still a gravity foundation, so the dimensions should be similar).

I also don’t see what happen with the conjunction element (embedded ring or anchor cage in the newer models): I suppose that it will be substituted by bolts enclosed in the precast modules, but I can’t visualize how it will work without the lower flange.

I don’t know how many companies are actives in this business: the picture below are taken from a presentation of Artepref, a Spanish company specialized in precast components.

Talinay Oriente 90MW EPC Wind Farm

Although I don’t normally post stories about wind farms I’ve worked at I want to do an exception for Talinay, a project with whom I have a relationship almost emotional.

Located in Chile, in the Coquimbo province, near the Limarí river, it has been a project entirely developed by Vestas with internal founds and my first “hands on” EPC experience.

We’ve had the pleasure of optimizing the layout both in the preliminary phase, working together with the wind & site team, and in the constructive project. It was tough, because it is located in a mountainous area where impressive earthworks are needed.

It is a mix of V90 and V100 turbines of the 2MW platform, with an installed capacity of 90 MW.

Connected to the grid in March 2013, it has been constructed at an amazing, “china style” speed: with almost 400 peoples working together on site during the busiest period, it was a record for the foundation (5 per week, with two concrete plants on site working full time day and night) and the turbine installation (4 WTG per week).

The wind farm was completed in 6 months.

Almost all the big players of the sector have been involved: from the engineering side support was provided by IDOM, SISENER and ESTEYCO, while the main subcontractor was GES who worked with local and international subcontractors (among them, Hormigones Melón, Burger Gruas and CJR).

On the electrical side, it was one of the first (or maybe the first) PASS installed in Chile. The transformer was developed at lightning speed (155 days ex works), while the substation was made by ABB and Siemens.

Now is property of the Italian utility ENEL Green Power, who also signed a service agreement. Part of the money of the deal comes from a loan from Denmark’s Export Credit Agency (EKF). ENEL has an aggressive expansive approach in the Chilean market, where is developing several other wind farms (some of them with Vestas).

Below you will find several interesting pictures: two trucks pulling a tower section due to the high slope of the road, PASS switchgear and line trap, concrete plant and other interesting views of the wind farm.

Artificial vision systems for bird impact

One of the problems of installing a wind farm in an area with a dense bird population is the possibility of impacts between the rotating blades and the animals.

A standard solution used in the industry is the use of a (very expensive) bird radar, a quasi-military technology that can spot very small flying objects and stop the turbines (hopefully) in time.

Working at the development of a wind farm in Jordan we have discovered the existence of an alternative: a Spanish company (Liquen) is developing an “artificial vision” system to be installed on the WTGs.

Basically the system is composed of 2 sets set of high definitions cameras installed on the WTGs or on the MET mast that are filming the space around the turbines, plus speakers for dissuasion sounds.

The software can analyze the images in real time and recognize if a bird is flying toward the machine. If this is the case, several countermeasures are possible:

  • Warning and dissuasion, using annoying signals. Clearly this signals are optimized to the type of birds in the area
  • Stop control, whit short duration (<2 minutes) stop of the affected turbine and automatic restart to minimize production loss

According to the company, real time detection is really fast (less than 1 second) and it is possible including in adverse weather conditions (fog, snow, rain) whit a very low power consumption.

The main problem that I see is that the system is effective only when there are at least 200 Lux (that is, from sunrise to sunset). So there is a clear problem with nocturnal birds – I wonder if in the future it will be possible to integrate the system with some kind of night vision, like the military infrared technology.

Another weak point is the low detectability of very small bird (12 centimeters or less): they can be easily spotted only if they came in a large group.

This technology looks promising and it’s not so “embryonic”: it has already been installed in a Vestas wind farm in Greece and several other wind farms around Europe (Spain, Norway and Greece).

If you are interested you can find more information in the DTBird Brochure or in the results of a study in a real wind farm in Norway.

Gestamp iConkrete wind turbine foundation

Some weeks ago a document describing a new type of wind turbine foundation, the “iCK foundation”, landed on my desk.

Also known as “Gestamp Hybrid Towers” (GHT) it has been developed and patented by iConkrete and Gestamp. Essentially it is a shallow foundation made of a slab to achieve a uniform pressure distribution, a central reinforced ring with his pedestal and several reinforced beams below the slab.

You can see how it looks like picture here:

The basic idea is to obtain a T section, for a better use of materials: compression is distributed on the top of the T head, with a reduced depth of the neutral axis.

This geometry, according to the developers, gives and improved fatigue behavior for concrete and a higher resistance reserve.

Among the other potential advantages, a (partial) prefabrication of the foundation’s elements is possible. This lead to a “cleaner” work and to a saving in time.

Moreover, the smaller excavation promises other savings due to reduced earthworks: this foundation is more superficial than the standard one, with an average depth of almost 3 meters. The excavation volume avoided can be around 50%.

Last but not least, according to a test design made by Gestamp, a 15% of steel can be saved thanks to a better use of materials.

If the soil below the foundation has a low bearing capacity, a geotextile can be used.

This solution can be adapted to any type of tower (steel, concrete or mixed).

 

Wind Energy in Jordan

Together with the projects in Chile and Uruguay I’ve been involved lately in several wind farm developments in Jordan. Currently the country has a near-zero wind energy production, but due to his very strong dependency on energy import (more than 95% of the demand, absorbing about 13% of the GDP) committed to an ambitious plan to add up to 700 MW of power from renewable sources.

The target, according to the Renewable Energy and Energy Efficiency Law voted in January 2010, is 10% power generation from renewable in 2020. That is around 2.3 GWh, of whom about 1 GWh from Wind. We are already late to reach it, but something is moving.

Among other things, the Renewable Energy Law  allows the ministry to negotiate with investors directly, bypassing a competitive bidding process, and allow to sell electricity generated by renewable energy back to the national grid.

In December 2012 a feed-in tariff of USD 0.12/ kWh has been introduced by the local electricity regulatory commission, stimulating the appearance of Direct Proposal on behalf of several developers. Due to the low expertise only a few developers are local, and including a not so aggressive target of 15% local content (needed to improve the tariff) may be hard to reach.

No international tender like the Mega Moroccan tender has currently been done.

Lenders, as often in these cases, are big international financial institution (World Bank, Gulf Cooperation Council, Global Environment Facility and several other banks consortiums). They are founding not only wind energy, but also solar (concentrated and photovoltaic).

Projects reasonably advanced in the pipeline are Kamsheh (40 MW) and Fujeij (90 MW). Fujeij has already a shortlist of 8 developers.

There are also voices about a 200MW wind farm to be done by energy company Nareva in partnership with International Power. Nareva (ONA conglomerate) is controlled by the Moroccan royal family.

The wind potential of the country has been studied in collaboration with RISO, producing the Jordan Wind Atlas:

You can read more about the wind energy potential of the country here: Wind Energy Potential of Jordan

Here an older document on the subject: Wind energy in Jordan - use and perspectives

Wind Energy in Chile

After my trip to Uruguay I’ve had the pleasure of visiting Chile, another promising destination in South America. The country enjoys a high GDP growth, with controlled inflation and a stable regulatory framework, and it’s a place where several big players are betting.

We are ending the construction of Talinay, a 90 MW EPC wind farm I’ve worked at together with my team. Initially developed with Vestas money it has recently been acquired by ENEL Green Power, a Utility that is active in the local market with several other projects such as Valle de Los Vientos. The money comes from the Denmark's Export Credit Agency and (at least as far as I know) no PPA has been signed.

This is a peculiarity of the Chilean energy market: several developers are working on projects without power purchase agreement, selling on a merchant basis at the spot price of energy (right now around 80 $/MWh).

Other financial solutions do exist: Irish developer Mainstream Renewable Power, with many active projects, is using Chinese financing and Chinese turbines (Goldwind, of course). Pattern Energy has signed a long-term power-purchase agreement (PPA) with Antofagasta Minerals (a mining company). They are not alone: copper, the commodity that is moving the whole economy, has energy intensive extraction, and this model will be probably replicated in the future.

The strong economic growth justify this approach, as the energy demand is increasing while several mega-project have been stopped due to environmental problem and lack of popular support, like the HidroAysén dam developed by ENEDSA/ENEL  in the Patagonia region.

From a construction point of view, local prices are sky high (concrete and steel sells at around 1.5 to 2 times the European price) and salaries of skilled laborers are growing unstoppably. The good news is that you don’t have to build hundreds of kilometers of high voltage lines, because due to the peculiar geography of the country the main electrical line is always nearby.

You can learn more on http://www.centralenergia.cl/proyectos/mapa-de-centrales-proyectadas/

Wind Energy in Uruguay

Uruguay is a small country (at least for South American standards) but it is intentioned to become a giant in wind power, somehow like Denmark in Europe.

The country has an ambitious plan of reaching 1,2GW of installed wind power in the next 3 years: considering that present generation capacity is about 2,6GW the figure appears even bigger.

Currently, only 2 wind farms are installed and operational, Sierra de los Caracoles and Kentilux (43MW).

Right now the Uruguayan energy mix is based mainly on a hydro plant shared with Argentina and several gas turbines.  Due to the strong economic growth experienced in the last years (GDP is growing at a steady rate around 3.5%), the country has an urgent need for more installed capacity.

Another very solid reason to increase the installed capacity is to sell energy to the neighbors. The line to Argentina can handle 200MW and the connection to Brazil 70MW (although there is a project to improve this connection in the next years up to 500 MW).

Several developers are active in the market: among the biggest players the argentinians Impsa and Fingano, together with Teyma (Abengoa group) and the local Ortegui Group, plus many other competitor asking for prices per MWh that are dropping quickly.

I’ve been visiting the country for a wind farm we are building there and my impression is that the 1,2GW target in such a short time is unrealistic for several reasons.

First of all, the size of the local companies: the biggest have about 2-3000 employees, a respectable number for a 3 million inhabitant country, but inadequate for the potential workload (if several wind farms are built together, we can easily saturate the concrete producing capacity and absorb a considerable percentage of the skilled workers).

Secondly, there are huge logistic problems: the harbor is not prepared to handle the amount of blades, tower section and nacelles needed for all the projects in the pipeline, not to talk about the special transport needed and the cranes for installation.

Then, there are some less obvious problems: UTE, the almighty local utility, take it’s time to analyze each problem and to answer technical questions. This too can lead to delays uneasy to forecast. And they must solve connection issues as well, because grid connection will not be easy.

After, there is a somehow peculiar local environmental regulation setting the minimum distance from a wind turbine to a property line from 170 to 300 meters (and an equivalent limitation asking for a buffer of 3000 meters to the nearest home): this can complicate the layout, affecting negatively the power output and complicating the project without clear benefits.

But looking at the brightest side of life, there are several positive aspects: the legal framework is stable, economy is growing with inflation under control, the local companies looks prepared and from a civil work point of view it’s an easy country, flat with an uncomplicated geology.