Road Design & Earthwork Optimization Software for Wind Farm Networks

I have been contacted by Erin Wasney, Business Development Manager at Softree Technical Systems.

She proposed to write a guest post on RoadEng, a software developed to design long roads and large networks of low volume roads faster and easier than other civil design software.

I am more than happy to share his post with you.

(Beginning of guest post)

Onshore wind farms often require a large network of roads to install and access turbines, and as previously shared by the team at www.windfarmbop.com there is often a need for quick planning and analysis. As followers of the blog, we were inspired to share some information on our software, RoadEng.

The video below shows an example of a wind farm project created in RoadEng Civil Engineer. As a software tool, RoadEng is a detailed geometric design software, but its focused functionality allows for it to be used for quick planning, analysis and visualization.

Created more than 30 years ago to support the design of forest road networks in complex terrain, RoadEng is now being widely used in renewable energy projects. There are many similarities between the requirements of forest road networks and those required to develop and maintain windfarm projects, mainly:

  • Projects are often time and cost sensitive, both from a planning and implementation standpoint,
  • Road networks are usually low volume resource roads that may include greenfield construction or upgrades to existing access infrastructure,
  • Pads and/or landings are usually required and built as part of the road portion of the project,
  • Location of the road is often influenced by other project factors and being able to quickly update a road design to account for other project parameters is important to help facilitate timely decisions and avoid expensive redesigns often encountered when using slower, less dynamic/interactive software, and
  • Often the personnel planning the access infrastructure have additional roles in the project.  Having a fast, easy-to-learn software that doesn’t require a drafting background to quickly become proficient makes adopting RoadEng as a design platform easy but more importantly reduces the need for more project personnel.  This often allows decision makers to have a more wholistic understanding of the project, do more design themselves, increasing productivity, and avoid some of the challenges associated with design review and communication.

In RoadEng, the horizontal and vertical alignments are connected, and a cross section geometry is attached to the 3D centerline automatically.  Pre-built customizable components make building smart cross section geometries easy, and in situations where more complicated cross sections are required (as in the video below), components can be combined and/or linked together:

As the user creates or adjusts their alignment, all aspects of the design update in real time; no need to manually prompt the software to recalculate and since the software is light, users can avoid having to deal with the frustration of click-wait, click-wait, click-wait as their computer struggles to keep up with the computation requirements. In other software, it is common for users to truncate their projects into short, workable segments to reduce computing requirements, in RoadEng it is not uncommon for users to do detailed designs for multiple alignments in a single file for roads over 50km long and based on large LiDAR data sets.

Aside from just considering site geometry, road costs are often significant and are worthy of careful consideration during the design process. RoadEng offers several tools that help designers quickly evaluate how much effort is required to build a project.  These tools include:

  • Traditional mass haul diagram, with cut and fill quantities
  • Opti Haul diagram, tracking excavation and fill volumes by material type; solving for optimal material movement by individual material types, definable quality requirements and movement direction constraints
  • Alignment Costing, including an ability to easily compare alignment options and get the associated sub-grade construction costs for each option (we call this “design time costing”).

Finally, construction costs and time spent designing can be further reduced by using Softree Optimal. It is a patented earthwork optimization add-on tool for RoadEng that can help reduce costs by generating a vertical alignment that minimizes earthwork costs (embankment, excavation, and movement costs for sub-grade materials).  According to a study completed by FP Innovations (2017) on low volume resource roads, vertical optimization reduced the estimated construction cost by 13% to 22%, on average, depending on road design standard.

Other notable functions included in RoadEng for wind farm design:

  • 3D symbols for turbines – allows for visualization of the turbines in the context of the roads and pads
  • Drainage tools – hydrology tools and watershed calculations, as well as a culvert editor tool for quick additions of culverts and cross-drains to projects
  • Graded pad object optimization – balances cut & fill for graded pad objects
  • Multi-Plot report builder – semi-automated creation of construction documentation
  • Field-focused tools – creation of Avenza georeferenced maps, GPS integration during design

Although not ideal for every civil engineering project, RoadEng performs well in rural infrastructure applications, particularly for quick planning and analysis, as is often the case for wind farm road networks.

From blades to cement - the experience of Veolia

A few days ago YouTube’s algorithm correctly has correctly suggested to me to have a link at this video.

Made by Business Insiders is an interesting addition to the theme of wind blade disposal – have a look at my previous post on the topic on how to use blades to make cement.

You will see that first GE has to pay Veolia to get the blades and that subsequently Veolia pays to send the final product to cement factories. This suggest that the technology is not cost effective yet.

I also notice that the video mention that the blades are between 8 and 12 years old. That’s very unusual – the typical life of a wind turbine is 20+ years (some are reaching 30 or even 35 years).

Tower cranes: a real alternative to lattice boom cranes?

The constant search for higher rated power, taller towers and longer blades has pushed wind turbine manufacturers in an arms race to secure a position in an extremely competitive market.

Today in the onshore market there are machines with rated power close to 6MW, hub heights in a range of 150-165m and blades longer than 80 m. Several projects are currently under development considering these massive sizes.

Lately I have had the opportunity to analyse in depth a new solution which is emerging as an alternative to the traditional lattice boom cranes: the tower cranes.

I have analysed two scenarios, one with the standard lattice boom crane and an alternative scenario with the tower crane.

Standard scenario: lattice booms crane

Lattice boom cranes such as the Liebherr LG1750 have been the standard solution for the installation of the latest generation of turbines, with a tower height in a range up to 140+m.

This type of crane can be moved fully assembled between positions under certain assumptions (such as a very low road longitudinal slope and minimum road width of more than 6m).

If the crane has to be dismantled a substantial area for the boom assembly and disassembly process will be needed (in red in the image below).

Other characteristics that can have an impact on the project are:

  • A mountainous landscape: in this case the boom assembly area would be even more essential. This will have a substantial impact of civil works cost.
  • Very high installation rates (such as 3 or 4 turbines per week). The limited stock of lattice boom cranes suitable for this hub heights worldwide create a risk: either you book the cranes two years in advance (giving up the possibility of changing the schedule) or you wait - with the risk of losing the crane availability slot.

Alternative scenario: tower cranes

The idea of using tower cranes for wind turbines installation is not new in the onshore sector.

Said that, as far as I was aware of, the use of this typology of cranes has been negligible in the last few years.

Not so many references can be found in America or Europe. One example would be the installation of Gamesa’s G114 of 2,5MW 156m steel tower at the Borja Wind farm (Spain). The crane used was the Liebherr 1000 EC-B 125.

Common sense tells me that the experience turned out not to be very positive (otherwise I presume that the concept would have been replicated, while that does not seem to be the case).

More recently, new models from Krøll Cranes have been used in wind farms at the opposite side of the planet, in Thailand and Australia.

Big players like ALE are suggesting that this new concept is reliable.

One of the main references is the Theparak wind farm project in Thailand, where 60 V136-3.0 MW where installed using this crane.

Here we have a list of some of the projects installed in Thailand with tower cranes:

The main pros of the tower crane are:

  • Road width required: only 4.5 m (even as little as 3.5 m according some sources).
  • Cranes boom is only 70 m long.
  • Advanced crane bases allow savings in the critical path.
  • Lower minimum lifting radius compared to lattice boom areas.
  • Installation rates about 2 hours per component. An installation rate of 1 WTG every 4 days has been reached in the Thai projects.
  • Operational up to wind speeds of 15m/s.

On the other hand, cons would be:

  • Lack of experience of the operators with these new set of cranes and low offer worldwide.
  • Uncertainty on the actual installation rates due to insufficient track record.
  • Real installation costs are still unknown.

Depending on the characteristics of the project, Kroll cranes has available these models:

How would an hardstand layout adapted to both the tower crane and the new generation of turbines look like?

It seems that a tower crane could work using a standard hardstand without the boom area:

Some 3d models where created on real WTG locations to assess the actual impact on cost of this new configuration. Quantity reductions in topsoil stripping, excavation and fill material may lead to a cost reduction around 5000€ per hardstands (being conservative).

A nice image with a 3D model of the hardstand analysed is included below:

Even if potential savings in the civil works seem to be easy to achieve, a real total project cost reduction can be confirmed only considering the actual installation costs, which are not so clear at this moment.

Are tower cranes going to be a more mainstream solution in the future?

Only time will tell.

Addenda (21/04/2021)

I have received this email from Jasper from Lighthouse projects. I think it
can be useful to other readers.

Regarding the tower cranes in compare to Crawler crane I would like to share with you some experience.

I have worked 2 years ago at windpark Krammer which consists out of 34 Enercon E115 turbines on a dyk with no space for storage components or installation of the cranes.Therefore we have used 2 Liebherr EC1000 Tower cranes in the project to build the wind turbines.

My experience is that with the limited space on site it is easier to install the crane.  Another benefit is that crane capacity because the crane can lift up to 100t  we could pre assemble the rotor and generator up front and lift the generator in one lift which is efficient. In addition what we saw is that you can lift longer you can lift up to 12 m/s or more.

A disadvantage of this type of crane is that it must be extended at some point. Mast sections must then be placed in between so that the hook of the crane becomes higher.

The importance of the geophysical survey for a Wind Farm

Today we speak about geotechnics…yes!, geotechnics, that activity that sometimes sounds strange but is so essential for the development of a proper wind farm project.

More specifically, we will see in detail tomographic refraction tests and MASW analysis.

This information is key for wind turbine foundation design but also can be needed for several other activities, such us for instance estimation of excavation (earthworks cost is linked to the hardness of the materials) and seismic design.

Geophysical works for a Wind Farm in Egypt, 2021
Geophysical works for a Wind Farm in Egypt, 2021

The analysis of the elastic modulus had been typically done with laboratory tests until a few years ago, when geophysics techniques began to be widely implemented (sometimes with unclear goals and misunderstood results).

The main advantages of these on site tests are:

  • Characterization of real terrain conditions taking into account the large magnitude of the structure it will support and its three-dimensional behaviour, rather than extracting small samples that could be not representative of the system as a whole
  • The possibility to obtain the dynamic parameters of soil stiffness, which are often the dimensioning factor due to the need to achieve a certain rotational rigidity for the wind turbine

It is important to highlight that some soils don´t seem to be apt to withstand the ever-larger loads of today's wind turbines if they are tested using “classical” methods (odometer, triaxial, etc…).

However, the same soils show a better performance when geophysical techniques are used to analyse them, mainly because they are less conservative, more realistic and more appropriate for dynamic loads and quite relevant foundation dimensions.

One more comment on dynamic parameters of soil stiffness: it´s worth noting that correlations that were widely used to estimate dynamic values from static values used to imply, depending on the type of terrain, wide uncertanties.

In some cases the values were unfavourable and did not allow to optimize the dimensions of the foundation. In others cases, unrealistic values reduced the level of safety in designs.

For all these reasons geophysical survey is strongly embedded in the way wind turbine foundations are currently designed, so the IEC 61400-6:2020 has made changes in its latest edition (see Annex L) to improve and adjust the calculation methodology.

Variation of shear modulus with soil strain

As a summary, take into account that optimization and accuracy within geotechnical calculation can lead into an optimization of the foundation, so be aware of the importance of geophysical survey for a wind farm and opt for a more comprehensive geotechnical study, appropriate to each case, modern and based on international regulatory updates.