Monthly Archives: April 2021

Site visits and information management tools

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This post complete the information of the previous article on how to plan a site visit for a renewable energy project.

I will try to answer this question: what is the better tool to manage the information obtained on site?

There are several very useful mobile apps that can help us finding the target locations and geolocate the position of all relevant elements of the project (wind turbines, substation, roads, crane pads, etc.).

They can also help us obtaining and storing information in an efficient and organized way.

Although none of these software has been specifically created for the wind business´s needs, they offer very useful features that could make our lives easier during a site visit.

As they are mobile apps, we should make sure we have enough battery and that is why I always recommend bringing a portable charger with you.

Google Earth / Google maps

These two apps are by far the most popular. Anybody who is familiar with the desktop software will rapidly recognize their strengths integrated in a very powerful GUI.

They allow the user to load kml files with very valuable information such WTG positions or road alignments or even connect to maps edited and stored in our personal Google account

I see three main drawbacks here:

  • The basemap loaded in the background is limited to the basic formats: Street, Terrain, Traffic, Satellite, etc. Unfortunately they do not offer the chance to insert our customized maps as a background.
  • The geolocation is based on the device´s built-in GPS, but the background map data is loaded only if network is available – and this could be a big risk in remote areas.
  • They are not really prepared to create and store points of interests with comments and link personal photos taken in the area of study – or at least, not as I would like.

Avenza maps

This app uses the device´s built-in GPS so that the correct positioning does not depend on the availability of the network.

One of the main advantages compared to the traditional GPS mapping apps like “Gaia gps”, “Google Maps” or “Google Earth” is that Avenza maps allows the user to import our own customized maps in different file formats such as geopdf, geotiffs.

These maps can be any kind of project drawings created with GIS tools such as QGIS or ArcMap.

This app can be used for free. With the free version we can download up to a certain number of maps at a time (usually 3). There is also is also Pro version which includes more features and increases the possibilities.

It also includes the option to create a store account. It is not required but is recommended though.

For more information about this tool, I recommend you go directly to the official web.

Maprika

This is a tracking map app used mainly by hiking lovers.

Initially, it looks like a very simple app without any special charm. However, it offers similar functionalities to “Avenza maps” and I personally consider it gives a good service to the actual needs in a site visit.

The main advantages are:

  • We track our routes and the elevation information (longitudinal profiles) is registered as well.
  • The photos taken along the routes are georeferenced and can be visualized over the route.
  • There is the option to add “Places of interest” with comments.
  • We can create our customized maps either by using the app or from the desktop tool called “Maprika map designer”. See below a link with a tutorial explaining how to do it.

As a drawback, we can considerate the lack of confidentiality: any map uploaded containing relevant wind farm information would be available to any user from the server.

Furthermore, it is quite easy to upload a map to the server but deleting is not as straightforward.

Here is the link to the website:https://www.maprika.com/

Road AI from Vaisala (old Vionice)

I leave to the end which, from my point of view, is the most promising from all the apps listed here and, surprisingly, maybe the less popular: Road AI

The first time I heard about this tool was in a Finish project I was involved in.

One of the contractors used to work with it and it ended up being a really nice discover.

Although addressed to cover infrastructure management, it can be “recycled” to work as an information management tool for site visiting. The mobile application provides a dynamic and flexible way to collect, manage and deploy data in a user friendly environment.

The main strengths are:

  • The user can record videos and make photos of the construction site which will directly be stored and available in a cloud service. E.g. We can make videos using a phone holder on the windscreen to record routes and the time and the GPS location will also be saved.
  • Make annotations associated to the audio-visual material recorded on site.
  • View all of the recorded routes and sites together with the annotations and metadata using the map interface available through a normal browser application.
  • We can share this information with anybody inside your organization or with a client.
  • It also allows to use filters and requests to visualize data following a certain criteria with a similar philosophy than in a GIS environment.

Surprisingly, it is difficult to find any reference to this application out from the local Finnish market. Only a few references are found in works at UK.

This is a link to the first of a series of video tutorials explaining the way to use and take most of the system (sorry it is in Finnish):

All in all, the proposals presented here are only a sample among a big offer presented in the market. Any tool with similar properties would work well enough used in a proper way. It is just a matter of personal preference as long as an ad hoc and convincing system is deployed and released into the market. Maybe one day…

Wind assessment: uncertainties in the horizontal and vertical extrapolation

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Behind every wind farm project there is a technical feasibility study, made to assess the potential for electricity generation of the selected site.

At the beginning of the wind farms era wind speed and wind direction was estimated using data from existing weather stations.

Due to large differences between predicted energy production and actual generated energy (which was usually overestimated) meteorological met mast are now designed and installed to have better estimates.

Any estimate of the Annual Energy Production (AEP) contains several uncertainties and paramethers that can vary such as:

Measurement CampaignDuration, tower setup, anemometer quality.
Long term adjustmentsSelection of a long term wind data source, correlation and long term prediction methodology.
Flow modelLinear model, computational fluid dynamics models, mesoscale for estimation from met mast into none measured positions.
Horizontal and vertical extrapolationHorizontal and vertical distance from the meteorological mast(s) to each Wind Turbine Generator (WTG) position and hub height.
Wind speed to energyUse of a wind turbine calculated/measured power curve together with the site conditions wind speed to estimate energy (if within constrain inflow angle, wind shear, etc).
Technical lossesCalculated losses i.e. electrical, environmental, curtailment, wake model selection.
Uncertainties and paramethers affecting wind farm energy production estimates

Giving all these project uncertainties, an AEP can be calculated with different levels of confidence in the results.

For instance, what is called a "P50" is a production expected to materialize in 50% of the cases.

It is possible to estimate more conservative energy productions, such as for example P99 (a lower production value, that should materialize in the 99% of the situations).

The wind site resource assessment is a careful identification and evaluation of different risks and uncertainties sources that are unique for each site. 

In this article we will focus on two uncertanties, arising from the horizontal and vertical extrapolation of data.

For the vertical extrapolation we can identify two sources of uncertanties:

The difference between measurement height and hub height.

When using a lower met mast compared to the selected WTG hub height different methods can be used to estimate the wind speed either by extrapolating for example with a power law/log law method.

The altitude difference (flow model)

It is possible to reduce the first vertical uncertainty by installing a met mast with a top anemometer at the same hub height.

Alternatively remote sensing devices such as a Sodar/Lidar can be used on site.

It is recommended to have a wind speed measurement of at least 2/3 of hub height to keep uncertainties at an acceptable value, as any methods for hub height wind speed estimation (i.e. power law or flow model) will add uncertanty to the calculation.

A typical range for this uncertainty is in the 1 to 4% range, varying depending on the type of terrain and the total vertical distance (for example, 0.5% per every 10 meters vertical difference).

Vertical difference between met mast and wind turbine hub height

The Horizontal Extrapolation is heavily influenced by the terrain and surrounding vegetation.

Measnet (Evaluation of Site-Specific Wind Condition V2 April 2016) recommends different maximum distances between measurement position and wind turbine generator (WTG) for a simple and complex terrain.

One of the reasons is that certain orographic traits (plain, rolling hills, mesas, mountain ridges) and roughness (native vegetation, agricultural, forest, lakes) at the measurement position should be “similar” to the WTGs position for the flow to behave in the same manner.

A typical range for this uncertainty is from 1 to 4%.

According to Measnet the data from a met mast are representative only for few km - up to 10km for a simple terrain and around 2km for a much more complex terrain.

After the assessment of 200 projects DNV-GL identifies the horizontal and vertical extrapolation to be responsible for approximately 35% of the total energy uncertainty.

For projects with a high spatial variation (i.e. with turbines very far away from each other) the value can be as high as 51%.

More information on the topic can be found here: Reducing Uncertainty in Wind Project Energy Estimates with Triton

Depending on the wind farm total size, terrain characteristics and mesoscales effects this values can be even higher.

It interesting to note that even if two projects have the same P50 AEP, the one with lower uncertainties and therefore a higher P99 AEP will have better chances to be built being more "bankable". 

Conclusion: very early in the project, after just a few months of measurements, the Horizontal and Vertical uncertainty should be calculated and simulated in cost to benefit financial model to find out the best quantity of measurement locations to have.

A factor to consider this important topic in the initial period is to be able to carry out correlation between measurement locations and assess flow model cross-prediction errors that will further reduce project uncertainties.

How to plan a site visit for a renewable energy project

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Today many resources can make the engineer life´s easier helping create a renewable energy project in any spot of the world.

Powerful GIS and CAD software and an incredible amount of data available from either public or private entities make possible designs with a sufficient level of accuracy to have good cost estimations, even at early stages of the project.

However no tool is good enough to give you the amount of information a site visit can provide. This is a step that can give a boost of extra quality to the design process.

Whenever possible, doing a visit to the project area is highly recommendable.

There are many circumstances which could make it impossible, such as aggressive delivery dates, excessive travel distances or lately pandemics.

Also priorities matters: we cannot compare the preliminary work needed for a tender phase in a very early stage with the final detailed execution design of a constructive wind farm project.

In this article I collected some tips to successfully plan a Site Visit:

Transport

Hiring a 4x4 car (4 Wheel Drive or similar) is a must. Take into account that we will usually find unpaved roads in uncertain conditions or even no roads at all.

Depending on the actual state, it would be wise sometimes pulling over, park the car and go to the targeted place walking.

Furthermore, companies are already offering already internally a 4x4 off road driver training. We can find a lot of difficulties and a skilled drive behind the wheel is a blessing. See below the state of a track in a recent site visit… Yes, we were able to arrive home safe.

Food and breaks

It could be the case that the site is in the middle of nowhere without direct access to any populated village. Even if that is not the case, we will have to assess the convenience of having lunch in a restaurant or canteen with the risk of losing valuable time in the travel. Anyway, we must prepare and take with us some food (e.g. sandwich and fruit would be a good combination) and enough bottled water for the whole journey. Short breaks every 3-4 hours to have some rest and eat some snacks is also highly recommendable. A well planned visit should have account for this moments and there should not be excuses for skipping them.

Clothing and HSE

For a good feet protection, construction security boots with reinforced toe will serve well enough. If construction has not started yet, hiking boots could be another option. Waterproof resistant trousers or, alternatively, with resistant fabric are also recommended. On the other hand, we should follow some common sense rules such as taking a hiking cagoule (raincoat) if we are expecting rain or a cap, sun glasses and sun protection for hot and sunny days.

A careful study of particular conditions at the project site shall be done to avoid any surprise.

Reflective vests were needed in a visit I made to Sweden because the wind farm was in an hunting ground. Anybody without proper clothes hiking in the mountains was in danger of being shot.

Another example was a visit I recently made to Australia. It was in December and the wave of forest fires was at its peak. Of course, temperatures raised easily to 35-40ºC and the initial temptation was to use short sleeved T-shirts. The fact is that the project area was full of ticks and a complete protection of the body was required to avoid any undesired surprise. I found myself shaking some of them out of my shoulders.

Visit planning

To make the most of our trip, we need to carefully plan our journeys beforehand.

Here goes a proposal with some key aspects. How to organize them will depend on the particular circumstances of the project:

  • If a route survey has already been done, follow the route sketched from the point of discharge (usually a maritime port) of the WTG components to the wind farm site and make sure that the report matches the reality. If there is not a route survey in place, try to find alternatives on site. If there is more than one option, we can use one route to go and other route to return.
  • Visit to the nearest towns or villages to assess the best place to stablish central headquarters and/or employee’s accommodations. A project execution phase will normally take, in the best scenario, several months. Finding a place within a one-hour radius to the construction site with leisure offer and good services will contribute to a keep the teams spirit up. As a rule of good practice, it is recommendable talking with the locals, as they will always be able to provide valuable information.
  • Go to commercial quarries close to the site. It is always good to know quality and properties of the available material, unit costs and availability. In general, no appointment is required but it would be a rule of good practice calling before to know whether anybody can receive us.
  • If not already defined, search for possible places to stablish the site compounds.
  • Inspection of suitable areas that may serve as storage points for the WTG components.
  • Check all the WTG positions one by one. As a rule of thumb, experience says that a realistic planning should contemplate a properly assessment of a range between 10 to 15 WTG locations. Of course, it will always depend on the site conditions, the state of the existing roads and how far the positions are from the nearest driveable path.
  • Visit to the substation area and the point of connection to the existing electrical network.

Of course, there will be always unexpected events that we will have to handle once on site. However, taking the good habit of following these rules before travelling reduces the odds of facing undesired surprises as well as gives the engineer the chance to work in a more efficient way and even enjoy the journey.