Vortex bladeless wind turbines

I have always seen the wind induced vortexes as a problem – they create vibrations in the tower, that in some cases can start to resonate with the eigenfrequencies (the natural frequencies of the structure) and in the most extreme cases even collapse.

The existence of such vibrations is one of the reasons why it looks like that steel towers for wind turbine have reached their maximum height. At around 100 – 120 meters they start needing dampers and other anti-vortex solutions during installation and for the operational life.

What I was not aware of is that there is a Spanish start-up trying to develop a “bladeless turbine” which exploits this phenomenon to produce electricity.

I have some doubts on the idea of a “bladeless turbine” (I suspect that a wind turbine has, by definition, a rotating part). However the concept developed by the folks at Vortex is for sure very interesting.

The Vortex Tacoma (this is the name of the industrial version under development) is expected to have a height around 3 meters, a weight around 15 Kg and a rated power output of about100w.

Currently smaller scale prototypes are available and the target date for launch of the full scale production is end of 2020.

It looks like a big cylinder oscillating when the wind blow. I also see that they selected the same combination of materials as wind turbines blades (resins reinforced with carbon fiber and/or glass fiber), while for the bottom section anchored to the ground they have selected a carbon fiber reinforced polymer due to its resistance of cyclical loads.

If you wonder how does it generate energy it is with an alternator system with coils and magnets. The cool part is that, unlike wind turbines, you do not have gearboxes, shafts or any other rotating element. The benefit is not only less maintenance but also a noiseless operation.

An additional interesting characteristic of this technology is that many machines can be clustered together in a narrow space. Standard wind turbines have a distance of hundreds of meters from each other to avoid the wake effect (basically the turbulence in the wind caused by the turbine itself). The wake effect can have an impact not only in the energy production of the turbine but also on its lifespan, shortening it due to the demanding operational conditions.

On the other hand the bladeless solution thrive on turbulence so you can pack more Tacoma Vortex together in what would probably look like a forest of artificial trees.

Another very cool feature of this machine is its ability to change its rigidity to adapt it to the characteristics of the wind. Different environmental conditions will request a different setup from the vortex in terms of mass distribution and rigidity. According to the website of the developer the machine will be able to automatically “tune itself” in order to maximize the oscillations.

How many of us are there? Wind energy sector employees

Workers in Renewable Energy. Copyright Statista (one of my favorite website)

It is no secret that the wind business is going through a turbulent period, with several players in the sectors experiencing a tough time.

I was wondering how many people are currently employed in Wind and I have found this interesting report from IRENA (the International Renewable Energy Agency).

I have discovered several interesting things:

  • Only 11 million people are working in renewable energy job. Not that many, if you consider that we are 7.700.000.000.
  • Out of these 11 million, only 1.1 million people work in wind. The biggest share is Solar PV, with over 3.5 milions.
  • The majority of wind job are in China. With an incredible 44% of jobs in the People's Republic of China it looks like I will have to improve my Mandarin.
  • One out of three is a woman, above all (45%) in administrative jobs but also (around 30%) in technical function. This is more of what I thought.

 

Wind turbine tower as a water battery: the Gaildorf Wind-Water Project

Did you ever think at the amount of empty, unused space in the bottom of a wind turbine? Any idea how to use it?

Well, the folks at Max Bögl (a German conglomerate active in several sectors) have decided that it could be a good idea to fill it with water (about 40.000 m3 per turbine, up to a height of 40 meters) and use it as a temporary energy storage, in what they call a “water battery”.

Basically, the idea is to use a pumping system to fill the bottom of the tower when energy consumption is low and production is high (for instance, during a windy night).

When needed, the water can be released opening a valve and, thanks to a network of pipes with a diameter of over 1 meter, it can be used to produce energy through three Francis turbine, with a total nominal power of around 16 MW.

The hydro electrical plant is relatively near, at a distance of around 3 Km and with a height difference of 200 meters.

The turbines installed are 4× 3,4 MW GE 137 on an hybrid Max Bögl tower. What is remarkable is the hub height, varying from 155 to a record 178 m. They claim this to be the highest onshore turbine tower currently in operation, and as far as I know with a tip height of 246.5 metres, this could easily be true.

The switching time between energy storage and energy production is not exceptionally fast (30 seconds) but is not outrageously long either.

Partially founded by the German Environmental ministry with over 7 mln. € the pilot project is currently being built in Gaildorf (southern Germany).

Among the benefits of this solution is noteworthy the high efficiency of conversion of the potential energy of the water into electricity using well-known, proven technologies.

The main issue that I see is that this system, to be implemented, need a hydro electrical plant nearby with his own “long term water storage basin”. Essentially the wind turbines are providing only an additional (and somehow limited) storage capacity. However, in order to be cost effective, this technology will also need a “standard” basin.

Order out of chaos: Risk Breakdown Structure

There is a good number of techniques that can be used to identify risks.

Some are techniques focused looking at past (every Tender Manager should be able to create a list of issues he had experienced in past projects), other tools are focused on the present (spending a few hours reviewing your current assumptions should help you identify a good number of “what if the assumption is wrong” risks) and other help you to think forward (for instance, a good brainstorming session with stakeholders and experts from different departments).

The outcome of such techniques is a list of risk, usually very long and, above all, unstructured. A qualitative risk assessment can be done, attributing to each risk a “probability and impact score”. My impression is that such exercise is somehow arbitrary (although this is probably better than nothing). What is not provided by the qualitative risk assessment is some visibility on risk patterns, concentrations of risks and correlation between risk causes.

An interesting tool that can be used for such scope is the Risk Breakdown Structure (RBS). Inspired by its more famous counterpart, the Work Breakdown Structure (WBS), it is basically a hierarchical structure (a “taxonomy”) defining several categories and sub-categories for risks. For a wind farm, an example of RBS could for instance consider at the first level the project, the customer, the management (internal) risks and the environmental risk.

Here I’ve made a very rough, unfinished example of how a RBS for a wind farm could look like – as I think it is an interesting exercise I will try to expand it and complete it in the future:

Which are the benefits of such approach?

I believe that the most important one is the identification of high-risk areas: are the majority of your risks coming from the same area? This can help focus the efforts on the most critical aspects. "Majority of risks" should not be considered the absolute number of risks (you can have dozens of low severity risks in the same area). A better way to do it would be to assign a numerical value to each risk, the "Probability x Impact" score and sum the value of such risk scores in all the areas (level 1), subareas (level 2) or sub-subareas (level 3).

Once it has been properly developed the RBS itself can also be used as a checklist for risk identification in future tenders or projects (assuming that your organization is working at comparable projects, as it usually the case in wind farms).

Last but not least, the RBS can be used to compare the risk level and concentration of two or more different tenders or projects, possibly weighting the lowest level risks with their probability / impact score.

Risk metalanguage: how to make a proper Risk Register

One of the key deliverables in project risk management is the risk register.

The idea is that after risk identification, qualitative and quantitative analysis, and planning of risk response the tender manger (or project manager) should end having a list with all the risk identified at that point in time.

I assume that the content and format of the list will vary depending on the type of project and organization. However I believe that it should include at least:

  • Risk description
  • Impact on objective
  • Risk response strategy
  • Risk owner

The Project Management Institute add to this list other concepts like category (the taxonomy of risks always looked somehow arbitrary to me), probability (even more difficult to define with accuracy in many situations) and cause.

If you are familiar with the topic you will remember that, if a risk materialize, it will be moved from the risk register to the issues (or problems) register.

And here the interesting parts – I have been reviewing some risk registers that I have done in the past noticing that the description of risk was mixing three different concepts – cause, risk and effect.

“Presence of strong Workers Unions in the area”, for instance, it is not a risk: it is a fact, a reality in several projects I have been involved.

The risk is to have many strikes in the construction site – the effect would be delays (impacting the “to be on time” objective) and payment of damages (impacting the “to be on budget” objective).

There is a proper way to fill the risk register: the use of risk metalanguage.

Risk should be expressed in sentences with this structure:

“Because of <cause>, <risk> might occur, which would lead to <effect>.

This language construction help bringing clarity and logic to the risk register. The previous example would become for instance:

“Because of <the presence of strong Workers Unions in the area>, <many strikes> might occur, which would lead to <delays and payment of damages>.”

There are some interesting implications. For instance this structure should be used in different languages – I would be curious to see if it can be replicated easily in all of them.

Additionally, it force you to think at the logical correlation between the causes of risks.

For instance, you can think at different situations were the same risk can have 2 different, independent causes:

“Because of <cause #1 AND cause #2>, <risk> might occur, which would lead to <effect>.”

I understand that in this case it should be split in 2 different entries of the Risk Register.

However in some situations two or more different causes need to be there at the same time for the risk to materialize:

“Because of <cause #1 PLUS cause #2>, <risk> might occur, which would lead to <effect>.”

Obviously you can increase the complexity ad libitum, as the same risk can have more than one effect:

“Because of <cause>, <risk> might occur, which would lead to <effect #1 AND effect #2>.”

I guess that also in this case the good practice is to split the sentence in two different entries for the Risk Register.

Rock slingers for a quicker trench sanding & backfill

This morning I found by chance this very interesting website (well, it is interesting if you like wind farm constructions…).

Basically it is an Australian company using “rock slingers” (that is, conveyors belts connected to a dumper) to backfill trenches mounted on small vehicles (2.5 meters wide). The equipment is made by CAS, an American company specialized in this kind of equipment.

It is a remotely controlled machine that can create the sandbed inside the trench accurately and at a great speed. According to the figures provided in the website the slinger can create 16 Km of bedding in a day, using up to 1000 tonnes of material.

I guess that they call it "slinger" because it can throw material at a quite remarkable distance (over 40 meters). Used in combination with one or two trencher it looks like it can lead to relevant savings, less labor and a more homogeneous distribution of the material.

EDIT (18/12/2019):

I have received an email from Penelope Smith from Rockslinger on the topic. As I beleive it can be interesting for several readers I'm including it in the post below.

Hi Francesco,
We are involved in many civil projects involving backfilling trenches and 'Rockslinger' is our trademarked brand of high speed conveyor equipment in Australia. It's super to see the machinery becoming noticed in the renewable energy sector, such as the other operator you mentioned in your blog.

Our site is www.rockslinger.com.au and we are the largest slinger fleet operating in the country. This type of machine actually speeds up the process of installation at the trench and material spreading stage incredibly using this equipment.

It has a movable arm and is externally operated if needed with advanced drive ability. The application rate is a tonne a minute accurately laid at the contractor's required depth.

We have found that the renewable infrastructure sector in Australia, including wind farms and solar farms, are beginning to realise the saving in construction when using more efficient machinery. I've had a read through your blogs and really appreciate you sharing your experience.

Now I've found your site, I'll keep an eye out for the next blog. Thanks again.

Risk & contingencies - a brief introduction

One of the hot topics frequently discussed in the creation of the budget for big projects is the appropriate contingency level and how to estimate it.

My colleague Giuseppe had found an interesting paper online that has been the starting point for this post.

So, what are contingencies?

Some far reaching definitions consider different typologies of contingencies:

  1. Money in the budget
  2. Float in the schedule
  3. Tolerance in the technical specifications
  4. Tolerance in the quality
  5. Tolerance in the scope of work

Possibly this is a very broad approach, so I will focus only on the first point.

Monetary contingencies are added to the estimate “to allow for items and events for which the state, occurrence or effect is uncertain” (the definition is proposed by the Association for the Advancement of Cost Engineering).

Several concepts are usually excluded from the contingency budget:

  • Major changes in scope
  • Extraordinary events (such as the one indicated in the Force Majeure clauses)
  • Currency exchange risk (this is usually hedged or it is included in a different section of the budget)

Basically in the definition of contingencies the focus is on the “negative risks” that can create a loss if they materialize (“positive risks” is a fancy way to call the opportunities).

Identified vs unidentified risks

A key distinction should be made between identified risks and unidentified risks.

Identified risks are “known unknowns” – that is, risks you are aware of (a classic example would be the geotechnical risk.

Unidentified risks are more similar to “unknown unknowns” - risks that come from situations that are so unexpected and difficult to foreseen even to subject matter experts that they would not be considered.

On top of this type of risk, there are also risk that emerge later in time – as a result of our actions and decisions or as a result of actions and decisions of external agents.

For this reason risk management processes include periodical risk reviews: you do your best to identify all risk at the beginning of the project but the situation can evolve in unexpected ways.

Identified risks can (and should) be managed: they should be included in a risk register, with a quantification, a predefined plan if the risk materialize, an owner, etc.

Strategies for identified risks

Additionally, several strategies are possible for identified risk: they can be

Avoided (if a subcontractor has a poor financial status it can be removed from the bidders list)

Transferred (if the failure of the main transformer can put at risk the viability of the investment, a business continuity insurance can be purchased)

Shared (if a project is very big, possibly a Joint Venture could be a good choice)

Mitigated (if a construction technology is very complex it could be a poor choice in an emerging country, where an easier solution could be a less risky choice)

Accepted (in this case, usually a monetary reserve is created for the accepted risks).

What about unidentified risks?

Unidentified (“unknown”) risks are conceptually different. Even if a great effort has been made to identify all possible risks the experience show that when the project is finally built several unforeseen events will happen, impacting the budget.

The quantification of the contingency for these unknown risk is a complex topic and a never ending source of discussions when budgeting a project.

I have found an interesting chapter on the subject on a book on Project Risk Management (by C. Chapman and S. Ward, ISBN 978-0470853559).

They consider that the residual uncertainty has three sources:

  • Explicit assumptions (known unknowns)
  • Implicit assumptions (unknown unknowns)
  • Bias (systematic estimation errors)

They suggest to use three different "scaling factors" to consider these sources of uncertainty, Fk, Fu and Fb, The product of the three factors is designated F3:

F3 = Fk x Fu x Fb

The authors suggest that even if estimating these factors is highly subjective not doing so lead to an even worst scenario, a "Conspiracy of Optimism".

The logic is that would be seriously irrational to believe that such factors do not apply to your project unless you have solid grounds to prove that.

Even if different stakeholders could have a different view on the value of these factors the debate itself inside the organization should prove to be beneficial: refusing to acknowledge and discuss the issue will not make it disappear.

I believe that the same logic should apply when a risk register is created.

The meaning of a qualitative analysis of a risk ("There is a high probability of a small impact on budget") should be made explicit.

Is an high probability 80% or 99%? How small is a small impact? And so on.

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.

Automatic cost estimator - the Holy Grail of BoP

Yesterday I had the pleasure to drink an overpriced coffe (2,90€ for an Espresso? Really?) with my good friend José Ramón. He told me that I’m not writing on the blog often enough so I’ve decided to make an effort and find some time to write this post.

The subject I have selected is an evergreen topic, the Holy Grail of BoP – the possibility to create a tool that could calculate quickly the cost of the BoP of a wind farm.

There is already a good amount of material on the subject online, for instance this website of the University of Strathclyde (Glasgow) that present a model created in collaboration with SgurrEnergy (now part of the Wood Group's Clean Energy business).

You can download the tool from their web or from this link for your convenience: BoP estimator tool

I have decided to take it as starting point to show why the task is not so easy and probably me and the other engineers in the team will not be substituted by an Excel file anytime soon.

The ultimate purpose of such models is to pick a small number of input (to make the tool usable) without losing to much in accuracy. The guys at the University decided to go for an extreme simplification and selected only 6 inputs:

  1. Number of WTGs
  2. Turbines Rating
  3. Km of new roads
  4. Km of existing roads
  5. Km of cabling to substation
  6. Km if cabling to grid

That is a very, very extreme oversimplification.

For instance, the model doesn’t keep into account the topography of the area (flat, hilly, mountainous) or other relevant factors (poor soils, inundable areas, etc.) and link the cost only to the rated power of the turbine. As a consequence the calculation of the crane pads cost show a big dispersion in prices (from 5.000 to 42.000 Pounds) and a very low R Squared value (0.26 – that is, the model isn’t explaining the correlation).

Additionally, the model doesn’t consider any monetary input but the output is monetary. I believe it’s rather hard to accept this simplification: for instance, around 50% of the price of cables is in raw materials like copper, that have a high volatility. This could easily bring a multi million inaccuracy.

Also, there is no such a thing as a standard substation – and this is why we have very good electrical engineer in the team. Even without considering the peculiarities of the local grids (something hard to ignore when they are weak, like in Australia) different customers have also different needs. A customer interested in business certainty will ask for redundancy in the substation – 2 main transformer instead of one, emergency “cold” spare transformer, etc.

Same for the foundations: there are currently so many technical solution in the market (precast, with rock anchors, braced, P&H, etc.) that it is really hard to find a correlation between wind turbine MW and foundation cost. There is so much money in foundation and so much pressure on prices that project specific foundations nowadays are the norm, not the exception.