The Levenmouth Monster (6 minute read...)

Nessie, "The Loch Ness" monster really needs no introduction, however, the Levenmouth monster (I mean this in an entirely good way) does!

A few weeks back I caught wind of a hackathon organised by the OGTC in Aberdeen, took a look at it (https://www.theogtc.com/events/code-less/) and it seemed quite interesting, as the initial 2 challenges (of which there are now 4), consisted of:

• Challenge 1: Modelling Pitch System Behaviour with Higher Frequency Data
• Challenge 2: Learning from turbine alarms integrated with SCADA

Shortly after, 2 other challenges were added. The subsequent challenges added included:

• Challenge 3: An analysis of the Buchan Field production well data; 
• Challenge 4: Building a Greenhouse Gas Meter to reduce emissions

So, there’s an even split between “hacking” in the wind energy space and within the oil and gas space. The first 2 challenges seemed quite interesting with wind being a relatively new-ish source of energy (on a massive scale, however, wind turbines for electricity generation have been a thing for over 100 years) and growing quicker than the existing oil and gas space.

The data for the first 2 challenges will come from the Levenmouth Demonstration Turbine, which has a pretty interesting history (less pretty site…) and raison d’etre.

Back to the Levenmouth Demonstration Turbine (LDT). This consists of a single 7 MW (Samsung made) testing turbine situated on a piled jacket base at the Fife Energy Park, Methil Scotland. It was actually originally owned by Samsung which later transferred ownership to ORE where it is now used as both a source of renewable energy and a veritable test site. There’s been some super interesting demonstration projects carried out on the site to date.

Wind Turbine Configuration

Wind Turbines are actually quite exciting pieces of technology (yes, really), I recently got to know quite a bit more about. Some of the main parts of a wind turbine include:

• Nacelle – The main body of the wind turbine containing and protecting most of the components from the elements;
• Blades – These are attached to the rotor hub (and ultimately, the nacelle) via the bearings. Wind flowing across the blades creates a differential pressure across the blades, producing both lift and drag. Turbines start moving when the lift is greater than the drag. However, the wind doesn’t always play nice and blows in different directions and at different velocities;
• Pitch system – This is a super-important part of the wind turbine that basically ensures the blades are aligned at the right angles to maximise lift (and blade rotation speed) within the turbines ideal wind velocity range. It also ensures that the blades are properly feathered (to avoid damage) during excessive wind events;
• Yaw system – This ensures the blades are facing the correct wind direction;
• Lubrication system – Ensures lubrication of vital system components including the pitch / yaw / generator bearings; 
• Drivetrain – This links the aerodynamic rotor and electrical output terminals and contains the generator and gearbox (or no gearbox for direct drive types). Where the gearbox is used, it converts the low speed rotations to high speed rotations in the generator to generate electricity. In the case of direct drive, these use large expensive magnets made from rare earth metals (research is ongoing on using super-conducting magnets);

Figure 1. Drive train with gearbox and with direct drive generators 

Figure 2. In greater detail – Drive train with gearbox and with direct drive generators (Advanced wind turbine drive train concepts – June 2010)

• Converter – This monitors and controls the generator frequency and voltage to satisfy grid code requirements;
• Generator – Typically consists of DC and AC (synchronous / asynchronous) generators and converts mechanical energy from the rotation from blades into electricity;
• Meteorological unit – This consists of the anemometer / wind vane and tells the turbine the current direction of the wind hitting the turbine and feeds into the input to the pitch and yaw controls;
• Control system – This is where everything comes together and is the brains of the wind turbine. It provides monitoring and control capabilities to ensure availability, efficiency and safety of the wind turbine. These include monitoring and control of blade pitch and generator torque, drivetrain performance and tower vibration amongst others

UK Electricity Supply

Wind power delivers a sizeable portion of the electricity generated in the UK, and at 1.30 am on August 26th 2020, #stormfrancis helped deliver a record 60% (14.2GW) of the UK’s electricity demand, beating the previous record of 59% (13.5GW) of the UK’s electricity demand, that was set just the previous week. These records will quite possibly continue to be beaten with increasing wind farm commissioning (assuming, older wind farms nearing end of life are also upgraded / replaced). So, it’s quite apt for this hackathon taking place at this time (it’s going on at the same time as this years’ Engenious conference - which is virtual). 

Figure 3. UK Electricity Generation Sources for 2018 / 2019

Back to the Levenmouth Wind Turbine...

The Levenmounth wind turbine happens to be the 2nd most powerful single turbine in use in Scotland (2020) tied with turbines on the Beatrice wind farm (with 84 wind turbines) in the Outer Moray Firth and behind the 8.4MW turbines of the EOWDC (yes, it’s a mouthful – European Offshore Wind Deployment Centre) in Aberdeen Bay. Incidentally, these are the largest wind turbines in the United Kingdom (Go Scotland! ;-)). The significant majority of wind turbines in Scotland happen to be sub-3.5MW types. 

Construction of the 3-bladed, 171 m rotor diameter, Samsung wind turbine was completed in late 2013. Some data related to this wind turbine is listed below.

Getting direct data on the specifications of this particular type of wind turbine was not very forthcoming so I’ve inferred (rightly or wrongly) some of the data below from Samsungs 2.5MW wind turbine.

I assume this is a permanent magnet synchronous generator (PMSG) type. Compared to the more popular (as at installation time at least), Dual Fed Induction Generator (DFIG). They do have their pros and cons as displayed below:

The Levenmouth wind turbine has a planned operational life of 15 years and was the largest offshore wind turbine (in the world) at the time it was announced, although this title now belongs to the recently announced 222 m rotor diameter, 14 MW Siemens Gamesa (Now, that’s a beast!).

The turbines rated wind speed is 11.5 m/s with a cut-in speed of 3 m/s and a cut-out speed of 25 m/s and it is fitted with a planet flexpin gearbox which is compact and can deliver a wide range of speed and torque ratios. The PMSG has a max voltage of 3000 V and maximum speed of 400 units per minute.

I’ll be publishing a few more articles particularly relating to the wind turbine operation in general and the pitch system in particular as this is the challenge (challenge 1) I’m interested in pursuing.

References:

Effect of flexible pin on the dynamic behaviors of wind turbine planetary gear drives – CaiChao Zhu, XiangYang Xu, Teik Chin Lim et. Al. May 2012

https://www.energy.gov/eere/articles/advanced-wind-turbine-drivetrain-trends-and-opportunities

https://www.renewableuk.com