We hear about newer and newer solutions for offshore. How do
technological innovations affect the sector today?
First, we have IT systems. Marine turbines are fundamentally different from those we have on land. At sea, their service availability is not so obvious, we are dependent not only on the distance of 30-40 km from the shoreline, but also on the weather. So it is known that these complex power systems,as we call them, work without direct operator supervision and must be remotely controlled. They work continuously, because the offshore turbine has to work at least 330 days a year for 25 years. Correct operation of wind turbines – i.e. with the highest efficiency and maximum power – requires the use of complex IT systems. Today we are talking about capacities of 14-15 MW. Translating this into the dimensions and weight of the wind turbine, we have a rotor diameter of 220-240 meters. The rotor with a drive unit weighing several hundred tons is seated at a height of up to 150 meters. And it's all spinning.
One issue is the IT system, which is to support people in the field of everyday use, and another one – diagnostic and service supervision. Working turbines must be periodically inspected and diagnosed. Here, artificial intelligence and robotics are used. I had the opportunity to visit the construction of a wind farm in Saint-Nazaire. I saw how such a system is being prepared and talked to representatives of companies that are involved in the construction of offshore wind farms in France.
And what did you find out there?
I had the opportunity to observe a lot of technological innovations, such as the possibility of assessing the technical condition of wind turbines with the use of drones adequately equipped with measuring equipment.
They also use robots to assess the technical condition of rotor blades. The latest British product is the Blade Bug inspection robot. It is able to move on a 100-meter rotor blade, registering the condition of its surface. It has special suction cups, similar to those used for ECG testing. It is a very complicated device. Interestingly, the founder, originator, and head of this company has Polish origins.
Which country appears to be the most technologically advanced for offshore?
Denmark has a monopoly in IT systems. About 20 years ago, Vestas patented SCADA (Supervisory Control and Data Aquisition). It is a unified system for monitoring the operation of wind turbines. It collects measurement data, visualizes data on computer screens and supports the control of the energy process. It consists of: switching on, switching off from traffic, load change, alarming, archiving and reporting of data. You can connect to this system from anywhere in the world, as long as you have access to the Internet.
SCADA is a system that was created 20 years ago?
Yes. It is unified and constantly improved. Most wind farms, not only offshore but also onshore, use this system, with the possible exception of China. The number of control parameters that this system monitors online is in the order of 30-50 and more.
There are also electroacoustic systems (SODAR, Sound Detection and Ranging) and electrooptics (LIDAR, Light Detection and Ranging). The first uses the frequency variation of the reflected audio signal. In this way, we are able to very precisely estimate the speed and direction of the wind. The second measures it in the same way with a laser beam.
How do these electro-optical systems work?
At sea, we have air with a certain humidity. In fact, it is dry air with water droplets, and most often salt is dissolved in them. We have a cloud that is not visible to the naked eye, but in an acoustic or laser image – it is. The use of optoelectronics is a new thing, it is a definite step forward when it comes to monitoring and control systems.
The basic parameter is wind speed. We have to adjust the angular velocity of the rotor's rotation to it. This is called speed ratio, which characterizes the speed of rotation of the blade tip in relation to the wind speed. We achieve the maximum power from the wind stream when this ratio is optimal. This, of course, has to be done by the automaton, especially at sea.
What are the other offshore challenges in which a robot can do the job?
Interesting challenges for offshore wind farm operators are related to carrying out maintenance. If something happens to the onshore turbine, the service team goes and gets to the nacelle upstairs. Sometimes it may be enough to enter the control system in the tower's base segment - the first one which goes above the foundation.
It must be more difficult at sea.
Replacing components in marine conditions is extremely complicated. We still have to take into account the dimensions and masses placed at heights (300-500 tons installed at a height of nearly 150 m). It all has to work without direct supervision.
At sea, wind turbines are at least three times larger in terms of generated power. The systems are more complex. On land, you can go, see what is happening, shut down the turbine wheel if necessary, and repair it. Such a prosaic matter - the use of sea turbines in winter conditions. At sea, in cold weather, there is a high probability of the rotating blades icing up, which translates into vibration. And if excessive vibrations occur, such a structure will sooner or later break, according to Wöhler's law. To prevent this, the blade heating system is activated - a signal from the sensor initiates the activation of hot air. It's a mechanical way. It can also be like in cars, where the heating coil is turned on on the rear windows. Example: the control system catches vibrations that show that we are dealing with the loss of stability of the mechanical system of the turbine rotor, e.g. due to material losses or deformation of the blades. Sea weather conditions do not always allow access to the property.
How is it organized?
Through two networks - Ethernet and Internet. Dozens of parameters that are observed characterize not only the operating condition of the turbine, but also the vibration condition of the entire structure. All of this is measured online. This is what the SCAIME control and measurement system is used for. It collects data from optoelectronic sensors embedded in the structural structure of blades, towers or foundations already at the stage of their production. Here, too, there is a problem with the availability of such a system and its repair in the case of an offshore turbine. A separate metrological problem is to ensure the measurement reliability of the optoelectronic converters used throughout the turbine's "life" cycle, ie for 25 years.
Of course, an offshore wind farm usually consists of nearly 30-70 turbines. The core of the farm is a substation to which the electricity generated in individual turbines is sent. It is properly processed there and as direct current it is sent via a submarine cable 30-40 km ashore to the shore station. Through this cable, in addition to the fact that there are electric wires in it, a fiber optic bundle is drawn, through which the measurement data is sent to the land station. Parameters must be processed and then submitted to diagnostic conclusions.
How is this information properly handled?
This is where AI (artificial intelligence) comes in - neural networks, expert systems that support the operator's decisions. Because at the end of this chain is the operator who operates the land-based diagnostic center. A whole team of people work there to check whether the use can be continued or if some regulation needs to be made. Worse if there is something wrong with the turbine. This can apply to any, even the most perfect technical object.
Can systems that inspect turbines eliminate human workforce?
Yes. They even have to! The basic activity of a diagnostician is examining the object by means of measurements. Then he carries out diagnostic conclusions and makes a diagnosis. Here, all these activities, starting with measurement, must be supported by the work of IT systems. The process of monitoring offshore wind turbines is almost entirely carried out by automatic and robotic devices. On the other hand, the decision to turn off the turbine when its control parameters do not exceed the threshold values is up to the human (operator).
What about servicing? Can automation also replace humans
Not that far. We automatically service turbines at the online condition assessment stage. It is not possible to perform repairs on a remote system.
I watched the Blade Bug robot in action, which replaces these characteristic figures of service technicians hanging on the ropes attached to the turbine blades that we see on the Internet. People go inside the shovel and check if something has broken. So it goes towards replacing humans with robots. The drone can also record and analyze optical and acoustic signals.
The fact that the team will go "to the turbine" should be a last resort. As I said, the weather can change rapidly at sea. Service crew can get there, but have trouble getting back. I know this from a message from an engineer friend who worked on offshore wind farms and mining platforms in the USA. In order to work on servicing the turbine, you must have the appropriate psychophysical features. And the Baltic Sea is not a pleasant sea, especially in the transitional seasons of autumn, winter and spring.
So it is better to prevent than to cure - that is, in this case, to service?
Be one step ahead of the moment when damage occurs. Take the turbine out of service before secondary damage occurs. For example, even the best-made bearing that is subjected to variable and excessive loads may fail. It is only a small element of a very complex mechanical system, but its damage, which we define as primary in diagnostics, may cause secondary damage to the entire drive unit, including the breakage of the rotor blade, breakage of the transmission shaft or reduction gear. This causes a huge scope of work on restoring the technical condition. It is complicated on land, too, but not quite like at sea.
How quickly could drones or robots like Blade Bug be spread?
When I was in St. Nazaire, not only offshore turbine giants, such as GE, Vestas or Siemens Gamesa, were present there, but also smaller companies specializing in technological innovations. Blade Bug was to be put into operation as early as 2022. Its possibilities are huge. We are talking about equipping robots and drones with appropriate measuring equipment. The basis here is the SCADA system - collecting parameters, their processing and inference. This should go hand in hand with the construction of offshore wind farms. However, the availability of information about innovations in this respect is not common. The information provided on the Internet is only rudimentary.
What is the future for offshore wind turbines? Will they be placed bigger and bigger or maybe more and more extended - that is, floating?
Floating wind farms are undoubtedly the future. Admittedly, these will also be bigger and bigger. If we have stronger winds at sea, we can build larger turbines. The larger the turbines, the greater the technical and technological challenges. However, as we are already betting, if the construction cost (at the investment stage it is estimated at 1.5-2 million EUR for 1 MW of power) returns, it is better to put the largest turbines at sea. However, this must be followed by ever larger ships and installation devices for building turbines at sea - jack-ups, cranes, etc. Vessels for erecting the largest turbines are available in a limited number. So there are additional investment costs. On the other hand, the world's leading centers, we also at the Gdańsk University of Technology, are currently conducting research into floating wind farms. Even if placed in the middle of the ocean, they will be able to generate and send electricity to land. Maybe it is an illusory vision today, but tomorrow it will be everyday life. Research work is moving in this direction.
I understand that in the case of "floats" inspection systems will be even more important, because servicing will be even more difficult?
Exactly. There is one more point. Research and development work is also aimed at recovering excess energy from the wind. This was the case recently when we heard from the media that the British had a problem because the wind was so strong that they didn't know what to do with it. It also happens that we have excess electricity from the wind. Therefore, the issue of its processing and accumulation in the so-called cogeneration systems of various types of energy. Here it is envisaged that the wind turbine will cooperate with an electrolyser that would produce hydrogen. This, in turn, would be used for the secondary production of electricity in a fuel cell, e.g. to power service ships. There are also pressure accumulators in which electricity is used to compress the air and store it in underwater pressurized warehouses. Later, when there is no wind, it could drive the air turbine along with the generator for the secondary production of electricity. Therefore, energy storage is a very important challenge. At the same time, hydrogen technologies are being developed.
Are the innovations in offshore winds implemented faster
than in other industries?
Today, technological research is practically not carried out without the participation of industry. In order to obtain a grant, universities cooperate with an industrial partner, the latter most often being the leading unit. Being in France at the Seanergy conference, I established many contacts with scientists and visited university stands. The stands of the University and the Polytechnic University of Nantes were crowded. I had difficulties in talking to a certain professor, because so many people in the industry seek specialist offshore consultations from French scientists. We in Poland do not have it yet, because we do not have working turbines in the Baltic Sea. It will be different when this technology finally reaches us and becomes more tangible.
Does it mean that Polish science will also benefit from offshore wind farms?
I hope so. The worst-case scenario would be if, for example, Danes, Germans or Americans would come, set up offshore wind farms, train 50-100 people in their operation and leave. After all, operational problems will always arise. As for the development of new production technologies, our possibilities are more limited, but at the operational stage there is hope that the owners of wind farms will use the help of Polish universities, at least in terms of specialist consultations, and maybe also commissioned scientific research.
Prof. dr hab. Eng. Zbigniew Korczewski - lecturer at the Gdańsk University of Technology at the Institute of Ocean Engineering and Ship Technology, Department of Marine Power Plants. Author of many publications, including: Operational diagnostics of marine piston and turbine internal combustion engines, Endoscopy of marine engines and Methodology of testing marine fuels in real operating conditions of a compression-ignition engine.