Seeking collaboration with a university of technology or university of applied sciences can significantly increase the innovative power of a maritime manufacturing company. Offering a graduation thesis and the facilities required for this is a good way to start. Alewijnse has gained good experience with this in recent years.
This article first appeared in SWZ|Maritime’s education special of February 2025. It was written by Hans Heynen, freelance maritime journalist, hans.heynen@casema.nl.
Alewijnse specialises in designing, building and improving complex electrical installations and automation systems, with offices in the Netherlands, Romania, France, Spain and Vietnam. Systems Engineer Zoran Malbašić, from the Power Conversion Team of Alewijnse, approached professor Marjan Popov, from the Faculty of Electrical Engineering, Mathematics and Computer Science at TU Delft, who specialises in Electrical Sustainable Energy, Intelligent Electrical Power Grids and High Voltage Systems, for a collaboration a few years ago.
He offered the faculty a research project with room for several students to write a thesis. The research involved developing and validating a mathematical calculation model with software for more efficient and better design of complex integrated electrical systems and a digital twin with which these integrated systems can be tested in (expected) practice.
‘Our engineering process for complex hybrid installations was not innovative enough in some areas at the time,’ says Hybrid Solutions Manager Mischa Habermehl of the Power Conversion Team. ‘Such as for making calculations for short circuit and selectivity. With the TU Delft students, we were able to develop a clear mathematical model for this, with which we could partly automate the calculations. This reduced the number of engineering hours and provided very reliable and accurate data within the dynamic behaviour of an electrical system. The application of mathematical models made it possible to accurately calculate the payback period for the customer in a sales process. We now no longer work with estimated values or expected patterns, something you often see elsewhere in sales processes.’
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Win-win situation
Malbašić calls the collaboration with TU Delft a win-win situation. ‘Every newly developed technology poses a risk to the person who is going to implement it. By building a bridge between academic research and practical application in industry, we can now realise hybrid and power conversion solutions that immediately add value to a system. The innovations reduce the chance of failure in the design and implementation phase and save on maintenance costs, fuel and emissions.’
Developing an optimal software tool for creating a digital twin of an integrated energy system was very important for this. ‘On ships you have systems with combinations of AC (alternating current) and DC (direct current) grids (networks)’, Malbašić explains. ‘With the introduction of battery systems, their integration into a single energy system has become much more complex. Accurate short-circuit calculations and good selectivity are essential to build a reliable system.’
With professor Popov and his team of a number of graduate students, Malbašić analysed a number of AC grids (networks) for the research using a new software package developed by the company ETAP that is suitable for building an AC grid electrical digital twin platform.
One of these students is the engineer Matthijs Mosselaar, who has since graduated and joined Alewijnse. With the support of Malbašić, he built an AC grid digital twin model of a diesel-electric offshore vessel built ten years ago with a dynamic positioning system (DP). The generators of the system were not running at the proper load when operating in DP mode. The aim of the digital twin was to find a hybrid solution to optimise the load on the generators.
AC grid network analysis
Mosselaar developed a software model with parameters for partially automating the short-circuit calculations that are required for building good protection and selectivity for a hybrid network with generators and batteries. The software reduced the number of engineering hours required to guarantee that a system was sufficiently protected. The development costs of this software will therefore pay for themselves in the long term.
‘The short-circuit calculation forms the basis for the protection and the protection strategy of a network,’ Mosselaar explains. ‘Good selectivity is required to prevent the entire system from going down in the event of an overload or short circuit. Strategically placed circuit breakers in such a network ensure that only the affected part of the system is switched off. To guarantee that this is done properly, it is important that all circuit breakers are set to the correct value for the component they protect.’
He adds: ‘This model makes it possible to verify these values efficiently. It shows what the system can still handle and when and where a red line is exceeded at a given moment. Only in the event of prolonged overload or a short circuit should the circuit breaker intervene to prevent the system from being damaged. Being able to accurately model the protection strategy is very important, because small differences can have major consequences for the strategy to be chosen. An additional advantage of the software model is that the generated values can be easily exported for the creation of an official document of a system.’
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Building the digital twin
To build the digital twin of the DP vessel, Alewijnse’s Power Conversion Team was given access to hundreds of thousands of stored data points from the ten-year-old vessel. ‘We entered all these references, such as the values of the generators and the specifications of the drives,’ says Malbašić.
‘We analysed the energy profile of the vessel when it was operating in DP mode and saw that the five generators were only loaded between ten and twenty per cent in DP mode. Based on that, we proposed adding a battery pack to increase efficiency in DP mode. That would significantly reduce the fuel and maintenance costs of the generators. Based on the analysis, we were able to calculate very accurately which battery pack would be optimal and what the savings would be.’
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Real-time simulation
A year after analysing the energy profile of the ten-year-old DP vessel and proposing an improvement using a battery pack, Malbašić, supervised the now graduated engineer Akhil Ajith in performing real-time simulations on the ship on the five generators, the propulsion units, the DP system and the other electrical components.
Based on the previously performed analysis and the calculated optimal battery pack, Ajith created a digital twin of the vessel using a powerful Typhoon HIL Simulator to perform the real-time simulations under operational conditions. This allowed him to demonstrate the effect of adding the battery pack (which had not yet been purchased) on the consumption and maintenance costs of the generators in real time.
‘With the digital twin, I was able to virtually distribute the energy demand of the consumers on the vessel between the diesel generators and the proposed battery pack’, says Ajith. ‘This simulated a hybrid energy system with an energy management system that ensures optimal use of the energy sources. The primary goal of the study was to demonstrate the reduction in fuel consumption and maintenance costs of the five generators. This was successful.’
‘In addition to the large savings on fuel consumption it showed that the maintenance costs of the generators would decrease by almost 50,000 euros per generator set per year. Only two generators had to run at the same time and these generators ran at a much more optimal load. The payback period for the purchase of the batteries could be calculated accurately. The project has not yet been fully completed, but that will happen in the future.’
DC grid simulation software
With the support of Malbašić, the graduated engineer Samit Goud, who also works at Alewijnse, built an implementation model for analysing and securing mixed energy systems with AC and DC grids on hybrid powered ships with batteries and possibly also fuel cells.
‘No good software package had been developed for this yet’, says Malbašić. ‘The direct current modules of software (from other companies) for AC grids were all based on 24 Volt DC systems, while we now work with direct current up to 1000 Volt. For DC short circuit calculations and DC selectivity, you really need a different package.’
In the new simulation model, based on Matlab/Simulink, all objects can be introduced, except for the relatively complex solid state circuit breakers. ‘We want to create a model for this this year and integrate it into our software package’, says Malbašić.
Goud states that at Alewijnse he was and is given the space to come up with solutions that really have an impact on the greening of the maritime sector. ‘The starting point was to develop a flexible DC simulation model with all the possibilities that you also see with an AC model. DC is becoming increasingly popular but is a bit tricky compared to AC. For example, there is still a lack of standards, even at classification companies such as DNV and Lloyd’s. They are also looking at this project.’
‘With a good simulation model, you can implement a DC protection system in the right way with the right circuit breakers and DC fuses. DC is not always better than AC, but in some cases it is. When you use more DC components in a mixed system, the number of conversions from AC to DC can decrease, which increases efficiency. On the other hand, the standards for the protection of AC systems are better developed,’ says Goud.
According to Goud, research into the suppression of common mode currents (floating currents) in DC systems plays an important role in expanding the DC simulation model with a module for solid state circuit breakers. ‘I am going to try to tune the DC simulation model to select the right filters to suppress these common mode currents.’
Charging at sea
Alewijnse is currently working with a major Dutch shipbuilder on the development of a system for a fully electrically powered wind farm vessel 2.0, whose batteries can be charged directly from the wind farm at sea. ‘We are mainly looking at DC solutions for this,’ says Malbašić. ‘If you want to charge the batteries directly at wind farms, you need a solution to transform the high voltages down to a lower level for the battery pack. But the market is asking for it and innovation is being embraced more quickly in the offshore sector and electrification is already taking place there.’
The ferry market is also embracing electrification. ‘There are many hydroelectric power stations in the Norwegian fjords, from which you can also charge green energy directly. For new construction, we work from the ship design and the operational profile to a solution. On existing ships, we first make a power analysis for a retrofit to electric, based on collected data. We then use that analysis to build a system.’
University of Twente
For more research into common mode currents, Alewijnse will enter into a partnership with the University of Twente in 2025. ‘In Twente, research is underway into the influence of common mode current on the lifespan of a battery pack,’ says Malbašić. ‘We have shared our measurement reports on common mode with the University of Twente. This allows them to build a simulation model and create a set-up for this research.’
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Opportunities for young talent
Collaboration with technical education makes maritime companies more visible and attractive as an employer for students. ‘Our goal is to be the partner in the field of energy solutions for the green transition in the maritime sector’, says Habermehl. ‘We want to offer young talent a platform and innovate together with them. These collaborations help the industry move forward in developing smart and sustainable energy solutions. A collaboration such as the one with TU Delft is not unique in itself, but we do place it very close to our projects. In this way, we also challenge our own engineers to further professionalize. We see a great synergy developing between the graduates and our own engineers.’
Picture (top): Alewijnse employees at work on a new-build vessel (photo by Alewijnse).
