For many maritime applications Li-Ion batteries are foreseen as energy storage units that can improve the performance of the on-board power system in terms of continuity of service, fuel consumption, emissions and running hours of main engines. However, one of main limitations of battery application in on-board power systems is the aging of batteries. Applications of instantaneous power input/output such as propulsion dynamic assistance and heavy seas operation of ships, have an adverse effect on battery lifetime meaning that degradation of energy capacity over time is accelerated. Additionally, limited by their maximum current rating, batteries cannot deliver effectively high C-rates and therefore are not able to fully absorb the engine fluctuations. A typical solution for this problem is to over-size the battery system. By paralleling more batteries, the max. C-rate is lowered, and battery lifetime can be extended. On the other hand, an over-sized battery system will result in additional capital cost and weight. Therefore, it is evident that in conventional approaches there is an undesirable trade-off between battery aging and battery size. As an alternative practical approach into this problem, this thesis proposes an on-board hybrid energy storage system (HESS) that comprises of a battery and a supercapacitor component. By placing the supercapacitor in parallel to the battery and by using it for high peak currents, it is possible to reduce the stress on the battery and thus extend battery lifetime while improving the availability and the reliability of the power system. In addition, by taking advantage of the high specific power of the supercapacitor and the high specific energy of the battery it is possible to optimize sizing of the energy storage system for high power applications. In this thesis, a parametric approach of combined sizing and energy management for hybrid energy storage system is developed and integrated into a typical DC shipboard power system . Based on a case load profile, the HESS operation is simulated and benchmarked to battery-only installations. The static outputs of the sizing process and the dynamic outputs of the simulation are extracted in the form of design exploration maps and arrays that are used to correlate them to the key design variables. Finally, through this work, it is demonstrated that for high power applications with significant fluctuations, the proposed battery-supercapacitor HESS, can lead into smaller and more cost-effective installations, without compromising battery lifetime and while maintaining same levels of reliability performance. ... Read more

In the GasDrive project, a solid oxide fuel cell and a reciprocating gas engine are used to provide electrical and mechanical power for a ship. One of the goals of the GasDrive project is to broaden the limits between knock and misfire for the gas engine. Extending the operating limit could be achieved by addition of anode-off gas. Before anode-off gas can be used in combustion together with natural gas in the GasDrive project, the combustion characteristics of anode-off gas must be known. In this thesis, a literature review is conducted in order to explore similar gasses. One such gas is producer gas, on which both experimental and numerical studies have been conducted by other researchers. To investigate the performance of anode-off gas, an altered in-cylinder model was used. The model is verified using producer gas as a fuel, with the experimental data from producer gas combustion in an IC engine. The model functions properly and is used to investigate anode-off gas combustion.
In modelling the combustion of anode-off gas, multiple parameters are kept constant and similar to that of producer gas. These parameters include the Vibe parameters, engine geometry, air excess ratio, T1, p1, and stoichiometric gas mass fraction from the previous cycle. The combustion duration relative to producer gas is modelled based on the ratio of turbulent flame speeds. This turbulent flame speed is a combination of laminar flame speed and turbulence intensity. At first the SOC is kept constant as well, only altering the EOC for different combustion durations. The maximum power output is 79 kWe for anode-off gas with a 50% fuel utilization rate. The maximum efficiency is 20%. The peak pressure is 104 bar, which is higher than for producer gas, but falls within the limits of what the engine can handle. The peak temperature is 2847 K, which is more than 700 K higher than producer gas. The engine, it is believed, can not handle this temperature. The lowest peak temperature is reached for anode-off gas with a 85% fuel utilization rate and is 2652 K. This is still outside normal engine operating temperatures. Combustion of anode-off gas under stoichiometric conditions in an IC engine is therefore not feasible. Increasing the air excess ratio could resolve this issue, but can not be done in the current model without having experimental data on anode-off gas. The fuel consumption is 6-18 times higher than conventional fuels, also showing that anode-off gas combustion would not be an advantage over conventional fuels. More power at lower temperatures can be reached when retarding start of combustion, achieving MBT timing. Peak power is achieved using anode-off gas with a 50% fuel utilization rate and is 82 kWe. The corresponding peak temperature is 2822 K, which is also outside normal operating conditions of IC engines. Based on the modelling results, it can be said that combustion of anode-off gas is possible in a IC engine, but power outputs will be lower than conventional fuels and fuel consumption will be higher. ... Read more

Emission regulations applied to marine industry for amongst others the propulsion system of a vessel are becoming stricter due to governmental
agreements to lower the greenhouse gas emissions. Engine manufactures
are enhancing their engine designs to reduce the engine fuel consumption, which is commonly done by implementing a turbocharger to downsize the engine. One large drawback which comes with a turbocharged engine is the low torque development for the low to mid engine speed range due to limitations set to prevent unstable turbocharger phenomena. Moreover, the engine is not able to follow the power request almost instantaneously due to a time delay between the engine and turbocharger response. Formula One engineers close this gap by introducing an integrated electric machine into the turbocharger structure (hybrid electric turbocharger) to, first, take power out from the turbocharger to increase the system efficiency, and second by assisting the turbocharger to improve the engine power delivery response.

However, the understanding of the effects of a hybrid electric turbocharger on both the system efficiency as well as the engine loading capability is lacking. One turbocharger limit, the compressor surge, is not concerned in most literature what rises the need for further research up to which extent the engine can be assisted with the hybrid electric turbocharger. In this work, the effect of taking power from the turbocharger to increase the system efficiency, called turbocompounding, is investigated. Turbocharger assistance is investigated for both steady state as well as dynamic operation. The effect of assisting the turbocharger for steady state operation is investigated to increase the engine’s operating envelope. Dynamic operation comprises the investigating up to which extent the assisting mode improves the dual fuel engine’s loading capability for four types of engine loading. These types of engine loading are: one instant load step, three consecutive load steps from 0 - 100% load, a load ramp and, last, a sinusoidal engine loading.

This has been done with a simulation-based study wherein a mean value dual fuel engine model is composed based on merging two available mean value engine models, after which it is verified and validated. Thereafter power take in/out together with an air excess ratio control strategy is included by means of adding/taking torque to/from the turbocharger shaft and limiting it with eight boundary controllers to avoid impractical situations. With turbocompounding the system efficiency can be increased at the expense of a deteriorated gas exchange and increased thermal loading of the engine. The maximum quantity of recovered energy to be obtained, requires a hybrid electric turbocharger which replaces a waste gated turbocharger instead of a non-waste gated single stage turbocharger. Taking power from the turbocharger lowers the power available for the compressor which leads to reduced inlet receiver pressure and corresponding lowering of the air excess ratio and deterioration of the scavenging process.

Assisting the turbocharger for steady state operation leads to a smaller operating envelope due to the limitation of compressor surge. Combining turbocharger assistance with gas exchange bypass valves, to avoid compressor
surge, results in a rise of the low speed torque output up to an almost constant engine torque output. The system efficiency can be improved for the low speed region when the turbocharger is assisted in combination with the gas exchange valves.

The load step capability, found by limiting the minimum air excess ratio during the load step event, cannot be increased with turbocharger assistance which starts to speed up the turbocharger immediately after the load step is applied to the engine. However, the recovery time needed before a second load step can be taken, is reduced with turbocharger assistance compared to the baseline engine. When the turbocharger assistance starts to speed up the turbocharger a couple of seconds before the load is applied, the load step capability can be improved. A load ramp can be taken in a shorter period of time with turbocharger assistance enabled. For cyclic loading, the hybrid electric turbocharger operates in turbocompounding mode for the lower load frequencies, and assistance is used for the higher load frequencies. With turbocharger assistance the air excess
ratio does follow the sinusoidal engine load while the air excess ratio of the non-assisted engine always lags due to the turbocharger lag.

Further research should be done with regard to a hybrid electric turbocharger for the natural gas combustion of the dual fuel engine. Using the engine speed drop should be implemented as limitation for the loading capability determination instead of the minimum allowable air excess ratio applied in this thesis. ... Read more

Pioneering Spirit, Allseas's largest pipelay vessel, will be outfitted with a novel Jacket Lift System (JLS). A jacket refers to the steel frame which supports the topside of a fixed offshore platform. The Pioneering Spirit was already capable of lifting the topsides of offshore platforms, like the former oil platform Brent Delta, but would have to leave the jacket behind. With the JLS it will also be able to remove and install jackets.

In offshore ship mounted crane applications wave disturbances can create unwanted oscillations in suspended loads. Anti-sway control systems have been developed to aid the crane operator in decreasing these oscillations. But not all crane types have actuators suitable for this compensation. The JLS will be a derrick type crane which will be positioned above a jacket using the dynamic positioning of the ship. The hoist systems of the JLS are then lowered and connected to the jacket. During this lowering process the ship motion induced by wave disturbances create a large oscillation in the hoist system.

In this thesis a controller is developed based on a proportional derivative controller found in literature to reduce the sway in the hoist system to make the connection process possible. ... Read more

Greenhouse gas emissions’ reduction goals of a 50% reduction by 2050 were established by the IMO. As a first step to achieve this reduction already by 2030 this project uncovers how much of the CO₂ emissions it is possible to reduce by combining the available state of the art technology.
The reduction of CO₂ emissions is done in two steps. The first step consists in reducing the power demand in terms of auxiliary and propulsion systems. After that, cleaner power supply alternatives are considered to further reduce the emissions.
In terms of auxiliary power, heavy consumers such the air conditioning, the lighting or water systems are considered. The reduction of auxiliary power is not only achieved with the introduction of more efficient equipment but also by the introduction of passive design strategies that enhance savings by reducing the loading on the systems. Altogether it is possible to reduce the auxiliary power demand by 33% in comparison with the benchmark design. The reduction of auxiliary power demand has a significant impact on the yearly consumption due to the significant percentage of operational time spent at anchorage.
In terms of propulsion power demand, the reductions achieved are even more significant, 51% and 70% power demand reductions are possible at cruising and maximum speed, respectively. The introduction of the Van Oossanen’s Fast Displacement Hull Form (FDHF), the reduction of displacement by making an aluminium hull and the application of the patented Hull Vane® are the main reasons for such a significant propulsion power demand.
Finally, the switch in power plant arrangement of the yacht results in further 10% reduction. In this case, simply the change from diesel direct arrangement to a hybrid arrangement leads to yearly savings, mainly because emissions at cruising are reduced due to the power take-off operational mode of the power plant, saving generator set emissions.
All in all, it is possible to already achieve a reduction of approximately 41% of the yearly CO₂ emissions on a 50 m motor yacht. One of the most important conclusions to be taken is that all these reductions are possible when finding the optimal interaction between components, from auxiliaries to power plant arrangement. Mainly, the CO₂ emissions reduction followed from a fuel consumption reduction, not yet introducing power supply from renewable energies nor alternative fuels which despite being the way to the future are not yet fully mature and suitable for this specific case.
... Read more

A conventional dynamic positioning system is used to control vessel motions in the horizontal plane, i.e. surge, sway and yaw. However, the safety and operability of several offshore operations can be increased when also the roll motion is actively controlled, especially in beam seas. A control system model is proposed for combined thruster induced roll reduction and DP station keeping when the vessel is operating in beam seas. The proposed control system model is applied to a offshore construction vessel and the performance is demonstrated by time domain simulations. The DP footprint is compared to a conventional dynamic positioning control model. The proposed control model enables active roll reduction while the effect on the station keeping performance is unaffected. ... Read more