Stefan Goranov, Program Manager – Hybridisation at engine designer WinGD discusses efficiency gains and the next steps in the engine designer’s hybridisation programme.
While the energy-saving opportunities offered by hybrid installations for certain types of short-sea vessels became increasingly evident over the course of 2019, the exploration of hybrid solutions for vessels equipped with two-stroke engines has been slower to develop.
Amid increasing interest in the possibilities of energy storage systems aboard larger vessels, Winterthur-based engine designer WinGD is about to announce a number of system integration services, enabling transformative solutions for ship owners, operators, and yards.
WinGD is introducing a number of hybridisation and related services for its customers in 2020, Stefan Goranov, Program Manager – Hybridisation at engine designer WinGD told The Motorship in an interview in March.
New hybridisation solution
Stefan Goranov revealed that WinGD was about to launch a series of services, enabling solutions for battery hybrid ships with two-stroke main engines, in response to customer demand. This applies to different degree of electrification of the ship power system, ranging from coupling the main engine with a PTO and enabling peak-shaving functionality for constant-load engine operation, to dimensioning and integration of battery and other components, including a full-system energy management system, aiming for the most efficient operation of the system as a whole.
“Following the successful conclusion of our technical use case studies, we can demonstrate that the integration of energy storage systems aboard a number of vessels with two-stroke main engines can deliver considerable savings, with a payback period of less than 5 years,” said Goranov.
The engine designer has initially evaluated the impact of hybridising container feeder vessels, LNG carriers, product carriers and pure car and truck carriers (PCTC).
Goranov noted that WinGD has already begun to offer some of its system integration services. Indeed, the engine designer was already collaborating in several pioneering newbuilding projects.
He declined to disclose the progress of concrete discussions at this stage.
Engine management changes
The introduction of energy storage systems and energy management systems aboard a vessel will have knock-on effects across the vessel’s systems.
One of the largest changes was philosophical, Goranov noted. “While OEMs previously focused on maximising efficiencies of individual components and sub-systems, we are now looking at maximising the overall efficiency of the system.”
There were a number of system modifications, Goranov noted. For example, the main engines’ speed controller functionality needed to be enhanced to permit efficient peak shaving. It has previously not been logically interfaced to the electrical machine on the shaft line for this purpose.
The speed controller function was an interesting example of where greater interaction between systems, even on a small scale, could lead to noticeably improved efficiency. Depending on the project requirements, this feature could be either enabled on the main engine side or implemented on a controller provided within the scope of a 3rd party system integrator. In the latter case, WinGD will provide an interface specification to ensure the optimum dynamic interaction among the systems.
Wider changes could be expected in engine tuning. Today’s engine tuning reflects the modes of operation when the main engine must alone provide propulsion power in a wide range of speed setpoints. This will change with the additional degrees of freedom enabled by alternative energy sources, increasing the importance of the tuning of the whole integrated system, so all the components work in harmony together, Goranov noted.
“The weight of impact of some areas on the BSFC maps will decrease, and even become irrelevant. This is an opportunity to streamline the operational field in certain areas on the map and aim for higher overall efficiency in a system context, whilst fulfilling the IMO requirements for BSFC-NOx trade offs.”
Technical Use Case Results
The launch of the system integration services represent the successful conclusion of project to identify the component-level energy demand aboard individual vessels. This data was combined with ship-specific operational profiles, including route specific information to include seasonal weather and environmental conditions to form a detailed analysis of data aboard a given vessel.
Initially, value of hybrid installations with two-stroke main engines was demonstrated aboard four main types of vessels: pure car and truck carriers (PCTCs), container feeder vessels, product carriers and LNG carriers.
“The initial focus of the project was to model the interaction of dual-fuelled vessels with hybrid energy systems, aiming to maximising the usage of LNG as a fuel due to its superior environmental performance, but the study also examined the potential benefits of combining hybrid installations with conventional diesel-fuelled systems,” Goranov explained.
The results of the studies revealed that when the system is designed and controlled optimally, overall efficiency and environmental performance were noticeably improved. “A conservative case study for container feeder vessel sailing in the North Sea and Baltic, equipped with diesel-fuelled auxiliary engines and a WinGD dual-fuel main engine, concludes that annual onboard diesel consumption could be reduced by about 68 percent, while the gas consumption increases by 22 per cent. As a result, the CO2 emissions from the ship are around 8 percent lower.” said Goranov, adding that the results varied according to component efficiency characteristics, battery capacities and types.
In this particular case, the system was modelled with a 7XRT-flex50DF rated 10.1 MW @124rpm main engine, coupled with a 1.3 MW shaft generator and 0.8 MWh battery pack. As an input, measured real-live power demand profiles were used.
The technical use case results varied between the different vessels. Goranov noted that where short-sea vessels’ operational profiles involved frequent stops, the potential savings were higher.
Container feeder vessels were a particularly interesting class, owing to the frequency of their port calls, but vessel-specific and route-specific factors also played a role.
The energy demand from an individual container vessel’s reefer demand varied according to the number of reefer slots, their capacity utilisation and even environmental factors. Refrigeration requirements in the Caribbean differ from northern European routes. A feeder vessel with 300 slots might require over 2MWh, based on an average 7kWh per plug demand, The Motorship noted.
The results of the technical use case revealed that there was a “sweet spot” in the relationship between investments and returns on investment.
“Oversizing components leads to diminishing returns,” said Goranov. “We found that there is marginal benefit in, for example, doubling battery capacity. On the other side, under-sizing them might expose to safety-relevant risks and lead to their premature ageing if the charging/discharging pattern is not optimum. It is imperative that all the system components, especially the main two-stroke engine, are appropriately sized in the design stage, tuned, and later optimally controlled as a system in operation.”
The study identified the use of batteries as spinning reserves as one particular area where auxiliary loads could be optimised, permitting one auxiliary engine to be used at a more efficient load point during harbour operations, rather than operating two or more gensets at lower loads during thruster manoeuvring. Other possibilities include manoeuvring for zero-emission propulsion in port.
The optimisation of auxiliary engine loads and reduced running hours would lead to reduced maintenance costs and extended service lives across the whole system.
The study found that the installation of energy storage systems would also lead to wider system-wide benefits. All the studies analysed reductions in the installed capacity of gensets aboard vessels. “We see the potential to optimise the number of gensets aboard 174k LNG carriers from four to three, for example,” said Goranov, adding that vessels with lighter energy consumption profiles could adopt two genset configurations.
The studies had narrowly focused on the system-wide energy requirements aboard the vessel, but potential reductions in main energy power requirements, subject to minimum propulsion power requirements, could allow main engines to be down-sized.
This would offer wider benefits to ship owners in terms of engine room space requirements, enabling the installation of additional equipment without negatively impacting the cargo capacity and ship design. This offers particular advantages to vessels that face regulatory pressures from the implementation of EEDI Phase 3.
The implementation of EEDI Phase 3 for container ships, general cargo ships, gas carriers and LNG carriers is expected to occur in 2022.
This includes the launch of a simulation platform, which will allow customers to visualise the potential impact of integrating a battery, PTO/PTI, and other related systems aboard a specific vessel.
“The platform will allow us to identify the best performing system configurations and control strategies, visualising different behaviours while changing the boundary conditions for a given route,” said Goranov.
The successful development and release of a modular full-system simulation platform containing transient-capable engine and electromechanical component models represents a significant achievement by WinGD.
Goranov mentioned in passing that comparing the operational performance of hybrid vessels with conventional equivalents had required the development of a series of statistical references.
WinGD has adopted a distinctive approach during the development of the simulation platform, preferring to implement a hybrid physical and data driven approach over the data model-led approaches favoured by other researchers.
The physical modelling during the project relied on the development of complex hardware-in-the-loop test systems at Winterthur. In a further sign of WinGD’s commitment to hybrid systems, the company is planning to enhance its global test centre near Shanghai with a full-scale advanced hybrid setup, permitting validation of new features and continuous enhancements, as well as bringing the real-life experience of operating such a system closer to potential customers.
The engine designer has also developed significant in-house expertise, collaborating with OEMs, ship design and research institutions in China, and a wider network of Swiss and EU research institutions.
“Although this is still a new area for WinGD, together with our innovative partners in the field of system integration, energy management and optimisation, we are striving to set the standard for hybrid ocean-going ships with two-stroke engines,” said Goranov.
The highly detailed models of the ship’s systems developed by WinGD during the project form the basis of a next stage of development. WinGD is planning to repurpose these models to model the operational performance of the system.
The Motorship notes that WinGD and technical university ETH Zürich have been collaborating in the development for combined physical and data-driven models for predictive maintenance for the engine designer’s two-stroke engines.
One of the advantages of the thermodynamic models developed by WinGD is that they can produce accurate results in transient operational conditions due to the deployment of phenomenological models and their inherent extrapolation capabilities. This is actually the outperforming factor in comparison to solely data-driven model approaches. However, the data-driven models enable predictions and prognosis of inefficiencies and failures. WinGD’s approach captures the best of both methods to maximise the system capabilities, Goranov concluded.