ABS launched the publication of Practical Considerations for Hybrid Electric Power Systems Onboard Vessels. The publication explores the different forms of Hybrid Electric Power Systems (HEPS) and offers practical insight into their application on board.
Power and propulsion
In hybrid propulsion, a direct mechanical drive provides propulsion for high speeds with high efficiency. Additionally, an electric motor powered by generators can be coupled to the same shaft through a gearbox or directly to the shaft driving the propeller. This can provide propulsion for low speeds, thus avoiding the need to run the main engine inefficiently at partial load. The motor could also be used as a generator to supply power for electrical loads on the vessels’ electrical network. Therefore, vessels that frequently operate at low speed can benefit from a hybrid propulsion system.
In this architecture, a combination of two or more types of power sources are used to provide electrical power. The power supply can be from combustion diesel engines, gas turbines or steam turbines, or electrochemical power supply from fuel cells, solar photovoltaic, wind-assisted ship propulsion (WASP), or stored power supply from energy storage systems such as batteries, flywheels or supercapacitors.
Renewable energy sources
#1 Fuel cells
Fuel cells as clean power sources are very attractive for the maritime sector. Proton exchange membrane (PEM), molten carbonate and solid oxide fuel cells are considered to be several promising options for maritime applications. Power capacity, safety, space arrangement, reliability, durability, and risk assessment are important factors that demand attention when applying fuel cells as marine power systems.
#2 Solar
Developments in solar photovoltaic technologies are spurring the integration of solar energy into many applications that were previously considered uneconomical. The maritime industry has been mainly focused on deploying this technology on smaller vessels and car carriers, but the use of photovoltaic solar technology in larger ships is slowly gaining acceptance and is seen as one of the viable pathways to reducing GHG from shipping.
The installation of photovoltaic (PV) arrays and its integration into the power system can help to reduce greenhouse gas emissions, improve energy efficiency, and contribute to the stability of the ship’s power system. However, installing a PV system requires significant attention.
#3 Wind assisted propulsion
Interest in wind power has increased as the maritime industry seeks to reduce the impacts of fossil fuels. The existing scientific literature has identified wind-assisted ship propulsion (WASP) technology as a promising option to increase the energy efficiency profile of the maritime transport industry and decrease the CO2 emissions produced by its operations.
Computed based modeling
Computer-based modeling and simulation is the process of developing a mathematical and/or logical model of a system and then using it to obtain data for decision making. The developed mathematical model emulates a physical system in a virtual form which provides flexibility for analysis, evaluation, optimization and testing in a safe and costeffective way. The key parameters of a physical system, assumptions, and design approaches used for a mathematical model must be accurate and clear to ensure that the outcomes of computer-based simulation are adaptable to real world applications.
Three different approaches are used to model, simulate, and evaluate physical systems: physics-based, data-based and hybrid approaches:
- A physics-based approach represents a physical system using mathematical models. This approach requires various specifications, design parameters and other key parameters of each component of a physical system. A physics-based approach requires a longer time for model building but provides high granularity for each component e.g., a digital twin of an engine.
- A data-based modeling approach approximates the behavior of a physical system using measured data from the same or similar system. This approach is usually adopted for low granularity black box models e.g., fuel consumption calculation of an engine model based on a look-up table from an engine manufacturer.
- A hybrid approach combines both physics-based and data-based modeling principles to approximate a physical system in a much faster way when compared with a complete physics-based modeling. A good example is the mathematical model of a propulsion motor simulated using measured shaft power of the same motor or similar motor with the same capacity. In general, the selection of an appropriate modeling and simulation approach is based on the level of granularity, available time, and purpose of the model.
EXPLORE MORE AT ABS’S REPORT ON ELECTRIC POWER
