Energy Efficient Design

The energy efficiency of a ship design is related to the performance of each individual system and how efficient the individual systems interact with each other.
Eventually it is the performance of the total assembled complex ship system that matters.

Individual ship systems are today normally design and delivered by expert sub suppliers. The responsibility to assemble the individual systems into the complexity of a fully functional ship lays on the shipyard.
Generally the individual systems have been developed and refined over many years and they provide a high level of robustness and reliability. Typically there are two short comings:

1. The systems are based on very conventional technology. The design can be quite refined and optimized  but still the conservative approach towards emerging technology leaves a great improvement potential uncovered
2. The suppliers optimizes the individual systems but the performance of the compiled complex system is normally not considered

We see two major task for the academia to contribute and enable development towards better total efficiency

1. There need to be research into the possibilities and potential to apply alternative and new emerging technologies to enable step-change development for significant efficiency improvement
2. Methods need to be developed to model several individual systems (eventually all ship systems) to see how they perform together and how to design them for the best total efficiency

The Department of Shipping and Marine Technology at Chalmers University of Technology has high competence, long term experience and several ongoing initiatives which will provide substantial value for improved total efficiency in shipping and ship design.

To organize the work for improved total energy efficiency it can be useful to divide the ship systems into different categories. However one must always keep in mind that interaction between systems eventually need to be carefully considered. One way is to initially separate the forces and energy effecting the outside of the ship from the forces, moments and energy that is generated and used inside the ship.

The most significant components that effects the forces, moments and energy inside the ship are the main engine, auxiliary engines, thrusters motors, pumps, fans, coolers, refrigerators and HVAC systems.

With in the division Maritime Environment and Energy Systems long term research has been addressing these areas. The work has involved both research of core technology were the intention has been to apply novel technology such as waste heat recovery, thermal energy storage and hybrid technology as well as research of how to virtually model the systems and the interaction between systems in order to find the best total design and configuration

Forces and energy effecting the outside of the ship are typically calm water resistance, added resistance due to wind, waves, water depth, propeller thrust etc.

The department has a long and solid experience in developing mathematic models to calculate the resistance of the hull, both under and above water as well as propeller thrust. An  crucial factor is how the flow around the under water hull effects both the resistance and the propulsive efficiency and the challenge is to catch the interaction effects and to optimize hull and propeller for best total performance.

Wind resistance of a ship in calm water conditions is small and is often neglected. At higher wind speed the wind effect is a significant contributor to the total resistance. A very interesting area of research is how active flow control can be used to reduced the wind resistance.

In order to catch the above described effects a generic energy systems model (Ship Systems Energy Model "SSEM") is being developed and the department. The model enables analysis of a specific or generic ship to see the combined effect of the performance and interaction of the individual systems and it also provides a method to simulate the performance over a certain route taking into account environmental conditions such as wind, wave water depth, currents etc.

The SSEM is utilizing a number of sub models that can be developed independently in order to benefit from all fields of the research in the department

Example of sub models that make up the SSEM:

• Calm water resistance
• Added resistance
• Wind resistance
• Propeller optimization
• Trim optimization
• Propeller hull interaction
• Main engine performance
• Main engine propeller interaction
• Degradation model for hull surface and fouling
• Waste heat recovery models including for example organic rankin cycle turbines
• Efficiency of main auxiliary systems such as generators and HVAC systems

We are currently working on the definition of the base-line designs and the bench-mark routes. The intention is to develop a number of base-line designs and to evaluate their performance for a number of standard routes. The base-line designs can be utilized for parametric variations of main dimensions and or other design alternatives. The effects of the design change can be evaluated for a bench-mark route.

Existing designs can of course also be evaluated