A novel dynamic simulative approach for the energy design and assessment of innovative HVAC systems onboard ships

In this paper, a novel dynamic simulation tool that considers the transient behaviour of both thermophysical parts of the ship and HVAC systems equipped onboard is presented. This approach allows for assessing thermal loads and energy needs of all thermal zones on the ship, properly designing air-conditioning systems, and assessing the energy performance of different HVAC energy system layouts. Furthermore, the tool can be adopted onboard as digital-twin for ships that are properly equipped with sensors. Therefore, the tool can be used for optimizing the energy performance of energy systems in real-time (if implemented onboard as digital-twin) or for conducting swift energy, economic, and environmental analyses for different energy plant system layouts. The methodology employed in this study involves developing a 3D geometrical model of the ship and integrating it into the energy performance simulation tool. Following this, actual cruise conditions, including real ship load profiles and hourly weather parameters, as well as the location and orientation of the ship, are incorporated. To demonstrate the potential of this methodology, a comprehensive case study featuring a medium-sized ship measuring 300 meters in length, 34 meters in width, and 46.2 meters in height, with 16 decks and 6 main frame zones, is presented. The 3D model of the ship includes 1595 thermal zones, and a total of 2630 people (1750 passengers and 880 crew members) are considered onboard. A reference case scenario including an energy ship plant system layout with all-air air conditioning systems is considered, whereas 13 different scenarios for enhancing energy efficiency of whole ship are explored. Notable findings include potential fuel savings ranging from 3.1% for the adoption of HVAC control strategy for setpoint temperature with usage-based criteria (equivalent to a yearly savings of 0.0546 tons of fuel) to 26% for the setpoint temperatures reconfiguration according to ISO 7730 with variable supplied fresh air according to usage-based criteria (saving 0.447 tons of fuel annually). This approach serves as a valuable tool for conducting energy analyses on existing ship systems and innovative technologies or strategies implemented on modern vessels.