Clean air: creating more efficient HVAC systems

The air conditioning system is one of the most demanding items on a passenger ship when it comes to electrical load-balancing. With a significant energy cost, operators demand that HVAC systems run as efficiently as possible while providing a comfortable environment for passengers. Teknotherm’s project manager Sigbjørn Tyssen explains that digital technologies such as data analytics could play a significant role in making HVAC systems more efficient.

“The traditional HVAC skills such as fan curves, noise calculations and knowledge about refrigeration cycles will not go out of style,” Mr Tyssen says, but he adds that automation is becoming ever more important. “Knowledge of systems such as AI, machine learning and neural networks is something we need to learn more about. The technology is there, and the data must be collected.”

Mr Tyssen suggests that, rather than simply responding to input data such as outside temperature or data from location systems such as keycards and ID cards being scanned, HVAC operations could take a predictive approach. This would enable the system to find patterns in demand and plan operations accordingly. For example, it could predict when guests are likely to be in different areas of the ship, such as the pool, cabins, restaurants and shops, and see whether these patterns differ depending on the weather conditions and if the vessel is at sea or in port.

“The future HVAC system will react faster, but also move energy to where it is needed, plan when it is needed and produce it in the most energy-efficient way,” he says. Recent and forthcoming deliveries illustrate the role HVAC systems can play in boosting energy efficiency on passenger ships.

Celebrity Cruises’ 101.5 m vessel Celebrity Flora, delivered this year, has been designed for the Galapagos Islands. The sensitive nature of this environment has influenced many aspects of the vessel, resulting in a 15% reduction in fuel consumption and a similar reduction in airborne emissions compared with Celebrity’s Xpedition class.

A low-energy HVAC system is integral to reducing energy consumption and formed one of the main targets for efficiency improvements on the vessel. Heinen & Hopman supplied custom-built chillers and Enigma fan coil units to assist in this.

The Enigma operates on the principle of a minimum amount of fresh air, calculated on a per-person basis being treated in an air-handling unit and distributed through a thermally insulated spiro duct system and into a CFCU unit placed in the cabin’s wet module. When in the CFCU, this fresh air is mixed with returned air from the cabin and supplied through ceiling boxes with diffusers. The system reduces the size of chillers and ducting needed on board and the number of air-handling units required.

Stena RoRo has chosen Heinen & Hopman to supply a complete HVAC system for a newbuild ropax vessel. The vessel is being built by AVIC International, a Chinese yard specialising in ropax and roro vessels. The 214 m ship is the fifth in Stena’s E-Flexer ropax class. On delivery, the vessel will start a 10-year bareboat charter with DFDS, plying a route in the English Channel between Dover and Calais.

Environmental concerns were high on the agenda in the vessel’s design, and it is expected to consume 25% less fuel than current operations.

Heinen & Hopman will supply HVAC for living quarters and ventilation for the cargo hold, engineroom, machinery space and provision cooling. The main challenges faced in the design are limited space and noise and vibration requirements.

A heat recovery wheel is being incorporated into the ventilation systems to aid energy saving. Comprising a circular honeycomb matrix made of heat-absorbing material, the heat recovery wheel rotates within the supply and exhaust air streams of air-handling systems.

As it rotates, heat is gathered from the exhaust air stream in half of the rotation and given to the fresh air stream on the other half of the rotation, transferring waste heat energy from the exhaust air stream to the fresh air stream via the matrix material.