Arkitech’s solution proved savings on the chiller’s energy consumption on the MSC Magnifica (12.8%), GNV La Suprema (18.2%) and GNV La Superba (11.2%). The savings on the chiller’s energy consumption were realised without causing an increase in energy consumption on the pumps and air handling units

Before activating the system, Arkitech monitors the HVAC system while in passive mode. This way we establish a baseline energy usage.  This baseline is later compared to actual energy usage while ARKM20 is managing setpoints. Depending on various factors, the length of time used to establish baseline may be varied. This baseline is updated when different weather patterns are experienced.

The factors that influence energy usage are the same that influence room temperature, because heat created in a space should be removed by the HVAC system. The factors are: Outdoor temperature, outside humidity, seawater temperature, occupancy, internal ship temperature, sun radiation and internal heat emission by ship’s systems. The ship itself may accumulate a large amount of heat.

The ARK-M20 system monitors real-time temperatures inside the ship especially in spaces such as: passenger cabins, show lounges, restaurants, atriums, or lobbys and when an air temperature increase is detected the ARK-M20 automatically reduces the chilled water temperature to meet the new conditions. When the temperatures are going down or the specific room air conditioner (fan coil or water valve) is closed, the system reverts to the most efficient setting.

High daily and seasonal variations in outdoor temperature and humidity increase the saving. Special temperature or humidity requirements in some spaces decreases saving. High internal heat emission at some spaces decreases saving. Rapid and frequent changes in occupation decrease the saving as requires rapid adaptation of water temperature to changing conditions. Open shell doors during embarkation or port stays will increase the internal heat and humidity  requiring additional cooling capacity. Good HVAC system design with some spare and separate cooling for special rooms, increases the saving.

All the systems provided by manufacturers deal mainly with the chillers using factory conditions and very little, if at all, with the environment. The chillers and the Air Handling Units are generally supplied by different manufacturers and so do not communicate with each other. ARK-M20 integrates a lot of parameters such as outdoor temperature and humidity, specific hours with higher occupation, sun radiation, AHU settings and more to calculate the required set point at any hour. It also monitors the room temperatures and adjusts the water temperature when required.

The ARK-M20 is non-intrusive, which means it doesn’t change the original chiller control as some optimization methods do, but uses the control options provided by the manufacturer. This eliminates any possibility to cause damage by wrong command. Some other systems control the room temperature instead of water, which gives very limited saving, causes changes in internal conditions and require a high installation effort as in most buildings today room thermostats have no remote control. The ARK-M20 is the only system available on the market that does the required analysis, performs planning and manages (under human supervision) automatic temperature control.

Set point changing by itself has no influence on chillers as it doesn’t cause any mechanical or electrical action. However, rising the water temperature may cause more frequent chiller’s stops and restarts.

Our experience is that during a hot summer there is no difference between the periods when the ARK-M20 is active or not, as in most cases the chiller is not stopping at all. When ARK-M20 is active most chillers will reduce their activity, but will not stop. When the outdoor temperature goes down ARK-M20 will cause more restarts as the chiller will reach earlier the required water temperature, but when the temperatures are going down the opposite happens as the periods between activations are longer in case of active ARK-M20 than without. For higher set-point more time is required to reach it.

The number of restarts depends however also on the HVAC system design. If the chiller is relatively big to the space it cools, it has more restarts then a small chiller, because it will work most of the time on low capacity and will reach the required set-point quickly and then stop. (The number of restarts acceptable by most of the manufacturers is 6 per hour)

Yes, the ship’s chief or reefer engineer has full control over the ARKM20 system. They may switch the system off via the user interface. When a parameter in the chiller’s control is adjusted, the ARK-M20 automatically switches off.