JAPAN: A new 21-storey office block in Yokohama is to incorporate an optimal air volume control air conditioning system developed by Daikin in collaboration with Japanese construction company Kajima Corporation.

The OCTPUS (Optimal Controlled Terminal Fan Powered Unit System) is said to optimise air conditioning air volume control by installing a fan-equipped air volume control device (FPU) in each air conditioning zone and linking it with the central air conditioning system.

The system will be installed in the Yokohama Gate Tower project, an 80,000m2 office building with commercial facilities, a spherical planetarium and restaurant. The building is currently under construction in Yokohama’s Minato Mirai 21 Central District.

OCTPUS is described as a system that supplies the minimum required air volume at the optimum temperature according to the heat load of each zone by controlling the FPU distributed in each air conditioning zone and the air supply fan in the air conditioner in cooperation with each other. Energy loss can be prevented because the ventilation is controlled for each branch duct path by operating the FPU.

In the energy-saving VAV system, the entire zone is blown by one air conditioner, and the lower limit of control air volume can only be reduced to about 30% of the maximum air volume. Since OCTPUS can control both the air conditioner and the FPU, it is possible to stop the air conditioner and supply air only with the FPU when the amount of heat to be processed is small. This makes it possible to reduce the lower limit air volume to about 10%, which saves energy. In a simulation modelled on a typical office building, it is estimated that annual air transport energy consumption can be reduced by up to about 44% compared to a VAV system.

Since OCTPUS can reduce the control lower limit air volume to about 10%, it is said to be easy to maintain a low supply air temperature. Simulations have confirmed that the relative humidity in the room can be maintained within a comfortable range of around 50%, the designers say.

OCTPUS can also reduce the space in the machine room because the fan size of the air conditioner is reduced by sharing the air supply pressure with the FPU. According to estimates for the installed buildings, the office area per floor increased by about 1%.

A total of approximately 1,200 FPUs will be installed.