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Energy saving strategies for HVAC systems

One of the most effective ways to address building’s energy and resource performance is by making them smart. For instance, Infosys employs the latest smart building practices for all its campuses across India. Punit Desai, Senior Manager with the Green Initiatives Team at Infosys, explains how energy saving intelligence or energy saving strategy can be built into building operations.

Automated energy saving strategies

The energy saving strategies for building air conditioning systems focusing mainly on the air handling system’s operation and control. A smart building using a combination of controllers, sensors, actuators, feedbacks, and energy saving intelligence makes the HVAC operation most energy efficient. Mentioned below are some of the strategies that have been incorporated at Infosys buildings with their real time performance data. These automated energy saving strategies and smart operations have helped us save as well as manage energy for HVAC, computing (UPS), lighting, raw power and water management.

Occupancy based control for HVAC in meeting rooms and cabins

Use of occupancy sensors to control lighting is a common practice in most buildings. At Infosys, we use the same occupancy information to control HVAC in meeting rooms and cabins. Meeting rooms and cabinsmostly have standalone air terminal units like thermadiffusers, VAVs or chilled beams and these spaces offer maximum occupancy diversity. The occupancy information is used to re-set the setpoint to a standby mode setpoint. Our proposed standby mode setpoint is 27deg C with a time delay band i.e.,in case the meeting room or the cabin or conference room is not occupied for 10 minutes the air-conditioning setpiontin the space will be reset to 27deg C. This strategy is expected to be more efficient than temperature based control as it is a quicker reacting system (based on occupancy sensor).

Optimal start strategy for air handling units

Conventionally, during start up the AHUs run without having the desired temperature of chilled water. This ends up being a non-productive operation as the AHUs operate at full speed without being able to provide any cooling. Each day this was an average of 30 minutes of operation. We changed this operation using our smart building system by opening up the AHU cooling coil valves at start to allow chilled water flow through them. The AHU fan starts only after the desired chilled water temperature has been achieved through the chiller plant. By applying this control strategy, for an operation for 10 hours a day, the saving in the AHU fan power translates into an average of 5%.

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