Auxiliary Energy

HVAC tab in model data - Simple HVAC

When using Simple HVAC, this data is used to calculate the electric energy consumption due to fans and pumps, control gear and any other HVAC-related equipment not accounted for elsewhere. The data used for this calculation depends on the Simple HVAC Auxiliary model options setting.

NCM Setting

When the NCM Simple HVAC auxiliary option is set, only one data item is required to define the auxiliary energy consumption. This data is used at the zone level and the auxiliary energy consumption for the building is displayed at building level in the Simulation results as System Misc energy.

Auxiliary energy

The total annual Auxiliary energy consumption can be entered as kWh/m2 (SI units) or Btu/ft2 (IP units). Auxiliary energy accounts for any additional energy consumption due to fans, pumps, control gear etc. It is specified per floor area and is modelled as being consumed 24/7 during the simulation. Note that when using the NCM option, auxiliary energy consumption will not vary according to mechanical ventilation flow rates or any other settings - it is a very basic way to account for auxiliary energy consumption.

The default auxiliary energy data provided in the HVAC templates is based on data published in the UK National Calculation Methodology (NCM).

The energy consumption related to Auxiliary energy is shown at building level in the results screen.

Separate Fans and Pumps Setting

When the Separate fans and pumps Simple HVAC auxiliary option is set, the auxiliary energy calculations are carried out separately for fans and pumps and their respective energy consumption values are displayed separately in the simulation results.

• Fan energy is calculated based on fan pressure rise and efficiency values as defined under Mechanical ventilation > Fans. The fan energy consumption data is displayed in simulation results as Fan energy and will depend on the actual mechanical ventilation flow rates applied in the simulation.
• Pump, control and any other electrical energy associated with the HVAC system is calculated using a power density value (W/m2 or W/ft2) plus a schedule to define time/seasonal variations.

Pump etc energy

The pump energy can be defined as a power density (W/m2 or W/ft2) and this is multiplied by the value of the associated schedule (below) to calculate the pump energy for each zone at any time in the simulation. The data is used at the zone level and the total energy consumption for the building is displayed at building level in the Simulation results as Pump energy.

Schedule

Select the schedule defining the time variation of the pump energy consumption.