Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
Outdoor Temp (Dry bulb) and Outdoor Relative Humidity will both come from the EnergyPlus weather (epw) file you use to run in conjunction with the input data file (idf) used to specify your building systems, materials, geometry, etc.
The indoor dry-bulb temperature/relative humidity are solved for when EnergyPlus is executed: they are not inputs, but rather output variables. You usually don't specify a constant indoor temperature as part of the input. You CAN however, specify HVAC setpoints, which are desired temperature values in the conditioned zone. The HVAC system will, depending on its control scheme, try to output a load to add to the Zone Air Heat Balance in order maintain the setpoint temperature, according to the setpoint schedule and HVAC controls.
Look at the EnergyPlus schedule object documentation to figure out how to specify constant heating and cooling setpoints for the entire year, 24/7, if that is your goal: https://bigladdersoftware.com/epx/docs/9-5/input-output-reference/group-schedules.html
Occupant density and internal gains associated with people come from the People object input: https://bigladdersoftware.com/epx/docs/9-5/input-output-reference/group-internal-gains-people-lights-other.html#group-internal-gains-people-lights-other-internal-zone-equipment.
There is a field for specifying the nominal number of occupants: (https://bigladdersoftware.com/epx/docs/9-5/input-output-reference/group-internal-gains-people-lights-other.html#field-number-of-people-calculation-method): if you just want to specify directly the number of occupants, use the "People" option for the Field: Number of People Calculation Method.
Note that this is the nominal number of people. The actual occupancy in a thermal zone at any given timestep will be the product of the nominal number of people and the Number of People Schedule value, as specified in this bit of documentation.
https://bigladdersoftware.com/epx/docs/9-5/input-output-reference/group-internal-gains-people-lights-other.html#field-number-of-people-schedule-name
Sensible Heat Gain / person and Latent Heat Gain / person can be specified using the sensible heat fraction field: https://bigladdersoftware.com/epx/docs/9-5/input-output-reference/group-internal-gains-people-lights-other.html#field-sensible-heat-fraction.
Normally this field is autocalculated but it can be a user input. "An internal algorithm is used to determine what fraction of the total is sensible and what fraction is latent."
Unsure where to look for Outdoor Intake/Introduction; are you referring to infiltration, natural ventilation, mechanical ventilation, or outdoor air being sucked into the airloop?
See here for the Lights input object: https://bigladdersoftware.com/epx/docs/9-5/input-output-reference/group-internal-gains-people-lights-other.html#lights-000
For lighting power density (LPD) during AC vs non-AC hours, you will need to have two separate lighting objects in the IDF. "you can use multiple Lights statements for a zone that has two or more general lighting systems that differ in design level, schedule, etc."
Similarly to the people object, you will specify a design/nominal LPD that is multiplied by the schedule value to give the instantaneous LPD at a given timestep. "The electrical input for lighting in a particular timestep is the product of the design level and the value of this schedule in that timestep."
Lighting Power Density (LPD) is defined as watts of lighting per square foot of room floor area (W/sf).
To specify a fixed design/nominal LPD value [W/m^2], use the option Watts/Area in the field Design Level Calculation Method.
https://bigladdersoftware.com/epx/docs/9-5/input-output-reference/group-internal-gains-people-lights-other.html#field-design-level-calculation-method.
and specify the numeric LPD value in the Field: Watts per Zone Floor Area
https://bigladdersoftware.com/epx/docs/9-5/input-output-reference/group-internal-gains-people-lights-other.html#field-watts-per-zone-floor-area.
You will likely find a similar pattern for Plug Load Heat Gain during AC hours, Plug Load Heat Gain during none AC hours.
https://bigladdersoftware.com/epx/docs/9-5/input-output-reference/group-internal-gains-people-lights-other.html#electricequipment
As before, there is a schedule value at a given timestep that is multiplied by the design level wattage to calculate the instantaneous electric equipment power in that thermal zone.
This part of the documentation details how heat gains are calculated from the electric equipment wattage: https://bigladdersoftware.com/epx/docs/9-5/input-output-reference/group-internal-gains-people-lights-other.html#heat-gains-from-electric-equipment.
Maximum Supply Air Temperatures (SAT) and Fan Efficiency I believe can be specified in some HVAC input objects.
I suggest looking in the EnergyPlus Input Output (I-O) Reference and Engineering Reference for more details or to answer further questions.
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