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What input is needed?

Zone usage data

“Zone usage data” refers to all data that depends on how the interior space of the zone is used. This includes

• the internal boundary conditions (heat, humidity, or CO₂ sources) to which the zone is exposed
• thermal properties of the zone (thermal masses) that are not modeled elsewhere
• the requirements for comfort conditions (temperature, humidity, CO₂ concentration, daylight) in the zone

Occupants

In IDA ICE, occupants are represented by a relatively simple metabolism model according to ISO 7730, that is accurate enough to describe their interaction with the interior space in a meaningful way. Depending on their clothing, activity level and room condition, a person emits sensible heat through convection, radiation and respiration, as well as latent heat through respiration, diffusion and transpiration (sweating). At normal room conditions, the emitted heat is approximately 70 W (46 W sensible and 23 W latent), but this can change dramatically up to even negative sensible heat emission at room temperatures above 37 °C.

Occupants data is

• number of people in the zone
• the schedule decribing the time course of the percentage of presence of people
• the people's activity level
• the range within which people can adjust their level of clothing to suit their comfort conditions

Sensible (left) and latent (right) heat emission of people

Equipment

Just like the occupants, the "equipment" in a zone can emit heat, humidity, and/or CO₂. However, the model is significantly simpler because the emission is predetermined and does not depend on the condition of the room. Electrical devices such as computers, refrigerators, television etc. as well as houseplants or room humidifiers can be modeled as equipment.

Equipment data is

• number of equipment units in the zone
• the schedule describing the time course of the precentage of equipment that is turned on
• the maximum heat emitted
• the energy meter measuring the used power for the equipment units
• the fraction of the heat that is emitted through longwave radiation (the other part will be emitted through convection)
• the maximum liquid water emission per unit
• the maximum dry steam emission per unit
• the maximum CO₂ emission per unit
• the proportion of all emissions that is given to the zone

Different examples for "equipment"

Lights

Lamps convert only a relatively small proportion of electricity into light, and even in the case of today's LED lamps, a larger proportion is converted directly into heat. Ultimately, the entire power consumption of artificial light is released somewhere in the room in the form of heat. For the zone model in IDA ICE it is important to take the following three proportions into account correctly:

• Convertion into light (shortwave radiation)
• Convertion into heat (convection)
• Convertion into heat (longwave radiation)

Light data is

• number of lights in the zone
• a possible control strategy for light dimming
• the schedule describing the time course of the precentage the light is swiched on
• electric power when fully swiched on
• luminous efficacy

Internal masses

An interior space is usually not just filled with air. It also contains objects such as furniture, stored goods, or partition walls. These objects give a zone additional thermal inertia by absorbing, storing and later releasing heat from/to the room. They are simplified as a wall exposed to the room, standing on both sides inside the room. 

If this model is to neglect long-wave radiation exchange because the object has no radiating surface (such as bookshelves, plants, or pallets of goods), they are considered “furniture”:

"Furniture" is modelled as a wall with two sides towards the room, thermally interacting with the room by convection only.

If long-wave radiation exchange is to be taken into account (as in the case of interior walls or slabs, especially also when several rooms are modeled as one zone), they are considered as “wall mass":

"Wall mass" is modelled as a wall with two sides towards the room, thermally interacting with the room by both convection and radiation.

Internal mass data is

• the surface area facing to the room
• the (convective) heat transfer coefficient for the area facing to the room
• the construction of a wall that represents best the object to be modelled
  (material layers with thermal conductivity, density and specific heat)
• for "Wall masses" only: Longwave emissivity of the surface facing to the room

Comfort setpoints

The comfort setpoints in a room indicate the comfort limits within which the controls in a room attempt to remain. Setpoints can be defined for:

• Room temperature
• Supply and return air flow rate
• Room air relative humidity
• Room air CO₂ concentration
• Daylight level at workplace
• Room air pressure difference relative to the outside air

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