Energy Modeling

Energy Modeling Glossary

Air Handling Unit

Air handling unit, often abbreviated AHU is a device that provides air treatment combined with air movement for an HVAC system. Air movement is generated via fan power contained in the AHU. The AHU usually feeds the ductwork on a building. They are often "packaged" to contain heating coils, cooling coils, compressors, and a heat source as well (which would be a self contained unit). They may also contain an airside energy recovery device. They are often found on rooftops of buildings and also in mechanical rooms.

Ambient

The ambient conditions are the conditions outside. This includes temperature, humidity, and solar heat gain

Block Load

The block load is the simultaneous load on a set of rooms, zones or systems at  a specific time.

Chilled Beams

A system type that uses pipes containing chilled water to passively cool a room. (There are passive and active chilled beams). The net goal of chilled beams is to save fan energy. It should be noted that chilled beams require very careful humidity balancing, or condensate will form on the chilled beams resulting in unwanted water accumulation in a space (In plain speach: be careful or you might make it rain inside)

Chiller

A chiller is a device that produces cold water via a refrigeration cycle. Typically, they are air cooled, or water cooled. In an air cooled chiller, the condensers are cooled by fans. In water cooled chillers, the condenser is cooled by water from a cooling tower.

Consumption

The total amount of fuel consumed over a period of time

Cooling tower

A device that cools water via exposure to ambient air. In a cooling tower, water is poured along stages, while air is blown across the water, which via evaporation - cools the water which is sent to cool a condenser

COP

COP is also the Coefficient of performance. It is a unit-less measurement of efficiency that represents the amount of cooling (energy displaced) divided by the amount of energy consumed. A higher COP means that a device is more efficient

CV - Constant Volume

In HVAC, Constant volume refers to a system type where the airflow is constant. In a CV system, the amount of heating or cooling is adjusted by the supply temperature of the air

Daylighting

Also known as "Daylight Harvesting", daylighting is an electric control strategy that effectively dims the electric lights when more sunlight is let in the room. To speak plainly, the goal is to maintain a consistent brightness at a location. Sensors are required for this to measure the brightness or what is technically called the luminous intensity. These sensors typically measure the luminous intensity at desk level (approximately 2.5-3 feet). Daylighting has a direct savings on lighting, and an indirect savings on air conditioning, as well as fan energy in VAV systems.