Mechanical Engineering: Radiant Ceiling Panels Analysis

The main heating and cooling system for the ELEMENT is a variation on a “cooled ceiling” system which is most commonly used as a cooling technique for tall buildings. The system used in the ELEMENT design can theoretically be referred to as a radiant ceiling system. This incorporates ceiling panels which comprised of small tubes with refrigerant running through them. The system uses a vapor compression cycle and is almost identical to a heat pump and air conditioner unit with the exception of fans. In a typical heat pump and air conditioner system fans are used to blow air over these coils, which in turn, heats or cools the air. In the system used by the ELEMENT, the fans are removed and the air movement across the coils will occur through natural convection. In that sense, the system is similar to a traditional radiator system. Another slight difference between the standard vapor compression system and the ELEMENT heating and cooling system is that a traditional system will use a refrigerant such as R-12, R-134a or R-410a whereas the ELEMENT’s system uses CO2 as its refrigerant.
The Typical Vapor Compression Cycle

The major issue with this type of cooled ceiling technique is the possibility of condensation on the piping of the ceiling panels. To avoid an indoor rain storm, the humidity levels of the air must be closely monitored and controlled with a humidifier / dehumidifying system. In order to adhere to the strict guidelines of the Solar Decathlon competition, this monitoring must take place anyway, so this issue really becomes less of a problem. The monitoring of the heating and cooling system will also benefit several other areas of indoor comfort. For example, the ELEMENT will not have any operable windows (firstly because of an increased cost and secondly because of the poor air tightness which would result) therefore, in order to maintain a healthy Indoor Air Quality (IAQ) a Heat Recovery Ventilator (HRV) or a Energy Recovery Ventilator (ERV) will be used to supply fresh air to the house (the principle difference between the two being the HRV only transfers sensible heat while the ERV transfers latent heat as well). The main reasoning behind the decision to avoid operable windows was decreased air tightness that would result from having operable windows.