In urban non-residential buildings air-conditioning systems are generally required to achieve acceptable air quality. To reduce the energy demand of HVAC-plants free cooling is proposed. The present study deals with free cooling by outdoor air (untreated or additionally cooled by evaporation) during the night. Therefore a sufficient building mass (about 600 to 800 kg/m²) is necessary which stores the heat produced in daytime and which is cooled down at night. In most conventional non-residential buildings, however, the building mass is at about 400 to 600 kg/m².
Ventilation is necessary to insure acceptable indoor air quality as well as to protect the building itself against damage due to condensation Ventilation rates however, must not lead to excessive energy consumption In order to comply with these requirements of hygiene, comfort and energy savings, French regulations stipulate that the ventilation of dwellings has to be general and continuous and achieved by specific systems by which fresh air is provided to the dwellings.
Designing a comfortable inside climate for office buildings to operate within comfort limits (PMV+/-0.5) requires a flexible operating strategy. Two systems a VAV and a VHV are identified and compared to each other. Dynamic simulation techniques are used to obtain an optimal design, based upon comfort conditions not temperatures. The control strategies are optimised to minimize energy consumption while controlling the HVAC system to remain within comfort limits in the occupied zone.
Total energy exchangers with a rotating heat storing matrix have been applied to air conditioning systems for more than 25 years with very good results for saving both heating and cooling energy. The efficiency of the hygroscopic coating of the rotors is very important to recover the latent energy, but there is the risk of cross contamination. To prevent odour transfer, the mechanism of the sorption and desorption process has to be investigated in detail.
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