Energy Optimised Heating/cooling Curves HVAC Systems in Air Conditioned Offices

Session 17 Paper 2, CIBSE Technical Symposium, Liverpool John Moores University, Liverpool
11-12 April 2013

Modern air conditioned office buildings which comply with the EPBD standards don’t perform as energy efficiently as expected. The majority of such buildings already show a cooling demand at low environmental temperatures (5ºC) coinciding with high indoor temperatures during the intermediate season (the period between high summer and deep winter). During the intermediate season air supply temperatures are too high in many existing buildings. This results in concurrent energy demand for heating at the whole building level and for cooling at the room level. Using energy to simultaneously heat and cool is unnecessarily wasteful. A five step methodology has been developed to optimise air supply temperatures in order to prevent concurrent heating and cooling; this results in 5 to 25% less energy consumption for heating and cooling and enhanced thermal comfort. The method does not require additional investment in hardware and can be applied to both new and existing buildings. Several case studies have shown an energy saving potential of up to 25%. Heating and cooling demand as a function of the environmental temperature is central to the methodology. For new buildings, this can be obtained from dynamic building simulation calculations. For existing buildings, this information comes from building energy management systems. The methodology determines at which outside temperatures the air supply temperatures can be lowered in order to prevent simultaneous heating and cooling. The methodology is applicable to most HVAC systems.