Delivery and performance of a ventilative cooling strategy: the demonstration case of a shopping centre in Trondheim, Norway

Nearly all retail locations use mechanical cooling systems to ensure indoor comfort temperatures and mechanical ventilation to ensure adequate air exchange, primarily for hygienic reasons. Because of the big volumes involved and the lack of knowledge in natural ventilation design, shopping centres designers have been relying on basic HVAC equipment, without considering the potential of ventilative cooling to reduce cooling needs and to maintain an acceptable indoor environmental quality.
The CommONEnergy FP7 project investigated the retrofit opportunities to exploit ventilative cooling in shopping centres’ common areas (shop galleries and atria) considering external climate conditions and architectural features. The paper presents the development and demonstration of a ventilative cooling strategy in the demo case located in Trondheim (Norway). The strategy combines the effect of opened sliding doors and skylight openings to enhance stack ventilation and ventilate/cool the common areas and thus to reduce fan operation time. In order to prevent cold draughts, skylights windows groups are controlled separately and the opening angle of the skylight windows is modulated according to the outdoor temperature and the indoor temperatures as measured by sensors distributed within the common areas. The control strategy was first tested on the building energy simulation model coupled with an airflow model, then implemented in the integrated Building Energy Management System (iBEMS). The building energy model supported the monitoring based-commissioning phase by providing a set of benchmarking scenarios.
Thanks to the ventilative cooling solution, the total electricity consumption for heating, cooling and ventilation of the common areas over the whole reference year is predicted to reduce by an 11%. Simulation results also showed that, with the defined control strategy, natural ventilation is effective in providing the minimum required air change rates for 98% of its activation time and to provide acceptable indoor environmental quality.
The proposed solution is active in the shopping centre since summer 2016. First monitored data showed that, when natural ventilation is activated, indoor temperatures stay below 26°C. When natural ventilation is not activated, indoor temperatures can increase up to 28°C. The first measured data clearly highlighted room for improvement of the implemented control strategy and continuous commissioning is ongoing.