Energy efficiency in shopping malls. Energy use and indoor climate.

Licentiate thesis, 2010

The purpose of this licentiate thesis is to describe energy use, heating and cooling demands and the relative importance of internal heat loads in shopping malls. It will be a foundation for a future doctorial thesis in which alternative energy efficient HVAC systems for shopping malls will be analysed. A shopping mall, as defined in this study, is a large shopping centre entirely within a roofed structure, controlled by a limited number of entrances. Stores and other services are only accessible via interior corridors. This thesis is based on information collection (literature reviews, interviews, collection of energy statistics and structuring of information) and a case study of an existing shopping mall (simulations and field measurements). There are countless studies covering energy use in complex buildings in general, but there are only a few published scientific papers on shopping malls. Results from interviews list the design factors that are considered to be of importance today in Sweden. To this date little statistic has been published on energy use in shopping malls. The Swedish national energy statistics reports energy use in retail, but excludes energy use in shopping malls. This is partly compensated by the recent Stil2 study which covers energy use in 30 shopping malls. This thesis contributes to this statistical foundation by covering purchased energy use for 41 shopping malls in Sweden and Norway. According to Stil2 the total purchased energy in shopping malls average 262 kWh/m2/year. The corresponding figure for the 41 studied shopping malls were 279 and 291 kWh/m2/year for Sweden and Norway respectively. There are significant differences in purchased energy between shopping malls, ranging between 162-545 kWh/m2/year. This large deviation and the fact that the number of shopping malls is increasing proves the importance of further work. In available energy statistics there are inconsistencies in use of notations, which is discussed in the thesis. During collection of energy statistics it has been evident that there are few shopping malls with well thought-out measurement systems. Purchased energy is always known but there are fewer measurements on how energy is distributed between functions in the building. Use of free cooling and heat recovery are rarely quantified. The first goal for future energy efficiency measures should be to reduce energy demand. Results from simulations show that decreasing the use of lighting provides a great potential for savings. If purchased energy for lighting is decreased it will result in a twofold gain, since less energy is needed for removal of surplus heat. After demands have been reduced new alternative HVAC systems can be designed and adjusted to increase energy efficiency. Due to the characteristics of the heating and cooling demands, HVAC systems with energy storage between day and night, i.e. night time ventilation, and seasonal energy storage, i.e. Borehole Thermal Energy Storage (BTES), are appealing to investigate.