Monitoring the energy performance in the tertiary building sector is challenging, especially in large-scale retail chain. In Italy, since the beginning of 2012, shops could stay open 24 hours per day, 7 days per week. This had a huge impact on large scale retail chains. Actually, the shops are opened 7 days per week from 9:00 AM to 9:00 PM. This means that the energy efficiency potential in this sector is particularly high.
The results shown have arisen from the data monitoring of ten buildings. Systems monitored are the HVAC system, lighting, positive temperature and negative temperature cooling cabinets. The main sale area has refrigerated cabinets served by two centralized systems. Both systems have reciprocating electric compressors and are air condensed.
The buildings analyzed are served by all-air HVAC system based on rooftop units. Some buildings have gas boilers and air condensed chillers which respectively provide hot and cold water to the rooftop heat exchangers. In some case the rooftops have a gas boiler and an electric chiller onboard.
Yearly data show a moderate variability of global electric specific consumption among the different shops. The variability is high for HVAC and other systems, demonstrating that electric consumption could not be forecasted just based on square meter of sales area (other typical factors affecting consumption are occupation, climatic conditions and internal loads).
Monthly consumption analysis shows different behaviors for specific loads, depending on climatic conditions and working days. The lighting consumption shows an almost constant trend, demonstrating that the buildings analyzed do not have automatic control of light flux. Since the average consumption is about 86 kWh/m2 per year, the possibility to dimmer the lighting power in accordance with measured light intensity has to be evaluated. HVAC system consumption shows the highest variability, as expected, demonstrating that the systems control are working at least sufficiently, decreasing the consumption during the middle season. Two of the buildings analyzed show exceptionally high consumption during summer. The high consumption is related to the specific condition of the chiller units, which suggests an inspection and verification.
Lighting systems have shown in some shops an ineffective control during nights, as seen in figure below. Energy analysis requires hourly monitoring data to focus on the most promising energy efficiency measures.