Carbon dioxide as coolant
The scientists have also optimized the choice of refrigerant, the agent which serves to absorb heat and transport it to the chilled areas. However between 5 and 15% of the refrigerant leaks out of any system annually. Conventional refrigerants have a high global warming potential, in other words, they contribute to heating the atmosphere. For this reason, the scientists utilized carbon dioxide, which has a global warming potential 3000 to 4000 times less than conventional refrigerants. Up until now, carbon dioxide has rarely been used as a refrigerant as the system must withstand high pressures. Moreover, the efficiency of the system is reduced during hot summer days. In order to compensate for losses at high ambient air temperatures, the experts integrated a third cooling stage in collaboration with their colleagues from Hafner-Muschler. When the sun beats down from the sky, the refrigerant is sub-cooled via a geothermal heat exchanger.
Lighting makes up the second largest share of the electricity bill. For this reason the scientists employ daylight to illuminate large stores. Light enters the store via triple-glazed skylights. A microscreen is fitted between the individual panes of glass to reflect direct sunlight which allows only indirect light to pass through. Artificial light in the form of lamps is additionally switched on and controlled in relation to the available daylight.
"Part of our concept has already been implemented by Aldi Sd in their new buildings. This enabled 20% energy savings to be achieved during the first year of operation", explains Rhault. "New control strategies have now enabled us to optimize these concept co
|Contact: Nicolas Rhault |