Air curtains open the door to energy savings
Replacing an air curtain at a shop in Holland with an automatically controlled Biddle Invisidor CA2 air curtain has reduced energy consumption by 65% and improved comfort levels for the shop — which has an open-door trading policy. Over a 6-month period, Biddle monitored the Jensen Family Shop in Joure, which sells clothes for all ages, to find out how well the existing manually adjusted air curtain was performing, the comparable effects of having no air curtain at all, and the impact of introducing an automatically controlled Biddle Invisidor CA2 air curtain.
The front door was open for an average of 50 h a week top promote trade. The retail environment was kept at a constant temperature of 21°C. During the study, outdoor temperatures ranged from -5 to +13°C, with an average of around 7°C. A small alley opposite the store causes draughts.
The existing air curtain was found to be ineffective. It was failing to provide a comfortable retail environment and was forcing staff to close the front door on many occasions, even though they knew this would discourage passing trade.
The air-stream setting for the existing air curtain was often too weak and too hot, and a lot of heat was escaping to the outside. The equipment used an average of 41.2 MWh a year, costing €2600.
Calculations showed that removing the air curtain completely and letting heat escape naturally through convection would use less energy — 37.1 MWh a year. However, it would be difficult to sustain constant comfort levels in the shop, and there would be little protection against draughts.
Following the installation of the self-regulating Invisidor air curtain, energy consumption fell to 14.4 MWh a year, saving €1690 a year on running costs. The indoor temperature remained at the requested 21°C, and the energy savings equate to a payback within two years. It is also possible for staff to keep the doors open for an extra three months a year.
Gary Fuller of Biddle said, ‘ We have always stressed that in terms of energy consumption, a poorly designed, installed or controlled air curtain can actually be worse than not having an air curtain at all.
‘At the time of installation, an air curtain is typically set to mid-speed and rarely adjusted — so it will only be right for some of the time and wrong for a lot of the time. The automatic control on our Invisidor CA2 delivers the right airflow and temperature at the right time.’