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Raising the curtain on big potential energy savings

Energy-saving equipment is high on the wish-list of most retailers, says Phil Chilton, and air curtains offer a great opportunity for installers to help their customers reduce energy bills
After a poor summer's trading thanks to the British weather and with energy prices on the rise again, any business or organisation wanting to keep an eye on running costs will be interested in ideas to reduce their fuel bills. The CRC Energy Efficiency Scheme has driven energy management for businesses for some years now, but these days straightforward economic pressures are creating more of an imperative to reduce costs, irrespective of the scheme's carbon reduction requirements.

For example, under the scheme, the carbon permit required to use the roughly 2000kWh of electricity which generates a tonne of CO2 costs £12; this electricity might cost around £200. Avoiding consumption of that electricity in the first place is always going to make a substantial saving on fuel bills, regardless of any impact from the CRC EES's 'carbon tax'. Installers can help commercial customers address building performance by giving them ideas to help keep tabs on running costs, and air curtains tick the energy-saving box perfectly.

In the past air curtains have frequently been regarded as net users of energy, in effect a large over-door heater for the purpose of improving user comfort. However, used in conjunction with other energy saving measures, air curtains can in fact make a very substantial contribution to energy losses through open doors and in fact should be regarded as net savers of energy, and an integral part of the solution to the challenge of improving building performance.

For all kinds of commercial premises, open doorways are one of the biggest challenges. Constantly-opening doors with high footfall, or doors that remain open to welcome customers, mean that expensively heated or cooled air is constantly being lost. 'Sealing' the gap with an air curtain can cut the costs of air conditioning and of heating systems by an industry-recognised 30 per cent, as well as creating a more comfortable internal environment. These kinds of savings give payback periods which can often be measured in months, rather than years, so these energy-saving units are an increasingly 'easy sell' to commercial customers.

Air curtains are able to achieve these significant energy reductions thanks to the advanced level of control offered by today's equipment. In the past, often a simple switching mechanism left it to the user to turn the equipment off, leading to wasted energy.

But some of today's air curtains incorporate the most recent technological advancements, moving away from simple on-board switching and control to a fully integrated air curtain that can be controlled directly by the BEMS system and/or controlled locally, according to door usage. Integrating the air curtain in this way can add considerably to the sustainable performance of the building as a whole, reducing running costs for the user and giving the installer a more challenging job.

Timing, temperature and airflow can be controlled automatically to maximise savings; for example, it's obvious that air curtains operate most economically when used on an 'ambient' setting, i.e. no heating or chilling of the air passing through the unit, and more much of the year this setting will be perfectly adequate to effectively 'seal' the doorway from draughts.

When specifying, look for products that allow automatic control and optimisation either centrally or locally via auto door controls - the best units will have these built in as standard, and ready to integrate easily with a BEMS system.

Additionally, it sounds obvious, but it's worth mentioning that air curtain efficiency and therefore savings are maximised when the equipment is correctly installed, covering the entire width of the doorway. Any gaps at the edges of the airstream where draughts can enter the premises will substantially reduce both efficiency and user comfort, so ensure when specifying that full coverage is achieved.

As the slow economy drags on, yet costs across the board continue to rise, commercial customers are very open to ways to cut energy consumption. Air curtains offer a fast return on investment, so there's a real opportunity for installers to switch their customers on to the cost cutting potential of these energy savers.

Air curtains in action

A greetings card retail outlet near Southampton noticed immediate benefits from the installation of a Dimplex CAB 1.5m air curtain.

The store's existing 12kW unit operated constantly during opening times - at least eight hours a day. It was replaced by a Dimplex unit, installed to cover the entire width of the entrance and set for automatic selection of its 'Eco' mode, and the default ambient setting, i.e. no heat. The thermostatically-controlled heating capability was only activated if the internal temperature dropped below the desired temperature.

For the 10-day test period during spring, the thermostat was set to 21.5 deg C to achieve an average internal temperature of 20 deg C. With external temperatures varying from 12-17 deg C, on some days there was no requirement for additional heat to bring the internal temperature up to 20 deg C. In fact, on six of the ten days, the air curtain operated entirely on its ambient setting, effectively keeping draughts and external pollution out of the retail unit, but with minimal energy usage.

Energy costs for the test period were estimated at £13.50 (based on £0.10 per kWh), compared with the £96, which the previous 12kW air curtain would have used. In terms of carbon emissions, based on an industry standard 0.51kg CO2/kWh, the Dimplex air curtain delivered a massive carbon saving of 420.8kg over the ten-day test period, with emissions of just 68.9kg compared with an estimated 489.6kg from the previous 12kW air curtain.

// The author is commercial product manager at Dimplex //
8 November 2012


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