Cutting costs, cutting carbon

As the UK subsides gently back into recession and the economy treads water, organisations of all kinds continue the struggle to balance rising costs with static profits. Coupling escalating energy costs with the unrelenting pressure from the CRC EES and other initiatives to meet energy targets, it’s no wonder that equipment with the potential to reduce both costs and carbon is looking increasingly attractive. Phil Chilton, Commercial Product Manager at Dimplex, explains why air curtains fit the bill perfectly.

With the first CRC EES performance league table published in November 2011, the much-vaunted transparency of the scheme is now in effect, with the best (and worst) performing organisations in the scheme listed in the public domain.

Keele University, Manchester United and National Museums Liverpool are  listed in the top-ranking companies in the CRC performance league table, showing clearly that carbon reduction and energy saving are now on the agenda for all kinds of businesses and organisations.

Although the CRC EES is currently under consultation with a view to simplifying its mechanics, there’s no closing this Pandora’s Box and measuring energy performance is now an inescapable feature of the business landscape.

Sustainability and carbon reduction has become ‘top of mind’, creating an  emphasis on carefully selected and installed products to retain energy and save carbon, enhancing building performance and improving EPC ratings.

Keeping control of costs

However, even without the obligations of the CRC EES, the pressing economic need to reduce costs wherever possible just to survive means there are great benefits to be had from installing energy saving measures like air curtains sooner, rather than later.

It’s one thing to consider the benefits of air curtains in terms of carbon saving, better building efficiency and improved building EPC rating. But it’s also key to realise the scale of the financial savings that air curtains can achieve in terms of reduced HVAC running costs, making them an extremely cost effective investment.

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’.

Air curtains have historically been viewed as primarily used in the retail sector, where they create a comfortable environment with a view to encouraging trade. To a certain extent, this has often been the case, since for retail premises, open doorways are one of the biggest challenges. Constantly-opening doorways 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 heating systems by an industry-recognised 30%, as well as creating a more comfortable internal environment.

Carbon saving

However, it’s estimated that around 40% of carbon emissions in Europe come from the commercial building stock, and carbon saving is now of key importance across the board. As a result, the potential of air curtains to cut energy use by retaining treated air is being recognised in all kinds of applications outside of retail, where people movement can substantially affect building performance.

Air curtains have been viewed in the past as a ‘nice to have’ add-on aimed primarily at improving indoor comfort. However, we need to reassess this outdated notion. Used in conjunction with other energy saving measures, air curtains can 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.

In the past, one of the main problems lay in the fact that a simple switching mechanism often left it to the user to turn the equipment off, leading to wasted energy.

But 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.

Control leads to savings

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. 

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 are ready to integrate easily with a BEMS system.

It’s also 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.

If you look at this improvement in energy performance in terms of cold hard cash, payback periods on investment in carefully selected air curtains are surprisingly short. Based on the industry-recognised 30% energy reduction, the payback on installing air curtains can often be measured in terms of months, rather than years, after which the savings in terms of reduced energy bills will continue to stack up. And there are not many forms of investment out there these days offering that kind of return on investment.

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.

Minimal energy usage

For the ten day test period during spring, the thermostat was set to 21.5°C to achieve an average internal temperature of 20°C. With external temperatures varying from 12-17°C, on some days there was no requirement for additional heat to bring the internal temperature up to 20°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 £96.00 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.

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