Published on 1 - November - 2007
How to use energy more efficiently
From Blue Peter to G8 summits, the energy question is constantly under discussion. UK industry is deemed to have a key role to play in reducing the national carbon footprint
BA's cargo centre is fitted with responsive air curtains
- exactly how it will achieve the energy savings targets is less clear. Keith Sprague of AmbiRad offers a practical guide to heating premises more efficiently
THE energy:carbon reduction equation is simple - reduce one and the other will follow in direct proportion. Achieving this cost effectively is another matter.
Defra says: "The most cost-effective way of reducing emissions is to use energy more efficiently." But exactly how individual businesses can implement the energy saving measures demanded by the EU and UK government requires further investigation - and this is where some companies drag their heels.
Why? Because, as Defra points out, for industries struggling to be competitive in global markets, "energy saving is rarely core business". Competing priorities are often a significant barrier, as are hidden costs, such as management time, finance and lack of information.
Working with UK industry, AmbiRad has learned two key points: there is an overwhelming will among businesses to save energy; and they need a complete view of energy reduction options relating to each of the building services.
Energy reduction in heating is relatively straightforward. The range of high-efficiency heaters now available is huge, with performance levels of 92%+ thermal efficiency.
The types of heating include:
Direct-fired warm air
Indirect-fired warm air
Air curtains - not strictly heaters, but a crucial support to building energy management
Radiant tube heating is arguably the most energy efficient type of large-space heating. All fuel consumed is burnt at the point of use with none of the heat losses associated with remote boiler plants.
Radiant heaters are positioned overhead in the roof cavity, usually at several metres above the working area. The burner fires into a tube which emits the heat as infra-red rays. Like the sun, the rays heat only what they touch - people, objects and (to a lesser extent) the building fabric. No energy is wasted heating the volume of air in the building and all the heat is focused where required.
Proven energy savings in heating decentralisation projects, where radiant is used to replace a failing steam-fed radiator system, have been in the order of 25-60%.
This year, AmbiRad has launched the Vision range, with NOx emissions around 40% lower than standard radiant heaters. A recuperative heat exchanger boosts thermal efficiency to 90% and radiant efficiency above 50%
Vision heaters were selected by pump manufacturer Gardner Denver Nash. Cost predictions indicated that replacement of the existing heating system with eight 50kW output VSX radiant heaters from AmbiRad, zoned across the large building and controlled by a SmartCom control panel, would have significant impact on comfort, economy and operating costs. The company is already seeing significantly reduced fuel bills.
Warm air comfort
Indirect- and direct-fired warm air systems can be externally or internally mounted to provide economic heating with ventilation if required. This is particularly useful where the process has airborne by-products, such as oil or welding haze, that compromise air quality.
An additional advantage of warm-air heaters is that they can be configured to reuse previously heated air, drawing it back into the unit from the interior. Systems may either mix the heated air with fresh air and recirculate it, or transfer the heat via a heat exchanger to reuse up to 60% of the reclaimed heat.
Futaba Industrial installed 25 Reznor indirect gas-fired warm-air heaters at its factory to provide warmth and fresh-air ventilation with free summer cooling. A combination of Reznor Europak PV and T2000E high-efficiency heaters was fitted. Room-sealed units were used to ensure separation of the combustion process from the heated space - an ideal solution where dust, draughts, negative pressure or non-corrosive contaminants are present.
Direct-fired gas heaters produce a slight pressurisation within the building, forcing a mix of the heated air with room air for even heat distribution and prevention of draughts - both of which can contribute to long-term energy efficiency.
At Bosch's state-of-the-art distribution warehouse in Kettering, Nordair-Niche heaters provide background heating and frost protection, using the air rotation principle. Two 300kW floor-standing heaters draw in cooler air at floor level and discharge it at high level across the building, forcing an effective mix with warmer air and forcing it down to lower levels. The results is gentle airflow and temperature destratification.
Air curtains, such as the Airbloc units, are a crucial element in the overall building energy management picture, capable of maintaining internal warmth by keeping out winds of up to 11mph.
Air curtains may be heated or ambient. Positioned across or down the side of doorways that will be regularly opened, the air curtain delivers a sheet of air that effectively separates the internal and external environments. Tests have shown that the temperature inside the doorway drops by just 1°C when an air curtain is operating, but by up to 10°C without it. The heating system must over-work to compensate for such a dramatic heat loss.
Occasionally, air curtains are used to supplement the building's heating. British Airways opted for this solution at its Heathrow cargo centre. The 15 air curtains over the loading bay doors operate at full heat when the doors are open, automatically switching to low speed when they are closed again. This maintains economical operation of both the air curtains and the heating system.
Improvements in energy efficiency will only happen if everyone takes action. Industry, as a major consumer of energy, has a key role to play. With straightforward guidance from manufacturers, added to the financial and other incentives offered by government, significant energy savings, and therefore carbon reduction, are achievable.