Air handling units
Zoning in on destratification
or many facilities managers, service operators and heating engineers, the large cavernous spaces typically found in entrance halls, warehouses and manufacturing sites present a challenge in terms of ensuring effective heating of the zone of occupation. While the implementation of advanced technologies including heat pumps, solar thermal and thermal storage have helped offset the costs of generating and storing heat, latest developments in a more traditional technology are resulting in major reductions in heat usage at a fraction of the cost.
F Traditional approach
Thermal destratification, or the effective redistribution of heat and air through large spaces, isn’t new, and anyone who has visited a manufacturing site or warehouse will be aware of the large number of box fans used to recirculate air. While used widely, the effectiveness of this technology in achieving its frequently stated 15 per cent energy savings has been called into question. The concern lies with the fact that the air flow is released at an angle and spread over a wide area, rather than being directed to the area of occupation. Despite this, with a typical floor-to-ceiling differential of 10 to 20°C in high
ceilinged spaces, the ability to harness and redistribute hot air has long been seen as a key way to reduce energy consumption. As a rule of thumb, the temperature increases by 0.5 to 1°C for every metre in height. In practice this means that to achieve a temperature of 21°C at the ground, or occupied level, the ceiling of a 10m by 10m room would need to be heated in the region of 26 - 31°C. As well as reducing heating bills and wear on HVAC equipment, effective redistribution of this wasted heat energy could increase thermal comfort of workers by eliminating hot and cold spots, as well as reducing condensation on equipment through better air circulation.
Technological advances
Thankfully, through advances in the technology, it is now possible to achieve a temperature differential as low as 0.5 to 1°C from floor to ceiling and wall to wall. More importantly this has led to typical savings of 30 per cent on annual heating bills in even the most energy efficient buildings, with additional reductions in air conditioning requirements of up to 30 per cent. In the case of industries where heat is generated as part of the production process such as bakeries and printing presses, which have even more need of suitable destratification, savings of up to 50 per cent have been achieved. Overall, the greater the temperature difference from floor to ceiling, the bigger the savings. As a result destratification is now recommended as one of the Carbon Trust’s effective energy-saving strategies. The step change has been realised through optimisation of design and
operation of destratification focused towards the zone of occupancy (ZOO). The latest ZOO Fans available from Elta Group Building Services create a gentle column of hot air that is directed towards the floor. This allows previously wasted heat to be channelled to the area that it is needed most. As a result, thermostats switch off quicker and heating systems cycle off sooner, reducing
22 September 2017
Ricahrd Johnston
With potential payback periods of under two years and typical energy savings of 20 and 40 per cent, Richard Johnston, national business development manager at Elta Group Building Services, outlines why it’s time the industry took another look at destratification
The latest ZOO Fan available from Elta Group Building Services
wear and increasing the lifespan of HVAC equipment through reduced use. Additional benefits of this approach include the elimination of hot and cold spots, as well as reductions in condensation on concrete, chillers and windows, as a result of the fans delivering one air turn per hour, all of which has the added benefit of improving the comfort level for customers and employees.
Cutting costs in energy efficient buildings
The United States provides a number of good examples to UK practitioners in terms of energy savings. PespiCo’s one million square foot facility in Wytheville, Virginia is one such example. The site was Leadership in Energy and Environmental Design (LEED) Gold Rated, one of the United States’ highest energy efficiency ratings and the equivalent to the more commonly used BREEAM here in the UK. Despite also having been classed as the most energy- efficient bottling plant in the world, heating costs dropped by 30 per cent within five weeks of installing ZOO Fans, with an added productivity gain of five per cent thanks to a more comfortable working environment. Energy efficiency has been key to maximising returns. The typical
destratification fan in Elta Group Building Services’ ZOO Fans range uses the same amount of energy as a 40 or 50 watt light bulb. Compared to the higher powered motors needed to power rooftop mounted air handling units, or big plate fans conventionally used to push air through a building, destratification fans achieve a better result at a fraction of the operating cost. As the result of the
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