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Giant speed-controlled fans help to cut heating bills

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Mitsubishi has supplied an innovative control system to enable Wardle Storeys to operate three 7.3m diameter fans and save energy.

Giant speed-controlled fans help to cut heating billsA set of three 7.3m (24ft) diameter NASA-inspired fans is proving effective at saving energy for specialist materials manufacturer Wardle Storeys at its manufacturing facility in Earby, Lancashire. One of the keys to the system's success is the innovative control system supplied by Mitsubishi, ensuring the fan always runs at the optimum speed.

Fans are often regarded as excessive energy users rather than energy savers, but companies using MegaFan's 24ft HVLS (high-volume, low-speed) fans are reporting savings in excess of 50 per cent on their gas bills in the winter. Said to be capable of replacing up to 25 conventional fans, yet costing the same to run as one, the HVLS fan draws on a NASA-developed aerofoil blade design and takes into account the physical laws of air movement that conventional fan designs ignore.

Traditional small fans run at high speeds, using the speed itself to increase air displacement. But what the developers of HVLS fans realised was that, when it comes to the effective movement of air around a building, the displacement – the volume of air that is actually moved through the fan – is of no real significance. Instead, it is the down-stream effects that are important.

A turbulent, high velocity air jet dissipates very quickly, so can only have very local effects. In contrast, MegaFan's HVLS fan is designed to run at low speed, recirculating the huge reservoirs of hot air that frequently get trapped high in large buildings and warehouses, unable to escape. The developers of the HVLS fans recognised the energy-saving potential of recirculating this warm air that would otherwise be wasted.

HVLS fans use an aerofoil blade design that has the physical properties needed to maximise its ability to capture and circulate large volumes of air. The air output velocity was carefully calculated to optimise the air movement effects.

Example application

So what does this all mean in practice? A case in point is Wardle Storeys' manufacturing facility in Earby, Lancashire. Wardle Storeys is a world leader in the manufacture of specialist technical foils, acoustic materials, fabricated components and related products. These products are used across a wide spread of markets, including automotive, contract upholstery, building and construction, medical and stationery.

A recent project saw three HVLS fans installed at the Earby facility. The fan assemblies were clamped to an RSJ, with power taken from a busbar and a communication cable running between the fans and the control panel. The control panel itself was developed by MegaFan and Mitsubishi, allowing the variabl- speed drives on each fan to be individually controlled, with speed and direction adjusted as required.

The control panel features a touch-screen HMI from Mitsubishi's E1000 range, giving easy operation and visualisation of the fan network. The HMI has a high-resolution TFT display and a touch-screen interface, giving operators direct access to all the fan functions.

In winter, setting the fans to run at a low speed of around 30rpm draws vast quantities of warm air into the fan from reservoirs trapped in the ceiling, and gently pushes that air downwards. Wardle Storeys says it was able to reduce thermostat settings by 4degC and switch off one-third of the heaters in the building, while still maintaining a comfortable working environment. This energy saving contributes to direct cost savings in the heating bill.

Furthermore, in the summer months, increasing the fan speed to around 54rpm generates a pleasant cooling breeze, unlike the localised, intrusive blasts of air from conventional, smaller fans.

Innovative and effective

Mitsubishi Electric energy spokesman Jeff Whiting comments: "One of the biggest challenges facing industry today is rising energy costs. This can have significant negative impact on a company's financial performance, biting deeply into hard-earned profits – and all at a time when shareholders are demanding ever better returns on their investment.

"One of the ways of reacting to this challenge is through both innovative thinking and effective technologies. The installation at Wardle Storeys shows exactly what can be done."

The installation at Wardle Storeys shows how the combination of MegaFan's HVLS fans and Mitsubishi's control systems makes good business sense for companies, enabling them to increase the comfort of workers while at the same time significantly reducing their energy bills. Savings of 50 per cent in energy bills are regularly reported, and one study showed up to 84 per cent energy savings when an HVLS fan was compared to five conventional fans. Despite its size, the HVLS fan is said to be economical to buy and inexpensive to run. While the fan itself may be large, the motors running them are certainly not, as they are rated below 1.5kW.

01 August 2008

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