Inverter Speed Control of Fans Could Save the Planet
26 August 2010
While many of the low-cost energy-saving measures being implemented today are the equivalent of rearranging the deckchairs on the Titanic, vast amounts of energy are being wasted across the planet by the simple expedient of over-sizing industrial and HVAC fans, which absorb an estimated 25% of industrial energy globally.
For many years, the 'lets make it big enough to be sure' approach has led to the output of most large centrifugal fans being controlled down by low-cost, high maintenance inlet and outlet vane controls. A much more sensible approach is to specify a high efficiency fan and size it correctly in the first place. Selecting any old off-the-peg fan means provisioning the next size bigger than that demanded by the process and that means inbuilt inefficiency right from the start. Halifax Fan has taken the bespoke approach and, working with the client, designs every fan to the precise fit of the application. Its fans, at full speed, are designed for the highest possible efficiency, so that's one aspect of over-sizing taken out of the equation. A standard off-the-shelf 220kW fan might typically be as much as 10% less efficient than one of Halifax's bespoke fans. Based upon current energy costs and 24/7 operation, that would account for around £20,000 extra running costs per year. However, the client's design specification may itself call for greater future capacity which means that for operation today, that fan is still oversized and needs to be controlled. The affinity laws by which fans operate mean that, in round terms, a speed and volume reduction of 20% will mean a power requirement of just 50% of the full speed power requirement. For this reason, speed control with its huge energy savings is the ideal method of trimming fan output. The alternative is damper control of some sort at a lower capital cost but this achieves a very small power reduction at reduced throughput compared to the vast savings from speed control. Inverters have become progressively cheaper while energy has, and will continue to become, more expensive, so inverter control of a high efficiency motor is the perfect solution.It's for this reason that Halifax Fan recommends inverter speed control where fan control is required, and has supplied many inverter driven fan systems across the globe. Fitting vane control to large fans is immensely wasteful and the worst kind of false economy. The difference in initial cost between inverter control and vane control would certainly be recouped within the first year of operation and in many cases, a much shorter time. Halifax Fan has proved this time and time again and with global warming and the need to cut our energy usage and carbon footprints, applying inverter speed control is the responsible, as well as the sound economic solution, to fan control.
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