Inverter technology controls airflow and saves energy
05 July 2011
When a major animal feed manufacturer, employing 200 people across the UK and producing over 34,000 tonnes of product every year, explored energy saving opportunities, it contacted Rewinds & J. Windsor, an official drives partner for Control Techniques inverters.
Electricity consumption at the plant was close to £94,000 per year and as prices are to rise even further, the company tasked RJW with a site wide, energy reduction survey.
Following the survey, 12 motors and motor/fan units were identified as potentially offering the greatest payback, according to the cost analysis software specially written by Control Techniques.
Once go-ahead was given, 12 drive panels containing ‘Commander SK’ inverters were built at RJW’s panel building department and installed by the company’s site installation team. The drives varied in size from 5.5kW to 37kW with an average size of 15kW.
By using inverter drives instead of other methods of controlling airflow, it was possible to reduce the speed of the motors running the fans and save the energy used in powering the motors. The saving made is equivalent to the square of the speed reduction, meaning that a speed reduction of only 20% creates close to a 50% energy reduction!
Significant results have been shown following a suitable period for analysis. The initial saving from the £14,000 investment was a £17,000 reduction in electricity costs, within a payback period of less than one year! This matched the payback calculations made by RJW during the planning phase of the project.
This relatively small investment has had a noticeable effect on the electricity usage for the plant as a whole, reducing consumption to £77,000 and lowering the cost per tonne of end product by 18%.
Additional benefits have been reported by the site’s engineers with greater plant reliability attributed to the introduction of the drives, which in turn has created maintenance savings with reduced downtime. The local environment has also benefitted with machines running a lot quieter.
With a boost in production planned for this year, plant energy efficiency gains per unit of product are expected to be even greater than before, whilst modifying the inevitable rise in electricity costs.
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