When a major animal feed manufacturer, employing 200 people across Britain and producing over 34,000 tonnes of product every year from its Merseyside plant, explored energy saving opportunities, the first company contacted was Rewinds & J. Windsor, an Official Drives Partner for Control Techniques inverters.
Electricity consumption at the plant was close to £94,000 (€110,000) per year and as prices are to rise even further, the company tasked RJW with a site wide, energy reduction survey.
Following the survey, twelve motors and motor/fan units were identified as offering potentially the greatest payback, this according to the cost analysis software specially written by Control Techniques.
Once go-ahead was given, twelve 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 therefore 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% (which is usually possible) 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 (ca€16,000) investment was a £17,000 (ca€19,500) 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 (ca€90,000) 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 more quietly.
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.