32 n ENERGY EFFICIENCY September 2025 www.drivesncontrols.com Upgrading quarry exhaust fan cuts its energy use by 38% Aquarry and asphalt manufacturer was looking for opportunities to save energy across its operation. A site-wide assessment quickly identified a key culprit: an exhaust fan system that was vital for maintaining vacuum pressure inside a dryer. The fan was operating consistently at full speed, regardless of the actual demand, resulting in excess energy consumption, adding unnecessary costs to every hour of operation. The quarry operator turned to the Northern Irish systems integrator, Technidrive, which saw an opportunity to introduce smarter, more dynamic control. Based on the square-cube law – the principle that slight reductions in speed can reduce energy use dramatically – Technidrive predicted substantial improvements. For instance, lowering the fan speed by just 10% would cut energy consumption by more than 27%. “The potential savings were immediately clear once we conducted the calculations,” explains Technidrive’s technical director, David Strain. “Our detailed analysis showed us how small adjustments to the fan speed could lead to significant reductions in energy use. It was clear that with smarter control, the quarry could achieve both immediate and long-term efficiency gains, while reducing operational costs." Technidrive installed a WEG CFW500 VSD (variable-speed drive) to adjust the fan’s speed in real time. The drive was able to match the fan’s performance to the precise vacuum requirements of the dryer. At the same time, the fan’s motor was upgraded to a 110kW W22 model, also from WEG. This motor has an IE4 energy efficiency rating, further boosting the potential for energy savings. While the concept was straightforward, implementation posed challenges. Stabilising the vacuum pressure required meticulous tuning of the PID control loop that governs the fan’s speed based on realtime pressure data. During initial tests, the pressure levels swung unpredictably. After extensive adjustments, the system was fine-tuned to perform with the consistency required. “Stabilising the vacuum pressure was like trying to set the cruise control in a car,” Strain explains. “At first, the system would surge and dip – much like a car speeding up and slowing down unpredictably. It took careful tuning to smooth out those fluctuations and achieve the consistent, steady performance we needed. Once we got it right, the system maintained the required vacuum pressure with precision, delivering the efficiency gains we promised.” To measure the impact of the new system, Technidrive conducted three evaluations using an energy cost of €0.27/kWh as the baseline. The first method was a straightforward comparison of the total energy consumed during a week, without variables such as the fan runtime or production output. Over the course of a week, the energy consumption fell from 4,974kWh to 3,900kWh – a 22% reduction, demonstrating a potential annual saving of more than €15,000. The second approach focused on energy cost per tonne of material processed, drawing on batch records to ensure accuracy. This revealed a 19% reduction, from €0.31 to €0.25 per tonne of material. Finally, the most significant efficiency gains were seen when analysing the energy use per hour of fan operation. A 38% reduction – from 96.02kWh to 59.72kWh per hour – translated to annual savings of more than €30,500. “From the outset, our focus was on identifying opportunities where engineering precision could drive savings,” Strain explains. “Through detailed consultations and extensive data collection, we demonstrated how even modest reductions in fan speed could yield dramatic energy savings. Our engineering expertise allowed us to translate these findings into a practical, highly efficient solution. What’s more, not only did these changes slash costs, but they also cut CO2 emissions by 757kg per year.” n A survey of energy-saving opportunities at a quarry revealed an exhaust fan system that was needlessly consuming energy at full throttle. By replacing the fan motor with a more efficient model controlled by a VSD, energy consumption was cut by 38%, saving more than €30,500 annually. Upgrading the efficiency of a fan drive system at a quarry is saving more than €30,500 a year.
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