Smart exhaust fan system cuts energy use by 38%: Energy saving solution for asphalt production

When a leading quarry and asphalt manufacturer sought to uncover opportunities for energy savings across its operation, it turned to Technidrive Ltd . What started as a site-wide assessment quickly zeroed in on a key culprit: an exhaust fan system that was needlessly consuming energy at full throttle. With a combination of precise engineering and advanced technology, Technidrive engineered a solution to achieve a 38 per cent reduction in energy consumption and over €30,500 of annual savings.?

The exhaust fan is a vital component for maintaining vacuum pressure inside the dryer. However, the fan was operating at full speed consistently, regardless of the actual demand. This approach was consuming excess energy, adding unnecessary costs to every hour of operation. Technidrive saw an opportunity to introduce smarter, more dynamic control.?

Leveraging the square-cube law — the principle of how slight reductions in speed dramatically reduce the total energy use — Technidrive predicted substantial improvements. For instance, lowering the fan speed by just 10 per cent would cut energy consumption by over 27 per cent.??

"The potential savings were immediately clear once we conducted the calculations. Our detailed analysis showed us how small adjustments to 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."?- David Strain , technical director, Technidrive Ltd .

Implementing adjustable fan speed?

The solution centred on installing a variable speed drive (VSD) to adjust the fan’s speed in real time. The team selected the CFW500, a high performance VSD from WEG. With the ability to match the fan’s performance to the precise vacuum requirements of the dryer, the system could shed its high-energy burden. In addition to the VSD, the motor was upgraded to a 110Kw W22 model, also from WEG. This motor boasts an energy efficiency rating of IE4, 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, which governs the fan’s speed based on real-time pressure data. During initial tests, pressure levels swung unpredictably, demanding expertise from the Technidrive team. After extensive adjustments, the system was fine-tuned to perform with the consistency the process demanded.?

"Stabilising the vacuum pressure was like trying to set the cruise control in a car," continued Strain. "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."?

Analysis of results?

To measure the impact of the new system, Technidrive conducted three comprehensive evaluations using an energy cost of €0.27 per kWh as the baseline. The first method was a straightforward comparison of the total energy consumed during a week, without factoring in variables such as fan runtime or production output. Over a week of production, total energy consumption dropped from 4974 kWh to 3900 kWh, a 22 per cent reduction, demonstrating a potential saving of over €15,000 annually.??

The second approach focused on energy cost per ton of material processed, drawing on batch records to ensure accuracy. When evaluated per ton of material processed, costs fell by 19 per cent, from €0.31 to €0.25 per ton.?

Lastly, the most significant efficiency gains were seen in an analysis of the total energy use per hour of fan operation. With a 38 per cent reduction of energy used — from 96.02 kWh to 59.72 kWh per hour — this study demonstrated annual savings of over €30,500.??

"From the outset, our focus was on identifying opportunities where engineering precision could drive savings," added Strain. "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 CO? emissions by 757 kilograms per year.” added Strain.??

You can find more information on Technidrive’s quarry solutions on the website. To speak to the team’s engineering experts directly, contact [email protected] or call +44 (0) 2837 518111 to arrange a consultation.?