We all know that efficient ventilation is crucial in workshops. But do you know what it takes, in practice, to optimise air quality while limiting energy consumption?
Any endeavour to optimise air quality in an industrial workshop must start with a thorough survey of the premises’ existing issues, systems and processes: ask the right questions, make an inventory of the air conditioning and air exchange equipment, produce a moist air diagram, separate the heating and ventilation functions. “The survey provides a better understanding of the conditions in your workshop and helps zero in on the solutions best suited to your constraints,” says Thierry Beaussé, energy engineering expert in industry. “But that’s not enough. Making a few adjustments in the way pollutants are handled and monitoring the system’s performance over time will enable you to reliably optimise air exchange in your workshop. Take my word for it!”
1. Remove pollutants at the source
Discharging pollutants where they are emitted greatly reduces the volume of air in the workshop that has to be conditioned. “Installing specific extractors, exhaust hoods or containment booths at the machines or production lines reduces the return on investment to between one and three years,” says Thierry Beaussé. “It’s a very cost-effective solution.”
2. Renew air by displacement rather than by mixing
Air in workshops is generally handled by mixing the entire volume of air in the building.To improve air quality around the building occupants, the pollutants in the air should be removed on the spot and discharged through the building’s ceiling. Exchanging air by displacement reduces the volume of conditioned air intake threefold for the same air quality, and energy consumption is halved, with static losses overall!
3. Optimise the fresh air rate
Clean air requirements vary with the workshop’s occupancy, activity and zones. “There is no need to ventilate everywhere with the same air flow. Each separate area of the workshop can be treated on the basis of its pollutant concentrations, which will be higher close to operating machines than in the stores, for example.”. And if presence detectors are installed, the air flow adjusts to each occupancy rate.
4. Preheat the outside air intake
When fresh, outside air is preheated by the energy recovered from the air extracted from the workshop or by a heat exchanger before it enters the workshop, the energy savings climb to a massive 50% to 70%!
5. Set a different regulation for each zone
For maximum energy savings, it’s best not to focus on precise set points. As Thierry Beaussé explains: “Regulation based on a range of set points (for example, between 17°C and 19°C and between 55% and 65% humidity) requires far less energy than regulation defined on a precise set point (such as 18°C with 60% humidity).” This type of regulation can yield energy savings of between 30% and 50%.
6. Install an efficient instrumentation and control system
In the between-season period, air handling units are less efficient because they require more finely-tuned regulation. “When the outside temperature is 16°C and we want 18°C in the workshop, the air handler starts to work,” says Thierry Beaussé. “An efficient instrumentation and control system, on the other hand, would analyse the situation and factor in the heat produced by the manufacturing processes so that it doesn’t turn on the air handler unnecessarily.”
7. Review different air circulation methods
Once you have followed the previous steps to optimise air exchange in the workshop, it’s time to review the various methods of circulating air. Have the heating and ventilation functions been kept separate? Is the air exchanged by displacement and based on actual requirements? Have air movement, mixing and speed been optimised? Review these factors regularly.
8. Monitor, check and adopt a shared, long-term approach
The final step is to maintain efficient air handling over the long term. To do so, you will need to monitor and check the air conditioning and air exchange parameters against the factory processes. Multivariable Big Data analysis over a lengthy period provides insights into these results and an overview of air handling in the workshop, and enables you to establish correlations among the systems. It also makes it possible to fine-tune the settings in order to maintain efficiency and cost savings. “The Big Data tool also gets workshop employees and management involved in the energy-saving initiatives,” concludes Thierry Beaussé. “On the analysis curves, they can see for themselves the progress that has been made in air quality and energy savings with their help: by entering the right settings, closing the windows and turning on an exhaust hood. It’s a guidance tool that gets them involved and tells them when they’ve got it right!”