Adding efficiency to your daily bread

Results from industry trials released by the Carbon Trust demonstrate that improved ventilation in ovens, through the use of variable speed drives (VSDs) and sensors can lead to significant energy efficiency improvements. Analysis showed that dynamically matching exhaust fans to the volume of gases produced within an oven could provide energy savings of nearly 5 percent. This equates to savings of up to £14,000 per site per year, with payback times varying from one to five years depending on the condition of the existing oven.

Currently gas flow through ovens is not optimised for efficiency. To investigate the potential for improvement the Carbon Trust conducted two trials with Campden BRI and Spooner Industries. The trials measured gas volumes produced during baking, both from combustion and from the product itself, and the effect on oven efficiency of improved management of flue gas.

Gary Tucker, head of baking and cereal processing department, Campden BRI Group commented: “The Carbon Trust project showed that improved exhaust gas control has potential for cost savings. This can be implemented by installation of VSDs to exhaust fans with links to burner fire rate. Further savings are possible by balancing gas flow rates in and out of the oven. One of the unquantified gas flows during baking is the volumetric flow rate of gases released from products. Campden BRI demonstrated that this was of similar magnitude to that from combustion products but increased towards the end of baking time as more steam was released. Further research is required before this can be taken into account using a gas flow optimisation algorithm.”

Dan Kirk, research and development manager at Spooner Industries commented: “Spooner has long championed energy efficiency across all of the industrial markets that our technology supports. The drive to save energy, to be more environmentally friendly and ultimately to reduce operating costs makes energy efficient operation of process machinery such as ovens a real priority for our customers.”

Al-Karim Govindji, senior manager at the Carbon Trust commented: “Improvements in industrial processes have the potential to make significant cross sector savings. The results of these trials are really positive and show that taking steps to improve ventilation in ovens thus optimising the gas flow rate can result in real financial savings.”

According to Carbon Trust figures ovens are responsible for 35-45 per cent of total site carbon emissions of a bakery. In a typical direct-fired gas oven around 20 per cent of gas use is wasted when hot air exits the flues. This energy makes no contribution to heating bread dough and is a direct loss.