While direct-gas-fired (DGF) ovens remain popular, they tend to require more upkeep because of the substantial number of burners. That’s why many oven experts, even manufacturers of DGF ovens, suggest turning to air-impingement ovens or convection heat to save cold, hard cash.
“The air-impingement ovens are hands down much more efficient in today’s environment than direct gas-fired ones,” said Jerry Barnes, vice president, Babbco. “Air-impingement ovens can change temperature very quickly because you’re using focused convective heating with powerful high-turndown burners. You’re not relying on a hot box.”
Additionally, these older radiant heat systems require much longer to heat up and cool down. Specifically, he noted, DGF ovens require 1 to 2 hours to preheat while air-impingement ones heat up in as short as 30 minutes.
“When you change products and change the bake profile of the oven, you reduce the latency with convective heating because it can change air temperatures more quickly,” Mr. Barnes said. “When you have a production gap, the typical oven will overheat and result in burnt edges on one part of the production run and light products on the other. Newer ovens, especially air-impingement ones, don’t suffer from that flash-heat effect.”
Ken Johnson, president, Gemini Bakery Equipment/KB Systems, also recommended considering an indirect gas-fired oven because it uses approximately 30% less energy than a DGF one. Energy is transmitted to products more efficiently with convection than with radiant heat only.
“Bake temperatures in convective zones are cooler due to this more efficient heat transfer,” he added. “Gemini/W&P’s turbulence zones provide for lower bake temperatures, less energy usage and a more uniform bake.”
He said the zones feature evenly spaced carbon steel tubes that form the upper and lower oven heating plenums. A mesh belt support grid is located on top of the bottom pipe plenum. Heating gasses then flow through the tube plenums and radiate energy into the baking chamber. Recirculated bake chamber air passes through spacing between these plenum pipes. Moreover, that variable-speed airflow is reversible and can be from top-to-bottom or bottom-to-top for different products.
Since introducing convection ovens more than a decade ago, Auto-Bake has converted many of its older thermal oil ovens to convection, noted Scott McCally, president of Auto-Bake Serpentine and Hinds-Bock, both part of Middleby Bakery Group.
“Generally speaking, cake producers have been averse to using convection heating because it causes the product to crack and creates issues with the crust,” Mr. McCally said. “Because of the way we can control top and bottom convection, we can virtually eliminate all the air flow on top of the product, which causes those problems, and produce a much better product than a radiant-type oven. They can bake the product faster, and instead of increasing temperature to drive heat into the product, we can turn the temperature down and the fan speed up and use the fan as the mechanical force to drive heat into the pans.”
Marie Laisne, product marketing manager at Mecatherm, said the company’s M-TA can offer multiple heat transfer modes, such as convection, radiant heat or a combination of both in each independent heating zone.
“By providing just the right quantity of required energy in a minimum baking time to reach the required product quality criteria, this oven offers an optimal energy consumption solution,” she said.
Mr. Johnson pointed out that Gemini/W&P provides an oven with radiant heat only, some zones with a combination of radiant/turbulence/convection heating or all zones with a combination of radiant/turbulence/convection heating. Turbulence zones come with two or four blowers for enhanced convection.
Mr. Barnes said hybrid ovens have been around for decades and compared their versatility to a Swiss army knife.
“Hybrid ovens give you multiple tools in your pocket to deploy based on the product, helping to make the oven future-proof,” he observed. “In today’s marketplace, producers have to be very quick in adapting to consumers’ tastes.”
Joe Zaleski, president of Reading Bakery Systems, said DGF ovens bake primarily with low-level radiation and convection air currents. The product develops and bakes in a still air and humid environment. Mixing and matching technology allows bakeries to tailor the baking profile to heighten the attributes of specific products.
“Many hybrid ovens use this very gentle heat to create their products’ texture and flavor profiles in the front oven zones and change to a much more aggressive, higher air flow environment in the last zones of the oven for drying the product to the final moisture content,” Mr. Zaleski explained. “Convection energy is more efficient in this drying area as heated air impinges directly on the product, providing moisture reduction with both heat and air.”
New technologies are also appearing. A few years ago, AMF Den Boer introduced the world’s first emission-free, hydrogen-fueled tunnel oven. The Multibake VITA tunnel oven offers industrial bakers an effective solution to reduce carbon dioxide emissions by 99.9% within the baking process.
The modular oven uses green hydrogen, also known as clean hydrogen, a carbon dioxide-neutral fuel. Though commercial ovens typically use natural gas as the resource for heating, the company stated, this new patent-pending technology will virtually eliminate carbon dioxide emissions from the oven while reducing the cost of utilities.
For specialty bakeries that prefer rack ovens, Koenig Bakery Systems offers the Roto Passat SE with a potential of 20% energy savings.
Christian Benedikt, group leader, oven design, for Koenig said the ovens use a flow-optimized heating coil, high-quality sandwich insulation with aluminum intermediate layer and a continuously adjustable steam and control system to minimize energy usage. Moreover, the oven has the double-walled baking door made of duplex steel with rear ventilation for low surface temperatures.
He added that the increased energy efficiency can pay off over a year’s time. A bakery operating six days a week, for instance, can thus save around 4,000 liters of heating oil, which corresponds to around 12 tons of carbon dioxide a year.
With energy prices showing no signs of abating, bakeries need to focus on oven maintenance and explore new technologies, so they burn less and earn more.
This article is an excerpt from the July 2022 issue of Baking & Snack. To read the entire feature on Ovens, click here.