When a baker looks at fuel costs, the oven eats up most of the bill. “They are normally the biggest single consumer of gas by a considerable margin, typically more than 75% of the gas used in a cookie and cracker plant,” said Keith Graham, marketing manager, Baker Perkins, Grand Rapids, MI. All this energy goes to good use, though, developing all the characteristics of the finished product — appearance, texture and moisture content.
Ovens that develop those characteristics more consistently, however, tend to save on energy as well. “Energy efficiency is all about using the bare minimum amount of energy to bake product,” said Mark Appleford, co-CEO, Auto-Bake PTY, Hornsby, Australia.
Bakers can gain savings by fine-tuning their ovens to specific products, using data to boost oven control and minimizing heat loss and waste
Baking needs meet energy costs
Ovens are energy hogs. They consume a lot of gas and electricity to turn dough or batter into delicious baked goods with perfect color and crumb. It is easy to assume that a baker must sacrifice the quality of an oven’s baking ability to make it easier on the utility bill. However, many of the adjustments made to ovens to improve their energy consumption stem from making them better at baking.
“Building a more energy-efficient oven does not affect the product quality,” said Cyril Munsch, director of sales, Mecatherm SA, Barembach, France. “On the contrary, it improves it as we work on better heat transfer and exchanges. Modern ovens bake a lot better and faster than older ovens, which reduces energy consumption.”
It’s that simple: A faster, better bake uses less energy. The J4 oven, sold in North America by Topos Mondial, Pottstown, PA, uses STIR technology, a ceramic layer applied to the interior surfaces of the oven radiator, which bakes products in about 15 to 30% less time. The hot radiator naturally emits electromagnetic waves, and the STIR coating changes the wavelength of the heat waves to be more like an infrared wave. These altered wavelength heat waves penetrate deeper into the product yielding more product volume and a faster bake time.
By building a greener oven with its WP Rototherm Green, WP Bakery Group USA, Shelton, CT, shortened bake times and increased volume and oven spring.
Before bakers can determine if they can use a more energy efficient baking platform, they must determine the specific proportion of thermal characteristics that their products require. “Many products have very specific thermal profiles for flavor and texture that require proportional amounts of radiant, convection and conductive heating,” said Shawn Moye, vice-president, sales, Reading Bakery Systems, Robesonia, PA.
Often, ovens use too much heat, trying to compensate for extra surface area, thick pans or removing the last morsels of moisture from the center of the dough. This leads to quality control issues as well as higher energy costs.
Controlled low-velocity impingement ovens, for example, direct heat straight to the product. These ovens employ a cross between impingement and convection technologies, explained Stephen Bloom, vice-president of Allied Bakery Equipment, Santa Fe Springs, CA. Their ability to focus the heating energy on the product and not the environment creates a shorter bake time.
Hybrid ovens can also deliver desired characteristics with energy efficiency. While convection ovens may provide an efficient bake, they sometimes cannot always deliver the same characteristics as direct–fired. The high heat input from direct-gas-fired systems creates the light texture in crackers. However, this lift happens at the beginning of the baking process, Mr. Graham explained. In later stages, when the oven removes moisture and colors the product, bakers can switch to convection heat.
Using a hybrid baking system can also prevent over-coloration issues while trying to achieve a full bake. As Tim Clark, president and CEO of Radio Frequency Co., Inc., Millis, MA, explained. As the oven tries to remove the last remaining moisture from the center of the product, the bake time extends, resulting in over-coloration, wasted energy and product defects. Radio Frequency’s post-baking dryer targets internal moisture and removes it from biscuits and crackers with less energy and without unwanted coloration.
Even heat distribution throughout the baking chamber also results in a better bake. While older designs may rely on one burner tower, today’s Gashor tunnel ovens, represented in the US by Cinch Bakery Equipment, Clifton, NJ, feature multiple towers. These towers are smaller than those that dominated older models, but they provide more consistent heat across the oven without having to run at maximum capacity.
Lowering an oven’s flash heat also reduces energy while improving baking quality. Thermal oil’s low flash heat creates a non-aggressive bake. “It allows more consistent moisture distribution throughout, more oven spring and longer shelf lives, all because it’s a softer bake with more thermal mass in the oven,” Mr. Bloom said.
AMF Bakery Systems, Richmond, VA, relied on NASA-developed technology to engineer its Emisshield Nano Emissive Oven Technology, which broadens the heat spectrum by re-radiating infrared heat produced by the gas burners. The result is, bakers can see greater oven spring, more even heat distribution, color uniformity and consistent heating — all while reducing energy costs.
Exerting control with data
Aiming for quality baking and energy efficiency, bakers have found value in oven controls. “The more efficient an oven becomes, the more controllable the oven is for the baker,” Mr. Appleford of Auto-Bake said.
Gathering data allows bakers to heat the product perfectly at each stage. “Product tracking, knowing how much and where the product is in the oven, allows the burners to automatically fine tune for the heat required,” explained Phil Domenicucci, AMF Bakery Systems.
The company’s ovens have zone heat control with product tracking, enabling bakers to set each zone’s temperature for targeted baking. If a gap between products occurs, the burners will modulate themselves. “As the next product begins to come through the oven, the burners will reignite,” Mr. Domenicucci said.
Auto-Bake also offers heat zone control programming as well as energy management software that delivers live data from the oven to the operators.
The J4 oven also can be designed to offer bakers tight control of the baking profile for the products being baked. The oven is designed to deliver a pre-determined heat profile to best suit the product. The oven constantly monitors the temperature curve in the baking chamber in order to use as little fuel as possible while still meeting the product’s baking needs.
Gashor’s multi-tower tunnel ovens also provide flexibility. Because each tower controls a different section of the oven, each can be heated to a different temperature. These parameters are governed by PLC, making them operator-friendly.
Werner & Pfleiderer/Gemini’s indirect-fired tunnel oven, the Thermador, expands a baker’s oven flexibility with its targeted product steaming and insulated oven belt return chamber. These features not only save energy costs but also give bakers tools to improve quality and extend their range of products.
To help operators understand how they impact the oven, Stewart Systems, Plano, TX, offers real-time utility consumption data on the operator console. By seeing trending information about gas, power, water, steam and air usage, operators can understand how their actions affect utility demand.
Reading Bakery Systems offers fuel flow meters that record fuel usage. By understanding the amount of fuel the oven uses, a baker can determine the actual amount of BTU’s used per kg of product baked. This will establish a baseline for future fuel reduction opportunities.
Collecting and understanding the data can then help operators act. Baker Thermal Solutions, Clayton, NC, offers its oven with process control tools to address lags in efficiency. “We’re analyzing oven control from the perspective of energy requirements — the heat input into the product. It’s more of a heat-loading control than it is a temperature control,” said Jerry Barnes, the company’s vice-president of engineering. These controls manipulate burners’ heat input as well as cool the oven down when needed.
Finding use for waste
A straightforward way to make ovens more efficient is to reduce heat loss and improve exhaust issues. Ovens can waste heat because of poor insulation and idling during product changeovers.
Auto-Bake improved its insulation materials, which helps the oven retain heat. However, there are other benefits to insulating the oven properly.
“More efficient insulation reduces heat loss from the enclosure in the bakery, reducing the overall ventilation requirements on building HVAC systems,” Mr. Domenicucci of AMF Bakery Systems explained.
Heat can also escape when the oven is opened, for instance, to change racks. Mecatherm cut the number of openings on its ovens to reduce these points.
WP Bakery Group USA improved its Thermogate feature so that when the door to the oven is opened, energy loss is minimized. This enables use of a falling baking profile and better batch-to-batch baking, said Patricia Kennedy, president, WP Bakery Group USA.
A popular solution for lost heat in an oven is heat recovery units, which capture escaping hot air and pump it either back to the front of the oven to pre-heat cold air or to heat the proofer.
Cinch Bakery Equipment’s craft ovens reuse heat from the ovens throughout the bakery. “On our craft ovens, we can easily reclaim the heat from combustion through the chimneys and repurpose the energy for hot water or room temperature inside the bakery,” said Cindy Chananie, the company president.
Mr. Moye further explained that Reading Bakery Systems offers heat exchangers that can use exhaust air to pre-heat the combustion make-up air, and usually these systems are employed in later oven zones when exhaust dampers are fully open.
Claus Abrahamsen, technical sales manager, Franz Haas Machinery of America, Inc., Richmond, VA, echoed this, saying exhaust stacks are where ovens lose the most hot air. “We give the customers the possibility to recover heat and put that back into the oven to pre-heat the cold air that gets sucked into the oven,” he said. Haas’ Meincke oven’s heat recovery can achieve up to 15% gas savings, Mr. Abrahamsen said.
The J4 tunnel oven also can feature heat exchangers that recover heat from the exhaust to either warm the air or heat the building’s hot water supply system. The cyclothermic ovens separate the fuel exhaust from the product chamber by running the heat and byproducts of combustion in sealed ducts through the baking radiators. These radiators radiate heat onto the product. Bakers can gain more efficiency by using Duotherm zones that include fans that force the oven chamber air to circulate between the radiator and oven baking chamber. These zones increase fuel efficiency by accelerating the heat transfer to the product.
Exhaust systems also impact how well an oven can maintain its temperature. “Managing the oven exhaust becomes a significant consideration for efficiency because too much humidity and moisture in the baking chamber actually dampens the burner output,” Mr. Barnes. Baker Thermal’s oven process control tools can measure the exhaust flow in real-time and weigh the results against optimal exhaust for that product. Operators can make adjustments to prevent the oven from working too hard to combat a humid environment.
The oven exhaust also contains the air pollutants — specifically, volatile organic compounds (VOCs).
“We have to control the combustibles,” said Bill Foran, chairman of BABBCO, Raynham, MA. The oven needs sufficient exhaust to avoid building up combustible gases within the baking chamber. BABBCO’s tunnel ovens do this by controlling not only the amount of exhaust but also its content.
Gemini/KB Systems addresses VOCs with its Werner & Pfleiderer/Gemini indirect-fired ovens. “The only exhaust containing VOC products of fermentation that needs to be treated by the oxidizer is the isolated exhaust from the oven bake chamber,” said Mark Rosenberg, the company’s CEO. “This reduces oxidizer gas consumption and reduces costs to operate the oxidizer.”
While an idle oven may not lose heat, it certainly wastes it. “Whether during a product changeover or some minor ingredient calamity, there are various times when all the equipment is running without product,” said Scott McCally, product manager, Thermal Group, Stewart Systems. “This is a tremendous waste of energy.” Stewart Systems’ On Demand program sends the oven into low-fire mode during a gap in production and alerts the oven to fire up when it’s time to get back to work.
At interpack this year, Franz Haas introduced Eco-Mode for its ovens. This feature senses when products are coming into the oven. When the infeed line is empty of products, the equipment will either go into Eco-Mode to save energy or alert operators that they may want to put the oven in Eco-Mode.
Reading Bakery Systems also features downtime software that sends the oven into low-fire mode during prolonged breaks.
There are many reasons a baker would choose to make ovens greener — improved baking, savings on energy and even social responsibility. “The message has gotten through that we want to be sustainable; we want to be eco-friendly,” Mr. Abrahamsen said. “It’s no longer just the payback: It’s also a conscious decision to be more sustainable.”