Some operators are clamping down on energy waste that has been going over their heads for years—literally.
Specifically, they are recapturing the energy dollars that go up the kitchen hood because exhaust fans run constantly regardless of whether cooking effluents are present. That also includes the energy dollars required to bring in makeup air to replace what has been sucked out of the building and to heat it or cool it as well.
To optimize energy efficiency, some of these operators are retrofitting their standard single-speed hoods with so-called demand ventilation control systems that adjust fan speed to match exhaust demand. Others are replacing canopy-style hoods with proximity hoods that wrap closely over cooking surfaces and require lower exhaust airflow to run.
“Someday, most ventilation systems will have some level of control,” said commercial kitchen ventilation expert Don Fisher. “You might think after a decade, this would be a fairly mature technology, but we’re just sort of getting traction on it now.”
Fisher is president of Fisher-Nickel Inc., which manages the Pacific Gas and Electric Company Food Service Technology Center, or FSTC, in San Ramon, Calif., a testing facility for kitchen equipment. FSTC field studies of operations that have replaced standard ventilation setups with demand ventilation control systems have reported annual savings of nearly $10,000 in a large hotel kitchen, more than $4,600 in a college dining facility kitchen and nearly $1,300 in a full-service restaurant kitchen.
Single-speed exhaust fans are relics of a day when energy was much cheaper. Over the past two years, energy costs for businesses have increased by more than 10 percent, reported the National Restaurant Association, citing Bureau of Labor Statistics research. With utility costs amounting to about 3 percent to 4 percent of sales for the average restaurant, there is a significant incentive for operators to cut energy outlays. Not surprisingly, about three in five operators said in an association study last fall that they were taking specific actions to combat rising energy prices, such as cutting back on unnecessary equipment use or switching to more efficient equipment.
According to Fisher, demand ventilation control emerged more than a decade ago, pioneered by a vendor that developed a system that places temperature and optical sensors in the hood that detect heat, smoke and grease resulting from cooking. The sensors link to a processor that raises fan speed to exhaust the effluents and slow it down when they are gone.
As straightforward as it may seem, demand ventilation control is found in only about 1 percent of kitchen hoods, Fisher said. Its spread has been hindered by factors like price, with systems costing anywhere from $5,000 to $25,000, depending on the size and configuration of the kitchen, and a payback period that can stretch to three years, Fisher said.
Another hurdle is the general complexity of ventilation issues. “There is probably no single system in restaurants that generates more calls for service than hoods,” Fisher said, noting that a ventilation system must be working properly before it can be retrofitted.
However, there are signs that the technology is poised for growth. Recently, three more manufacturers have launched demand ventilation control systems, bringing the prospect of price competition. In addition, the cost of the variable frequency drive, the system component that controls fan speed, has dropped dramatically. What’s more, utility companies in California and some other places are offering rebates to operators who install or do a retrofit with approved systems.
“The time is right for demand ventilation control,” Fisher said. “I think the stars are starting to line up.”
At Culver’s Restaurants, a 396-unit quick-service chain based in Prairie du Sac, Wis., energy-efficiency efforts include both demand ventilation controls and proximity hoods, according to director of design Tom Williams. To make the proximity hoods over griddles and fryers run effectively, the company has worked with a manufacturer on a flue bypass system that prevents hot flue gases from baking cooking effluents onto the air filters and reducing airflow.
“What that has allowed us to do, in round numbers, is reduce our total exhaust from 4,600 CFM [cubic feet per minute] down to 3,000 CFM,” said Williams. “We know that our makeup air is one of the contributors to high energy cost, and if we reduce it, we save a significant amount of money.”
