Blog Post

Venting about Sustainable Commercial Kitchens

February 18, 2009

Despite the economic downturn and the trend toward smaller crowds at building trade shows, Efficiency Vermont's 2009 Better Buildings by Design Conference was a great success and actually increased attendance this year. The enthusiastic response is a tribute to the sustainable building community at large and to Efficiency Vermont, which put on a conference that was well organized, informative, and pragmatically optimistic. The quality of the presenters and workshops was impressive. William Miller from Oak Ridge National Laboratory, Steve Selkowitz from Lawrence Berkeley National Laboratory, Kevin Dowling from Philips Solid State Lighting Solutions, John Straube from Building Science Corporation, and others, spanned topics ranging from high-performance roofs to the latest in LED technology. I attended a commercial kitchen ventilation (CKV) workshop featuring Don Fisher, co-founder of Fisher-Nickel and the Food Service Technology Center (FSTC). Administered by Pacific Gas and Electric, FSTC is a pioneer in the testing of water- and energy-efficient commercial kitchen appliances. (Anyone interested in commercial kitchens has to visit www.fishnick.com). Fisher's presentation was geared toward experienced kitchen and/or HVAC professionals and discussed his company's work improving the efficiency of existing ventilation systems. For background information, commercial kitchens require massive CKV systems to remove heat and fumes generated by gas ranges, broilers, fryers, and — the biggest emitter — the grill (think of a large, white-hot barbecue burning indoors for 12-18 hours a day).
Most CKV systems contain rooftop-mounted fans and controls, ductwork, dampeners to control fire risk, stainless-steel hoods, and grease removal "filters," and may also include automatic controls such as Melink's Intelli-Hood system to monitor and vary the fan speed, or additional grease removal in the form of UV or water spray systems. CKV systems run as much as 18 hours a day exhausting air from commercial kitchens at rates up to 12,000 cubic feet per minute (institutional kitchens can be as much as 30,000 cfm), which has to be replaced by make-up air that often comes from the conditioned building space, i.e., the restaurant. About 30% of a restaurant's total energy and 75% of its HVAC load are consumed by kitchen ventilation, and it typically does a lousy job of capturing grease, which is deposited on duct walls or condenses on the building's roof, creating a serious fire hazard. Fisher suggests improving CKV performance through better make-up air diffusion and by adding stainless-steel sides and back walls to the hoods to focus the ventilation and limit cross breezes, but even at their best, these units are energy hogs. Fisher discussed improving CKV, but how does a restaurant owner reduce the ventilation needed in a kitchen in the first place? What if we minimize, or even eliminate, the use of these energy-consuming, high-emitting appliances? Are there alternatives? Perhaps we need to start by rethinking our choice of food and how it's prepared. Raising cattle, for instance, requires more resources and creates more greenhouse gases than most other proteins and should be consumed sparingly. But even if chefs use beef (and they will), eliminating the grill could, potentially, be healthier for the diner and environment, without compromising taste. As we know, grilling food creates carcinogens, which is — obviously — not a good thing, especially when there are alternatives. The main benefit to using a grill is that grilling meat is fairly simple and the surface is large, so a lot of food can be prepared at once by cooks with limited skills, providing an easy way for a chef to manage the staff and menu at a busy restaurant. But with careful menu planning, other cooking methods can be equally easy and effective. For instance, pan-searing proteins leaves residues in the pan that are typically used as the base flavor for sauces, and poaching can infuse food with flavors without introducing a lot of fat. And there is an alternative to poaching or sautéing on ranges that generate heat and combustion gases; Cooktek will be offering a six-burner commercial induction range in the upcoming months — the first available commercial-quality induction range in the U.S. Induction cooktops use electromagnetic fields to heat iron-based cooking pots (aluminum, copper, and most stainless steel pots will not work) at efficiencies of up to 84% compared with <40% for gas. The flat surface of the cooktop stays cool to the touch and only the pan gets hot. There is no flame or combustion gases to exhaust. Though restaurant-grade single "burner" induction cooktops have been around for years, due to novelty and cost, their rollout in the U.S. has been limited. But a durable, six-burner induction range that can stand up to a commercial kitchen's abuse is an exciting development. Using these units could result in faster cooking times; cooler, safer, more comfortable employees; fewer emissions and improved indoor air quality; faster cleanup with fewer chemical cleaners; and, most importantly, significant energy savings upfront and via a reduced need for restaurant ventilation, heating, and cooling. While expensive, an induction range could pay for itself fairly quickly through these reduced HVAC demands. Completely eliminating external ventilation from a commercial kitchen may be unrealistic, but decreasing the size of an HVAC system offers benefits that go beyond energy consumption. Fewer HVAC intrusions mean designers would have more options with the interior space. And on the facilities side, with no grill or gas range, less money would be needed at start-up for installing gas lines; interior surface, duct, and hood cleaning costs would be reduced; and the roof would be saved from grease damage, creating a cleaner, safer, better looking restaurant inside and out. And, as we all know, in the restaurant business, presentation is everything.

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Comments

March 3, 2009 - 10:04 pm

Grease is the word, Grease traps aka filters do exist and unless properly maintained cause obvious on site health and safety issues. If it was possible to isolate the main sources of grease production from the overall air streams then I think you'd have a sporting chance of making the best of a difficult environment. Whose leading in this area?

August 29, 2009 - 11:55 am

They exist. We manufacture these systems for most of the major restaurant chains in Canada. You can watch a Discovery Channel feature at our under construction website martinairsystems.com.

February 19, 2009 - 10:33 am

Very interesting idea. I have been told in the past that CKV is difficult to implement with heat recovery, because of the grease.

February 20, 2009 - 10:28 am

I think Don Fisher has some slides of old and new CKV energy recovery attempts, so these systems are out there, but you would need good grease filtration. Some restaurants owners are actually doing the opposite of energy recovery by insulating ducts to make sure the grease particles stay hot, don't condense on the duct walls, and are vented out of the building.

September 4, 2009 - 8:55 am

Our web site is at www.innoventair.com

September 4, 2009 - 8:54 am

Our company also has an energy recovery sytem that can be used on kitchen hood applications. We use an air-to-air plate heat exchanger to recovery the energy from the exhaust stream - after the grease hood. Our plate heat exchanger has an automatic water wash system that keeps it clean. This wouldn't be recommended for fast food type restuarant, but has been used for many school cafeterias.

February 19, 2009 - 4:09 am

Interesting dynamics involved in commercial kitchens, surely there is scope for heat recovery, systems to be incorporated in the system to use the excess energy for space heating, hot water with short term storage to manage the input/outputs involved.

September 1, 2009 - 12:29 pm

Thanks for responding, Jeff! I look forward to learning more about your system. Can you send me product information?