Demand Control Kitchen Ventilation

Traditionally hood exhaust in commercial kitchens are tied to a make-up air unit which balances building pressure during the kitchen operation. Generally, this hood is on at full speed for entire daily operation of the foodservice facility, which range from 18 to 24 hours per day. The concept of Demand Control Ventilation system leverages infrared and temperature sensors to determine the amount of exhaust air required to capture and contain the effluents from cookline. Depending on the amount of cooking taking place, the ventilation system and make-up air vary their speed using a variable speed controller to meet the exhaust air requirements. This allows for the exhaust system to run at the lowest possible speed to perform the required job. Initial assessment in 2002 showed considerable savings was in targeted foodservices facilities.

Commercial kitchen hoods (hoods) are a significant component of energy consumption in restaurant and fast-food kitchens. They function to reduce fire hazards and exhaust cooking effluent to comply with air quality standards within a commercial kitchen. Exhaust hoods in these kitchens are normally tied to a make-up air (MUA) unit that balances building pressure during the kitchens operation. Generally, the hoods’ exhaust requirements are sized to peak cooking usage of each appliance under the hood. Typical hoods have a simple “on” or “off” control strategy. When the hood is on, its exhaust and make up air fans are on at full speed or not at all. In reality food is not being cooked at all times therefore not needing the peak exhaust requirements. Due to the common control strategies employed in most commercial kitchens a significant amount of energy is wasted on venting unnecessary cubic feet per minute of air when appliances are not fully used. It is evident that there is an opportunity for energy efficient savings. The Melink Intelli-Hood demand control ventilation system (DCV) is an energy management system for commercial kitchen hoods. It optimizes energy efficiency by reducing the exhaust and make up air fan speed. This is accomplished by leveraging an infrared and temperature sensors to determine the minimum amount of exhaust air required to capture and contain effluent from the cookline. The primary objective of this project is to verify field performance and demonstrate how the Melink Intelli-Hood demand control ventilation (DCV) system can reduce energy costs. The projects secondary objective is to evaluate the market sectors impacts on field performance and energy reduction on a DCV system. The different market sectors can have different hours of operation, appliances, and kitchen exhaust hood configurations. For this field evaluation two hotels and three quick-service restaurants were chosen. Also in this field evaluation only the exhaust and make up air fan motor energy savings were accounted for. Air conditioning savings, due to heat load reduction in the kitchen area, were not accounted for. The Melink Intelli-Hood DCV system was shown to significantly reduce the energy consumption and electrical demand associated with operating a commercial kitchen exhaust hood. Table 1 lists the average kW draw, percentage reduction, daily operational values, daily energy consumption, annual energy consumption, annual savings, percentage energy usage reduction, and estimated annual operational cost for all hood data at each site. The savings results from the Melink Intelli-Hood DCV system installation can realize a 37-62% energy savings over current commercial kitchen hoods. The DCV system was most effective in the hotel market sector due to the amount of hoods, amount of HP servicing the hotel, and the hours of operations. Hotel kitchens are sized for peak food production - defined as the maximum food prepared at any given time in a hotel’s kitchen. The hotel’s kitchen sizing also means there are multiple hoods and higher amounts of HP needed to meet the maximum food demands. Since maximum food demands rarely happen, the hotel market sector has a high potential for savings. Most of the time there is limited kitchen use occurring in a given day, allowing a DCV system to save energy by running at minimal exhaust settings.