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Food Service

Introduction

The term "food service" basically encompasses the restaurant industry. Many commercial restaurants come and go with changing public desires and thus stress appearances -- what can be seen by the public. They often consider used equipment and are not amenable to any energy-saving high first cost approaches. Others, such as institutional facilities, are designed for 20 or more years of use, so high quality and low operating cost alternatives should be emphasized.

Definition

The three main divisions of food service are fast food (also called quick serve), institutional, and full service (also called sit down). There are variations on each, such as delicatessens and cafes.

Fast Food (Quick Serve):

These include snack bars, pizza and short order restaurants. They may include a seating area or perhaps only a take-out service. The kitchen is designed for quick preparation and convenience.

Institutional:

These include service line operations (cafeteria style) where the menu is often somewhat limited. They are common in corporate cafeterias, school systems, hospitals and prisons.

Full Service (Sit-down, Full Menu):

Food is served to patrons seated at tables or booths. Coffee shops are a variation of this division.

There are a number of differences in how these three sectors operate, what type of equipment they have, what their goals are, and how they make decisions.

HVAC

The HVAC systems must meet the widely varying needs of temperature and humidity control with large swings in occupancy, plus proper ventilation and odor control to keep kitchen odors out of the eating areas and to keep secondhand smoke out of the no-smoking dining areas. These facilities frequently pose comfort conditioning problems such as:

  • Extremely variable loads with high peaks in energy demand.
  • High sensible and latent heat gains due to people, food preparation and presentation, as well as any gas venting requirements.
  • Localized high sensible and latent heat gains in dancing areas.
  • Potential for unbalanced air flow conditions in areas adjacent to kitchens and in smoking and non-smoking areas.
  • Kitchen systems need to be separate from other areas to avoid odor contamination and heat migration during higher indoor summer design conditions
  • Heavy influx of outdoor air through entrances, especially during peak hours.

Typical System

The most common cooling and heating systems are unitary systems, particularly in stand-alone facilities. Where the building is 1- or 2-stories and interior building space is at a premium, rooftop equipment is often specified. Since these facilities typically have low sensible heat factors (that is, they have high latent loads) and therefore require relatively high ventilation air; all-air systems are generally specified. Smaller establishments often use direct expansion or roof-top systems, while larger establishments may use central chilled/hot water systems.

Ventilation and infiltration are important considerations due to short patron occupancy and the consequent frequent door use. Also, large quantities of outdoor air are needed to replace air exhausted through hoods for kitchen appliances and for smoke removal. Use of vestibules or revolving doors is suggested to reduce this infiltration.

The system must be able to operate efficiently at part load performance due to the widely varying conditions. Since these systems have high ventilation air quantities, exhaust air from the conditioned space can also be used over air-cooled or evaporatively-cooled condensers to improve energy performance. Odor removal is also important. Conditioned air from dining areas can be drawn in to the kitchen to both provide some cooling effect and to assure odor control. Bars and nightclubs should also consider charcoal filters with manual purge control for 100% outdoor air to exhaust. Filters should be 35% efficient or better in patron areas.

Recommendations/Energy Services Opportunities

Upgrade older, inefficient cooling equipment to modern high efficiency units. This may also solve any perceived CFC problems, as well as reducing energy bills. Where gas heating/electric cooling units are used, consider heat pump replacements, including the geothermal option.

Heat recovery system concepts should also be considered and employed where economically attractive. Energy conservation concepts must be simple: cooling with outdoor air using economizer cycles, heat pipes for ventilation in smoking areas, outside air damper control during system shutdown when main areas are not in use.

Water Heating

Restaurant kitchens have a high hot water usage, largely for dishwashing. Other uses include food preparation, cleaning pots and pans and floors, and hand washing for employees and customers.

Typical System

Many food service establishments heat water with conventional gas water heaters, and to a lesser degree electric resistance water heaters. Hot water is then stored in an insulated tank until used. In some cases, larger tanks are used with the electric heaters programmed for off-peak operation.

In public places, the National Sanitation Foundation (NSF) or local health departments require that bacteria be killed by rinsing the washed dishes with 180 to 195°F water for several seconds. An ample supply of general-purpose 140 to 150°F hot water is required for the wash cycle. The lower temperature water is distributed for general use, but the high temperature water should be confined to the requiring equipment and should be obtained by boosting the temperature.

Recommendations/Energy Services Opportunities

  • The NSF allows lower temperatures when certain types of machines and chemicals are used; investigate if local codes permit and consider implementing this concept. Add insulation to the hot water storage tanks to minimize heat losses.
  • A heat pump water heater may economically produce hot water while providing inexpensive cooling to the kitchen.

Cooking

The term "commercial cooking" refers to the preservation and preparation of quantities of food for the general public. Even though the term "commercial" implies that the sales of food are for the purpose of making a profit, the term is used here also to designate large, non-profit cooking establishments and employee cafeterias.

Typical System

Cooking systems can vary widely from one establishment to another. Equipment is typically either electric- or gas-based (natural gas or bottled propane). A variety of equipment with specialized functions is used - based on three basic methods: conduction, convection and radiation.

Recommendations/Energy Services Opportunities

Upgrade to more modern equipment and change-over from gas to electric. For details, refer to the Food Service Equipment segment.

Refrigeration

Another major energy user is the refrigeration equipment needed for food preservation prior to cooking and serving. Refrigeration is only a means to an end. In most cases, that end is the preservation of foods. Refrigeration is often a significant, steady use of year-round electricity since this equipment runs even when the building is unoccupied. Therefore, it is usually cost effective to install the most efficient refrigeration practical. Consequently, the electric utility representatives welcome the opportunity to work closely with their energy customers during the early planning stages to help them understand their options. Consider expansion needs and the potential replacement of old inefficient equipment with new, improved and efficient units.

Typical System

Most restaurants use a combination of refrigerators and freezers, ranging from reach-in type to walk-in type boxes. These are cooled by one or more refrigeration compressors often using air-cooled condensers. They may be arranged randomly or in racked banks for ease of service and space economy. Some use CFC refrigerants; most use HCFCs.

Recommendations/Energy Services Opportunities

Most opportunities are in retrofitting to either more efficient motor-compressors, or to use non-CFC refrigerants, or both. In some cases, tying the HVAC and Refrigeration systems into a geothermal loop can improve the overall system efficiency, reduce energy costs, and avoid noisy outdoor equipment that is subject to vandalism.

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