In a departure from its typical store layout, Giant Eagle, one of the nation’s largest food retailers and distributors, has entered a new realm within the food retail industry. Opened in November 2009, Giant Eagle’s Market District store in Robinson Township, Pa., is a food utopia.
One of four district locations, this 150,000-square-foot facility was recently awarded Leadership in Energy and Environmental Design-gold certification through the U.S. Green Building Council. The store incorporates a slew of sustainable features, both structurally and within its everyday operations. Used in the design is recycled steel from both regional and national mills prevalent in the exposed beams that support the structure, adding to the overall aesthetic. Other eco-friendly enterprises included the use of low-emitting adhesives, sealants, paints and coatings, indoor environmental quality management during construction, controllability of comfort and lighting, and verification of thermal comfort.
Inspired by the open-air markets of Europe, the design itself, however, was susceptible to the phenomenon of stratification.
What happensStratification occurs when less-dense hot air rises in a space. The air supplied by a forced-air heater at 100°F to 125°F is approximately 5 percent to 7 percent lighter than the ambient 65°F to 75°F air, resulting in a significant temperature difference between the floor and the ceiling. A de-stratified space has only a slight temperature difference from floor to ceiling, creating a more energy-efficient area because less heat will escape through the walls and roof.
The savings incurred by de-stratifying a space with large-diameter ceiling fans, which equalizes the temperature in the space and lowers the heat loss through the roof, can be 20 percent to 40 percent of the energy used to heat the space.
Taking into account the likelihood of stratification, 22 small ceiling fans were specified to prevent the costly provision. To ensure consistent temperatures and to eliminate drafts or air pockets, the specifications were changed to incorporate two 12-foot diameter Element fans from the Big Ass Fan Co. The 10 patented airfoils with winglets, similar to the design of aircraft wings, generate smooth, consistent airflow without creating a draft. Because it’s designed to move air efficiently without excessive drag, the fan is slowed in the winter - not reversed and sped up - to re-circulate the heat without the strain on the motor and resulting energy waste. Element’s gearless direct drive motor operates silently, allowing shoppers to enjoy the store without having the added noise that accompanies typical large industrial fans.
A marriage of efficiencyThe relationship between large-diameter fans and air-handling systems is a marriage of energy efficiency and comfort. A fan’s effectiveness lies in its ability to move large volumes of air slowly and gently without disrupting the atmosphere of the facility, improving comfort year-round.
In the hot summer months, with the fans operating between 60 percent to 100 percent of capacity, the additional air movement does not cool the air, but rather it creates a cooling sensation as the breeze passes over occupants’ skin. The cooling effect provided by elevated air speed allows users to turn the thermostat up several degrees, reducing cooling costs by as much as 15 percent.
Brad Morris, Giant Eagle’s manager of engineering, said the store’s atrium required thermal de-stratification in the winter months due to the cooling effect caused by the open-air produce refrigerators lining the walls. By slowing the speed of an HVLS fan down to 10 percent to 30 percent of its maximum rotations per minute, warm air is redirected from the ceiling to the occupant level, increasing employee comfort and reducing the heating time.
“From both an aesthetic and performance standpoint, the Element fans have exceeded our expectations,” Morris said. “They bring the heat down from the ceiling providing nice, gradual air movement.”
EffectiveEffective air movement doesn’t occur simply through fan rotation alone. The type of blades - or airfoils - and the angle at which the airfoils are placed play an important role. An angle of attack approaching 30 degrees or more will increase drag and therefore require a larger motor that moves less air. This results in increased energy costs and lower aerodynamic efficiency. At the same time, a flat airfoil that is almost horizontal will typically not move much air at all. That said, it is extremely important to choose a fan with 10, moderately pitched, narrow aerodynamic airfoils to achieve efficient air movement without incurring excessive drag. Similar to aircraft wings, airfoils allow for a much smaller energy-efficient motor.
To further enhance the efficiency of the airfoils, winglets are added at the tips to help eliminate wing-tip vortices that can induce drag and lower overall efficiency of the airfoils.
In addition to the energy concerns, maintaining consistent year-round temperatures can ensure employee and patron comfort as well as prevent premature spoilage from produce not adequately shielded from extreme temperatures. Since extreme temperatures lend themselves to moisture buildup, eliminating the hot and cold pockets of air in the space can theoretically prevent moisture-related food damage. It is also crucial to maintain moderate temperatures (50°F-100°F) in a space to reduce the risk of spoilage.
An ongoing measurement program tracks energy consumption every 15 minutes to determine efficiency. Operating a store in a sustainable fashion such as this conveys to its customers and team members that Giant Eagle is committed to saving energy, providing employees with a safe working environment and constructing an environmentally responsible building.
This article and its images were supplied by Big Ass Fan Co.