Wal-Mart Superstore
Wal-Mart is the largest corporation in the world with revenues of well over $200 billion annually. It is currently expanding at a rate of over 40 million square feet per year and is the largest employer in the U.S. with over 1.2 million associates. Today, Wal-Mart’s annual electric bill is approaching $1 billion annually. This represents the company’s largest non-labor expense. In a typical Wal-Mart Supercenter, electric lighting consumes roughly a third of the electricity used annually and in Wal-Mart’s ~3500 stores in the US, this translates into an estimated annual lighting electricity load of 3,646 MWh/year excluding the added HVAC loads attributed to electric lights and skylights.
Wal-Mart has been a leader in implementing energy-efficient technologies over the past few decades. Some measures it has adopted include using skylights for daylight harvesting (using dimming ballasts to save electric lighting energy when the skylights keep the light levels high), retrofitting over 900 stores nationwide from T-12 fluorescent to T-8 fluorescent lighting, using white-colored roofs to save cooling load, and demand based ventilation (measuring CO2 levels in the stores and clubs to control the amount of ventilation air brought through the rooftop units). More recently, several technologies are being evaluated in the McKinney, Texas supercenter with ORNL technical support to determine their technical and economic viability. Hybrid Solar Lighting is one of the technologies being evaluated at the McKinney, Texas superstore.
Wal-Mart has extensively assessed the non-energy benefits of using natural light in stores. It has concluded, among other things that the stores are perceived by customers to be cleaner, the products are more appealing, and, customers prefer and are attracted to areas illuminated with natural light. For this same reason, Wal-Mart is in the process of relamping all of their stores with high correlated color temperature (CCT) lamps that closely match the spectrum and color temperature of sunlight (~5100K). Unfortunately, stores that incorporate skylights have ~1250 linear feet of roof penetration. This often creates maintenance problems associated with roof leaks. Further, skylights cover an area of ~1,000 sq.ft. on each roof-top, and thus contribute considerably to the buildings HVAC load.
A Hybrid Solar Lighting system is installed in the electronics area of the store where it is incorporated into spot lighting to highlight the various products in the area. Since hybrid lighting systems can provide distributed sunlight in store areas where skylights are not feasible and eliminate many of the problems related to skylights, Wal-Mart is interested in evaluating hybrid lighting technology. The optical fibers distribute sunlight directly to the individual fixtures as seen in the picture, and the electric lamps are supposed to modulate light levels in response to the amount of sunlight available. A reference lighting system is installed adjacent to the hybrid solar lighting to use for some sales comparisons.
LSI Industries is currently Wal-Mart’s largest supplier of fluorescent luminaires. LSI Industries is one of largest independent OEM suppliers of commercial indoor and outdoor luminaires in the U.S. LSI Industries is investing internal resources to work with ORNL researchers to develop a, UL listed hybrid luminaire compatible with the specifications of Wal-Mart Stores. As part of this development, LSI Industries will be supporting the hybrid lighting technology demonstration at a Wal-Mart Store by developing and providing hybrid luminaries currently under development to distribute the collected light into the retail area.