Sustainability: Why lighting is important
March 29, 2011
by Lime Energy
When Thomas Edison first produced a reliable, long-lasting light bulb in 1879, no one in their wildest dreams could think that 130 years later, businesses would have other choices for electric light that would be at least seven times more efficient than Edison’s incandescent bulb. The chart below shows the evolution of lighting for production and warehouse applications.
By far the most common fixtures in food production are the metal halide high bay lights found in production areas and warehouses. New metal halide lamps have tremendous light output at very high efficiency, but manufacturers' ratings over time show a degradation of the light output — losing 40% of the initial output after 80% of the useful life, even though the energy use stays the same as that of new lamps.
The replacement for metal halide that is most often selected is a multi-lamp fluorescent fixture with high-output lamps and often with high-power ballasts. These lamps degrade by only 10% over their entire useful life, so during the vast majority of operating hours, they are producing the needed light output with about half the energy.
Next in order of the most common lighting upgrade is replacement of older-style fluorescent T-12 lamps and magnetic ballasts with current-generation T-8 or T-5 lamps and more efficient electronic ballasts. The age and location of plants, warehouses and depots often dictates where T-12 lamps were still in use — they are most often found in older buildings and in cities with low energy rates.
Fluorescent lamps with the right type of electronic ballasts can be operated with motion sensors and photocells without harming lamp life. This simply keeps lights off when they are not needed, and the use of sensors can significantly add to the energy savings. Use of photocells in a warehouse is ideal for the aisles that are visited less frequently.
The new lighting design must be compatible with operations, particularly in food production. First, food manufacturing areas require that lamps cannot shed glass from the fixture in case of breakage, so in these areas, the specified lamps are behind a lens or include a coating that holds broken glass pieces in place if it were to break inside the fixture. Second, a new lighting design must handle the temperature extremes of hot and cold that might be specific to each plant. This is particularly important in refrigerated warehouses, where LED lighting may be a viable option. Third, the effective color temperature of the light sources is important because the color temperature of the light source influences the perceived color of objects in the warehouse or production floor.
The dollar value of the utility cost savings and the return on investment depend mainly on the annual hours of operation of the lighting system, and on the electricity rate. It is not unusual to achieve annual savings on the order of 20 to 30¢ per sq ft, so across several large plants or a large portfolio of smaller facilities, this quickly turns into thousands of dollars of savings per month that flow straight to the bottom line instead of out the door to the utility company. The cost of a lighting retrofit is easily offset by utility rebate programs, federal tax deduction and tax treatment for abandoning the existing system — not to mention significant savings in maintenance costs because maintenance for the new system will be virtually zero cost for several years after the replacement. The average return on investment ranges from 25 to 35%, which generally exceeds the return of other projects that might be contemplated in a plant or business.
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