Last week, we started a series on the benefits of LED retrofits for consumers and businesses, mostly focused on the commercial sector. As LED bulb prices have come crashing down from a couple years ago, retrofits are becoming more economically feasible by the day.
Our first article took a look at how public utility companies can reduce load and maintenance costs on their own equipment by reducing demand from end users. The most visible way they do this is through the various energy rebates and subsidies they provide homeowners and businesses for switching to more efficient lighting products.
The second article in the series examined maintenance costs of lighting systems, replacing bulbs and ballasts, and labor time. While some of those costs are just as large with LED compared to older tech, other costs can decrease significantly, ladder time being the most notable.
In this article, we'll discuss another hidden cost of older types of lighting: cooling. First, a few facts:
- The temperature on the surface of Mercury, the closest planet to the Sun, is around 800° F.
- Magma from a volcano can reach up to 2,400° F.
- The fire from an average stove is around 3,000° F.
- The filament of an incandescent light bulb can reach upwards of 4,500° F.
So let's talk about cooling costs and retrofits.
Costs of Cooling Large Buildings
According to the Energy Star Building Upgrade Manual section on lighting (PDF), "Lighting consumes close to 35 percent of the electricity used in commercial buildings in the United States and affects other building systems through its electrical requirements and the waste heat that it produces." BizEnergyAdvisor puts the estimate at 40% for lighting for large office buildings with more than 100,000 square feet, along with 14% for the cooling system.
For most larger office buildings in the U.S., cooling represents the largest energy operating expense. In these multi-story buildings hundreds of workers and just as many computer workstations contribute heat to the interior space. With the considerable heat from overhead and task lighting systems added to the mix, building HVAC systems are normally in cooling mode. According to a lighting expert at Standard Products of Canada, "a typical rule of thumb on cooling is that it can cost a facility 2 1/3 to 3 times more to cool than to heat."
Older Lighting Technology
Filament-driven lighting systems, which utilize halogen and incandescent lamps, can put an unseen and largely unmeasurable burden on cooling equipment (and bills) in commercial and industrial buildings. You don't install a bunch of bulbs that burn at thousands of degrees and expect a cool workplace.
And the problem doesn't stop at filament bulbs. Compared to newer technology, T12 fluorescent bulbs with magnetic core and coil ballasts are also very hot to operate. This is one reason these systems have been legislated out of existence in the United States.
Newer, More Efficient Fluorescent & LED Systems
This is another reason retrofits make sense. While switch to LED should have the greatest impact, newer fluorescent technology is nearly as efficient. T8 bulbs have 30,000-40,000 hour lives, while electronic ballasts run much cooler than magnetic ballasts. Screw-in and twist-and-lock CFLs also operate at much lower temperatures than incandescent and halogen.
However, because LEDs win on wattage (and thus overall energy input), they should contribute more to reducing cooling load than any other type of technology. According to CSE Mag, "Recent developments in solid-state LED technology show superior performance for both the space fraction and radiative fraction numbers. As compared to incandescent fixtures, the fraction of heat transfer due to radiation vs. convection is typically much higher for LEDs resulting in more of the lighting load being stored delaying its conversion to room cooling load." In layman's terms, this means LEDs produce more visible light with less energy cost and lower heat.
One problem with LED retrofits for commercial buildings at this point is the lack of data on how much they can reduce cooling load compared to other lighting types. Cooling load analysis and modeling of lighting systems will continue to develop as more buildings switch to LED, but all the numbers aren't in yet.
So consider reduction of cooling load as a bonus benefit of LEDs until the lighting and construction engineering industries have more hard data to present the case.
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