Related Efficiency Upgrades - Lighting
One of the first things to consider when evaluating a cooling system is lighting. The fact is a large portion of the energy consumed by the lighting system shows up as heat in the conditioned space. Therefore, improvements in lighting efficiency (technically called efficacy) decrease building cooling loads. However, this will also increase the heating load during the heating season. While uncommon, this increase can be a concern if the original building design was "counting on" the heat given off by lights to reduce the size of (or even eliminate) a heating plant. Estimates of .the final impact of a lighting retrofit or change should be made by qualified professionals taking into account the specifics of a building.
In general, if the original building design was conservative, the heating system will usually be able to handle the added load. And, in most air conditioned commercial and industrial buildings annual total operating costs are lowered through improvements in lighting efficacy (since heating operating costs are usually smaller than cooling). Once again, the final economic evaluation should be made by qualified professionals familiar with the building in question as well as the prevailing power and fuel use and costs for the building.
As a general rule of thumb, any air-conditioned commercial or industrial building with a high percentage of incandescent lighting will find that conversion to a more efficient and effective lighting source will have a significant impact on building cooling and heating loads. Only 10 percent of the energy going into an incandescent light is converted to light, the rest of the energy is given off as heat. For a fluorescent light, twice as much of the energy is converted to light, but this is still only 20 percent of the total energy.
This makes it easy to understand why improving the efficiency of the lighting can result in a 20 percent savings in cooling costs in an office building.
The formula used to calculate the heating load for incandescent lighting looks like this:
12,000 Btu/Ton
12,000 Btu/Ton
As an example, forty 100-watt incandescent lamps require 12,283 Btu of cooling (slightly over one ton). The site could use 27 four-lamp fluorescent fixtures (or 4400 watts) at the same one ton of cooling load, yet produce 10 percent more light.
Are lighting efficiency improvements important for other reasons? They may be! While certainly not an answer to the CFC phaseout question, proper lighting selection may offer a lower cost alternative to adding or replacing chillers. And, there are numerous situations where an upgrade in lighting can improve occupant comfort and productivity. Coupled with the energy savings, this all adds up to improved profitability.
