Reduce your energy bill, part two of three
May 12, 2010 | 7:00 pm CDT

Energy conservation and cost reduction can be tied to five major energy areas in the plant. The two we are dealing with here are heating and cooling and lights.

Conserving energy and reducing costs do not need to involve the time and talents of a technologist or a capital expenditure program. All they require is a little knowledge. With this in mind, we can go through an array of suggestions for keeping electric costs down in every part of the plant.

Heating and cooling

Our first concern in employee heating is performance; a cold employee is not a safe or efficient employee. But, if we can save on heating without affecting performance, let's do it!

The small 1- to 5-kW space heaters often used in the office and on the shop floor on cold mornings are very expensive. Although the power they use only costs $0.06 or $0.27 per hour (respectively), they add $7.50 or $37.50 to the demand for the month.

First consider what it takes to keep someone warm. Our bodies and clothing constantly lose heat by radiating energy to our surroundings. To control workers' comfort, heat losses from the body must be controlled. We do this by heating the work area. In a large space, heating the entire space is inefficient. Therefore, we use a spot heater -- a very hot radiant heater (1000 F or more)- -or a convective heater, which blows warm air. With either type of heater, employees are heated, but so are other nearby things in the mill. Efficiency is further reduced if the heated area is not effectively sealed from the cold, outside air. Because the body loses as much as one-fourth of its heat from the head, and the amount of heat being lost determines a person's comfort, employees will feel comfortable at a cooler temperature if they are wearing warm caps.

It should be noted that the changes in temperature which are critical for employee comfort have little effect on wood. Wood does not change its properties, or shrink or swell, with these moderate changes. Between 30 F and 150 F, wood shrinks and swells only when the relative humidity changes. So, when heating for employee warmth, do not be concerned about the wood, only the employees.


Safety, as influenced by adequate lighting, is of utmost concern when considering lighting and energy conservation. Because 70 percent of the cost of lighting an area is for electricity (30 percent is capital expense and maintenance), the efficient use of the light produced is essential. Lighting should be sufficient for the area, but not excessive. Different lighting systems have different efficiencies -- their efficiency is a measure of the amount of power used for the amount of light produced.

Lighting efficiency

Incandescent 10 percent

Fluorescent 20 percent

Mercury vapor 24 percent

Sodium halide 33 percent

In addition to the inherent inefficiency shown in the table above, the output of lights drops with the age of the bulbs and with increased operating temperatures. With fluorescent bulbs, for example, if the output is 100 percent at or below 80 F, it drops to 80 percent at 115 F and 75 percent at 130°F.

View  Part One   and  Part Three  of this series.

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About the author
Gene Wengert

Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 45 years. He is extension specialist emeritus at the University of Wisconsin-Madison.