Home Energy Management A Review of Energy-Saving Systems and How They Work

A Review of Energy-Saving Systems and How They Work


With the recent push by the White House to address environmental issues, energy conservation has, once again, come into sharp focus. Some hotels do nothing to conserve energy, while others make a cursory effort at it. The fact is that for some nominal cost and effort, real energy savings can be gained, along with the hotel doing its part to reduce greenhouse gases.

The two biggest energy costs in a hotel are lighting and heating. The other two, air conditioning and “base load” (fans, motors, etc.) are also significant. Lighting can account for up to 30 percent of a hotel’s energy costs. The simplest way to reduce lighting costs is to replace incandescent bulbs with fluorescent lamps. These lamps do cost more than standard incandescent bulbs, but last much longer. Improvements in fluorescent bulbs actually enhance room ambience, rather than detract from it. Retrofit projects can be eligible for rebate programs, thus reducing overall project costs. Overall energy cost savings from a retrofit project can exceed 20 percent.

The modern incandescent bulb has not changed that drastically since Thomas Edison invented it in 1879. Bulbs have a metal base with two contacts that form an electrical circuit. The contacts are attached to two wires which, in turn, are attached by a thin metal wire called a filament. The bulb is filled with an inert gas (usually Argon). When connected to electricity, electrons flow from one contact to another, creating energy by heating the atoms in the bulb. The atoms release mostly infrared light photons when the heat in the bulb reaches 4,000 degrees Fahrenheit.

How Fluorescent Bulbs Work

The fluorescent bulb has similar components but works differently. The lamp is a sealed glass tube containing mercury and inert gas (Argon). The inside of the glass is coated with a phosphor powder. There are two electrodes, one at each end. As electricity flows through the tube, the mercury changes to a gas. Electrons and charged atoms collide with the mercury electrons to increase the energy level. When the electrons return to their original energy level, they release light photons. The phosphors coating the tube emit light when exposed to the photons.

The reason incandescent bulbs are not efficient is the heat required to make light. Much of the energy required to heat the bulb is wasted. Because fluorescent bulbs do not require nearly as much heat to produce light, they are four to six times more efficient. As an example, a 15-watt fluorescent bulb produces as much light as a 60-watt incandescent bulb.

Another, sometimes overlooked, area of energy savings potential is preventive maintenance. Because heating and cooling can require as much, if not more, energy than lighting, special attention should be paid to the equipment in these areas. Equipment configurations for heating/cooling vary among hotels, depending on the size and age of the property. One common component of all systems are heating/ cooling coils.

For cooling, the unit’s compressor compresses cool Freon, causing it to become hot. The gas passes through a set of coils that dissipate the heat and condense it into a cool liquid. Air passes through the cool coils, absorbing heat that is in the room.

The Importance of Coil Cleaning

If the outside of the coils is dirty or clogged, the compressor has to work harder to achieve the temperature demanded by the thermostat. Regular cleaning of coils can increase the efficiency of any unit, prolong its life, and save energy. There are many other areas of preventive maintenance that require attention such as motor/fan revolution, proper belt tension, and correct Freon levels, to name a few.

There are numerous energy saving control units on the market today, ranging from simple guestroom devices to sophisticated, computerized energy systems that monitor everything. The most basic of these controls is the thermostat.

An analog thermostat uses a mercury switch in a glass vial. There are also two thermometers, one that displays the temperature on the front of the unit and another that controls the operation of the heating/cooling units. The second thermometer is a bimetallic strip rolled into a coil that expands with heat and contracts with cooling. The mercury switch is mounted on top of the coil and is tripped to engage the proper unit (either heating or cooling).

One problem with analog thermostats is that they are not very accurate. The device can be off by as much as 5 degrees either way. A digital thermostat uses a device called a thermistor (an electronic resistor) to measure temperature instead of a metallic coil. This device is much more accurate in recording temperatures. Digital thermostats are also programmable so they can cut back on energy when it is not needed and also control minimum and maximum temperatures in a guestroom. Digital thermostats can save up to 5 percent off heating and cooling bills, with no additional energy control devices required.

Geoff Griswold is the general manager of The Omni Group, an Atlanta-based technology services and consulting company. Founded in 1979, The Omni Group has provided services to major chains, management groups, and hundreds of individual hotels. Geoff can be reached at (678) 464-2427 or at geoff@atlantaomnigroup.com.