How It Works:CoolSaver
AC systems are designed to remove a certain amount of moisture at peak conditions. This is known as the latent heat ratio of the system. Sensible heat is the heat measured in degrees on a common thermometer. Latent heat is the heat in terms of moisture removed.
A building's air conditioning removes moisture from the air in order to provide for both human comfort and mold-and-mildew control. Warm moist air is blown through a cooling coil to cool the air below its dew point temperature. The dew point temperature is defined as the temperature of the air when the relative humidity is 100 percent. Relative humidity is defined as the amount of moisture in the air relative to the most moisture the air can hold at the same temperature.
As air is cooled it loses its ability to hold moisture. So, relative humidity is increased by cooling the air, as well as by adding moisture to it. For example, as the air cools on a muggy night the relative humidity increases. When the relative humidity reaches 100%, the air has been cooled to its dew point and dew forms on surfaces. Similarly for the air conditioner, once the air is cooled below the dew point, the air releases moisture which collects in a drain pan, and drains out of the system. The cooled and dried air is delivered to the building. The air now has a lower dew point called the exit dew point. Many air conditioning systems do not remove adequate amounts of moisture for a tropical climate.
At peak conditions there is more sensible heat than latent heat. At night and on cooler days, the amount of sensible heat shrinks but the amount of latent heat does not. And, on wet days, the amount of latent heat increases. During humid and/or cool weather, standard AC systems cool the buildings, but they dont dehumidify adequately.
Furthermore, some new air conditioning units have sacrificed latent (moisture removal) capacity in order to increase their nameplate SEER ratings. (SEER stands for Seasonal Energy Efficiency Ratio and is a measure of energy efficiency.) One way manufacturers increase SEER is to raise the cooling coil temperature. Unfortunately, this means that the air blown through the coil does not reach a low dew point temperature. Some of these high efficiency units have a latent heat ratio of 15 percent or less at design conditions.