Desiccant Systems: A new way to cool

There is a new form of cooling and heating on the horizon that is hoping to replace the inefficiency of the current systems that dominate the market. Desiccant systems, also known as thermally driven air conditioning, what? Desiccants remove moisture to reduce humidity, improve air quality, and energy efficiency. Desiccant materials are those that attract moisture due to differences in vapor pressure. Desiccant materials can be dried, or regenerated, by adding heat supplied by natural gas, waste heat, or the sun. How does it work? A wheel that contains a desiccant turns slowly to pick up humidity from incoming air and discharge that humidity to the outdoors. A desiccant system can be combined with a conventional air conditioning system in which the desiccant removes humidity and the air conditioner lowers air temperature.

One promising desiccant cooling system is being developed in conjunction with energy recovery ventilators (ERV). An ERV is designed to recover energy in a mechanical ventilation system during the heating season, more specifically, recover heat and humidity from indoor air to preheat and humidify incoming fresh air. The combination of desiccants and ERV’s provide year-round energy recovery for buildings with mechanical ventilation increasing energy efficiency of the heating and cooling process.

Typically, air that is dried by desiccants is subsequently cooled by an air conditioner or evaporative cooler. But another newly patented desiccant cooling cycle creates two dry air streams which uses indirect evaporative cooling of one air stream to cool the second stream. In turn, direct evaporative cooling delivers cool and dry air to the building. Through this system, regeneration exhaust heat can be used to heat water. This step can be taken one further by combining the system with a solar air heating unit and now you have passive solar heating, cooling, and hot water all in one well balanced and energy efficient system.

Given the fact that low temperature heating is the primary energy hog of all residential, commercial and industrial buildings, significant technological advancement in heating and cooling systems is in high demand. For numbers sake alone, nearly 61% of the energy used throughout all sectors of the U.S. economy is for low temperature heating uses and the second greatest energy end use is cooling at 13% of energy consumption. Desiccant cooling/heating systems hope to reduce those staggering numbers significantly in the not so distant future.

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