Desiccant Cooling
From Swikipedia
Introduction
Desiccant cooling is effective in warm and humid climates. Natural cooling of human body through sweating does not occur in highly humid conditions. Therefore, a person’s tolerance to high temperature is reduced and it becomes desirable to decrease the humidity level. In the desiccant cooling method, desiccant salts or mechanical dehumidifiers are used to reduce humidity in the atmosphere. Materials having high affinity for water are used for dehumidification. They can be solid like silica gel, alumina gel and activated alumina, or liquids like triethylene glycol. Air from the outside enters the unit containing desiccants and is dried adiabatically before entering the living space. The desiccants are regenerated by solar energy. Sometimes, desiccant cooling is employed in conjunction with evaporative cooling, which adjusts the temperature of air to the required comfort level.
Brief Description
When to use Desiccant Cooling:
Desiccant cooling technologies can be used in the following situations:
When moisture levels are high due to high building occupancy
When potential cost savings are significant
High electrical demand charges applicable
Low natural gas rates available
Low cost central steam available
Heat recovery options available
Tight control over moisture levels is required
Moisture is problematic to interior spaces like Hospitals, Hotels etc.
Occupant comfort cannot be compromised
Benefits of Desiccant Cooling
1. Increased Comfort – Desiccant unit controls humidity and provides for increased comfort to the occupants of the building.
2. Lower Operating Costs – It utilizes lower cost natural gas for regeneration, which results in lower operating costs.
3. Lower Peak Electric Demand – The demand on electricity can be reduced by switching to latent cooling to alternate energy sources such as Natural Gas, Steam and Heat Recovery options (Engine Driven Chillers, Co-generators, Condenser Heat and, Steam Condensate).
4. Dry Duct Systems – As high humidity air and dust in ducting result in fungus growth and bacteria growth, desiccant cooling technology makes use of dry duct systems.
5. ASHRAE 62-89 - The Standard addresses increased levels of outdoor air which include increased total cooling load and increased latent load. Desiccant systems can directly address this problem.
6. CFC Free - Desiccant systems do not use CFC's for moisture removal, thus, they are CFC free.
7. Improved Indoor Air Quality – Desiccant cooling technologies result in appropriate levels of fresh air, reduced levels of air borne bacteria, and air treatment chemicals with liquid desiccants.
8. Reduced Building Maintenance – A number of maintenance issues are related to high humidity levels in buildings such as mold and mildew growth, corrosion of metals, spoilage of wall and window coverings and carpeting. Thus, with desiccant cooling, the building maintenance activities are reduced.
References:
http://www.daviddarling.info/encyclopedia/D/AE_desiccant_cooling.html
