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Summer Air-Conditioning Systems/Saving Natural Resources
Published in Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo, Energy Conservation Guidebook, 2020
Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo
An acceptable level of humidity in air that has been heated or air conditioned can have an effect on how warm or cool the air feels to humans. In winter heating, a heating system operating at 68 degrees Fahrenheit with 60% relative humidity provides the same level of comfort as a system set at 72 degrees Fahrenheit at 30% humidity. Therefore, adding moisture to the air can result in creature comforts with lower energy expenditures. In cooling season, the opposite is true. An air-conditioning system operating at 78 degrees Fahrenheit at 30% humidity provides the same level of comfort as a system operating at 74 degrees Fahrenheit and 70% humidity. In summertime, the lower level of humidity will increase comfort and lower bills. Humidification is primarily achieved by four primary methodologies. The first and perhaps most common is the flow-thru humidifier. In this method, a media capable of aiding in the evaporation of water is placed in the direct path of air flow. Through some sort of continuous wetting process, the media is wetted, and evaporation improves the humidity. Another method, spray humid-ification simply directly sprays water into the flow of air to improve evaporation. Drum-type humidifiers allow air to be passed through a drum-shaped object that is slowly rotated through a bath of water. The evaporation of water from the slowly rotating drum increases the humidity in the air that passes over it. Perhaps the best and most costly method of humidification is steam. In a steam humidification system, a heating element provides a source of heat energy that boils water in which it is immersed, or that passes over it, and the steam discharged by this system is allowed to enter the flow of air. Dehumidification can be obtained by mechanical devices called dehumidifiers that use air conditioning technologies to desiccants, materials to absorb the water or humidity from the air.
Auditing, Planning, and Retrofitting
Published in Stan Harbuck, Donna Harbuck, Residential Energy Auditing and Improvement, 2021
If your initial audit of the home reveals that moisture in the home is a significant problem, you can recommend any of the following: Educate the homeowner. If you notice a clothesline by the washer or wood drying in the home, let your client know that these activities increase moisture problems. Tell your client to close windows and doors during warm, humid periods. If possible, remove materials that are susceptible to moisture issues.Make repairs. Repairing and clearing downspouts and gutters typically solves some of the minor drainage issues. Repairing an existing sump pump can be more useful in removing condensation than adding mechanical dehumidification.Close the vents of the crawlspace to the exterior and convert the crawlspace to a conditioned area to prevent condensation.Place a vapor retarder on the ground in the crawlspace, such as in Figure 7-5. This will bring the surface temperatures in the crawlspace above the dew point. If the problem is severe, you can excavate around the outside perimeter of the basement and install a drain tile to collect water. This solution is extremely expensive, usually only done as a last resort in the private arena and is beyond the scope of the weatherization program.Install a dehumidifier to remove moisture. Dehumidifiers pull the humidity from the air using a refrigeration process to cool the air (cold air holds less moisture than warm air). Then the dehumidifier heats the air, which by definition reduces its relative humidity. Since air conditioning cools air and dehumidifiers heat air, these should not be operated simultaneously for efficiency reasons.Install fans to circulate air throughout the house. Unfortunately, using fans to circulate air, and mechanical dehumidification will only help with light to moderate condensation.
A review of desiccant evaporative cooling systems in hot and humid climates
Published in Advances in Building Energy Research, 2021
Ismanizam Abd Manaf, Faisal Durrani, Mahroo Eftekhari
Solid desiccant dehumidification systems can either use rotating wheels or the packed-beds. The dehumidifiers showed in Figure 2 (Dwyer, 2014) are of the solid wheel type and operate using two air streams; the larger air volume which is to be dehumidified, and the smaller air volume for reactivation of the desiccant rotor. As the larger air volume (process air) passes through the slowly rotating rotor, the water vapour is adsorbed by the rotor material. It reduces the humidity of the air which then leave the dehumidifier as dry air. This dry air is then supplied into the specified space. The smaller air volume known as reactivation air which flows counter to the dry air, is heated up by a heating coil before entering the rotor to remove the moisture captured in the desiccant rotor. As this warmer air is passed through a smaller segment of the rotor, the rotor material releases its moisture also known as desorb into the heated air volume. The moisture is leave the dehumidifier as wet air, which is then discharge from the space that is to be humidity controlled. Typically, 60% of the face area would be used for the dehumidification process. In the packed-bed type system as illustrated in Figure 3, air to be dehumidified is blown over the solid desiccant bed using a blower. The desiccant bed is subsequently regenerated using hot dry air. Usually, two packed-bed alternates between the dehumidification and regeneration processes to have provided continuous air supply (Alizadeh, 2002).