Solar Assisted Household Clothes Dryer

Energy savings for domestic appliances have been an emphasis for several years. The efficiencies of several appliances have improved dramatically as a result of this attention. Refrigerator, water heater, and washing machine energy consumptions have been reduced. One appliance has not experienced significant improvement, the clothes dryer. Typical household clothes dryers use large amounts of electricity or natural gas to heat air that is circulated with the clothes. The energy to heat the air is a function of the amount of air and heat needed to remove moisture from the clothes. Using solar heat to augment or replace the other energy sources can provide significant energy savings. Conventional house construction includes features which collect and concentrate solar energy in the air occupying the attic space. Typical home design provides a roof which functions as a large area solar energy collector. Many roofing materials have solar absorption of 80% or more. Insulation of the roof decking is uncommon so that absorbed solar heat conducts through and heats the attic air. Through simple, low-cost ducting and minor modification of a clothes dryer air inlet, this energy resource becomes available for use. This study evaluates the potential energy savings of using solar-heated attic air as a clothes dryer air source. Considering house construction as well as seasonal and regional climate variations, attic air can augment and may fully replace utility energy as the heat source for drying air during daylight hours when solar energy is incident on the roof. The energy savings can be up to 3.5 kilowatt hours (or the heating equivalent for natural gas) for each dryer load.