Solar Lumber Kilns Jake Altemus The Sun Provides huge amounts of low intensity energy (Wengert and Oliveria) Really Dispersed Harnessing the Power Free power! Free Power! Save money, Save Fuel, Save the Planet? So This Means What? Applying the Principles: Wood needs a low moisture content (6-8%) to be used in furniture and construction applications. So after lumber is milled, it has to be dried. Lumber drying consumes over 10 TRILLION BTUs per year. (Scanlin) Fortunately, by drying wood the value of the lumber is increased by % (Scanlin) So How Do You Dry Wood With Solar Technologies? Solar Collection South Facing Since these will be set collectors, best year-round performance will be achieved by setting the angle of the collector equal to the latitude. + or 10 degrees to accommodate for better performance in summer (- 10 or flatter) or winter (+ 10 or steeper) Need a temperature between 100 180 degrees Fahrenheit. (Scalin) Drying time depends on thickness and density of the species of wood. Higher temperature, lower humidity and controlled air flow dry lumber the fastest. Parts of The Solar Lumber Kiln Glazing Framing Material Absorber Insulation Fans Venting Glazing: As with all collectors tempered glass is ideal. Lets heat in, doesnt let it escape. 2nd layer of glazing can add up to 35% improvement in performance. Framing Materials: 2x lumber PVC Piping Metal Studs Absorber: Dark Color, Conductive Color, Color, Color! Allows for an air chamber to circulate heat. Fans and Venting: Depend on size of kiln. Fans are at the warmest part of the kiln. Vents at the top. Types of Solar Kilns Greenhouse Semi-Greenhouse Opaque Walls with Separate Collector Greenhouse Designs Glazing on East, South, and West walls. Need 2 layers of glazing to be effective. Loses heat via conduction. No absorber. Least Efficient Semi-Greenhouse South wall or roof is glazed. Other walls are insulated. Low heat loss through conduction. Two layers of glazing. Collector is integrated into the kiln More Efficient. Opaque Wall Design All walls opaque. Collector Separate Good for Hybrid systems or supplemental heating. Most Efficient. Design Considerations: Storage Circulation Ventilation Glazing Insulated Walls Collector Size Supplemental Heat Heat Storage 1) this energy can be used immediately when it is received, thereby making the dryer very hot at midday but with very little temperature difference in the nighttime; OR 2) the energy can be stored and used throughout a 24-hour period, thereby keeping temperatures more uniform. Air Circulation 150 CFM Lumber is stickered, stacked with spacers, to allow air movement. Fans should only run when humidity is low Ventilation Must control humidity. Vents serve as exhaust for warm moist air. Too much venting results in heat loss, too little = excess humidity. Glazing Ratio 1sq ft to 10 board feet of capacity. OR 1 sq ft to 3 bd ft. (Scanlin) Glazing must be selected based on performance, durability, and cost. Insulated Walls and Collector Size More insulation and tighter construction result in lowest heat loss. Use of moisture barrier needed to improve durability of framing due to high humidity. Must be based around the type of species that is being dried. 10 bd ft to 1 sq ft Must have access for placing and removing lumber. Supplemental Heat Slab Woodstove Boiler for Water Heater Gas Furnace Can result in wood drying to quickly and checking or warping. Landfill Gas Management Methane is considered a strong greenhouse gas. According to U.S. Environmental Protection Agency (EPA) figures the global warming potential (GWP) of methane, (a measure that uses carbon dioxide as a reference gas) is 21. A GPW of 21 means that over a period of 100 years, methane is 21 times more effective at trapping heat in the atmosphere than carbon dioxide. (Energy Xchange) Unfortunately: The current EPA program focuses on energy generation rather than heat generation. The unused methane is flared or burned. This potential heat source would synthesize with solar drying. My Design: Semi-Greenhouse Supplemental heat provided by methane gas. Three designs 5000 bf, 7500 bf, bf. According glazing 500 sq ft, 750 sq ft, 1000 sq ft. Access in north wall. Fans operated by methane energy production on site. Angle of collector is 36 degrees. Latitude of Boone. Bibliography Wengert, E. and Oliveria, L. SOLAR HEATED, LUMBER DRY KILN DESIGNS. Department of Forest Products. Virginia Polytechnic Institute. Available at: Scanlin, Dennis. The Appalachian Solar Lumber Kiln in Home Power. #63. February/March Available in your course packet.