Solar Kiln Designs 3 -- Solar Heated, Lumber Dry Kiln Designs - Part 3

      An in depth article by Gene Wengert and Luiz Carlos Oliveira

Dryer No. 10

LOCATION: Dehra Dun, U.P., INDIA
(Latitude 30 N; longitude 78 E)
STATUS: Operational
TYPE: Greenhouse with three walls and the roof transparent
HEATING SYSTEM: Solar hot air collectors; double covering of glass 7/32-inch (0.55 cm) thick on the outside; polyethylene sheet 0.01-inches (0.025 cm) on the inside with a gap of 1-1/2 inches (3.7 cm) between the glass and plastic; blackened metal absorber inside dryer
CIRCULATION: Two 36-inch (91 cm) diameter fans; 1 kW each
VENTILATION: Intake vent near bottom of south wall; exhaust vent near bottom of north wall; part of north wall can be removed to have dryer act as a single pass system rather than as a recirculation system
CAPACITY: 3000 board feet (7.1 cubic meters)
COLLECTOR AREA TO CAPACITY RATIO: 80 square feet per thousand board feet (3.1 square meters per cubic meter)
LOADING: Door in east (and west?) wall
OVERALL DIMENSIONS: East-west, 19-ft (5.76 m); north-south, 12-ft (3.66 m); height, 11-ft (3.33 m)
CONSTRUCTION: Framed with 2 x 6 framing; corrugated sheet metal covers lumber and plenum between lumber and fan; rear (north wall is plywood and several inspection doors; concrete floor
STORAGE: None
PERFORMANCE: Drying time for a variety of Indian woods, 4/4-inch (2.5 cm) thick is 7-16 days; 2-1/2 inch (6.2 cm) thick is 25-30 days. Drying time is about .4 of air drying times
REFERENCES:
Articles Sharma, S. N., P. Nath, and B. I. Bali. 1972. A solar timber seasoning kiln. J Timber Development Association of India 18(21):10-26.
Rehman, M. A. and O. P. Chawla. 1962. Seasoning of timber using solar energy. Indian Forest Culletin No. 229. 18p.
Sharma, S. N., P. Nath and S. P. Badoni. 1980. Commerical trials on a 7.1 cu. M. solar kiln. Indian Forest Bulletin No. 274. 50p.
Kumar, s. 1981. Utilization of solar energy in India. Forest Products J 31(9):10-12.
Present Contact: S. N. Sharma
Wood Seasoning Branch
Forest Research Institute
Dehra Dun
U. P., INDIA

Dryer No. 11

LOCATION: Dodgeville, Wisconsin, USA
(Latitude 43 N; longitude 90 W)
STATUS: Small scale production since 1958
TYPE: Semi-greenhouse
HEATING SYSTEM: Solar hot air collectors; single layer of glass; black painted metal absorber several inches under the glass
CIRCULATION: One 14-inch (36 cm) centrifugal fan just underneath the roof driven by a windmill; windmill is 54-inches (137 cm) in diameter
VENTILATION: Small slot in the floor
CAPACITY: 400 board feet (0.9 cubic meters)
COLLECTOR AREA TO CAPACITY RATIO: 93 square feet per thousand board feet (3.7 square meters per cubic meter)
LOADING: Hand loaded through hinged door on rear (north) wall
OVERALL DIMENSIONS: East-west, ca. 8-ft (2.4 m); north-south 8.2-ft (2.5 m); overall height, 7.6-ft (2.3 m)
CONSTRUCTION: Framed with 2 x 4 and 2 x 6 framing covered with 1-inch boards and roofing felt
STORAGE: None
PERFORMANCE: Drying time for a mixed load of cherry (16% MC to 8% MC) and white oak (60% MC to 6%MC) 1-inch (2.5 cm) thick is 52 days during warm weather
Drying time for black cherry 4/4-inches (2.5 cm) thick from 50% MC to 20% MC is 75 days (wintertime) and from 20% MC to 8% MC is 20 days. No checking; lumber was bright
REFERENCES:
Article Johnson, C. L. 1961. Wind-powered solar-heated lumber dryer. Southern Lumberman (October 1)

Dryer No. 12

Location: Dodgeville, Wisconsin, USA
(Latitude 48 N; longitude 90 W)
STATUS: Operational
TYPE: Semi-greenhouse
HEATING SYSTEM: Solar hot air collector; single glass glazing; black painted metal absorber about 2-inches below glazing
CIRCULATION: Two overhead fans, spaced evenly; 1200 cubic feet of air per minute each (0.6 cubic meters per second)
VENTILATION: Two openings in the floor, each 4 x 10-inches (10 x 25 cm) located in the central plenum; two vents at the bottom of the collector, 3 x 8-inches (8 x 20 cm)
CAPACITY: 850 board feet (1.9 cubic meters)
COLLECTOR AREA TO CAPACITY RATIO: 56 square feet per thousand board feet (2.2 square meters per cubic meter)
LOADING: Manually through door in east wall
OVERALL DIMENSIONS: East-west, ca. 8-ft (2.4 m); north-south, ca. 10-ft (2.5 m); height, ca. 6.5-ft (2 m)
CONSTRUCTION: Wood 2 x 4 framing with lumber siding and -inch (1.9 cm) plywood flooring; metal roof; 2 x 4 framing for collector with windows of 1 x 6 lumber supports; glazing is 8 pieces of 24 x 26-inches (61 x 66 cm) for lower two sections and 4 pieces of 24 x 16-inches (61 x 41 cm)
STORAGE: None
PERFORMANCE: Drying time for a mixed load of black cherry, 4/4-inches (2.5 cm) thick, from 60% MC to 6% MC: and white oak, 4/4-inches (2.5 cm) thick, from 16% MC to 7% MC is 52 days in summer
Drying time for a mixed load of cottonwood, 8/4-inches (5 cm) thick, from 130% MC to 10% MC; and black walnut, 4/4-inches (2.5 cm) thick, from 85% MC to 12% MC is 47 days in the summer
Drying time for black cherry, 4/4-inches (2.5 cm) thick, from 50% MC to 8% MC is 218 days in winter and spring. No drying defects were noted
REFERENCES:
Article Bois, P. J. 1977. Constructing and operating a small solar-heated lumber dryer. USDA Forest Service State and Private Forestry Forest Products Utilization Technical Report No 7. (Madison) 12p.

Dryer No. 13

LOCATION: Fort Collins, Colorado, USA
(Latitude 41 N; longitude 105 W)
STATUS: Experimental (1965-1974)
TYPE: Greenhouse with transparent roof and 3 walls
HEATING SYSTEM: Solar hot air collectors with a single layer of corrugated fiberglass reinforced polyester; everything inside the dryer painted flat black
CIRCULATION: Two horsepower, 24-inch (61 cm) diameter reversible fans; air velocity through the lumber of 100-350 feet per minute (0.5-1.8 m/s)
VENTILATION: Four vents, two each on the east and west walls near the floor; vent size is 8 by 12-inches (20 by 30 cm)
CAPACITY: 1200 board feet (2.9 cubic meters)
COLLECTOR AREA TO CAPACITY RATIO: 150 square feet per thousand board feet (5.9 square meters per cubic meter)
LOADING: Forklift loading through a door in the lower half of the north wall
OVERALL DIMENSIONS: East-west, 18-ft (5.5 m); north-south, 10-ft (3 m); north wall height 10-ft (3 m); south wall height 7-ft (2.1 m)
CONSTRUCTION: Frame construction with 2 x 4 framing; east, west and south walls and roof are covered with corrugated fiberglass sheets; floor is concrete; north wall, lower half is an upward sliding door; upper half is non-movable; both halves of north wall are framed with 2 x 4s and covered with plywood inside and out.
STORAGE: None
PERFORMANCE: Drying time for lodgepole pine and Engelmann spruce, 4/4 inch, from 50% MC to 15% MC is 14 days Drying quality was much better than air drying; no severe degrade
REFERENCES:
Articles Troxell, H. E. 1963. Solar lumber drying in Colorado. In Proceedings 15th Annual Meeting of the West Coast Dry Kiln Clubs (Portland).
Troxell, H. E. and L. A. Mueller. 1968. Solar Lumber Drying In the Central Rock Mountain Region. Forest Products J 18(1):19-24.
Wengert, E. M. 1971. Improvements in solar dry kiln design. USDA Forest Service. Forest Products Lab Research Note FPL-0212 (Madison, WI). 10p.
Present Contact: Dr. Craig Schuler
Dept. of Forestry & Wood Science
Colorado State University
Fort Collins, CO 80521
USA

Dryer No. 14

LOCATION: Griffith, New South Wales, AUSTRALIA
(Latitude 34 S; longitude 146 E)
STATUS: Experimental
TYPE: Opaque walls
HEATING SYSTEM: Solar hot air collectors; single glass layer; black painted copper clad steel, v-groove absorber
VENTILATION: One intake vent in the south wall and one discharge vent in the north wall.
CAPACITY: 2800 board feet (6.5 cubic meters)
CAPACITY TO COLLECTOR AREA RATIO: 220 square feet per thousand board feet (8.7 square meters per cubic meter)
LOADING: Track loaded from sides
OVERALL DIMENSIONS:
Chamber - east-west, 15.6-ft (4.77 m); north-south, 11.6-ft (3.54 m); height, 8.4-ft (2.55 m)
Collector east-west, 57-ft (17.5 m); sloped height, 10.5-ft (3.2 m)
CONSTRUCTION: Chamber prefabricated aluminum panels
Collector standard flat plate collector construction; insulated ducts connect collector to kiln
STORAGE: A chamber under the kiln of the same dimension as the kiln contains 550 cubic feet (15.5 cubic meters) of crushed basalt
PERFORMANCE: Drying time for alpine ash (Eucalyptus) 4/4-inch (2.5 cm) thick from 100% MC to 6% MC is 20 days with kiln approximately half full
REFERENCES:
Article Read, W. R., A. Choda and P. I. Copper. 1974. A solar timber kiln. Solar Energy 15:309-316

Dryer No. 15

LOCATION: Homer, Alaska, USA
(Latitude 60 N; longitude 152 W)
STATUS: Operational
TYPE: Semi-greenhouse; only roof is transparent
HEATING SYSTEM: Solar hot air collectors; corrugated fiberglass polyester glazing; interior of dryer is painted black
CIRCULATION: One fan; 1/15 horsepower motor; return air plenum with 7 openings into the kiln is on the outside, bottom of north wall; fan blows in one opening at top and downward along collector; fans only operate above 65 F (18 C)
VENTILATION: Manually operated vents in rear wall return plenum
CAPACITY: 2000 board feet (4.7 cubic meters)
CAPACITY TO COLLECTOR AREA RATIO: 85 square feet per thousand board feet (3.3 square meters per cubic meter)
LOADING: Manually through doors on east and west walls
OVERALL DIMENSIONS: East-west, 18-ft (5.5 m); north-south, 6.75-ft (2 m); height, 9.5-ft (2.9 m)
CONSTRUCTION: Frame construction with 2 x 4 framing; flooring with 2 x 8 framing; 5/8 inch (1.6 cm) plywood on exterior walls; 3/8-inch (1 cm) plywood on interior walls; 3-5/8-inch fiberglass insulation in walls and floor
STORAGE: None
PERFORMANCE: Dries to 7-1/2% MC
REFERENCES:
Article Anon. Ca. 1982. Solar kiln to dry wood. Alaska Council on Science and Technology (Juneau). 6p.
Present Contact: Bruce Forster
PO Box 1021
Homer, Alaska 99603
USA

Dryer No. 16

LOCATION: Kampala, UGANDA
(latitude 0 N; longitude 33 W)
STATUS: Experimental
TYPE: Greenhouse; all four walls and the roof are transparent
HEATING SYSTEM: Solar hot air collectors; two layers of plastic film 1-3/4-inches (4.4 cm) apart; two aluminum reflectors ca. 6 x 15-ft (1.8 x 4.6 m) one on each side outside the kiln reflect additional energy; reflectors are adjusted hourly
CIRCULATION: Two 18-inch (45 cm) diameter electric fans; reversible
VENTILATION: Two vents, one at each end act as inlet or outlet depending on fan direction.
CAPACITY: 1400 board feet (3.3 cubic meters)
CAPACITY TO COLLECTOR AREA RATIO: 62 square feet per thousand board feet (2.4 square meters per cubic meter)
LOADING: Door at end
OVERALL DIMENSIONS: East-west, 6-ft (1.8 m); north-south, 15-ft (4.6 m); height, 4-ft (1.2 m); all dimensions are internal sizes
CONSTRUCTION: Lumber framing; concrete floor; all surfaces painted black
STORAGE: None
PERFORMANCE: Drying time for Sterculia dawei 4/4-inch (2.5 cm) thick from 112% MC to 12% MC is 27 days
Drying time for Erythrophleum guineense 4/4-inch (2.5 cm) thick from 50% MC to 15% MC is 41 days Quality better than air drying
REFERENCES:
Article Plumptre, R. A. 1967. The design and operation of a Commonwealth Forestry Review 46(4): 298-309.

Dryer No. 17

LOCATION: Madison, Wisconsin, USA
(Latitude 43 N; longitude 89 W)
STATUS: Experimental
TYPE: Greenhouse
HEATING SYSTEM: Solar hot air collectors; two layers of plastic film; black painted metal absorber 1-1/2 inches (4 cm) from plastic
CIRCULATION: One 24-inch (61 cm) electric fan powered by 5/8 horsepower motor; located near roof
VENTILATION: Two vents each on east and west walls; each vent is 8-inches (20 cm) in diameter; located near floor; electrically controlled damper using a wood element hygrostat inside the dryer
CAPACITY: 425 board feet (1.0 cubic meters)
CAPACITY TO COLLECTOR AREA RATIO: 220 square feet per thousand board feet (8.7 square meters pre cubic meter)
LOADING: Doors in north wall; manual
OVERALL DIMENSIONS: East-west, 7.5-ft (2.3 m); north-south, 12.7-ft (3.9 m); height, 8-ft (2.4 m)
CONSTRUCTION: Frame construction with 2 x 4 framing on walls and 2 x 6 on roof; black painted corrugated aluminum on inner framing surfaces; two layers, separated by 2-inches (5 cm) by another frame on outside; rectangular opening in aluminum throughout to provide air flow past both faces of metal; wood framed floor with plywood covering
STORAGE: None
PERFORMANCE: Drying time for red oak, 4/4-inch (2.5 cm) thick, from 75% MC to 20% MC is 34 days in late spring; from 70% MC to 20% MC is 24 days in late summer; and from 80% MC to 20% MC is 105 days in winter Quality superior to air drying
REFERENCES:
Articles Peck, E. C. 1962. Drying 4/4 red oak by solar heat. Forest Products J 13(3): 103-107.
Peck, E. C. 1962. Drying lumber by solar energy. Sun at Work 7(3):4-6.

Dryer No. 18


A: Fiberglass Cover
B: Air Space for Circulation
C: Charcoal Heat Absorber
D: Sand
E: Ground Line
F: Concrete Blocks (Hollow Core)
G: Preservative-Treated Wood Sills
H: Wooden Battens

LOCATION: Madison, Wisconsin, USA
(Latitude 43 N; longitude 87 W)
STATUS: Prototype (approximately scale) for kilns in Philippines, Burma and Sri Lanka
TYPE: Opaque wall
HEATING SYSTEM: Solar hot air collector; fiberglass reinforced polyester film 0.04-inches (0.1 cm) thick; absorber is granulated charcoal, 1.2-inch (1.25 cm) thick, 6-inches (15 cm) below the glazing; air is circulated in the collector by a horsepower blower.
CIRCULATION: In the dryer, two horsepower fans circulate air through the lumber pile
VENTILATION: Two roof vents
CAPACITY: 1000 board feet (2.36 cubic meters)
COLLECTOR AREA TO CAPACITY RATIO: 200 square feet per thousand board feet (7.9 square meters per cubic meter)
LOADING: Door in north wall of chamber
OVERALL DIMENSIONS: Chamber east-west, 8-ft (2.5 m); north-south, 9-ft (2.7 m); height, 10-ft (3.0 m)
Collector east-west, 8-ft (2.5 m); north-south, 25-ft (7.6 m)
CONSTRUCTION: Walls framed with 2 x 4s with -inch (1.25 cm) thick plywood on the inside and 5/8-inch (1.6 cm) thick plywood on the outside; polyethylene vapor barrier on the inside of the wall; fiberglass insulation inside the wall between the framing; roof is similar using 2 x 8 framing and roofing paper
STORAGE: None
PERFORMANCE: Dryer conditions are controlled with electric venting and humidifying equipment to maintain 60% relative humidity Drying time for northern red oak, 4/4-inch (2.9 cm) thick, from 84% MC to 9% MC is 54 days in summer Solar dried lumber had 3.5 times fewer cracks than air dried lumber
REFERENCES:
Articles Tschernitz, J. L. and W. T. Simpson. 1979. Solar-heated forced-air, lumber dryer for tropical latitudes. Solar Energy 22:563-566
Tschernitz, J. L. and W. T. Simpson. 1977 solar kilns: feasibility of utilizing solar energy for drying lumber in developing countries. USDA Forest Service Forest Products Laboratory unnumbered report. (Madison) 63p.
Present Contact: Dr. John Tschernitz
Forest Products Laboratory
PO Box 5130
Madison, Wisconsin 53705
USA

Dryer No. 19

LOCATION: North San Juan, California, USA
(Latitude 39 N; longitude 120 W)
STATUS: Operational
TYPE: Semi-greenhouse; south sloped wall only is transparent
HEATING SYSTEM: solar hot air collectors; two layers of fiberglass polyester; black painted metal absorber
CIRCULATION: One 1/3 horsepower motor powered by photo-voltaic panel (24 volts); centrifugal blower
VENTILATION: A 14 x 18-inch (36 x 46 cm) louvered vent near the top of the east and west walls for intake; a vent pipe in the roof with electrically operated damper for exhaust
CAPACITY: 3000 board feet (7 cubic meters)
CAPACITY TO COLLECTOR AREA RATIO: 83 square feet per thousand board feet (3.3 square meters per cubic meter)
LOADING: Fork lift loaded through removable panels in north wall
OVERALL DIMENSIONS: East-west, 20-ft (6.1 m); north-south, 16-ft (4.9 m); height, 16-ft (4.9 m)
CONSTRUCTION: Frame construction with 2 x 6 framing; concrete floor and pressure treated wood foundation; lumber siding on exterior; gypsum wallboard on interior
STORAGE: Forty tons of 1 to 3-inch (2.5 to 8 cm) diameter rocks underneath lumber pile
REFERENCES:
Article Anon. 1982. Solar kiln can dry 3000 bd ft of lumber. Timber/West (March):2627.
Present Contact: Mr. Jeff Gold
PO Box 165
North San Juan, California 95960
USA



Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?


Have you reviewed the related Knowledge Base areas below?
  • KnowledgeBase: Primary Processing: Kiln Construction

  • KnowledgeBase: Primary Processing: Kiln Operation



  • KnowledgeBase: Knowledge Base


    Would you like to add information to this article? ... Click Here

    If you have a question regarding a Knowledge Base article, your best chance at uncovering an answer is to search the entire Knowledge Base for related articles or to post your question at the appropriate WOODWEB Forum. Before posting your message, be sure to
    review our Forum Guidelines.

    Questions entered in the Knowledge Base Article comment form will not generate responses! A list of WOODWEB Forums can be found at WOODWEB's Site Map.

    When you post your question at the Forum, be sure to include references to the Knowledge Base article that inspired your question. The more information you provide with your question, the better your chances are of receiving responses.

    Return to beginning of article.



    Refer a Friend || Read This Important Information || Site Map || Privacy Policy || Site User Agreement

    Letters, questions or comments? E-Mail us and let us know what you think. Be sure to review our Frequently Asked Questions page.

    Contact us to discuss advertising or to report problems with this site.

    To report a problem, send an e-mail to our Webmaster

    Copyright © 1996-2016 - WOODWEB ® Inc.
    All rights reserved. No part of this publication may be reproduced in any manner without permission of the Editor.
    Review WOODWEB's Copyright Policy.

    The editors, writers, and staff at WOODWEB try to promote safe practices. What is safe for one woodworker under certain conditions may not be safe for others in different circumstances. Readers should undertake the use of materials and methods discussed at WOODWEB after considerate evaluation, and at their own risk.

    WOODWEB, Inc.
    335 Bedell Road
    Montrose, PA 18801

    Contact WOODWEB











  • WOODWEB - the leading resource for professional woodworkers


      Home » Knowledge Base » Knowledge Base Article