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Efficiency of Solar Kiln in Timber Drying

Study on the performance of an industrial solar kiln for drying timber, assessing its suitability in New Zealand and comparing it to traditional drying methods. The research includes measurements, results from multiple runs, and conclusions on its effectiveness.

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Efficiency of Solar Kiln in Timber Drying

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  1. PERFORMANCE OF INDUSTRIAL SOLAR KILN FOR DRYING TIMBER M. N. Haque Forest Research, NZ & T.A.G. Langrish Department of Chemical Engineering, University of Sydney

  2. Outline • Background to this research • Description of this solar kiln • Materials and methods • Actual measurements & assessment of performance • Comments on suitability in NZ • Conclusions

  3. Solar kilns for drying timber

  4. Solar kilns for drying timber Solar kiln at Boral Timber’s Herons Creek site, NSW, AUSTRALIA Recent design of solar kiln by Solar Dryers Australia, Bellingen, NSW

  5. Air-drying site

  6. Typical drying example

  7. Materials & methods INPUT SOLAR KILN MODEL OUTPUT Timber MC, air T & RH Boral’s Solar Kiln Ambient T & RH Timber properties Quality prediction

  8. Procedure for measuring MC • Biscuit samples: 2025043 mm, oven-dry test • Kiln sample boards: 30025043 mm • estimated MC based on biscuit samples

  9. Results- run 1 (May-June)

  10. Results- run 2 (July-August)

  11. Results- run 3 (Sep-Oct)

  12. Results- run 4 (Nov-March)

  13. Results- run 5 (March-May)

  14. Results- summary

  15. Measured solar radiation

  16. Results- HEX status

  17. Some NZ facts • About 2 million m3 timber dried each year (mainly radiata pine) • Average 3 GJ/m3 energy requirements • Total 6 PJ energy consumption • 95% thermal, 5% electrical • 60% thermal from wood residue • Processing of alternative species is growing

  18. Solar radiation at Rotorua, NZ (NIWA, 2002)

  19. Initiatives in NZ • Greenhouse companies • Redpath: www.greenhouse.co.nz • Harford: www.greenhouses.co.nz • Do not have drying tech experience but an engineering company can be brought together

  20. Conclusions • Solar energy, ambient T & RH, kiln T & RH and wood MC were measured. • Average increases in kiln air T (compared with ambient) were: • 17.3C (May-June) • 13.8C (July-August) • 10C (September-October) • 8.2C (November-March) • 7.5C (March-May)

  21. Conclusions (continued) • Drying times were 3 to 4 months from initial (43 to 62%) to final MC (12 to 22%). • Overall solar kiln is considered as an acceptable alternative to air-drying method for pre-drying of hardwoods (e.g. blackbutt, Eucalyptus pilularis). • So Australasian timber industry is showing an increasing interest in use of solar kilns.

  22. Acknowledgements • Boral Timber Division & • Faculty of Engineering, The University of Sydney for financial assistance

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