Solar tunnel drying
A covered structure using solar gain with ventilation. The main technical answer to wet-season harvests.
A solar tunnel dryer is a transparent covered structure with controlled ventilation, using solar gain to raise the internal temperature above ambient while keeping rain off the beans.
It addresses the specific problem that causes most drying faults: producers in wet-harvest regions need weather independence, and the available alternative has been direct wood firing with its smoke taint. Solar dryers give the gentleness of sun drying with much of the reliability of a mechanical one, and much of the improvement work in Papua New Guinea, the Solomon Islands and Cameroon has been about installing them.
What it does
Dries beans under cover using solar gain and ventilation, avoiding both rain interruption and combustion-gas contact.
Why it matters
It is the practical fix for the two faults that most damage wet-region origins — mould from stalled drying and smoke from direct firing.
- Typical duration
- 4–10 days
- Optional?
- One of several drying approaches, and the preferred one in wet-harvest regions.
When it goes wrong
Inadequate ventilation, which raises humidity inside the tunnel and stalls drying as effectively as rain would.
Related
Covered in
- Drying cacaoThe covered tunnel alternative to open sun drying, and what it protects against.
Techniques that depend on this
- Setting up a chocolate tastingThe covered compromise between sun and machine drying, and the reason some wet-season lots reach the bar without smoke taint.
Sources
- ChocolateHQ editorial synthesis — ChocolateHQ(citation identity confirmed; passage not re-read)
- Chocolate Science and Technology — Wiley-Blackwell(citation identity confirmed; passage not re-read)