Tidying up
Painting:
If corrugated iron is used for the roof it is essential that it be painted black on the underside. This is easiest done before it is nailed on. Any kind of black paint will work unless the galvanising is of the hot-dipped type, then it will need a galvanising primer first. If the upper surface of the iron is to be painted there is no preferred colour, though black may get too hot at times and extra ventilation will need to be opened.
Plastic or fibreglass roofing materials. If a transparent sheet is used then it is important to paint as much as possible of the chamber interior in a dark colour (black). This converts the incoming light to interior heat. Translucent materials (green or milky) are intended to reduce incoming light and are therefore to be avoided in this application. Painting their undersides black would improve performance.
If there are rocks being put into the unit, either in the pre-heater or in spaces between the trays, these could also be painted black to encourage heat absorption.
For timber walling, general weather protection from painting the exterior surfaces is recommended. Little performance improvement can be expected. For metal or plastic walling a light colour would be best.
Run-off:
The inclusion of guttering on the roof and a coarse gravel covering the ground are both highly recommended to keep ground surfaces mud-free. Deep, gravel-filled drains leading to the perimeter of the area are a cheap and practical means to deal with run-off.
The gravel surfacing will also help keep the area weed-free. A dark-coloured gravel would be an advantage to help heat up the air around the drier, encouraging convection currents and improving its drying capacity.
Security & shelter:
The work zone around the drier needs to be fenced off with a lockable gate. The high value of dried cocoa makes it a real target for thieves. Ideally the fencing should also be wind-resistant, either timber or hedge, sheltering the area as much as possible to help improve drying during otherwise marginal conditions.