Articles
OVERCOMING HORTICULTURAL PROBLEMS IN SOLAR GREENHOUSES
Two commercial solar greenhouses are compared to exemplify some solutions to these problems.
The glazing panels became discolored with milky patches when stored uncovered in the sun.
Plants tend to lean toward the south glazing, and require regular turning of the pots.
A shaded strip along the rear wall in summer causes the grower to shift pots on the bench when spacing.
A tall ridge, large end-wall vents, and shaded air inlet prevent accumulation of hot air at plant level.
Stagnant air is prevented by a jet tube circulation system and ceiling turbulator fans.
Restricted air exchange in these greenhouses causes pesticides to linger.
Solar 1 casts a shadow on Solar 2, requiring the grower to select suitable crops for the shaded area.
In Solar 1, individual heat curtain tubes have gaps at the ends which allow thermal siphoning.
In Solar 2, a continuous tube successfully seals the gaps along the end walls.
Thin (9 mm) ceiling tiles in Solar 1 have warped and buckled, and do not provide a good seal at the edges.
In Solar 2, thick (5 cm) tiles have not warped, and abut to form a tight seal at the edges.
To improve the greenhouses, the alignment should not be staggered since it causes one of them to shade the other, the end walls need a glazing strip below the vent panels to help warm the cold peak air in the mornings, and a deeper rock bed with perforated-tube air circulation system is needed to improve heat storage.
The brevity of these suggestions indicates the effectiveness of the systems.