D-1310Solar Drying

How it works

1. The idea — A greenhouse, a concrete floor, and a machine that turns the sludge over. The sun does the evaporating. Everything else in the building exists to make sure the water that leaves the cake actually leaves the building.
2. What a square metre can do — Take the irradiation, keep the third to half of it that becomes evaporation rather than heating the structure, and divide by the 0.675 kWh it takes to evaporate a kilogram at around 30 °C. Two to five kilograms per square metre per day is the real band — and it sets the whole footprint.
3. The turner is the machine — Without it the surface crusts over in a day and the bed goes anaerobic underneath. The turner breaks the crust, brings wet material up and keeps the pile aerobic. A greenhouse without one is a smell complaint, not a dryer.
4. Weeks, not hours — A thermal dryer holds the cake for minutes. This holds it for weeks. That is a genuine cost in land and in working capital — but it is also storage, which on a works with seasonal disposal is worth having.
5. The trade — Against a thermal dryer the energy saving is well over ninety per cent, because the only thing drawing power is the turner and the fans. What you pay instead is roughly half a hectare of building for a mid-sized works. Compare the two bars on the right.
6. Ventilated greenhouse — The standard arrangement. Moving the saturated air off the bed is worth more than any amount of extra glazing. Fans and dampers on humidity.
7. Size it on the worst month — Annual average irradiation gives a house that works beautifully for eight months and overflows for the other four — and sludge does not stop arriving because the sun went in. Pull the irradiation slider down to a winter figure and watch the area you would need.

Design parameters

The panel opposite runs the same correlations as the D-1310 design sheet, so the animation and the calculator cannot disagree. Every parameter below is live — drag one and the picture responds.

Open the full D-1310 design sheet for the other five inputs, all twenty-four results with their envelopes, the four equations printed beside the numbers they produce, and a calculation record you can export and put in a design file.