Liquid Film
The Liquid Solar process for capture of thermal energy and concurrent cooling of the Controlled Environment uses a simple mechanical process which pumps our Soap Solution from the Soap Solution Tank to the peak of the Sola Roof buildings - that is, this liquid is released along the ridge and forms a thin Liquid Film that flows to the lower elevation of the Cavity Space. Thus for a DIY Tunnel Greenhouse the liquid returns to a reservoir along both sides of the tunnel, where the Cavity Space reaches the ground or the bench where the reservoir is "in ground" or beneath the bench level.
The Soap Solution will flow as a thin sheet of Liquid Film over the top-side of the inner cover and this flow takes a few seconds to flow down from along the ridge which forms the peak of Tunnel Greenhouse. It falls by gravity back to the bottom of the Cavity Space, which is effectively the main Soap Liquid Tank. A submersed pump can be located within this tank and flexible hose conducts the liquid up to the ridge where it is distributed by sprinkler outlets. The soap in this liquid helps it to sheet out into a thin film over the inner cover. This means that the inner cover is maintained at the temperature of the Liquid Thermal Mass - and the Soap Solution can be coupled to larger reservoirs of water that are located under benches.
The Liquid Film is able to control the temperature within the Controlled Environment since the plants in the greenhouse are able to efficiently and effectively convert the thermal solar to hidden latent heat of vapor as the leaf canopy cools by means of Plant Transpiration?. In a closed greenhouse, with limited ventilation, the heat removal is accomplished by the condensation of the transpired moisture on the underside of the inner cover. Condensation will be streaming down the inner cover, but will not drip because of the slope and anti-drip property of the cover.
Using Poly Film? and Poly Fabric? for the inner cover material is optimized by establishing an under-atmospheric pressure within the Cavity Space. This method prevents the inward rippling of the film, which helps the Liquid Film to sheet out and also to prevent dripping of condensation forming on the underside. The smooth surface of the inner skin allows the condensation to form a thin film rather than forming drops. The Condensation Film? is much thinner then the cooling Liquid Film. At the lowest edge of the inner film the condensation will drip off and fall into a condensation collector. As much as one liter of condensation water per square foot of greenhouse area can be produced by this Sola Roof process of closed atmosphere cooling.
The same system can operate overnight during the summer (and in hot climates) so as to reject accumulated thermal gain, which is radiated to the chill night sky. Furthermore an evaporative chilling mechanism can be established that will also reject thermal energy.
Only this Liquid Solar process, using the Liquid Film to cool the inner cover, is able to remove the thermal solar gain at a rate that prevents overheating. The Bubble Shading system when used for shading provides a degree of additional cooling, but on its own, the Bubble Tech process is not able to control temperature and humidity within the greenhouse. If the Liquid Film is not in use then, on hot sunny days, Bubble Tech process should be combined with a low rate of ventilation.
Low rates of ventilation with no overheating problem is a normal mode of operation since a completely closed system (while totally sustainable) would have the additional technical challenge of supply of CO 2 into the Controlled Environment since a mature crop will consume all CO 2 in a mere 10 minutes. But, if we can establish simple systems for CO 2 enriched atmosphere growing for the DI Yers, then this is a very significant advantage.