The sun scope
During the day the south facing cavity is emptied of bubbles, by a process described in the chapter on the bubble regeneration cycle. In this state, even before any solar energy collection system is utilised, the SolarBubbleBuild has a solar advantages over the conventional greenhouse. The bubbles maintained in the north cavity not only insulate the interior environment from heat loss from that side of the structure, but also act as a ‘sun scope’ reflecting IR energy back into the environment from the sun in the south.
Solar Energy Collection
When solar energy is available, a continuous film of surfactant solution is run inside the south cavity over the inner skin. This surfactant solution film is pumped from and returned by gravity to a insulated tank buried beneath the structure. In this phase of operation the surfactant properties of the solution is not being utilised as the liquid is simply acting as a vehicle for collecting and transporting low-grade solar energy from the south cavity to the liquid thermal mass.
Solaroof Thermal Energy Collection: New thinking, Ancient Processes
When the sun is bright, even in winter, the cavity space can become quite hot. This will initially raise the temperature of the out-coming water film when the film is first switch on, but it is not the primary mechanism for collecting thermal energy from the building. Nether does direct radiation from the sun in this system have a significant effect on the film as it passes through the transparent cavity space to the interior of the building. Thus, once the cavity space has cooled, which happens very rapidly, during cooling/collection mode, virtually all the thermal gain we collect is coming from phase change energy released by the transpiration/condensation process discussed in a later chapter. This higher efficient mechanism utilised millions of years of plant evolution.
In this project the out-coming soap solution film is returned to a plastic bladder, which is in turn located within a large insulated tank beneath the structure. This tank contains about 1300 litres of plane water. As the bladder skin is thin the thermal gain collected in the soap tank during collection mode, quickly transfers to the larger surrounding volume of water. We call this water our warm thermal mass. Due to the very high thermal capacity of water, we can store large amounts of thermal energy in this thermal mass to be drawn on at night when it is required to warm the interior space.