The Bubble-Greenhouse System


A team of Murdoch University researchers have designed an efficient, small-scale greenhouse combining desalination with food production

They say the Bubble-Greenhouse represents an easy-to-operate, low-maintenance option for remote regions and communities faced with groundwater salinity issues.

The key to the concept is its novel humidification-dehumidification (HD) process, which projects to have a much higher water-production capacity than existing small-scale desalination technologies.

In the HD system, solar or wind generation powers a regenerative blower which pushes air through finely-pored sinter discs located within a six-chamber column evaporator filled with .

The result is thousands of fine bubbles, with some special properties.

"The key to our effective evaporation process is the large air/water interface produced and maintained by a unique property of salt water," PhD candidate Mario Schmack says.

"Unlike in a freshwater bubble column where bubbles would continuously collide and join together as they oscillate upwards, it has been discovered that by adding salt to a floatation chamber, bubble coalescence is inhibited by a still unexplained property."

A finer bubble stream means more surface area for evaporation.

When the saturated air exits the top of the evaporator it is channelled under pressure into a multi-stage condenser which collects fresh water and releases cooled vapour to humidify the .

Greenhouse provides benefits around the clock

The researchers suggest a 150m2 greenhouse could produce up to 30kg of crops daily while providing additional fresh desalinated water through night-time condensation.

The Bubble-Greenhouse design is suitable for northern WA's climate, with a lightweight aluminium frame and a special polycarbonate skin that allows the penetration of 60 per cent of photosynthetically active radiation while screening out most infra-red radiation, thus helping to moderate temperatures.


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