The Bubble-Greenhouse: A holistic sustainable approach to small-scale water desalination in remote regions

• Multistage bubble column based thermal desalination with latent heat recovery • Greenhouse food production in remote regions as a by-product of water desalination • Strongly reduced plant water demand of greenhouse plants in humid environment • Social, economic and environmentally sustainable development for remote settlements

By combining the three elements — bubble evaporator, bubble condenser and condensing greenhouse — into a desalination system for remote communities, the individual components can be tailored for varying population rates and for economical water and food production. As the system is technically simple to manufacture and operate, it allows for local people to tap into their ‘bush mechanic’ skills and work towards self determination, capacity building and social development in remote places. Generally, based on their availability in respective locations, a range of renewable low grade energy sources such as solarthermal, photovoltaic, wind turbine, bio-energy, geo-thermal and solar gradient pond can provide the energy for this new technology. Optimal utilisation of latent heat recovery and radiative cooling processes further improves energy efficiency and thus, reduced investment and operating cost of the Bubble-Greenhouse system. Depending on their presence in individual locations, waste heat outlets for example from diesel power generators can be utilised as the energy driver for bubble evaporation, thus transforming power plants into more efficient cogeneration systems. Evolving energy storage concepts such as the thermal oil containing parabolic mirror array at Sundrop Farm will allow for sustainable operation independently from sunshine hours. More research is needed to further develop and trial multistage HD modules, to optimise the latent heat recovery cycle for energy efficiency, to select and assess high pressure blower and compressor technology and to improve energy storage systems. With these objectives in mind, the conceptualisation of a Bubble-Greenhouse with a strong focus on ecologically, socially and economically sustainable fresh water production may soon become a reality.