SOLAR DESALINATION TECHNOLOGY BRIEF

ALPHA-OMEGA SOLAR DESALINATION TECHNOLOGY BRIEF ALPHA OMEGA ECOLOGICAL SOLUTIONS Athens Office: 8, R. Garibaldi & Sofroniskou str. Tel. +30.210.9228225 Email: info@alpha-omega.com.gr Page1of 8

ALPHA OMEGA S SOLAR DESALINATING TECHNOLOGY The advanced technology of glass evacuated tubes is the key component of the solar collectors used in our Solar Desalinating Units. The evacuated tube is similar to a conventional Dewar flask and consists of two borosilicate glass tubes, a glass with high chemical and thermal shock resistance. The outer side of the inner tube is coated with a sputtered solar selective surface. This coated inner tube is closed at one end and sealed at the other end to the outer tube. The annular space between the outer tube and inner tube is evacuated to virtually eliminate heat loss by conduction and convection. All our tubes operate under vacuum thereby reducing process time to bring the fluids to flash temperature. The evacuated tubes have a heat stagnation operation temperature of 270 300 C, and can operate effectively at pressures up to 1000 kpa. The liquid in the heat pipe changes into vapour which rises to the condenser. The heat conducts the water inside the tank and the vapour becomes liquid, returning to the base of the heat pipe. This continuous circulation transfers heat from the heat pipe to the cold water in the tank as long as sun is heating the collectors. Our evacuated collector tubes are produced according to two new patents from the Sydney University exclusively licensed to our company. Page2of 8

Our heat pipe series solar collector are always connected with the existing Solar Desalinating Unit, the selective coating on the inner cover of the evacuated tubes converts solar energy into heat energy and transfers heat to the heat pipes by aluminium fins. The liquid in the heat pipe changes into vapour which rises to the condenser. The heat then passes through the heat exchanger and the vapour becomes liquid, returning to the base of the heat pipe. As the units are connected in series (the number required depends upon the water production required on a daily basis i.e. smaller production for a household, would only require a single unit) with each unit having an effective working area of 2.320 M2. Page3of 8

HOW THE SYSTEM WORKS ALPHA OMEGA S SOLAR DESALINATION TECHNOLOGY Due to the system unique solar tube technology, boiling is conducted at reduced pressures. This presents enormous advantages for a solar desalinating unit whereby when the pressure is reduced to 0.1 atmospheres the boiling point of water falls to below 50 C. The low working temperature dramatically reduces energy losses to the environment and the higher energy recovery gives a larger multi effect and greater output. Solar energy passes through the unique solar tube technology with over 80% transmittance. The solar absorber takes up this energy with over 90% efficiency producing a large hot surface. This is the driver of the distillation process. Air molecules that strike the absorber surface are heated; the hot air expands and rises drawing fresh air and water vapour from beneath. Convection current is set up. Water evaporates from the surface of the seawater, passes through the absorber and is carried into the condensation layer where it forms a clean water supply. The air in the convection current is returned via air channels to just beneath the absorber. The outgoing clean water transfers its heat to incoming seawater in the counter current heat exchanger. Consider next the surface layer of seawater and the central region of the tank. As the seawater loses water vapour by evaporation, it becomes denser. Its salt content will increase from 3%-4%-6% and as it becomes heavier the saltier water falls to the bottom of the central chamber. Note that boiling water has a density of 0.96g/cc, seawater 1.03 and brine up to 1.1 and greater. The brine discharge surrenders its heat to incoming seawater and a tap on the discharge pipe can allow the brine to be of 5%, 10%, 20% or whatever salt content is considered appropriate and the brine is returned to the sea. Page4of 8

The configuration is designed to ensure maximum energy recovery. Thus the latent heat of condensation is completely recycled and of the energy content of boiling water, the large majority is reabsorbed by incoming seawater in the counter current heat exchanger. This is further dramatically reduced by the boiling being conducted under reduced pressure. The air in the unit is at a pressure of 0.1 atmospheres; this reduces the boiling point of water and the working temperature of the desalination tank to below 50 C. By such rigorous elimination of energy losses it can be expected that 95% of the energy used in heating and evaporating water is recovered and recycled. In that case there will be a multi effect or gained output ratio of 20. (The GOR is defined as the ratio of the energy consumed in the production of condensate to the energy input.) As an example multi effect distillation using fossil fuel energy has been a reality for over 40 years and a GOR of 10-20 is commonplace. Multi effect solar desalination is however relatively recent, and in conjunct with our own research and development, we that Tanaka et al achieved GOR 1.6 using successive surfaces for evaporation/condensation. Müller-Holst et al have developed a small commercial plant using one chamber for successive evaporation/condensation by natural convection. Page5of 8

This has achieved a daily average GOR of 3 to 4.5 in the field and over 8 in steady-state laboratory conditions. These findings demonstrate that with a large scale commercial plant operating at reduced pressure and much lower temperature, a GOR of at least 20 is attainable. Area solar absorber r 2 = 3.14 x 1.16 = 3.6424 M2 In Greece the annual average annualised insolation is 5.04kwh/m 2 /day Assume 80% transmittance through glass 90% efficiency solar absorber Total solar energy absorbed = 0.8 x 0.9 x 3.6424 x (number collectors) = joules/day Energy required to heat 1 gram water from ambient temperature to 50 C and to evaporate = 30 + 540 calories = 570 x 4.2 joules = 2,400 joules But if there is a gained output ratio of 20 Actual amount of energy consumed per gram water desalinated is 120 joules Page6of 8

CONCLUSION ALPHA OMEGA S SOLAR DESALINATION TECHNOLOGY Fresh water is our single most valuable resource, without it, terrestrial life can not survive. With the worlds increasing populations and increased demand for food production and clean potable water, our current fresh water resources are quickly depleting or becoming contaminated. The strategic implementation of economical and efficient technologies that is able to address this increasing demand for fresh potable water are now at the forefront of meeting and addressing this need. Alpha Omega s Solar Distillation Technologies for both commercial and individual needs are designed to meet the demand of fresh potable water. Solar Distillation is not a technology that is new, but how we approach and design the technology for today s needs is, and with this approach Alpha Omega is able to supply solutions to either the commercial or individual needs. Through extensive research and with the inclusion of our solar tube technology we are now able to produce units of varying scales and sizes, which would fit the needs of single families, to medium commercial situation, with the ability to produce clean potable water from 250 litres per day, up to 50,000 litres per day. Page7of 8

Here is some of our early R&D work. ALPHA OMEGA S SOLAR DESALINATION TECHNOLOGY Page8of 8