Abstract- This research paper covers different types of low cost solar water desalination techniques. This paper also describes methods for solar water desalination process at large scale with less cost.
Keywords- solar water desalination, sea-water desalination, brackish water desalination, low cost water desalination, water purification.
Introduction
Our world consists of 97.2% water but this water is not in useable form.[1] This water can be usable if it gets purify. Purification of sea water is very costly task. This paper describes methods to reduce cost of this purification process which are currently used by different countries.
Solar water desalination
Water desalination is the process in which we purify seawater or brackish water and make it useable.
Solar water desalination is the process in which we purify seawater or brackish water through solar energy and make it useable for drinking.
Fig. 1 Solar water desalination process[2]
Ambient energy system
Working
In this system, energy required for condenser and evaporator is generated through solar panels. This technology is suitable for model villages. The basic idea in this technology is that fix the solar panels on the roof of each house. Connect these panels with heat pump that generates electricity. This heat pump is then connected to the evaporator and condenser. Sea water is then pumped in evaporator and condenser. After this process we get fresh water that can be stored in tank.
Fig. 2 Ambient energy system for water desalination.[3]
Cost
This system is implemented in most of the countries. Its average cost is US$ 1.8/m3.[3]
SOLAR STILL PLATE DISTILLATION
Working
This method can commonly be use at home as shown in fig.3. In this method, flat solar still is used. This system is not suitable for large amount of desalination. As you can see in fig.3 in which fresh water is getting store in a glass. In this process water is passed through the surface of flat solar still and by sunlight these plates get heated and then water get boil. This water is store from the lower side of solar still. One 120 cm long and 60 cm wide with a collector area of 0.7 Sq. m solar still plate can desalinate 2.5 – 3.5 litres of water in a day. 4 solar still can purify 10 – 12 litres of water in a day which is enough for single family.
Cost
This desalination process is very cheap and its cost is Rs.300 per litre production.[4]
Fig.3 Flat plate solar distillation[4]
Simple sea water desalination plant
Working
In this system, spherical shaped tank is used which is made up of solid glass. firstly connect spherical tank and reservoir tank through pipe. Connect the top of the reservoir tank with the cooling system so that vapours can again convert into liquid state. Cooling system is not necessary; it depends on the temperature of surrounding area. The working of this process is that fill the spherical tank with sea water. Filled spherical tank behaves like a big, solid and powerful convex lens. This convex lens will focus on a single point with its specific alignment to the sunlight. Water will get boil after some time because of continuous heating. Then water will change its state from liquid to vapour state. These vapours will move towards the reservoir tank and the cooling system at the top of reservoir tank will again change the state of water from vapour to liquid. This liquid is purified water and can be use for daily purposes.
Fig.4 Simple sea water desalination[5]
Cost
The cost of this system depends on the size of sphere. The sphere with capacity of storing 5 litres water is costs Rs. 1500.[5]
CONCLUSION
These are the different techniques that can be used for low cost water desalination. As far as reduction in infrastructure cost, PVC pipes can be used instead of cement pipes.
It is clear from the study that ambient energy can be used for water desalination in temperate climates. In hotter countries where there is more solar energy available, the potential for using the technology to produce low-cost desalination systems is even more significant.
Solar still plate distillation process can be build at the roofs of the houses. Like windmill at the roof of house, this desalination process will work fine.
Simple sea water desalination plant is also suitable for hot areas as it also requires sunlight to boil the water.
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