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Energy Footprint of Water Desalination

Antonyan, M. (2019) Energy Footprint of Water Desalination.

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Abstract:Demand for the freshwater is growing due to the growth of world population that entails growing demand of freshwater for agricultural and industrial purposes. However, the fresh water availability on Earth is limited and many countries face severe water shortages. Water desalination could be a possible solution for this problem. Among the variety of existing water desalination technologies, three are particularly promising, these are: reverse osmosis (RO), multi stage flash (MSF), multi effect distillation (MED). Energy consumption of desalination processes are determined by factors like capacity of desalination plant (small, medium, large), the energy source (electricity vs thermal), type of feed water (brackish (BW) vs seawater (SW)), desalination method (thermal vs membrane), use of renewable energy sources (solar, wind, geothermal), and necessity of feed pretreatment (mechanical and/or chemical). In this paper, I compare the total energy consumption of different methods considering each influential factor and categorizing the existing desalination techniques. Results suggest that the membrane-based technologies are the least energy intensive. BW RO of medium and large scales require 1.9 kW h/m3. Then comes SW RO of medium size and SW RO of large scale with 4.3 and 4.4 kW h/m3 energy consumption. The thermal desalination techniques, primarily MSF and MED have much higher energy footprint, than the membrane ones. They consume 17.1 and 11.9 kW h/m3 respectively, however, thermal technologies are more efficient for desalination of very salty waters. Nevertheless, membrane-based desalination methods due to their less energy-intensive nature and small footprint became more popular than the thermal technologies and substantial efforts have been observed in integrating RO with renewable energy sources, mainly wind and solar. Energy footprint of this type of desalination techniques is in between the membrane and thermal routes. The energy consumption of renewable powered desalination plants ranges from 1.5 to 21.1 kW h/m3. Their main drawback is small capacity, which makes them non-competitive with conventionally powered plants. We could say that globally humanity spent 7 kW h energy for desalination of 1 m3 of water. For the most of developed countries desalination has large contribution to the total fresh water supply. However, the conventional energy sources are forecasted to be depleted in the near future. The main question is: can desalination satisfy the total fresh water demand at least in the coastal regions within 100 kilometers, where presently about 40% of the world’s population live? And should we consider desalination only for municipal purposes or for industrial and agricultural purposes as well? Rough estimation was done regarding the land requirement for solar panels to be able to supply the energy demand from SW RO desalination that is based on solar energy. As a model for such a study I decided to choose a city with 1 million inhabitants located in the territory of Saudi Arabia. To supply 1 million people with fresh water, desalination plant should have 270 000 m3/day capacity for municipal purposes and 1 470 000 m3/day capacity for industrial and agricultural purposes as well. Desalinating freshwater to meet only the municipal purposes a 5.18 km2 of land is required for building a solar park or almost 700 modern soccer fields and for the industrial and agricultural purposes the land requirement increases to – 28.22 km2, which is 3804 soccer fields. The results change, if we change the location of desalination plant, owing mainly to the difference in the amount of radiance that earth surface receives. The sensitivity analysis of a land requirement dependency on radiance was further calculated.
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
Link to this item:http://purl.utwente.nl/essays/78100
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