(254bl) Solar Powered Reverse Osmosis Desalination

Authors: 
Bhosale, R., Qatar University
Sutar, P. N., Qatar University
Kronberg, A., Encontech B.V.

Reverse osmosis (RO) is one of the most widely employed technologies for water desalination. A drawback of this technology is high consumption of electricity by electric motors used for high-pressure water pumping. Energy consumption can account for up to 70% of the desalination costs. Due to the high energy intensity, the carbon footprint of desalination processes is substantial. Most of pumps and compressors including those used in RO desalination plants are driven by electric motors or internal combustion engines. Pumping systems account for nearly 20% of the worldâ??s electrical energy demand and range from 25-50% of the energy usage in certain industrial plant operations. To improve economics of water desalination plants we propose innovative energy efficient, inexpensive, robust water pump powered by heat. The basic principle of the pump is the same as that of regenerative type external combustion engines. Regeneration of heat makes pumps of this type very energy efficient. The novelty of the pump comprises a new working cycle in combination with the use of a dense working fluid which is liquid in the cold space of the pump and gas or supercritical fluid in the hot space of the pump. Carbon dioxide, water-alcohols mixtures or mixtures hydrocarbons can be used as the working fluids. This pump does not have any high precision parts and even does not require super alloys and any other expensive materials. The pump can generate very high pressures (hundreds bars) and therefore can be used instead of modern plunger pumps driven by electric motors, thus eliminating completely the consumption of electricity for pumping in RO processes. Another important feature of the pumps is that no high temperature heat sources are needed. Heat sources with temperature of 200 â?? 300oC could be sufficient to create pressure drops typical of RO processes. Therefore, renewable energy sources such as solar radiation can be used to power the pump. Replacement of fossil fuels with renewable energy sources in desalination processes will minimize greenhouse gas emissions. In addition, a substantial improvement of the economics of the RO processes is expected due to the use of solar power.

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