Exergo-Economic Evaluation of the Cost for Solar Thermal Depuration of Water

A detailed assessment of the cumulative cost of clean water production by a natural circulation solar thermal system is presented. The system is designed and sized for sufficient residence time for pasteurisation, in a buoyancy-driven self-compensating circuit. Since it does not consume electricity, it is suitable for developing countries or emergency locations with safe drinking water issues. The principles for design and off-design simulations are explained and discussed. The simulations were performed for seven different locations, representing variable climate conditions in selected regions where there is an evident need for safe water. The results include an exergy and exergo-economic analysis. The production capacity reaches typically from 0.04 to 0.1 m3/day per m2 of solar collector depending on the location. The annual cost of water production ranges between 2.2 and 6.8 €/m3 making the proposed system fairly competitive; the energy- and price-performance of the system is compared to a reverse osmosis/photovoltaic system, representing a high-tech alternative for the purpose of water purification.