J. Mi, Q. Li, E. Jones, Y. Zhu, X. Li, L. Zuo
Keywords: membrane desalination, portable desalination, wave-solar hybrid renewable energy
Summary:Water is one of nature’s most important gifts to mankind. It covers 71% of the earth's surface and constitutes 60–70% of weight of an organism. However, only 1% of the world’s water is usable to us. In addition, over 53% people live within 50 miles of coastal line in USA. Many areas, such as California, are short of fresh water. There are more than 50,000 islands in the world, which accounts for 17% of the total land area of the world and accommodates about 10% of global population. Lack of fresh water has become one of the most important friction for the global economic and social development. Desalination plants have been built to supply fresh water. However, the plants need substantial energy and produce large greenhouse gases (GHG) emissions. Hence, saline water desalination powered by renewable energy should be developed and promoted. To address the aforementioned water challenges, the objective of this project is to develop a kind of low-cost self-sustainable portable desalination system using wave-solar-hybrid renewable energy, which can provide basic daily fresh water consumption per capital. The system is composed of a wave energy converter (WEC), a solar heating unit, and a membrane distillation module. There are main body and floating bodies in the proposed system. The floating bodies can be driven by waves and rotate around main body by hinges. Mechanical motion rectifier (MMR), a R&D 100 award-winning power takeoff (PTO) system, is applied to convert the bidirectional rotation into unidirectional rotation, and then pump water for the desalination efficiently. MMR is a very compact design composed on three bevel gears and two one-way clutches, enabling the bi-directional rotating shaft to drive the hydraulic pump (or generator) in unidirectional rotation, with efficiency up to over 80%. System dynamics are analyzed based on target wave and solar conditions to figure out optimized parameters and identify system characteristics. In-lab tests are carried out to verify dynamic modeling and figure out performance under different test conditions.