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Application of Electret Technology to Low Cost Desalination

University of Denver; Denver CO.
June 2002

Report #73 - Abstract -

Desalination using permanent electric fields generated by electrets is investigated and described. Electrets are fabricated from non-conducting polymers such as polypropylene sheets. Electrets do not give up their charges but force positive and negative charge migration out of the flowing stream of salt water. Since electrets do not supply an electric current, the process is viewed as low cost as the stream flow or thermal energy can be used for the energy needed for ion separation. This work tests Douglas MacGregor's patents (4,958,514 and 5,061,376). The work provides a critique of these patents and of MacGregor's reported results.

The work tests electric fields strengths up to 18kV/cm. To allow better temperature control, the tests are with column lengths of 4 and 8 feet rather than the 18 foot length in MacGregor's design. The study also investigated a shorter, wider configuration. The modest results to date have not supported the large removal efficiencies reported by MacGregor.


For more information about the DWPR program, contact Kevin Price at: Bureau of Reclamation, 86-69000, PO Box 25007, Denver CO 80225; phone (303) 445-2260; or e-mail a message to MPrice@usbr.gov.