LIFE - CYCLE COST ASSESSMENT OF OCEAN - WATER DESALINATION FROM AMBIENT VS. WARM WATER SOURCES.

摘要

Many proponents of large-scale ocean-water desalination have looked at co-location with power facilities as a potentially beneficial approach. Co-location could conceivably provide access to existing intake and discharge infrastructure, coastal land zoned for industrial/utility facilities, electric power and an ocean-water source which is warmed by the condensers of the power plant's once through cooling system. Sourcing feedwater for a desalination facility from the warm-water power plant discharge has been previously implemented in several full-scale facilities and received strong consideration for several projects under development. Of the reasons for consideration indicated above, most are very site specific. While the savings associated with use of existing intake and discharge infrastructure can be substantial (the costs associated with building new intake and discharge structures can exceed twenty- five percent of the total project cost), not all power plants have excess intake capacity available. Those that do are often abandoned structures from decommissioned power units requiring refurbishment. Finding land within a power plant site or adjacent to it can incur quite a range of costs. Regulations pertaining to the supply of power directly from a power plant to a desalination facility can in some locations be obstructive to cost savings. The ability to source warmed ocean-water from the power plant discharge is often cited as a benefit to a proposed project due to avoidance of constructing a new intake structure, no need to use intake capacity from the power plant, no additional draw of ocean-water beyond the existing power plant intake and perceived benefits to the operating costs of desalination resulting from the elevated temperature. While the impact of intake infrastructure cost should not and cannot be disregarded, the comprehensive consideration of the impacts of warm-water on the desalination process costs is enlightening. The principle that increased temperature increases water permeability of reverse osmosis (RO) membrane is widely understood and indeed results in lower operating pressure. However this is just part of the story when it comes to the impact of temperature on RO performance and the resulting cost of water production