SWRO and Energy Costs

SWRO and Energy Costs

Technological advances, coupled with innovative approaches to reduce energy costs (i.e. by using solar, tidal, or ocean thermal energy) have helped to make SWRO a potential solution to water supply or hedge against climate change for large cities like Perth - rather than simply a novelty for wealthy countries. In the 1970s, SWRO costs hovered around $2.50/m³. Currently, costs for the most efficient plants are well below $1/m³, or between ~$1000-2000 per acre-foot (Figures 3 and 4). This is still more expensive than imported surface water or groundwater in most areas (these costs range from $400-1000/acre-foot, depending on location), but in the realm of viability for areas without those sources, or to augment limited supply. The total costs include everything from construction costs for the facility (amortized over its expected lifespan), land access, permitting for discharge and intakes, and operation & maintenance.

Despite its promise, it remains to be seen if SWRO will be a universal or large scale answer to water scarcity. In particular, key challenges include the (still relatively high) costs and associated energy demand; management of the environmental impact associated with intakes and disposal of the brine waste stream; delivery of SWRO water to regions away from the coast; and the up-scaling that would be necessary to meet demand for irrigation or industrial use.

Figure 3. Reductions in energy required for SWRO from 1970-2008, driven largely by advances in membrane technology.
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Reductions in Energy Required for SWRO (1970-2008)

Year	Power Consumption (kWh/m3)
1970	16
1980	8
1990	5
2000	~3
2004	2
2008	~2

Source: Seawater Desalination: Can it Become a Significant Lever to Reduce Water Shortage? Figure used by permission of the Pacific Institute.

Figure 4. Reductions in the cost of SWRO-generated water since 1982, showing the proportion of cost associated with capital expenditure (i.e. plant construction), maintenance, and energy. Note that the primary reductions in cost have come from increased efficiency
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Reductions in the cost of SWRO-generated water since 1982, showing the proportion of cost associated with capital expenditure

Year	Electric	Maintenance	Capex Charges	Total
1982	0.7	0.2	0.6	1.5
1992	0.6	0.15	0.4	1.15
2002	0.3	0.1	0.3	0.7
2010	0.35	0.1	0.3	0.75

Source: Seawater Desalination: Can it Become a Significant Lever to Reduce Water Shortage? Figure used by permission of the Pacific Institute.