MULTIPLE EFFECT DISTILLATION OF SEAWATER WATER USING SOLAR ENERGY - THE CASE OF ABU DHABI SOLAR DESALINATION PLANT - Energy Research Developments: Tidal Energy, Energy Efficiency and Solar Energy - page 66

It should be noted that all water costs given in this section do not include seawater intake
and outfall costs or cost of land. These additional costs are very much site dependent and has
to be added to the cost estimates given here.
12. Results of the Economic Study
Figure 31 shows how the cost of water varies with the number of effects and cost of
collector (in $/m 2 ) for a solar MED plant having a capacity of 130 m 3 /day which is identical
to that of the test plant. The design maximum temperature T b = 90 o C and the fuel cost is
assumed to be c b = 50 $/barrel. The cost of water is seen to be quite sensitive to the number of
effects and to a lesser degree on the cost of collector with the cost of water varying between 8
$/m 3 and 4 $/m 3 . The water cost tends to decrease with increasing the number of effects and
reducing the cost of collector. The increase in the number of effects results in an increase in
the performance ratio and thus leads to a reduction in the heat demand of the evaporator for a
given water production. Since this heat demand is produced by a field of solar collectors, the
reduction in this demand is expected to cause a similar reduction in the area of the collector
field and thus in its corresponding capital cost. On the other hand, the increase in the number
of effects results also in an increase of the capital cost of the evaporator due to the increased
structural complexity of the evaporator but this increase in capital cost is usually small
compared to the benefits of larger number of effects.
Figure 31. Effect of the number of effects and the collector cost on the resulting water cost - fuel cost,
c barrel = 50 $/barrel, max. brine temp. , T b = 90 o C (solar MED plant capacity = 130 m 3 /day).
Figure 32 shows the influence of the number of effects and cost of fuel (expressed in
$/barrel) on the resulting cost of water for a solar MED plant having a capacity of 130
m 3 /day. The evaporator is assumed to have a maximum brine temperature, T b = 90 o C and the
collector cost is assumed to be c col = 300 $/m 2 . It can be seen that increasing the cost of fuel
to the diesel generator results in an increase in the water cost due to the increase of the cost of
electricity produced by the diesel generator.