(GP/GT) for Additional Water Supply in the Lower Rio Grande

m-43
Exhibit IIID-S
Comparison or Purchased Power Costs Versus On-Site GP/GT Power Generation
Information regarding the process electrical energy consumption involved in the RO and EDR process
is provided on page 8 of the preliminary evaluation by Mr. Reahl of lonies Inc. and, for the treattnent
of the Group I waters, is summarized as follows:
Process
Reverse Osmosis (RO)
EDR
Total KW HRlDay/lMGD Product Water
3220
3950
Comparable information for the well field pumping, which constitutes the other primary consumptive
element of a desalination project using ground water as a source of feedwater, has previously been
developed by the Desalting Manual used in the proformas for Exhibits C and D. Based on the
calculations from that Manual, the consumption associated with the well fields for the RO and EDR
process is estimated as follows:
Well Field
Reverse Osmosis (11 wells)
EDR (10 wells)
Total KW HRlDay/IMGD Product Water(!)
1568
1454
Based on a 5 MGD capacity plant complex operating 24 hrs/day and 330 day/year, and using the sum
of the consumptive factors presented above (i.e. process + well field), the total KW Hrs. expended in
a year from the RO and EDR facilities are estimated as follows:
RO = 4788 KW HRlDay/MGD x 5MGD x 330 Days/Year = 7,900,200 KW Hrs.
EDR = 5404 KW HRlDay/MGD x 5MGD x 330 Days/Year = 8,916,600 KW Hrs.
A comparison of these projected amounts to the total projected capability of the 3000 KW GP/GT
powered complex, i.e., about 23.65 million KW HRlYear, indicates that the complex would easily have
the capability to serve a 10 MGD desalting facility, either RO or EDR, as opposed to 5 MGD plants.
Accordingly, estimates of the Projected annual savings in power cost to be derived from the use of onsite
GP/GT power generation, as opposed to purchasing power rom the utility grid at an assumed rate of
$0.07IKW HR, are presented as follows:
Projected AMual Savine for 10 MGD Capacjty RO Plant = 15,800,400 KWHRlYr. x $0.038IKWHR
cost differential (Le. $0.07 -0.032) = $6QQ,415
Projected Annual savim:s for 10 MGD Capacity EDR Plant = 17,833,200 KWHRlYr x $0.038IKWHR
cost differential = $677 ,662
(1) Based on the relation that the power requirement is equal to the product of the TDH (total dynamic
head, i.e., well depth + 100 feet) x a factor of .004 KWHRlftTDH/l000 gallons.