Field Experiments

References: Liu, C.C.K., Park, J.W., Migita, R. and Qing, G. (2002). Prototype Experiments of a Wind-Driven Reverse Osmosis Desalination System, Journal of Desalination, Vol. 150, No. 3, pp. 277-287.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

2 3 4 5 6 7 8 9 10

Wind speed, m/s

Energy conversion Efficiency

99.189.1)438.0exp(73.0 UU

Wind-powered Two-stage Pumping

0

20

40

60

80

100

120

12:14:24 12:57:36 13:40:48 14:24:00 15:07:12

Time

Pre

ssu

re, p

si

Field experiments on System Operation Under Varying Wind Speed

500

600

700

Pres

sure

, kPa

Time, hrs

Win

d s

pe

ed

, m

/sO

pe

rati

ng

pre

ss

ure

, k

Pa

Reverse osmosis sub-system

Water flux

)}(779.0{ pfw CCpkJ

Salt flux

)( pfii CCkJ

kw and ki = coefficient for water and salt flux, respectivelyp = imposed pressure gradient (kPa)Cf = TDS concentration of the feed water on RO membraneCp = TDS concentration of the product water.

Concentration of the feed water as it flows over the RO membrane

Cfn

Qfn

Cbn

Qbn

Cn, p

Cpn, Qp

n

dA, k, kNaCl

membrane

nth control volumen-1th n+1th

Cfn

Qfn

Cbn

Qbn

Cn, p

Cpn, Qp

n

dA, k, kNaCl

membrane

nth control volumen-1th n+1th

)(0779.0 np

nfw

np CCpdAkQ

dAkQ

dACkC

inp

nfin

p

System simulation: Feed water flow and pressure

0

1

2

3

4

5

6

7

2 3 4 5 6 7 8 9 100

0.5

1

1.5

Pum

ping

rat

e, g

pm

Wind speed, m/s

100 psi (690 kPa)

80 psi (552 kPa)

60 psi (414 kPa)

Pum

ping

rat

e, m

3 /hr

120 psi (827 kPa)

Wind speed, m/s

Pu

mp

ing

rat

e, g

pm

Pu

mp

ing

rat

e, m

3 /h

r

System Optimization

Maximize the rate of permeate flow Qp = f (p, Cf, U, and membrane area)

Constraints414 p 965 kPa (60 p 140 psi) (1)

Qb / Qp ≥ 5 (at any element) (2)

Cp 400 ppm (3)

Qf 6 gpm (1.4 m3/h) for 2540, 16 gpm (3.6 m3/h) for 4040 (4)

Objective function

Reference: Park, S. and Liu, C.C.K. (2003). Experiment and Simulation of a Wind-driven Reverse Osmosis Desalination System, Water Engineering Research, Vol.4, No.1, pp. 1-17.

Effective RO membrane area of available RO configuration types

TypeRO Membrane Configuration

Effective areaMaximum recovery rate

A 2540 1 2.32 m2 (25 ft2) 15 %

B 2540 2 4.65 m2 (50 ft2) 25 %

C 2540 3 6.97 m2 (75 ft2) 35 %

D 4040 1 7.43 m2 (80 ft2) 15 %

E 4040 1 + 2540 1 9.75 m2 (105 ft2) 20 %

F 4040 2 14.9 m2 (160 ft2) 25 %

System design guide

Input:a. Wind speedb. Feed water salinity

System parameters:a. Membrane configurationb. Operating pressure (kPa)

Output:a. Permeate flow rate (m3/hr)b. Permeate salinity (ppm)

System optimization and design/operation guide

14-foot WindmillFeed Water Concentration (TDS, ppm)

1000 2000 3000 4000 5000

AveragedWindSpeed(m/s)

2

C1 4142 C 483 C 483 A 621

0.103 834 0.10 179 0.07 322 0.03 318

3C 552 C 621 C 621 C 690 B 758

0.15 61 0.14 129 0.11 222 0.11 315 0.07 372

4F 414 F 414 F 483 C 827 C 896

0.22 80 0.17 195 0.16 308 0.15 245 0.14 324

5F 414 F 483 F 552 C 896 C 965

0.22 77 0.21 162 0.20 258 0.17 215 0.16 283

6F 483 F 483 F 552 F 621 C 965

0.27 67 0.22 158 0.21 250 0.20 351 0.16 269

7F 483 F 552 F 552 F 621 C 965

0.27 66 0.26 138 0.21 246 0.20 344 0.17 261

8F 483 F 552 F 621 F 621 C 965

0.27 65 0.26 137 0.25 216 0.20 340 0.17 257

9F 483 F 552 F 621 F 758 C 965

0.27 65 0.26 136 0.25 214 0.24 301 0.17 255

Pilot Plant Design

Cost Analysis for a Scaling-up System with 50 20-ft Windmills

Cost Analysis for one single unit

Capital cost: $45364.00Capital recovery factor: 0.0736 (20 year project period at 4% interest)Annual operational cost: $4330.00Total annual costs: $6968.00

Total freshwater produced: 1,285,000 gallons

Freshwater Production Cost: $5.40 per 1,000 gallon

Technological Transfer Wind-powered RO Desalination Station on Penghu, Taiwan

1. Water and energy are critical natural resources and are inextricably linked.

2. Conventional water desalination processes are energy intensive and cannot be adopted by coastal and other similar remote communities where both freshwater and electric power are in short supply.

3. A renewable-energy--driven reverse osmosis system was designed and successfully tested at a pilot experimental site on Coconut Island, Hawaii.

4. A design guide for the system used for brackish water desalination was prepared based on mathematical simulation and optimization.

5. A pilot plant with 50 windmill units was designed and analyzed. This pilot plant can produce a freshwater of 0.20 million gallons per year per unit at a cost of $5.40 per 1,000 gallons.

IV. Concluding Remarks