Primary Energy Consumption for the Efficiency Comparison of all

Desalination ProcessesMuhammad Wakil Shahzad

(Research Scientist)Water Desalination & Reuse Center,

King Abdullah University of Science & Technology,Saudi Arabia

Overview

Desalination in GCC

Performance Ratio Definition: whole World is wrong?

Desalination Energy: Derived & Primary

CCGT+Desalination Analysis

Universal Performance Ratio (UPR)

Desalination Hybrids

Lab to Industry: A way Forward

Bahrain currently produces 142 million gallons of water a day.

33% increase and 400 million investment predicted.

Water Scenario in Bahrain

Desalination in GCC

Condenser

TBT 70oC

MED operation limit

Stage-1 ΔT

for M

ED

op

eration

Stage-n

Cooling tower operation limit

40oC

30oC

Q, in

Q, out

𝑃𝑅 =

𝐸quivalent ℎ𝑒𝑎𝑡 𝑜𝑓 𝑒𝑣𝑎𝑝𝑜𝑟𝑎𝑡𝑖𝑜𝑛𝑜𝑓 𝑑𝑖𝑠𝑡𝑖𝑙𝑙𝑎𝑡𝑒 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛

𝐸𝑛𝑒𝑟𝑔𝑦 𝑖𝑛𝑝𝑢𝑡≅

2326

3.6 𝑘𝑊ℎ𝑒𝑙𝑒𝑐𝑚3 + 𝑘𝑊ℎ𝑡ℎ𝑒𝑟

𝑚3

Performance Ratio (PR)

Inherent Weaknesses No distinction between grade of energy Susceptible to conversion efficiencies Predicted on an arbitrary constant, 2326

Rabigh Reverse Osmosis PlantThe world's first 3-stage RO plantTotal Capacity: 192,000 m3/day

Yanbu MED Desalination Plant5 effects, PR=9, TBT=60CTotal Capacity: 68,190 m3/day

Yanbu-3 MSF Desalination Plant25 fashing stages, 9-units, TBT=114CTotal Capacity: 288,000 m3/day/unit

Reverse Osmosis Multi-Effect Distillation Multi-Stage Desalination

Electricity (kWh_elec/m3) 5.2 Electricity (kWh_elec/m3) 2.6 Electricity (kWh_elec/m3) 3.75

Thermal Input(kWh_ther/m3)

- Thermal Input (kWh_ther/m3 at 60oC)

76.0 Thermal Input(kWh_ther/m3 at 114oC )

79.5

Questions: (1) Which of the three processes is more efficient ? (2) Are the derived units, kWh, a suitable units to be used for the efficiency comparison ?

Desalination Energy

Primaryenergy

Derivedenergy

2.12 kWhpe1 kWhelec

Primaryenergy

Derivedenergy

1 kWhpe29.5 kWhther

𝑈𝑃𝑅 ≅ℎ𝑓𝑔

3.6 𝐶𝐹𝑒𝑙𝑒𝑐 𝑘𝑊ℎ𝑒𝑙𝑒𝑐𝑚3 + 𝐶𝐹𝑡ℎ𝑒𝑟 𝑘𝑊ℎ𝑡ℎ𝑒𝑟

𝑚3

Derived Energy to Primary Energy

Primary Energy to Electricity Primary Energy to Thermal

𝐹𝑜𝑟 𝑀𝑆𝐹 120𝐶 , 𝐶𝐹𝑡ℎ𝑒𝑟𝑚𝑎𝑙 =1

18.5

𝐹𝑜𝑟 𝑀𝐸𝐷 (𝑎𝑡 65𝐶), 𝐶𝐹𝑡ℎ𝑒𝑟𝑚𝑎𝑙 =1

29.5

Each process have thermodynamic lost work to produce useful effect.

𝒊𝒏

𝑶𝒖𝒕

𝑬𝒙 = 𝒎 𝒊𝒏

𝒐𝒖𝒕

𝒉 − 𝑻𝒐 𝒊𝒏

𝒐𝒖𝒕

𝒔

These losses must be charged to corresponding useful effect.

Process

Conventional Energetic

method (%)(Ignoring lost

work)

Proposed Exergy

method (%)

% over/less charged as

compared with exergy method

GT (including combustor, air compressor)

43.67 73.17 -40.32%

ST (HRSG, HP, MP and LP)

39.58 23.43 +68.92%

MED Desalination 16.75 3.4 +393%

Desalination over-charged by energy method 393%

Water cost (Opex) by exergy method 0.213 $/m3

Water cost (Opex) by energy method (conventional)

1.049$/m3

Water over-charged by energy method 0.837 $/m3

Savings for a 30.8x106 m3/day desalination capacity of the GCC countries (2015)

= 9.16 billion $/yr

*Fuel cost used for calculation= US$5 per thousand cu ft or 1055 MJ.

CCGT+ Desalination Process

Des

alin

atio

n p

roce

sses

Derived

energy

Conversion efficiency

Pri

mar

y en

erg

y

KW

hp

e/m

3 =

.

UP

R=

hfg

/{3.

6x

(kW

hp

e/m

3 )}

Ele

ctri

cal

en

erg

y co

nsu

mp

tio

n(k

Wh

elec

/m3 )

Th

erm

al e

ner

gy

con

sum

pti

on

(k

Wh

ther

/m3 ) Exergy destruction of primary

energy

Wei

gh

ted

fa

cto

r f

or

CC

GT

Ste

am f

or

ME

D p

roce

sses

=

SWRO 3.5 NA

47.0% 3.4%

7.45 86

MSF 3.0 80.6 9.1 71

MED 2.3 71.7 7.36 87

MEDAD 2.5 36 47.0% 3.4% 6.56 98

Universal Performance Ratio (UPR)

UPR contd..

Desalination Hybridization to Overcome Limitations

MED+AD Pilot at KAUST

2.1LPM 3.1+1.0*=4.1 LPM

*Last stage vapors adsorbed on AD beds

KAUST Pilot Experimentation

Desalination Processes Comparison

Conclusions

All desalination technologies must be compared on common platform,primary energy consumption.

Performance ratio must be defined based on primary energy, not on derivedenergy basis.

Currently, all desalination processes are operating 10-13% of TL, notsustainable for future water supplies.

Future sustainability can only be achieved with 25-30% of TL, by innovativehybrid desalination processes.

MEDAD Technology winner of Aramco-GE “Global Innovation Challenge” Award .Below USD 0.5 / m3, life cycle costing.

H.E. Prince Turki bin Abdullah (former governor of Riyadh) presenting award to Professor Kim Choon (KAUST),

H.E. Abdullah Al Hussayen, Minister of Electricity of SA,H.E. Dr Abdulrahman Al Ibrahim, Governor of SWCC,Professor Jean-Lou Chameau, President of KAUST,Dr. Adil Bushnak, Moya Bushnak

A Global Award Technology

Translation to Industry:Inauguration of KACST AD Plant (Feb 21, 2017)

Yanbu MEDAD Hybrid MOU