**4. Thermal process and their integration: energy and environmental impact**

The present share of thermally driven desalination processes is about 58% within the GCC countries. Typically, the energy requirements for such processes are reported as 2.0 kWhelec/m<sup>3</sup> electricity and 60–70 kWhth/m<sup>3</sup> of thermal energy. For energy efficiency, the thermally driven desalination processes are designed as an integral part of a cogeneration plant, producing both electricity and water from the temperature cascaded processes. The thermal energy is low-grade bleed steam extracted from the last stages of steam turbines. Based on the exergy destruction analysis of the primary energy input, the gas turbines consumed 75 ± 2% and steam turbines (via the heat recovery from turbine exhaust) extracted 21 ± 2% of input primary energy, leaving a mere 3 ± 1.5% of the total exergy input to the thermally driven desalination processes. Consequently,

the overall primary energy required by thermal desalination processes is merely 6.58 kWhpe/m<sup>3</sup>

**Table 7.** Major thermal desalination plants in operation and future proposed projects in Saudi Arabia. They need only

We examine the major online thermal desalination plants in Saudi Arabia as well as the future

from the thermal input) [138–140].

from electricity +2.33 kWhpe/m<sup>3</sup>

Jubail phase (3) 15,00,000 40 2021 SWCC [148, 149]

proposed projects, and a summary of the analysis is outlined in **Table 7**.

Khobar 4 250,000 2020 Khobar 5 220,000 2020 Yanbu 5 100,000 2020 Jubail 3 150,000 2021

(equivalent of 4.25 kWhpe/m<sup>3</sup>

light pretreatment and can achieve 40% recovery.

Future projects

**Plant name Capacity (m<sup>3</sup>**

**/day) Overall recovery (%)**

Yanbu Phase-II 68,190 40 2012 SWCC Yanbu 1 100,800 1981 SWCC Yanbu 2 144,000 1999 SWCC Yanbu 2 expansion 68, 190 2007 SWCC Yanbu 3 550,000 40 2016 SWCC Jubail 1 137,729 40 1982 SWCC Jubail 2 947,890 40 1983 SWCC Khobar 2 223,000 40 1982 SWCC Khobar 3 280,000 40 2002 SWCC Khafji 22,886 40 1986 SWCC Jeddah 4 221,575 40 1981 SWCC Shuaiba 1 223,000 1989 IWPP Shuaiba 2 454,545 2002 IWPP Shuqaiq 97,014 1989 SWCC Rabigh 2 18,000 2009 SWCC AlWajh 3 9000 1979 SWCC Umluj 3 9000 2009 SWCC Farasan 2 9000 SWCC AlQunfutha 9000 SWCC AlLith 9000 SWCC Alazizia 4500 1987 SWCC Rabigh 1 1204 1982 SWCC

Ras Al Khair 728,000 40 2014 SWCC [141–147]

**Commissioning Operator Ref.**

http://dx.doi.org/10.5772/intechopen.77019

109

Renewable Energy-Driven Desalination Hybrids for Sustainability


The proposed AD cycle recovering 51% more from SWRO retentate booting overall recover to 81%. The final reject concentration was observed as 185,000 ppm from AD cycle. This integration will not only help to save overall energy but also environmental pollution. The summary of savings is presented in **Table 5**. It can be noticed that proposed integration can save up to 100%

**Table 6.** The comparison of impact of conventional SWRO and proposed hybrid cycle. The hybrid cycle reduced all

**Impact** Probability 1 2 3

Energy 3 × 3 3 × 1

 emission 3 × 3 3 × 1 Chemical rejection 3 × 3 3 × 1 Brine concentration 3 × 2 3 × 2 Brine temperature 1 × 1 1 × 1 Pumps noise 3 × 2 3 × 2

1 2 3

The impact matrix as presented in **Table 1** for conventional SWRO processes can be modified for hybrid cycle as presented in **Table 6**. It can be observed clearly that most of the parameters impact is reduced to medium and low from initial high value. This shows that hybridization will not help to produce more water but also with minimum impact on environment and

**4. Thermal process and their integration: energy and environmental** 

The present share of thermally driven desalination processes is about 58% within the GCC countries. Typically, the energy requirements for such processes are reported as 2.0 kWhelec/m<sup>3</sup>

desalination processes are designed as an integral part of a cogeneration plant, producing both electricity and water from the temperature cascaded processes. The thermal energy is low-grade bleed steam extracted from the last stages of steam turbines. Based on the exergy destruction analysis of the primary energy input, the gas turbines consumed 75 ± 2% and steam turbines (via the heat recovery from turbine exhaust) extracted 21 ± 2% of input primary energy, leaving a mere 3 ± 1.5% of the total exergy input to the thermally driven desalination processes. Consequently,

of thermal energy. For energy efficiency, the thermally driven

SWRO Hybrid cycle (I × P) (I × P)

emission. In addition, it will also help to reduce chemical rejection to sea.

energy and CO2

parameters impact to medium and low.

108 Desalination and Water Treatment

CO2

**impact**

marine life along with energy efficiency.

electricity and 60–70 kWhth/m<sup>3</sup>

**Table 7.** Major thermal desalination plants in operation and future proposed projects in Saudi Arabia. They need only light pretreatment and can achieve 40% recovery.

the overall primary energy required by thermal desalination processes is merely 6.58 kWhpe/m<sup>3</sup> (equivalent of 4.25 kWhpe/m<sup>3</sup> from electricity +2.33 kWhpe/m<sup>3</sup> from the thermal input) [138–140]. We examine the major online thermal desalination plants in Saudi Arabia as well as the future proposed projects, and a summary of the analysis is outlined in **Table 7**.


The material development already reached to asymptotic limit, but processes improvement still have gap and need immediate research data for industrial application. We presented detailed experimentation on thermal system hybridization for industrial reference for future design.

Renewable Energy-Driven Desalination Hybrids for Sustainability

http://dx.doi.org/10.5772/intechopen.77019

111

Thermal desalination processes, MED/MSF, can be integrated with AD cycle to enhance their performance by extending their operational range. In these cycles, low temperature heat is supplied to first steam generator only and their performance depends on number of recoveries. The AD cycle hybridization can extend the last stage operational range to as low as 7°C as compared to conventional operational range of 40°C. This extension of LBT helps to insert

To investigate hybrid MED performance, a four-stage MED was designed, fabricated and installed in KAUST. This MED is a miniature form of Yanbu MED plant installed by Doosan, Korea. The last stage of MED was integrated with solar thermal-driven AD cycle to extend last stage temperature to below ambient condition. **Figure 10** shows AD and MED pilots installed

The AD regeneration heat, 65°C hot water, is supplied from evacuated tube solar thermal collectors installed on one of the rooftop building. Experiments were conducted with straight MED as well as the hybridized MED + AD cycle to compare the performance. **Figure 11(a)** shows the control of MED pilot. For MED heat source, a small boiler is installed to inject steam into hot water circuit to maintain any set temperature. Feed is supplied parallel to all four stages after extracting condensation heat from last condenser. Distillate and brine are collected in separate tanks via u-tube to maintain the inter-stage pressure difference. Straight MED experiment was conducted for 72 hours continuously to validate the stability of operation. The temporal profile of all components showed stable operation of MED as presented in **Figure 11(b)**. After successful MED testing, it was hybridized with AD cycle to operate as a hybrid cycle. Integration

**Figure 10.** Solar-driven AD pilot and four-stage MED plant to investigate as a hybrid cycle. The pilot plant was designed

**4.2. Thermal process integration with AD cycle**

in KAUST, Saudi Arabia.

for overall capacity of 10 m3

/day.

more number of recoveries and hence boosts the performance.

\* Electricity consumption = 2.0 kWhelec/m<sup>3</sup> , thermal energy consumption = 70kWhth/m<sup>3</sup> , power plant conversion efficiency = 47%.

\*\*CO2 emission rate = 0.527 kg/kWhpe.

\*\*\*Pretreatment chemical values are taken from operational plants and published literature [150–154].

**Table 8.** Energy consumption, CO2 emission and chemical rejection by all thermal desalination plants in GCC. Their impact is less severe as compared to SWRO.

All major integrated thermal desalination plants in Saudi Arabia are under SWCC and their recovery is about 40%. Since thermal desalination processes are robust, they need less chemicals as compared to SWRO processes. We analyzed the energy requirement, CO<sup>2</sup> emission and chemical rejection based on total capacity of GCC.

#### **4.1. Thermal systems and hybrid cycle results and discussion**

We analyzed the operational conditions of all major MED/MSF plants in the World and in Saudi Arabia. All mentioned MED plants are operating between top brine temperature (TBT) 60°C to bottom brine temperature (LBT) 40°C. The MSF operational range is slightly wider, between 120 and 40°C. The high temperature of MED/MSF is controlled by scaling and fouling chances and lower brine temperature is by ambient conditions. Limited rage of operation put the cap on the performance of thermally driven desalination systems even they are dominating in GCC region. The detailed analysis of all thermal desalination plants in GCC and their impact are presented in **Table 8**.

It can be noticed that impact of thermal desalination processes is less severe than SWRO, but still same trend will have high impact in long-term operation. To maintain secure water supply in GCC, thermal desalination processes need to improve.

The two ways for thermal process improvements are material development for high heat transfer and process improvement to overcome thermodynamic limits of conventional processes. The material development already reached to asymptotic limit, but processes improvement still have gap and need immediate research data for industrial application. We presented detailed experimentation on thermal system hybridization for industrial reference for future design.

#### **4.2. Thermal process integration with AD cycle**

All major integrated thermal desalination plants in Saudi Arabia are under SWCC and their recovery is about 40%. Since thermal desalination processes are robust, they need less chemi-

, thermal energy consumption = 70kWhth/m<sup>3</sup>

emission and chemical rejection by all thermal desalination plants in GCC. Their

We analyzed the operational conditions of all major MED/MSF plants in the World and in Saudi Arabia. All mentioned MED plants are operating between top brine temperature (TBT) 60°C to bottom brine temperature (LBT) 40°C. The MSF operational range is slightly wider, between 120 and 40°C. The high temperature of MED/MSF is controlled by scaling and fouling chances and lower brine temperature is by ambient conditions. Limited rage of operation put the cap on the performance of thermally driven desalination systems even they are dominating in GCC region. The detailed analysis of all thermal desalination plants in GCC and

It can be noticed that impact of thermal desalination processes is less severe than SWRO, but still same trend will have high impact in long-term operation. To maintain secure water sup-

The two ways for thermal process improvements are material development for high heat transfer and process improvement to overcome thermodynamic limits of conventional processes.

emission

/day

/day

/day

, power plant conversion

cals as compared to SWRO processes. We analyzed the energy requirement, CO<sup>2</sup>

\*\*\*Pretreatment chemical values are taken from operational plants and published literature [150–154].

**Parameters Quantity Units** Total GCC capacity 26 mm3

Thermal share (68%) 17.7 mm3

Total feed 53.0 mm3

Scale inhibitor, polyphosphate (1–8 ppm) 424.3 ton/day Acid, sulfuric acid (100 ppm) 5304.0 ton/day Antifoam, poly othelyne ethylene oxide (0.1 ppm) 5.3 ton/day Oxidizing agent, foam of chlorine (1 ppm) 53.0 ton/day

Total primary energy (PE) consumption\* 116.5 GWh/day

emission\*\* 61,388.8 ton/day

and chemical rejection based on total capacity of GCC.

their impact are presented in **Table 8**.

Electricity consumption = 2.0 kWhelec/m<sup>3</sup>

emission rate = 0.527 kg/kWhpe.

impact is less severe as compared to SWRO.

**Table 8.** Energy consumption, CO2

CO2

\*

\*\*CO2

**Pretreatment**

110 Desalination and Water Treatment

efficiency = 47%.

**4.1. Thermal systems and hybrid cycle results and discussion**

ply in GCC, thermal desalination processes need to improve.

Thermal desalination processes, MED/MSF, can be integrated with AD cycle to enhance their performance by extending their operational range. In these cycles, low temperature heat is supplied to first steam generator only and their performance depends on number of recoveries. The AD cycle hybridization can extend the last stage operational range to as low as 7°C as compared to conventional operational range of 40°C. This extension of LBT helps to insert more number of recoveries and hence boosts the performance.

To investigate hybrid MED performance, a four-stage MED was designed, fabricated and installed in KAUST. This MED is a miniature form of Yanbu MED plant installed by Doosan, Korea. The last stage of MED was integrated with solar thermal-driven AD cycle to extend last stage temperature to below ambient condition. **Figure 10** shows AD and MED pilots installed in KAUST, Saudi Arabia.

The AD regeneration heat, 65°C hot water, is supplied from evacuated tube solar thermal collectors installed on one of the rooftop building. Experiments were conducted with straight MED as well as the hybridized MED + AD cycle to compare the performance. **Figure 11(a)** shows the control of MED pilot. For MED heat source, a small boiler is installed to inject steam into hot water circuit to maintain any set temperature. Feed is supplied parallel to all four stages after extracting condensation heat from last condenser. Distillate and brine are collected in separate tanks via u-tube to maintain the inter-stage pressure difference. Straight MED experiment was conducted for 72 hours continuously to validate the stability of operation. The temporal profile of all components showed stable operation of MED as presented in **Figure 11(b)**. After successful MED testing, it was hybridized with AD cycle to operate as a hybrid cycle. Integration

**Figure 10.** Solar-driven AD pilot and four-stage MED plant to investigate as a hybrid cycle. The pilot plant was designed for overall capacity of 10 m3 /day.

of AD cycle to the last stage of MED bring down the last stage temperature to below ambient and also inter-stage temperature was observed as 5–6°C as compared to 2–3°C in case of straight MED as shown in **Figure 11(c)**. The excellent thermodynamic synergy of hybridization of two thermally driven cycles boosted water production to more than twofold as compared to straight MED at same top brine temperature. **Figure 12** shows the water production comparison of straight MED and hybrid MEDAD. It can be clearly seen that water production improve-

Renewable Energy-Driven Desalination Hybrids for Sustainability

http://dx.doi.org/10.5772/intechopen.77019

113

Based on thermal cycle hybrid results, the impact matrix has been revised and presented in **Table 10**. The hybridization greatly improved the energy efficiency and reduced the environmental impact as compared to conventional processes. In GCC, to maintain the confidence on thermally driven desalination processes, their hybridization is very important. It will help to achieve future water targets to maintain the GDP growth but following the COP21 goals for

**Figure 12.** MED and hybrid MEDAD cycle water production comparison. Integration of AD to the last stage of MED can

**Parameters Thermal system Hybrid cycle % Saving by hybridization (%)**

**Table 9.** Comparison of thermal desalination and its hybrid with AD cycle. The superiority of hybrid cycle can be seen

boost water production to twofold by extending inter-stage temperature (**Table 9**).

Total PE consumption (GWhpe/day)\* 116.5 84.2 38.3

Scale inhibitor, polyphosphate 424.3 235.7 80 Acid, sulfuric acid 5304.0 2946.7 80 Antifoam, poly othelyne ethylene oxide 5.3 2.95 80 Oxidizing agent, foam of chlorine 53.0 29.47 80

.

emission (ton/day) 61,388.8 22,373.1 38.3

ment is more than two times by AD cycle integration with last stage of MED.

environmental emission.

CO2

\*

**Pretreatment chemicals (ton/day)**

clearly from summary table.

AD electricity consumption = 1.38 kWhelec/m<sup>3</sup>

MEDAD hybrid cycle improvement factor = 2.0 [155–173].

**Figure 11.** MED and AD pilot results installed in KAUST. (a) Control of MED pilot and (b) straight MED components temperature profiles. Inter-stage temperature varies 2–3°C for 72-hour experiment, (c) MED hybrid cycle components temperature profiles. Inter-stage temperature increased to almost double as compared to straight MED. Also, hybrid cycle can operate below ambient temperature as can be seen last stage temperature.

of AD cycle to the last stage of MED bring down the last stage temperature to below ambient and also inter-stage temperature was observed as 5–6°C as compared to 2–3°C in case of straight MED as shown in **Figure 11(c)**. The excellent thermodynamic synergy of hybridization of two thermally driven cycles boosted water production to more than twofold as compared to straight MED at same top brine temperature. **Figure 12** shows the water production comparison of straight MED and hybrid MEDAD. It can be clearly seen that water production improvement is more than two times by AD cycle integration with last stage of MED.

Based on thermal cycle hybrid results, the impact matrix has been revised and presented in **Table 10**. The hybridization greatly improved the energy efficiency and reduced the environmental impact as compared to conventional processes. In GCC, to maintain the confidence on thermally driven desalination processes, their hybridization is very important. It will help to achieve future water targets to maintain the GDP growth but following the COP21 goals for environmental emission.

**Figure 12.** MED and hybrid MEDAD cycle water production comparison. Integration of AD to the last stage of MED can boost water production to twofold by extending inter-stage temperature (**Table 9**).


**Table 9.** Comparison of thermal desalination and its hybrid with AD cycle. The superiority of hybrid cycle can be seen clearly from summary table.

**Figure 11.** MED and AD pilot results installed in KAUST. (a) Control of MED pilot and (b) straight MED components temperature profiles. Inter-stage temperature varies 2–3°C for 72-hour experiment, (c) MED hybrid cycle components temperature profiles. Inter-stage temperature increased to almost double as compared to straight MED. Also, hybrid

cycle can operate below ambient temperature as can be seen last stage temperature.

112 Desalination and Water Treatment


**Acknowledgements**

**Abbreviations**

(KAUST) for financial support for MED and AD pilots.

COP Conference of parties

Btu British thermal unit

GCC Gulf Cooperation Council SWRO Seawater Reverse Osmosis

MED Multieffect desalination

BAU Business as usual

MSF Multistage flash AD Adsorption cycle

pdf) [Accessed: Dec 15, 2017]

(2017).pdf [Accessed: Feb 05, 2018]

**Author details**

Kim Choon Ng

Saudi Arabia

**References**

IEO International Energy Outlook

The author would like to thank to King Abdullah University of Science and Technology

Renewable Energy-Driven Desalination Hybrids for Sustainability

http://dx.doi.org/10.5772/intechopen.77019

115

*OECD* Organization for Economic Cooperation and Development

Muhammad Wakil Shahzad\*, Doskhan Ybyraiymkul, Muhammad Burhan and

Water Desalination and Reuse Center, King Abdullah University of Science and Technology,

[1] International Energy Outlook 2016 with Projections to 2040. A report by U.S. Energy Information Administration (EIA), 2016. https://www.eia.gov/outlooks/ieo/pdf/0484(2016).

[2] International Energy Outlook 2017 with Projections to 2040. A report by U.S. Energy Information Administration (EIA), 2017. https://www.eia.gov/outlooks/ieo/pdf/0484

\*Address all correspondence to: muhammad.shahzad@kaust.edu.sa

**Table 10.** The comparison of impact of conventional thermal desalination system and proposed hybrid cycle. The hybrid cycle reduced all parameters impact to medium and low.
