CSP-Powered Desalination Prospects in MENA

Conventional large-scale desalination is cost-prohibitive and energy-intensive, and not viable for poor countries in the MENA region due to increasing costs of fossil fuels. In addition, the environmental impacts of desalination are considered critical on account of GHG emissions from energy consumption and discharge of brine into the sea. The negative effects of desalination can be minimized, to some extent, by using renewable energy to power the plants.

What is Concentrated Solar Power

The core element of Concentrated Solar Power Plant is a field of large mirrors reflecting captured rays of sun to a small receiver element, thus concentrating the solar radiation intensity by several 100 times and generating very high temperature (more than 1000 °C). This resultant heat can be either used directly in a thermal power cycle based on steam turbines, gas turbines or Stirling engines, or stored in molten salt, concrete or phase-change material to be delivered later to the power cycle for night-time operation. CSP plants also have the capability alternative hybrid operation with fossil fuels, allowing them to provide firm power capacity on demand. The capacity of CSP plants can range from 5 MW to several hundred MW.

Three types of solar collectors are utilized for large-scale CSP power generation – Parabolic Trough, Fresnel and Central Receiver Systems. Parabolic trough systems use parabolic mirrors to concentrate solar radiation on linear receivers which moves with the parabolic mirror to track the sun from east to west. In a Fresnel system, the parabolic shape of the trough is split into several smaller, relatively flat mirror segments which are connected at different angles to a rod-bar that moves them simultaneously to track the sun. Central Receiver Systems consists of two-axis tracking mirrors, or heliostats, which reflect direct solar radiation onto a receiver located at the top of a tower.

Theoretically, all CSP systems can be used to generate electricity and heat.  All are suited to be combined with membrane and thermal desalination systems. However, the only commercially available CSP plants today are linear concentrating parabolic trough systems because of lower cost, simple construction, and high efficiency

CSP-Powered Desalination Prospects in MENA

A recent study by International Energy Agency found that the six biggest users of desalination in MENA––Algeria, Kuwait, Libya, Qatar, Saudi Arabia, and United Arab Emirates––use approximately 10 percent of the primary energy for desalination. Infact, desalination accounted for more than 4 percent of the total electricity generated in the MENA region in 2010. With growing desalination demand, the major impact will be on those countries that currently use only a small proportion of their energy for desalination, such as Jordan and Algeria.

The MENA region has tremendous wind and solar energy potential which can be effectively utilized in desalination processes. Concentrating solar power (CSP) offers an attractive option to power industrial-scale desalination plants that require both high temperature fluids and electricity.  CSP can provide stable energy supply for continuous operation of desalination plants based on thermal or membrane processes. Infact, several countries in the region, such as Jordan, Egypt, Tunisia and Morocco are already developing large CSP solar power projects.

Concentrating solar power offers an attractive option to run industrial-scale desalination plants that require both high temperature fluids and electricity.  Such plants can provide stable energy supply for continuous operation of desalination plants based on thermal or membrane processes. The MENA region has tremendous solar energy potential that can facilitate generation of energy required to offset the alarming freshwater deficit. The virtually unlimited solar irradiance in the region will ensure large-scale deployment of eco-friendly desalination systems, thereby saving energy and reducing greenhouse gas emissions.  

Several countries in the MENA region – Algeria, Egypt, Jordan, Morocco and Tunisia – have joined together to expedite the deployment of concentrated solar power (CSP) and exploit the region's vast solar energy resources. One of those projects is a series of massive solar farms spanning the Middle East and North Africa. Two projects under this Desertec umbrella are Morocco’s Ouarzazate Concentrated Solar Power plant, which was approved in late 2011, and Tunisia’s TuNur Concentrated Solar Power Plant, which was approved in January 2012. The Moroccan plant will have a 500-MW capacity, while the Tunisia plant will have a 2 GW capacity. Jordan is also making rapid strides with several mega CSP projects under development in Maa’n Development Area. 

Conclusions

Seawater desalination powered by concentrated solar power offers an attractive opportunity for MENA countries to ensure affordable, sustainable and secure freshwater supply. The growing water deficit in the MENA region is fuelling regional conflicts, political instability and environmental degradation. It is expected that the energy demand for seawater desalination for urban centres and mega-cities will be met by ensuring mass deployment of CSP-powered systems across the region. Considering the severe consequence of looming water crisis in the MENA region it is responsibility of all regional governments to devise a forward-looking regional water policy to facilitate rapid deployment and expansion of CSP and other clean energy resources for seawater desalination.

Desalination Outlook for MENA

Desalination is a water treatment process that separates salts from saline water to produce potable water. The desalination process uses large amount of energy to produce pure water from salt water source. Salt water is fed into the process, and the result is an output stream of pure water and another stream of waster with high salt concentration. Desalination techniques are mainly classified into two types:

  • Processes based on physical change in the state of the water, and
  • Processes using a membrane that employ the concept of filtration.

There are more than 15,000 industrial-scale desalination units worldwide, with combined capacity exceeding 8.5 billion gallons per day. The market leader is the membrane desalination process with around 44 percent of total capacity, followed closely by the thermal process of multi-stage flash (MSF) with about 40 percent market share. The main sources of feed water for desalination are seawater (58 percent), brackish ground water (23 percent), and other sources such as rivers and small salt lakes.

Water Problems in MENA and Desalination

Access to clean drinking water is one of the major health issues today. The Middle East and North Africa (MENA) region is the most water scarce region of the world. High population growth rate, urbanization and industrialization, coupled with limited availability of natural potable water resources are leading to serious deficits of freshwater in many parts of MENA. Freshwater sources in the MENA region are being continuously over-exploited and increased use of desalted seawater is unavoidable in order to maintain a reasonable level of water supply.

Conventional large-scale desalination is cost-prohibitive and energy-intensive, and not viable for poor countries in the MENA region due to increasing costs of fossil fuels. In addition, the environmental impacts of desalination are considered critical on account of emissions from energy consumption and discharge of brine into the sea. Brine has extremely high salt concentration and also contains leftover chemicals and metals from the treatment process which poses danger to marine life.

The negative effects of desalination can be minimized, to some extent, by using renewable energy to power the plants. Renewable energy-powered desalination offers a sustainable method to increase supply of potable water in MENA countries. The region has tremendous wind and solar energy potential which can be effectively utilized in desalination processes like reverse osmosis, electrodialysis, and ultrafiltration and nanofiltration. The cost of renewable energy desalination is expected to become more attractive with technological advancements and coupled with rising costs of freshwater and fossil fuels.

Solar-Powered Desalination for MENA

Solar energy can be directly or indirectly used in the desalination process. Collection systems that use solar energy to produce distillate directly in the solar collector are called direct collection systems while systems that combine solar energy collection systems with conventional desalination systems are called indirect systems. The major drawbacks with the use of solar thermal energy in large-scale desalination plants are low productivity rate, low thermal efficiency and large area requirement. Solar thermal-based desalination plants are more suitable for small-scale production especially in remote arid areas and islands having scarce conventional energy resources.

Concentrating solar power (CSP) offers an attractive option to power industrial-scale desalination plants that require both high temperature fluids and electricity.  CSP can provide stable energy supply for continuous operation of desalination plants based on thermal or membrane processes. Infact, several countries in the region, such as Jordan, Egypt, Saudi Arabia are already developing large CSP-based solar power projects that promises to usher in a new era in the Middle East.

The MENA region has tremendous solar energy potential that can facilitate the generation of energy required to offset the alarming freshwater deficit. The region would be facing a grave water crisis with the population expected to be double by 2050. Solar-powered desalination combined with efficient use of water reserves and re-use of wastewater can help in easing the water crisis in the region. It will also help in reducing the financial load on MENA governments from power and water sectors, and thus diverting funds to much-needed educational, health and industrial sectors.