Desalination powered by renewable energy

Seawater desalination is increasingly being used as a means to augment freshwater supplies in regions with high water stress. Renewable energy powered desalination helps to produce water at costs competitive with that of fossil powered desalination plants while also eliminating greenhouse gas emissions.

Desalination is more energy intensive than traditional water treatment methods and depending on the technology, both electricity and heat are required. Total online desalination capacity has been increasing globally, both in the Gulf Cooperation Council (GCC) countries and elsewhere. Seawater reverse osmosis (SWRO) has rapidly increased, and thermal desalination technologies have plateaued.

SWRO is projected to remain the dominant desalination technology owing to the lower costs and energy consumption and technological improvements. Nevertheless, while the energy consumption for surface freshwater treatment is about 0.6 kWh/m³, the least energy intensive SWRO desalination plants today still consume around 3 kWh/m³. Consequently, conventional SWRO plants are heavily dependent on diminishing and costly fossil fuel resources. In addition, the burning of the fossil fuels results in greenhouse gas emissions, only further contributing to one of the causes of water scarcity – climate change.

Featured analysis

How can renewable energy based desalination help overcome the current issues with SWRO desalination? Solar photovoltaic based electricity is nowadays the least cost source of electricity in most regions of the world and as the cost of renewable energy technologies and energy storage further decrease, renewable energy powered desalination provides a cost effective alternative to fossil fuel based desalination. To show this, we can estimate how much desalination may be required in future, and its cost of production using renewable energy and fossil fuels.

Interpretation:

• Desalination demand is expected to be higher where there is high water demand, but especially where there is high water stress. Specifically, demand can be estimated with a logistic function of water stress and total water demand. The estimated desalination demand for all sectors is 2.6 billion m³ /day. As of 2015, the total online desalination capacity was 44.3 million m³ /day.
• Levelised cost of water, in €/m³, indicates the cost of water production from the desalination plant and the cost of water transportation from the desalination plant to the demand site.
• Hybrid renewable energy (RE) power plants are comprised of solar photovoltaic and wind power plants for electricity generation. Energy storage, to ensure the continuous running of the SWRO plants even during times of low renewable energy generation, will be provided by battery storage and in some places also by power-to-gas plants.

 

• When hybrid RE power plants are used to run the SWRO plant capacities estimated for 2030, the global LCOW range is 1.0 €/m³ – 4.5 €/m³. The most common LCOW range is between 1.0 €/m³ – 2.0 €/m³ .
• The cost of water production from current fossil based SWRO plants has been reported to be about 0.6 €/m³ – 1.9 €/m³. This water cost does not include the cost of transportation. The analysis shows that in the near future, SWRO desalination plants can be run by renewable energy power plants at costs competitive with that of current fossil powered SWRO plants

Key assumptions:

• Water stress and total water demand for 2030, is derived from the World Resources Institute’s Aqueduct Water Atlas and the FAO Aquastat database.
• Capital costs of SWRO plants are projected to reduce in future, based on the SWRO learning curve.
• The costs of solar PV and wind power plants is also projected to decrease, spurred on by the increase in installed capacities of these RE power plants. This is also modelled using learning curves.