Desalination Using Renewable Energy – is it the answer to water scarcity?

This blog is part of WLE’s participation in the conference on “Water in the Anthropocene: Challenges for Science and Governance. Indicators, Thresholds and Uncertainties of the Global Water System“. A series of blogs have been written click here for more information.

The famous quote, “Water, water, everywhere, nor any drop to drink”, may become a quote of past, at least for the coastal cities, if desalination by renewable energy takes off. Desalination is a process that removes salt and other minerals from saline water.  It is becoming an increasingly popular technology as it can ease water scarcity in urban areas and free up water for the environmental flow regulations, while also reducing pressure on agriculture.

Solar powered desalination plant by Thermosolar in Oman. Photo Credit: Robert Kyriakide's web blog

Nature has been providing desalination services ever since water has been on the planet. The sun provides unlimited energy to evaporate water out of sea; clouds with the aid of wind distribute the fresh water over large stretches of land. The freshwater eventually comes back to the sea, thus maintaining the salt concentration in the oceans. Can humans replicate this natural cycle?

The current state of desalination

Desalination by humans has been practiced for hundreds of years, although at commercial scale it only picked up since the mid-1970s. From a mere global capacity of less than 1 million m³/day in 1970s, it has progressed to over 70 million m³/day capacity in 2012. This looks impressive, except most of the desalination is concentrated in a few countries. Its development has only taken place in either energy rich regions (i.e. where energy is very cheap) or affluent nations.  Energy cost forms a large component of costs of desalination – up to 45% of the operative cost, which is the constraining factor in the widespread use of desalination.

Currently the top 3 countries in desalination are Saudi Arabia, USA and UAE. The Middle East and Northern African region of the world (where energy is abundant), accounts for 38% of the global capacity. In spite of high energy costs, the desalination cost has come down substantially over the last four decades. In terms of 2010 USD, the cost of desalination has fallen from USD 9/m³ in 1970 to about USD 0.5/m³. This can be attributed to improvements in desalination technology and increases in the scale of operations. This is still too high for many regions of the world (for example, based on data collected by GWI from 180 cities around the world, the average water tariff per cubic meter of water in 2010 USD for different regions are: sub-Saharan Africa -  $ 0.09, in south Asia – $ 0.08/m, Eastern Europe and Central Asia – $ 0.28, Latin America – $ 0.41 etc.).

Can renewable energy save the day?

As the energy prices rise, desalination might seem out of reach but can renewable energy save the day? As of now there is very small renewable energy based desalination capacity (about 1% of the total desalination capacity) but the cost of producing water using renewable energy is very high – almost 3 to 8 times of that from conventional energy.  Renewable energy technology such as photovoltaic (PV) is relatively new and the cost of such technology is falling rapidly. In 2010 USD, the cost of PV module has fallen from about $70/W in 1975 to less than $2/W in 2010.

Two trends give hope for the future. First, the current data shows that with the increasing per capita GDP, people pay higher tariffs for water. Second, both, the desalination technology and renewable (in this case PV) technology are still developing and have a much greater scope for price reduction.

In a study conducted at IWMI, we looked at the historic trends and developed relationships between production and cost of production for desalination (without the energy component). In the research, the world was divided into 7 regions. Based on projected per capita GDP, we projected the water tariffs that people would be willing to pay in each region. Using the existing relationships (from literature) developed for PV, along with the relationships developed for desalination, we tried to find out at what global production level of each technology would it be viable to use desalination by renewable energy to meet the people’s water demand at their willingness to pay rates, within 100 km of the coast.

If energy is not a constraint, desalination will become a viable option by 2040 in most of the regions of the world. Sub Saharan Africa and South Asia, where water tariffs are low, require about 32 and 56 million m³/day capacity development each year till 2050 to be viable. This has to be seen in the context that the current global production of desalination is 70 million m³/day. Even with PV energy, desalination is feasible with minimal growth in most of the regions of the world (less than 1 million MW new capacity each year). For feasibility in Sub Saharan Africa and South Asia, growth of roughly 170 and 350 MW/year new production is required. Since 1992, the PV production has grown at a rate of 2.2 GW/year.

But desalination does not come without environmental costs.  Disposing brine and other chemicals used in the desalination process can be environmentally harmful.  When looking at greater scales of desalination expansion, the environmental costs of desalination needs to be considered, although we did not address them in this analysis.

Will desalination become a viable option by 2040 in Sub Saharan Africa and South Asia? This will depend on the market forces and government policies.  The incentive to invest in desalination will likely increase as renewable energy prices decline and as countries experience increasing pressure from water scarcity.

For more information:

See Aditya Sood's presentation from the Global Water Systems Project Conference: Water in the Anthropocene.