4. Desalination with Renewable Energy– An Essential Solution for the Developing World

Main takeaways:

• Water scarcity is becoming one of the most pressing environmental issues
• Water and energy have a dual relationship. On one hand, energy costs are one of the biggest components of the cost of water. On the other hand, the energy sector is one of the biggest consumers of water
• The shift to renewables is important as renewables consume very little water as compared to thermal power generation

“Water, water everywhere, but not a drop to drink.”

?(The Rime of the Ancient Mariner, Samuel Taylor Coleridge)

Environmental issues come in various hues. They vary by the type of pollutant, by the area they cover, or by the time over which they impact society. Smog, acid rain and radioactive fallout are localised issues and hit the affected zones relatively quickly. On the other hand, climate change caused by excessive greenhouse gas concentrations is a global issue, and takes much longer to become evident.

One of the most pressing environmental issues involves not the presence of a pollutant, but the absence of an essential commodity – Water. Emerging water shortages are a result of three factors:

1. Rapid population growth in traditionally water-deprived areas such as the Middle East and Saharan Africa leads to over-abstraction of ground water
2. As countries get industrialised, high levels of effluents render water sources unfit for domestic or agricultural usage. China has lost over half of its 50,000 rivers, and only 10% of the residual river flows are considered fit for usage
3. Higher standards of living result in more per capita water consumption. This includes not just higher water use at the end-user level, but also the indirect impact of higher per capita energy use. The power sector is an extremely heavy user of water, by some estimates accounting for nearly 80% of annual industrial freshwater demand and 15% of all freshwater withdrawals

The last point is key to this discussion. The numbers may vary from region to region depending on the level of industrialisation. But its certain that our energy choices impact both the volume and cost of water.

A part of the water supply can be met by recycling and treating our waste water. But for true security of water supply, after all else has been done, we might well need to turn to the most abundant source – sea water. Except that desalination doesn’t exactly come cheap. It ranges in cost from anywhere between 2 to 5 times the cost of waste water treatment. And power costs constitute a large share of the operating and maintenance costs of desalinated water – 60% according to a BoA Merrill Lynch study from 2012. Reducing the cost of energy is therefore key to improving the security of water supply.

Power plants in fact have a dual relationship with the water sector – thermal power plants require large amounts of water. The bulk of this water is used for cooling purposes. Thus a move away from water-intensive fossil fuel and nuclear plants will reduce the overall water demand. Renewables such as wind and solar PV have a very low water footprint. For solar PV, while water has typically been needed to clean solar panels, even this is changing. Recent advances in water-free robotic solar panel cleaning systems has further reduced the water intensity of solar PV from low to nearly zero. Solar PV is thus becoming an extremely attractive proposition, not only because it’s getting much cheaper, but also because it doesn’t use much water. And in its newer avatars like BIPV, these come completely embedded in building materials, and hence with no incremental water consumption (over and above the usual cleaning of glass facades).

Our ability to manage the energy-water nexus will be critical to global development. Cheap renewable energy coupled with intelligent water use will play a big role in the Convergence of sectors that collectively shows the road to a sustainable world.