NATURE FOR WATER / 22 Mar 2018
Blog: Nature for Water - Sustainable Solutions for Renewable Desalination
The Earth’s current water reserves are insufficient to cater for the ever increasing population. The percentage of potable water available to mankind is just 0.008% of the total amount of water on Earth*. Thus, solutions to provide fresh water from non-potable water are needed. Conventional desalination produces fresh water from oceans but depends upon fossil fuels and is therefore not sustainable. However, a greener solution is technically possible by integrating renewable power with desalination, making it a great example of using nature to overcome water challenges.
The challenge of fresh water
The total water reserves of the world are approximately distributed as follows:
- Oceans: 97.5%
- Freshwater: 2.5%, of which about two thirds is stored in the form of ice in the glaciers, and the rest as groundwater.
According to the UN, 2.1 billion people live without safe drinking water today. Given the vast amount of water stored in the oceans, one of the available solutions to provide fresh water consists of producing it from the non-potable salt water source of the oceans. This is the so called desalination process.
Conventional desalination processes, such as membrane and thermal desalination are costly processes both commercially and environmentally: they require a significant amount of energy - in the form of electricity or heat respectively - and generate pollutants in the form of greenhouse gas emissions, brine and chemicals, which are disposed of into the feed water source, subsequently affecting the aquatic life and ecosystem.
In countries that can afford to use conventional desalination sources, their policy makers are faced with the paradigm of bringing new desalination plants into operation whilst addressing their inherent impact on the environment; without a long term perspective desalination is not a sustainable solution.
Our future generations need a dependable source of potable water, but not at the expense of permanently damaging the marine and aquatic environment; thus engineers and consultants are ethically compelled to find alternative, more sustainable solutions to decrease the conventional desalination footprint on the environment.
The solution is in nature: renewable energy sources for desalination
Fortunately, both membrane and thermal desalination process are good candidates for hybridization with renewable energy sources. In particular, Reverse Osmosis (RO), Multi Stage Flash (MSF) and Multi Effect Desalination (MED) thermal processes can easily be integrated with solar energy, RO with photovoltaics (PV electricity) and MSF and MED with low temperature solar distillation (thermal energy).
Integration of desalination with renewable sources not only helps to mitigate the environmental footprint of desalination, but helps to reduce the dependency on fossil fuel sources, having a positive effect on the overall economy of those countries that rely on desalination to produce potable water.
Because of its higher efficiency, simplicity and lower cost, the focus is on integration of RO with PV. Studies conducted by Pöyry show that RO desalination driven by solar generated electricity (PV) can be cost competitive measured by price/m3 with conventional RO desalination when the actual cost of fossil fuel vs solar power is considered. With the decrease of PV module costs seen during the last few years, solar driven desalination has become more and more competitive.
Despite certain technical limitations associated with the intermittency of renewable electricity, there are several other renewable solutions using hybrid schemes: batteries, pumped storage, wind, grid back-up, etc. that would ultimately lead to the optimum water production.
The path forward: pioneering the first entirely renewable desalination plant
Building RO desalination plants that are entirely driven by renewable sources is technically possible today.
At Pöyry, we have developed a renewable desalination model that shows the path forward. We are ready to put this model to the test and produce the first entirely renewable desalination plant in the world.
Let’s leave to our children a better planet than the one our forefathers left to us.
Author: Jose Carmona
Head of Engineering & Advisory Services, Thermal Power and Renewable Energy
*The total amount of water on a planet is known as the hydrosphere. The Earth’s hydrosphere includes water that is on the surface of the planet (as liquid i.e. in oceans, lakes and rivers or ice i.e. glaciers, ice caps and icebergs), underground (i.e. groundwater, etc) and in the air (as vapour i.e. clouds and fog).