Desalination processes based on renewable energy (RE) could be a solution to India’s perennial water woes. Desalination is the process of distilling sea or polluted water (called source water) using thermal (heat) or electrical energy. However, these processes have a major drawback — they consume a large amount of energy, most of which is derived from fossil fuels.
Some of the commercialised and extensively used desalination technologies are Multi Stage Flash (MSF), Multi Effect Distillation (MED) and Reverse Osmosis (RO). Adsorption-based desalination shows great economic promise, but the technology is yet to mature.
There are many probable RE candidates, such as Parabolic Trough Collector (PTC), Compound Parabolic Collector (CPC) and Solar Photovoltaic (PV), that can be used to power commercial desalination technologies.
PTCs and CPCs use reflectors such as mirrors to capture solar energy and convert it to thermal energy using metallic receivers, which are in the form of circular tubes. PTCs and CPCs can power MED and MSF as these desalination technologies consume thermal energy.
PV, on the other hand, converts solar energy directly into electrical energy. Therefore, PV can supply the required electrical energy to power RO systems. Combining RE-based technologies with the desalination process ensures that the production of pure water is non-polluting.
As an immediate solution, we recommend solar thermal/PTC with MED system as the best combination based on the following rationale: That it can operate for 24 hours and, hence, cater to large water requirements; that it can handle a wide range of water quality, and finally, it allows water production at a low cost.