Sustainable Water Desalination

By Edmund Kelly

This article in next big future highlights the rapid advances in large scale desalination deployment that Israel has led over the last decade. Israel, a country of 8 million people, has gone from a precarious water supply situation to a position today where 50% of its water supply is from desalination and by 2020 it will be 70%. Fortuitously for Israel this has occurred while the Middle East is in the middle of a multi year drought which would otherwise have had a serious economic impact, as has occurred elsewhere in the Middle East.

As this recent paper illustrates in detail, reverse osmosis (RO) desalination has been steadily improving and is being deployed on an increasingly large scale worldwide, not just in Israel. The Israeli company IDE is selling water from the latest plant at Sorek for 58 cents a cubic meter. That is about $690/acre-foot, or less than much of the water purchased in California, some of which costs as much as $1,200/acre-foot. As the paper illustrates there are strong  prospects for further cost reduction.

Reverse osmosis currently consumes about 3kWh of electricity to produce a cubic meter of water. At $0.06/kWh that is $0.18/m3 or about one third of the cost. Providing the energy for desalination from a cheap and sustainable, high utilization source would alleviate a major environmental concern that limits a broader acceptability of desalination, particularly in California.

Currently wind and solar alternative energy sources are expensive and worse, have a low utilization. The low utilization means desalination plants would have an equally low utilization. The combination of high cost and low utilization makes desalination powered by current intermittent alternative energy multiple times the cost from fossil fuels.

The StratoSolar solution of high utilization PV combined with gravity energy storage provides a cheap, high utilization, clean sustainable source of energy for desalination. Its lower cost over time will help further reduce the cost of clean water. The continuous cost reduction learning curve of RO desalination combined with StratoSolar electricity would reduce water costs to around $0.20/m3 ($230/acre-foot) by the early 2020s. This would make desalination the cheapest and most environmentally friendly source of water, potentially reducing some of the environmental impacts of the current exploitation of natural clean water sources.