Reinventing Desalination

by Richard T. Stuebi

Many informed observers consider the inadequacy of clean drinking water to be one of the world’s most serious problems. By some estimates, 20% of the human population lacks access to good water supplies.

That’s not to say that these people live nowhere near water: indeed, most of humankind lives fairly close to an ocean. However, seawater is saline, and desalination is required to render it usable as drinking water.

Desalination is no theoretical pipe-dream: two desalination approaches have long existed to remove salt from water, distillation and reverse-osmosis. Regrettably, both are rather energy-intensive. No problem for the wealthy, but the world’s ultra-poor populations typically cannot afford either the construction or the operation of such desalination technology. And, so they go without good drinking water.

As reported in an article entitled “Current Thinking” in the October 31 issue of The Economist, a pair of entrepreneur/inventors (Ben Sparrow and Joshua Zoshi) from Vancouver BC has launched a company called Saltworks Technologies that to commercialize a completely novel “thermo-ionic” approach for desalination, based on evaporation and ionic conduction, powered mainly by sunlight.

There are three beauties of this new approach concocted by Saltworks:

1. It is based primarily on solar thermal energy sources – and sunlight is often plentiful in some of the world’s poorest and most remote corners.
2. It theoretically requires only about 30% of the electricity requirement of the most efficient reverse-osmosis approaches now available for desalination.
3. It should be upward- and downward-scalable, making it a plausible solution for megacities and tiny villages alike.

All three of these factors imply that the Saltworks technology could dramatically reduce the cost of desalination and bring it into economic reach for the untold billions of the world’s thirsty poor.

This is yet another shining example of how high-tech innovators are solving the world’s biggest problems. The future health of our planet and success of our species demands more people like Mssrs. Sparrow and Zoshi. And, political, corporate, financial, academic and civic leaders around the globe would be well-advised to keep improving the environments within which those like Sparrow and Zoshi come up with and pursue unconventional and sometimes brilliant ideas.

Richard T. Stuebi is a founding principal of the advanced energy initiative at
NorTech, where he is on loan from The Cleveland Foundation as its Fellow of Energy and Environmental Advancement. He is also a Managing Director in charge of cleantech investment activities at Early Stage Partners, a Cleveland-based venture capital firm.

Low Cost Desalination – Saltworks Breakthrough

Canadian firm, Saltworks Technologies, just came out of stealth in relation to their desalination technology, which they claim reduce the electrical energy required for desalination by over 70%. They report they can produce 1m3 of water with 1kW hour of electrical energy, compared to the 3.7kWhr per m3, which is what is currently achievable using reverse osmosis with the use of energy recovery devices.
So how to they do it? Well its novel. It appears to be a new approach. And novel and new are two things scarce as hens teeth in relation to desalination technologies.
They use solar heat (or waste heat) to evaporate water and concentrate salt water. They are converting solar energy into osmotic energy by doing this. They then use this osmotic energy to desalinate water.
They then expose the concentrated salt water to two separate solutions of regular salt water via two different ‘bridges’, one which is porous to chloride ions, the second which is porous to sodium ions.

The sodium and chloride ions migrate across the respective bridges into the salt water solutions to equalise the difference in ion concentration between the solutions.
This creates two charged solutions, one enriched with sodium ions (positively charged), the second enriched with chloride ions (negatively charged).
These two solutions are then exposed across two similar bridges to the water to be desalinated. This draws sodium ions into the chloride enriched solution and draws chloride ions into the sodium enriched solution: Net result desalination. Doing this they reckon they can produce 1m3 of water using 1kWh of electrical energy, which is used to pump fluids around the pipework.
Because the system is not under pressure, they can use plastic pipes instead of steel pipes, potentially reducing capital costs also.

I met with Saltworks about six months ago in Vancouver and I was impressed by the methodical way they have been going about technology commercialisation. Despite winning a technology innovation award in British Columbia in May 2009, they have kept this remarkably quiet. An article in the Economist provides a good review of this.

Paul O’Callaghan is CEO of Technology Assessment Group, O2 Environmental Inc and author of Water Technology Markets.