From The Editor | October 20, 2017

Will Solar Desalination Save Our Water Supplies?

Peter Chawaga - editor

By Peter Chawaga

Two of the most exciting emerging technologies for water treatment are focused on harnessing abundant natural resources: solar power and desalination. Now, the two have reached a point where progress can be made to combine them.

The U.S. Department of Energy (DOE) has announced a solar desalination funding program with a total of $15 million meant to go to projects that utilize solar thermal energy to create freshwater from otherwise unusable sources.

It’s an effort on the DOE’s part to improve the ascendingly-popular practice of desalination.

“The most advanced desalination technologies available now use reverse osmosis to force salt water through a membrane that blocks salt from making it to the other side,” said a representative from the DOE’s Solar Energy Technologies Office (SETO). “This pressure is generally driven by electric pumps, making the desalination process heavily dependent on electricity. Solar thermal desalination has the potential to greatly reduce the amount of electricity needed to desalinate water and enables desalination plans to be disconnected from the grid. SETO is looking to enable new, innovative desalination methods to make that process more affordable and efficient.”

SETO and its program are funded by the U.S. Congress and any selected project will be required to share between 20 and 50 percent of costs. The DOE anticipates awarding seven to 10 projects with between $500,000 and $5 million, and these could be geared toward a range of solutions.

The funding opportunity will focus on four main topics meant to lower the cost of water and/or the heat for solar thermal desalination systems:

  1. Developing novel or improving established thermal desalination technology and equipment
  2. Creating low-cost solar thermal collection systems through improved collectors, thermal storage systems, receivers, heat transfer fluid systems, and operation/maintenance reductions
  3. Improving the feasibility of entire systems by demonstrating that solar thermal technology can effectively drive the desalination process in a reliable and scalable way
  4. Conducting analyses that will help to identify regions and opportunities for effective solar desalination

“Each project will also need to demonstrate significant improvements over best-in-class, near-commercial systems, produce repeatable results, and include clear, market-driven objectives,” said the spokesperson.

If the above criteria are met, the DOE sees a range of applications for better solar desalination. For starters, municipalities and the agricultural industry could benefit from desalination technology that makes it easier and less expensive to increase potable freshwater supplies.

“Municipal and agricultural markets are large consumers of fresh water,” said the spokesperson. “As increasing stress is placed on our freshwater resources, it makes sense to explore innovation that may lower the cost and energy demands of using non-traditional sources of water. Just as development of energy generation technologies is accompanied by improving our energy efficiency, novel desalination technologies are complementary to increasing water conservation and reuse.”

But the DOE is particularly interested in leveraging solar desalination to improve processes at industrial operations.

“Solar desalination makes sense in reuse situations like at oil and gas well sites,” said the spokesperson. “Water that is created by oil and gas operations typically has high salt content and is produced away from electric grid infrastructure. This makes reverse osmosis desalination technologies impractical, but presents a significant market opportunity for solar thermal desalination.”

The DOE would like to see a mobile desalination technology arise for oil and gas operations.

“Because solar desalination can happen off-grid and be portable, we can envision a situation where a portable solar desalination plan can move from site to site in an oil and gas well, cleaning up wastewater and allowing that water to be reuse,” said the spokesperson.