Solar Desalination Solves Many Problems

(3BL Media/Justmeans) - It seems fitting, with World Water Week just behind us, and with news of the latest, even more dire assessment of the impacts of climate change from the IPCC still making the rounds, that we should share this story which shows one very effective way to connect the dots.

Given the changes coming down the climate pipeline, water is going to be an area of particular  concern, because we are so completely dependent on it to live, and because it’s going to be getting harder to find. Droughts are expected to increase. Snow melt, which often provides water in many regions for most of the year, is accelerating, often providing floods instead of nourishment, and changing rainfall patterns can deprive areas of water that previously had plenty.

Water and energy are inextricably linked. It takes lots of energy to pump water from one place to another and today’s thermal power plants with their cooling towers are among the nation’s largest consumers of water.

For all of these reasons, the announcement of a new solar desalination initiative is welcome news.

WaterFX is using a 377 foot-long solar array to turn brackish water, a mixture of fresh and salt water, into pure distilled water, also producing concentrated mineral salts as a byproduct. Brackish water is commonly found in estuaries, deltas and mangrove swamps, but it is becoming increasingly common as agricultural drainage as freshwater aquifers are depleted. This phenomenon is known as saltwater encroachment. It can also be expected to increase as sea level rises.

The Water FX technology, which has been dubbed “drought buster,” is currently being demonstrated in a $1 million project at the Panoche Water and Drainage District in Firebaugh, which serves the agriculturally rich Central Valley in California. Their Aqua4™ Concentrated Solar Still uses an approach that differs significantly from conventional desalination technology. Not only is it powered by the sun instead of electricity or other means, but it also relies on evaporation rather than reverse osmosis (RO) which is more commonly used. RO has been considered the more cost-effective approach due to the high energy cost associated with evaporation, but with the Concentrated Solar Still, the energy is free and clean. The rate at which fresh water can be recovered from salt or brackish water is also higher, as much as 93%, compared to 50% for RO systems. It also produces commercially desirable concentrated mineral salts as a byproduct.

A larger, commercial version of this plant, will be built later this year on 31 acres of land, capable of producing roughly two million gallons per day.

Each 400kW module produces up to 65,000 gallons per day, they call it an “engineered aquifer.”

The solar collectors are configured as troughs, and a mineral oil-based solution is used to transfer the heat. The heat is fed into a multi-effect distillation system that can handle salt concentrations up to 100,000 ppm of total dissolved solids (TDS).

The system also utilizes thermal energy storage to allow the system to continue to operate when the sun is not shining. The system is surprisingly comparing, considering its capacity, requiring a space of only 160’ x 40’ (6400 sq. ft.). The system is small enough to be modular and portable and is available for leasing.

What’s wonderfully synergistic of the Panoche project is the fact they need to dispose of this drainage water anyway, since it contains harmful chemicals. If it wasn’t constantly being drained off, it could potentially poison the crops. New environmental regulations have made it more costly to get rid of the stuff, which used to be simply dumped in nearby rivers. Salt contamination has caused farmers to abandon 100,000 acres over the past several years, not a good thing when people are going hungry in many places. This type of waste-to-water scheme is reminiscent of the various waste-to-energy schemes that have recently come on the scene.

The other synergy here is that farmers in California are facing record-breaking droughts. The shortage of water is causing farmers to drill for more groundwater, which further depletes aquifers, inviting more saltwater encroachment, not to mention the fact that many of these aquifers are non renewable.

Once a farmer taps into the aquifer and begins making withdrawals, that lowers the water table, causing his neighbors to drill deeper wells, thus creating a downward spiral.

It's great to see solutions like this one that solve multiple problems at once. They bring tremendous value to the quest for a more sustainable existence.

Image Courtesy of WaterFX