First solar desalination plant to be built in California


Due to Californian draughts, 2015 was the second year in which agriculture in the Central Valley was left with a water allocation of 0 %. A company wants to fix this problem using solar thermal technology to recycle unusable water for agricultural irrigation.

HydroRevolution, a subsidiary of WaterFX, wants to recycle impaired agricultural water from irrigation drainage. Due to the fertile soil of California’s Central Valley, after irrigation of crops, a salty residue is left behind: the irrigation drainage. This high salinity of the soil can harm the environment and prevent farmers from using the land again for crops, if it is not removed.

There are around 1,233 million m³ of this irrigation drainage water available in the Central Valley that could potentially be treated through solar desalination.

In California’s Central Valley there are nearly 530,000 ha of salt-impaired land, which means that there is a lot of drainage to get rid of. Additionally, farmers need a sustainable and reliable water source to irrigate their crops even if there are further draughts.

According to HydroRevolution, their solar thermal distillation method “Aqua4” is capable of recovering 90 % of freshwater from impaired water – as compared to a 50 % recovery rate for seawater desalination. The system is comprised of solar thermal parabolic trough collectors heating mineral oil, a Multi-effect Distillation system for water evaporation and a heat storage system, to ensure that desalination can take place even at night. After distillation, the remainder could be treated further to isolate useful salts or minerals.

It will be the first plant of this kind in California. In 2013, HydroRevolution already realized a six-month-long demonstration project in the Panoche Water and Drainage District in Central Valley. “The demonstration plant proved that we can reliably treat drainage water, and also showed that the treated water is not a waste product; it is a valuable new source of freshwater” said Aaron Mandell, Chairman of HydroRevolution. “Using a sustainable source of energy to recycle or desalinate water will become a mainstay in regions with water scarcity.”

The new plant will be an expansion of this demonstration project, which is operated by WaterFX. It will be constructed on approximately 14 ha of farm land, which is at the moment being used to grow salt-tolerant crops. If the project works well, it could be expanded to an area of about 28 ha. HydroRevolution says their solar desalination plant will be able to generate up to 6 million m³ of water per year. With this 800 ha of farmland could be irrigated. All the freshwater generated by the project will be made available to Panoche District and other nearby water districts.

The Panoche Water District participates in the San Joaquin River Improvement Project, which aims to restore San Joaquin River’s natural water bed and improve water quality to reintroduce native fish species.

HydroRevolution wants to start an investment crowdfunding campaign to help fund the new plant. The Direct Public Offering has not yet started but will be open to all residents of California. More information.

Tanja Peschel