Innovative desalination technology

In recent decades, over-exploitation, pollution and climate change have led to severe water stress across the world. Desalination could help resolve this, but large-scale desalination technologies are energy intensive. Fresh Water Nature (FWN) is a clean-tech company specializing in green water treatment with a low impact, low carbon desalination technology called Cool Steam.

Desalination projects widespread use

Since 2015, SWEP has been providing heat exchangers and technical support to Spanish based Fresh Water Nature. (FWN) FWN’s key application is a low-carbon and low-impact desalination technology called Cool Steam.

Based on once-through multi-stage low-temperature vacuum distillation, Cool Steam has several advantages over today’s most common desalination method (reverse osmosis). Firstly, it consumes approximately half the electrical energy (and thus COemissions) per m3 of desalinated water. It also produces significantly purer water than reverse osmosis. This water can then be used – without additional processing – in demanding applications in, for example, the pharmaceutical industry. In addition, Cool Steam neutralizes the marine impact of brine by its previous costless dilution.

Vista interior planta piloto

A look inside the operational demonstration plant in Barcelona.

Thermal energy gains from heat exchangers

The thermal energy that Cool Steam requires can be taken from renewable sources or other industrial processes. This is where brazed plate heat exchanger technology plays a role. Thermal energy from low-grade heat sources is both harvested and dissipated by SWEP heat exchangers to drive water evaporation and condensation in various stages of Cool Steam.

At the start of the project, compact heat exchangers from SWEPs B-range were used (B3 and B25 units for example), performing phase change under vacuum conditions. Over time, larger heat exchangers have been put in place, and more recently Sealix® units have been used – when dealing with seawater, its anticorrosive properties have been highly effective.

FWN has chosen SWEP products for Cool Steam because of their quality and reliability, advantages that reduce operating costs. There is an operational demonstration unit at the Barcelona Desalination Plant, which can be transported by truck or ship to clients’ facilities for field pilot testing. These transportable and fully automated plants produce fresh water with a conductivity as low as 10 microS/cm and 55% conversion rate. The minimum activation point for these devices is set up at just 60 °C. There are plans for Cool Steam to be implemented in more sites both in Spain and in India.

Cool steam desalination

How Cool Steam desalination supports green hydrogen generation.

From desalination to green hydrogen

Cool Steam desalination technology can also support cost-effective green hydrogen production. Water electrolysis is potentially an emission-free way of producing hydrogen, but it normally requires large quantities of water for cooling, as well as ultra-pure water as a raw material.

Cool Steam itself cools electrolysers, thus reducing their operational expenses. It also supplies ultra-pure water after an additional processing stage (electrodeionization), lowering the cost of raw materials. This resultsin a water positive process.

Electrolysis releases waste heat which, with the help of SWEP heat exchangers, can be used as an input to the desalination process. Combining Cool Steam desalination with electrolysis means that surplus outputs are transformed into useful inputs throughout the process, bringing us closer to a completely circular solution.

This system has been successfully validated at pilot scale at a LNG Regasification Plant. Electrolysis in this plant makes use of the water from the Cool Steam process, while Cool Steam utilizes the released waste heat from the electrolysis.

Cool steam pilot testing

Cool Steam pilot testing for green hydrogen production by electrolysis.

Role of SWEP

In addition to supplying heat exchangers, SWEP's Iberian staff supported with technical knowledge in innovative ways to support the customer. As Engineer Naeria Navarro at FWN explains: “SWEP had an important role in this project as technological adviser. SWEP engineer Giancarlo Soler Zabala was helpfully involved with heat exchange system design and sizing, as well as the integration of all components within the overall system.”

Three heat exchangers were used in the electrolysis part of the process, for stack cooling, oxygen recovery and hydrogen recovery. Other three heat exchangers were used in the desalination process, for heating, cooling and cryogenic temperature cushioning. SWEP also has a key role in other Cool Steam applications in agriculture, food, cosmetics, and zero liquid discharge (ZLD) processes.

Who is Fresh Water Nature?

The Fresh Water Nature (FWN) story begins with the International Center for Numerical Methods in Engineering (CIMNE). CIMNE is a research center that originated from a consortium involving the Government of Catalonia and BarcelonaTech (also known as the Technical University of Catalonia). More than a dozen companies have emerged from CIMNE as spin-offs and start-ups, working in areas as diverse as civil engineering, robotics, data analysis, meta-materials and inflatable structures.

FWN was founded in 2013 to work on the final development phase and market transfer of desalination and water treatment technologies developed in CIMNE, bridging the gap between academic research and commercially viable applications.