Unleashing energy efficiency: Utilizing renewable and recovered heat sources in desalination through exchanger technology
In recent decades, overexploitation, pollution, and climate change have led to severe water stress around the world. Desalination can help solve this problem, but large-scale desalination technologies are energy-intensive. Fresh Water Nature (FWN) is a cleantech company that specializes in green water treatment with a low-impact, low-carbon desalination technology called Cool Steam.
Desalination projects are widely used
SWEP has been providing heat exchangers and technical support to Fresh Water Nature in Spain since 2015. The main application of FWN is a low-carbon and low-impact desalination technology called Cool Steam.
Based on one-time, multi-stage cryogenic vacuum distillation, cold steam offers several advantages over the most common desalination method (reverse osmosis) available today. First, it consumes about half of the electricity (and therefore CO2 emissions) per m3 of desalinated water. It also produces purer water than reverse osmosis. This water can then be used for demanding applications in the pharmaceutical industry without additional treatment. In addition, Cool Steam neutralizes the effects of salt water on the ocean through previous cost-free dilution.
An overview of the interior of the Barcelona Demonstration Plant
Thermal energy gain of a heat exchanger
The thermal energy required for the Cool Steam can be harvested from renewable energy sources or other industrial processes. This is where plate heat exchanger technology comes into play. Thermal energy from low-grade heat sources is collected and dissipated by SWEP heat exchangers to drive water evaporation and condensation at all stages of cold steam.
At the beginning of the project, compact heat exchangers of the SWEP B series (e.g. B3 and B25 units) were used for phase change under vacuum. Over time, larger heat exchangers have been put in place, and more recently the Sealix® unit has been used – which is very effective at protecting seawater from corrosion.
FWN chose SWEP products as Cool Steam products because of their quality and reliability, which has the advantage of reducing operating costs. The Barcelona Desalination Plant has an operational demonstration unit that can be transported by truck or ship to the customer's facility for field trial testing. These mobile, fully automated plants produce freshwater with a conductivity as low as 10 μS/cm and a conversion rate of 55%. The minimum activation point for these devices is set to only 60 °C. Cool Steam is planned to be implemented in more locations in Spain and India.
How Cold Steam Desalination Supports Green Hydrogen Production
From desalination to green hydrogen
Cold steam desalination technology can also support cost-effective green hydrogen production. Water electrolysis may be an emission-free way to produce hydrogen, but it typically requires large amounts of water for cooling, as well as ultrapure water as a feedstock.
The cold steam itself cools the electrolyzer, reducing its operating expenses. It also provides ultrapure water after an additional processing stage (electrodeionization), which reduces raw material costs. This leads to a positive process of water.
Electrolysis releases waste heat, which can be used as an input to the desalination process with the help of SWEP heat exchangers. Combining cold steam desalination with electrolysis means converting excess output into useful inputs throughout the process, bringing us closer to a fully circular solution.
The system has been successfully validated on a pilot scale at an LNG regasification plant. The plant's electrolysis utilizes water from a cold steam process, while cold steam utilizes waste heat from electrolysis.
Pilot test of cold steam for the production of green hydrogen by electrolysis
The role of Surip
In addition to the supply of heat exchangers, SWEP's Iberian employees support customers with technical know-how in innovative ways. As FWN's engineer Naeria Navarro explains: "SWEP played an important role in this project as a technical consultant. SWEP engineer Giancarlo Soler Zabala was involved in the design and selection of the heat exchange system and the integration of all components in the entire system.
Three heat exchangers are used in the electrolysis process for stack cooling, oxygen recovery and hydrogen recovery. The other three types of heat exchangers are used in the desalination process for heating, cooling, and low-temperature buffering. SWEP also plays a key role in other cold steam applications in agriculture, food, cosmetics and zero liquid discharge (ZLD) processes.
Who is Freshwater Natural?
The story of Freshwater Nature (FWN) began with the International Center for Numerical Methods in Engineering (CIMNE). CIMNE is a research center that originated from a consortium between the Government of Catalonia and the Polytechnic University of Barcelona, 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 different fields such as civil engineering, robotics, data analytics, metamaterials, and inflatable structures.
FWN was founded in 2013 to bridge the gap between academic research and commercially viable applications by working on the final stages of development and market transfer of desalination and water treatment technologies developed by CIMNE.