It’s been decades since humankind has been looking for alternatives to freshwater resources. One of our primary target has been to make seawater drinkable through efficient seawater desalination. As we’ve traveled on, lived by, and fished from the majestic ocean since we’ve set foot on earth, it continues to be the greatest water source.
However, the issue is consuming salt water would make the human body dehydrated. Instead, our body needs fresh water to dilute the salt and maintain the body’s blood salinity. If we go back to 340 BCE, Aristotle published his observation related to saltwater. He mentioned that it loses its salt content when converted into vapor and becomes sweet upon condensation. We’ve derived seawater thermal distillation from this concept. Let’s trace back other concepts of energy intensity further.
Energy intensity 1.0: Thermal Distillation
The process of distillation comprises a phase separation approach. The seawater is heated, and water vaporizes without the salt, as it has an entirely different boiling point. Hence, when the vaporized water is condensed back to the liquid state, only the H2O is left.
The energy required to heat the saltwater is comparatively higher than the energy required to collect rainwater or draw water from a stream or well. Because of this, seawater thermal distillation has typically only been utilized as a last resort and on a small scale, such as when early seafarers boiled pots of seawater and used sponges to collect the condensed steam.
However, things started to change with the industrial revolution when oceangoing ships started to employ steam for power supply. Marine distillation was made more popular and energy-efficient throughout the 1800s because of a number of innovations, such as the multiple-effect evaporators still used today.
The year 1928 witnessed large-scale and land-based thermal distillation with the installation of a multiple-effect distillation (MED) using a 60 m3/day plant was installed on Curacao. In the later part of the 1900s, the world saw the installation of hundreds of distillation desalination plants as an initiative for efficient seawater desalination. These first-generation units are still currently in use regardless of their relative energy intensity.
During the 20th century, engineers brainstormed ideas and made great improvements to increase the energy efficiency of thermal distillation plants.
Energy intensity 2.0: Reverse Osmosis
Reverse Osmosis stands apart from all the techniques known to humankind for water filtration at different stages of their life. Undoubtedly, filters can effectively separate minute particles from the water. However, dissolved chemicals are something they cannot possibly remove. This is where RO steps in to save the day. Reverse Osmosis exerts pressure and forces water to pass through the semi-permeable membrane. It only lets H2O permeate through and restricts dissolved salts and other contaminants.
Back in 1959, two research scholars named Srinivasa Sourirajan and Sidney Loeb UCLA created the first ever RO membrane. Fast-forward to six years later, Coalinga in California saw the first successful pilot program that involved the use of this technology by the municipal corporation. Since then, we’ve come very far along in terms of improvements in energy recovery, high-pressure pump, and membrane technology for efficient seawater desalination.
From conventional cellulose acetate hollow fiber membranes developed by Loeb & Sourirajan to the present-day thin-film composite membranes, technology is the catalyst that pushed energy efficiency to the top.
Energy intensity 3.0: RO + Isobaric Energy Recovery
The invention of the isobaric energy recovery was a big move that improved the energy efficiency of desalination. Although isobaric ERD appeared in the later part of the 1900s, its development can be traced back to the mid-1960s. After decades of innovation and evolution, they paved the way for the SWRO plants and are a huge commercial success.
Isobaric ERD cuts down the high pressure required by pumps to pump, resulting in reduced power consumption by the SWRO plant. Isobaric ERD achieves energy recovery of upto 98% through the use of a positive displacement technology, which is nothing like the centrifugal predecessors. Hence, the plants become 10 to 30% more efficient as compared to plants using turbochargers or turbines and 60% more energy-efficient than plants not having ERD.
Plants that have manufacturing dates before 2005 enjoy reduced operating costs by incorporating the use of isobaric ERDs. Another advancement in SWRO is the use of axial piston high-pressure pumps, which use less energy than centrifugal high-pressure pumps. This efficiency disparity is especially noticeable in small and medium-sized installations, as seen in the chart below. In 500 m3/d plants, axial piston pumps are roughly 20% more efficient than centrifugal pumps, but this efficiency differential drops to 4% in 10,000 m3/d plants.
Energy Intensity 4.0: What’s Next?
Will the next desalination technology cut down energy consumption by more than half? Can we expect incremental SEC developments in highly-efficient SWRO technology to be the next breakthrough? One thing is certain humankind can expect the introduction of evolved technologies in the future that’ll bring down the carbon footprint of desalinated water. Below are a few upcoming innovations you can expect:
Improved Membranes
Renewable energy fueled desalination.
More efficient ERDs
Replacements of SWRO plants
Conclusion
Given the combined effects of climate change, water scarcity, and demographic growth, the next generation will desperately need desalinated water. Therefore, the scholars are brainstorming ideas day in and out to improve efficient seawater desalination further. The World Bank backs the desalination industry and states that thermal desalination powered by solar energy will drop to a mere $0.90/m3 by the year 2050.
Keikeen Engineering is a pioneer in equipping the market with the latest technologies. It offers advanced technology for efficient seawater desalination, photovoltaic installations, and comprehensive water treatment. For further queries, reach out to us via mail at info@keiken.es or call us at +34 910 577 254.
