Whether it’s a 25-foot pleasure boat, million-dollar yacht, luxury cruise ship or large tanker, they all have one thing in common: they need potable water. That’s why marine desalination systems continue to receive so much focus and research.
The search for a space-efficient, lighter weight seawater desalination system is ongoing as space is precious on most marine vessels.
The need for space efficiency is balanced by the desire to:
It takes energy to separate salt from water. Historically, desalination was an energy-intensive process that only could be handled in a large industrial plant. But innovations in technology and design have made it possible to create smaller, more efficient, portable systems.
Desalination by reverse osmosis is typically preferred because RO systems offer better energy efficiency, economics and a smaller footprint. But there are other promising technologies on the horizon.
One example is desalination based on ionics, where a cationic diode is combined with an anionic resistor. The key advantage is the system’s low energy requirements and the use of no moving parts. It is estimated, however, that an ionic desalination system may still be about five years out from being market-ready. The search continues for more robust materials that won’t quickly disintegrate as a result of the ionic process.
The next big thing in desalination technology will be small, and we will continue to see designs getting smaller and more modular. This is so they take up less space without compromising the amount of salt water they can convert in a certain amount of time.
Parker is leading the way in this area. It recently filed a patent pending for its energy recovery technology for reverse osmosis systems used in the leisure market. At a dry weight of only 21.7lbs /10 kg, it will be the smallest energy recovery device on the market.
A reverse osmosis system with Energy Recovery system uses one-third the amount of energy of a standard RO unit. The system recovers energy using backpressure from the RO membranes and the movement of dual pistons that generate higher pressure. A similar design with a larger pump is being explored for larger commercial applications.
This allows boat builders to run the watermaker off battery power instead of the generator without compromising freshwater production.
The market is excited about the potential of wave energy to produce wave-powered water purification. In Hawaii, testing is under way on a new system that will produce electricity from wave energy to provide water for an entire island. If successful, the new wave-powered system will replace the existing generator as a more environmentally friendly alternative.
Wind power also has been suggested as an option, as has desalination of sea water using solar energy. Challenges remain on how to make this potential power source more consistent.
Islands that rely on converting sea water for their drinking water have demonstrated an interest in mobile water purification systems. These containerized systems are especially valuable for disaster relief efforts that have been supported by multiple Parker products. As is the case on marine vessels, size is a critical issue. All components need to fit within the space of the container.
Engineering innovations are focused on making smaller desalination systems without sacrificing water output. Efforts to date have not relied on making material changes as much as they have on packaging changes.
The way equipment is mounted can affect space requirements. So, engineers need to look at systems that can operate as efficiently when mounted horizontally as they do when mounted vertically. That means testing must be conducted in all directions.
Change has been slow to come in the marine market. Many of the designs and technologies currently used today, especially on larger commercial vessels, are not that different than they were years ago. That is partially a result of the rigorous certification process required for most major components used on commercial vessels. Commercial operators largely base their purchasing decisions on a manufacturer’s experience, a product’s proven performance and certification.
But that doesn’t mean there isn’t room for innovation. There is substantial focus on identifying ways to lower costs of the more expensive system components, including membranes, pumps and filters. Newer membrane materials, such as graphene and carbon nanotubes, can impact costs by optimizing production levels and/or lasting longer.
With more cities running out of clean water and an increase in the number of serious storms creating drinking water shortages, the greatest push for marine desalination technology advancements may come from the land rather than the sea.
This article was contributed by Paul Kamel, Product Manager II, Parker Bioscience and Water Filtration.
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