From Waste Heat to Waste Not
It’s always satisfying when you can see a bit more about something than AI does. There is hope for us humans yet!
You’d have thought this a straightforward question:
‘What are the benefits of RO (Reverse Osmosis) versus traditional distilling plants on ships?’
For sure – ChatGPT scoured the internet in seconds and described most of the main points succinctly (much more succinctly than I’m capable of doing).
This is what it had to say:
Reverse Osmosis (RO) systems offer several advantages over traditional distilling plants on commercial ships. Here are the key benefits:
1. Energy Efficiency
RO Systems: Use pressure to push seawater through membranes, which is inherently more energy-efficient, especially with modern energy recovery devices.
Distilling Plants: Rely on thermal energy, either from the ship's exhaust or dedicated boilers, which consumes more fuel and increases overall energy costs.
2. Elimination of Plastic Bottled Water
Carrying plastic bottled water onboard creates logistical challenges, generates significant waste, and contributes to marine pollution if not disposed of properly. RO systems allow ships to produce clean, potable water directly from seawater, eliminating the need for plastic bottles. This not only reduces the vessel's environmental footprint but also aligns with global efforts to minimise plastic waste in the oceans.
3. Maintenance and Complexity
RO Systems: Have fewer moving parts, are less complex, and require less frequent maintenance.
Distilling Plants: Involve complex heat exchangers and condensers, which are more prone to scaling and corrosion, increasing maintenance demands.
4. Environmental Impact
RO Systems: Can operate without creating greenhouse gases or relying heavily on fuel, making them more environmentally friendly.
Distilling Plants: Consume more fuel, indirectly increasing emissions. They also require more chemicals to manage scaling and corrosion, which can impact the environment.
5. Water Quality
RO Systems: Remove salts, impurities, and microorganisms, providing consistently higher-quality water for drinking. They can also be designed to produce Technical water suitable for machinery systems.
Distilling Plants: May produce lower-quality water as contaminants and carryover can affect purity, especially with aging equipment.
6. Footprint and Weight
RO Systems: Are compact and lightweight, saving valuable space on the ship.
Distilling Plants: Require larger installations, including boilers and condensers, and add more weight to the vessel.
7. Operational Simplicity
RO Systems: Can operate autonomously with minimal monitoring, simplifying crew tasks.
Distilling Plants: Require careful monitoring of temperatures, pressures, and chemical levels to ensure efficient operation.
8. Compatibility with Modern Energy Systems
RO Systems: Pair well with renewable energy sources or energy recovery systems, enhancing sustainability.
Distilling Plants: Usually depend on fossil-fuel-based thermal energy, limiting their compatibility with modern, eco-friendly technologies.
9. Flexibility and Scalability
RO Systems: Can be scaled up or down based on the ship's water requirements and can adapt easily to different operational needs.
Distilling Plants: Are less flexible, with production rates tied to the thermal energy availability and system capacity.
Conclusion
RO systems surpass traditional distilling plants in energy efficiency, environmental impact, water quality, and operational simplicity. They align well with the modern shipping industry's goals of reducing fuel consumption, minimizing waste, and enhancing operational efficiency. While traditional distilling plants were once a staple, RO technology represents a significant advancement in maritime water production.
9/10 Chat. Good effort / impressive, but there is something else important missing.
Like a lot of people, I’m a deep thinker in my sleep. In fact, for me, it is second only to long dog walks on the beach. I often wake up early in the morning and scribble some stuff down and wonder where on earth it came from. I know I’m not alone on this front. From my notes last week…
A few years ago (well…decades ago), as an Engineer on a ship, I remember my profound disappointment when the Mate asked me to dump over 100MT of domestic freshwater that we’d invested much effort in producing on the ballast leg. Alas, load port intake requests & under keel clearance requirements were not in agreement! Freight income priority triumphed yet again. I shed a tear.
But what has this got to do with RO systems?
There is a relationship between a ship’s draft and specific fuel oil consumption. Naval Architects optimise hull design, or, in other words, for any ship, there is a ‘perfect’ draft. Go deeper and the wetted surface area increases - that increases hydrodynamic resistance and therefore the power required to achieve the same speed. Go lower and the wave-making resistance increases with the same effect as going deeper.
The point is this: distilling plants depend on waste heat from the main engine (of any type). This drives one understandable behaviour: make as much water as you can when the main engine is running and hope there is sufficient to last until the next opportunity. Make hay when the sun is shining. The same does not apply to RO. Crews can operate systems irrespective of the whether the main engine is in operation (and in a condition where there is sufficient waste heat to operate a distilling plant – think ‘slow steaming’…), or not. This flexibility promotes draft optimisation and therefore specific fuel consumption. Every little bit helps.
Stonefort Marine are delighted to be working with several managers who are now discovering the many benefits of RO. We work closely with clients to discover their exact needs and challenges. We facilitate design, manufacturing, system integration and installation. Oh…and we don’t charge a $ for the consultation because we are confident on receiving orders once clients have done their own calculations. Curious? - please do drop us a line if you are interested to see what you could save.