There has been a lot written about ‘Hybrid’ yachts, often with some hype about being eco-friendly, having green credentials, etc., but with very little information of substance to support the claims.
Hybrid, in the context of motor yachts, just means there is more than one system capable of providing propulsion and/or electrical power.
Apart from a couple of innovative examples, all these systems rely on burning diesel fuel (MGO/MDO) as the primary energy source. This is sometimes glossed over where batteries are concerned.
Hybrid motor yachts and tenders have also been compared to Hybrid vehicles, but completely ignore the fact that they generate power from coasting or braking to increase their efficiency – something not available to yachts.
So, in this piece, I take a more in-depth look at Hybrid systems in an effort to provide some much-needed clarity on their benefits. I also question whether it is a transitional technology, or if it will be here for the longer term?
No Standard Operation
When it comes to superyachts and their operation, this is true. It’s what makes optimising the propulsion and electrical package challenging.
Main engines (ME) must be able to deal with variable speeds e.g. manoeuvring, cruising, maximum speed.
Generators (GEN) must handle variable loads and the ‘cycling’ of equipment that is dependent on the operational mode e.g. underway, guest-on, guest-off, in port or at anchor.
Given the variability of speed and load it can be difficult to size the main engines and generators for their best performance. This matters, because running engines at optimal load increases efficiency, reduces fuel consumption and emissions such as CO2; this is where ‘Hybrid’ can help…but, more on that later!
A Little History
Traditionally, superyachts used diesel main engines to provide propulsion power, and diesel generators to provide the electrical power for auxiliary and hotel loads – independent systems.
Fig 1. Traditional – ME to drive the propellors and GEN’s that power the hotel and auxiliary loads.
Although Diesel Electric has been used in shipping for many years it was not until the launch of M/Y Limitless in 1997 that it started to receive attention in the superyacht industry. And, in 2005 we saw the launch of M/Y ICE a Diesel Electric yacht that also used Azipods – interestingly both were built by Lurssen.
The story goes that many shipyards were reluctant to adopt Diesel Electric due to the complexity, engineering risks and the associated costs of developing a new platform – concerns that still apply to any new technology. However, their benefits, and the demands from yacht owners and their technical team saw a steady increase in use – especially on the larger yachts.
Fig 2. Diesel Electric – GEN’s provide electrical power for propulsion through Permanent Electric Motors (PEM’s) and the hotel and auxiliary loads.
Diesel Electric has many benefits. Having a number of generators (can be different sizes) that can be brought on-line for propulsion, and the hotel and auxiliary loads, meant the engines could run at optimal loads with better efficiency. It also provided a high degree of redundancy, greater flexibility in the technical layout – no longer limited by shaft lines – and, reduced noise and vibration which improved comfort.
You could say Hybrid is a mix of ‘Traditional’ and ‘Diesel Electric’ systems, combined with batteries (BAT) and sophisticated Power Management System (PMS) to optimise engine performance and efficiency.
The diagram below is an example of a Hybrid system.
Fig 3. ‘Hybrid’ Arrangement
Propulsion can be driven by ME’s, PEM’s or both (Boost), electrical energy can be generated from the ME and/or GEN’s and stored in batteries. The PMS takes care of managing the loads for propulsion, hotel and auxiliary systems.
The 83m Feadship, M/Y Savannah, delivered in 2015, is often cited as the first Hybrid motor yacht; though, just like Diesel Electric, it was not new to shipping. Since then we have seen am increase in its use across a variety of different sized motor yachts.
As mentioned, although diesel fuel is the primary energy source, there are some examples of innovative Hybrid motor yachts that use ‘Alternative Energy’. These include Artifact that uses solar, and the recently announced Lurssen project that will use Methanol in the energy mix.
No doubt the use of alternative energy will increase over time as the industry strives to reduce its carbon footprint.
It’s All About Efficiency
There are different types of marine diesel engines, two-stroke, four-stroke, slow speed, medium speed and high speed, each with their own performance characteristics. We use four-stroke high speed diesels on superyachts for both main engines and generators.
Whilst diesel engines are the most efficient internal combustion engines (ICE) at approx. 45% energy out vs. energy in, there are challenges to improve this – we may be close to the max with modern engine designs and materials.
What may not be so obvious, is that diesel engines have an optimal load; a point where the power generated requires the least amount of fuel. For many marine diesels this is at or near the Max Continuous Load and can be found from a table or graph of Load (kWh) vs. Specific Fuel Oil Consumption (g/kWh) in the engines test/technical file.
The example below is the SOFC for fixed speed 340 kW generator.
Fig 4. SOFC for 340kW GEN
The lowest fuel consumption 205 g/kWh is at 100% load. As the load decreases fuel consumption increases at a shallow and near linear slope until about 40% load, where it starts to rise exponentially.
The effect of running at or near optimal load on fuel consumption can be seen in the below.
Fig 5. Using one GEN at 80% load instead of two at 40% load can reduce the fuel consumption by approx. 9%.
Providing the generators are sized correctly it is unlikely they would run at less than 40% load – a point to bear in mind when looking at fuel efficiency claims for ‘Hybrid’ systems as they may be based on the more extreme ends of the SOFC curve.
This is also relevant to main engines though because they are able to run at variable speed, the difference is less pronounced – one of the advantages of variable speed generators as fitted to Artifact.
In the example below of a 3600 kW main engine, the SOFC slope is shallow and near linear from 100% load down to 25% load, where it starts to rise exponentially. There is about a 5% difference in fuel consumption between 25% and 100% load – a much wider load range and lower fuel saving compared to the fixed speed generator.
Fig 6. SOFC for 3600 kW ME
Unless ME’s are significantly over-sized to eke out that extra 0.5 knot of top speed, the only times when running at less than 25% load would be whilst maneuvering and/or motoring at sub-optimal speeds – you can determine this by comparing power/speed graph with SOFC.
What About Batteries
Batteries are just one form of Energy Storage System (ESS) others include devices such as capacitors and flywheels but, they all need an external energy source to charge them e.g. generators, solar, shore power.
Batteries perform a number of functions in a Hybrid system.
Buffer and avoid start/stop of additional generator
Backup for running generators
Fewer generators needed online
Improve fuel efficiency and reduce emissions
Reduce engine hours and maintenance
Instant power on demand
No startup delay
Each of the above helps to improve performance and efficiency of the yachts systems by keeping the engines operating at their optimal load, reducing fuel consumption and CO2 emissions.
Batteries with sufficient capacity can also power propulsion and/or the hotel and auxiliary loads for short distances or time.
Engine Free Operation
Whilst it is clear that batteries are an integral part of a Hybrid system – though not essential as I have sailed on a Hybrid yacht without batteries – whether they offer significant benefit when used for ‘Engine Free’ operation is another matter.
Engine Free, often described as ‘silent’ or ‘zero emissions’ mode, is perhaps a little more nuanced than might be suggested.
One reality is that emissions are not really reduced or prevented, they are merely displaced by time and location and do nothing for the overall CO2 footprint of the yacht – you still need to burn diesel fuel to generate the electrical energy stored in the batteries.
When it comes to noise, I also found that on larger yachts that with proper isolation, sound insulation and dry stack exhausts, it was difficult to tell if a generator was running in the guest areas. It was often the air-conditioning that emitted the most obvious noise and shutting down the a/c often resulted in an eerie silence, even with generators running.
With the above and, given the known issues with Li-ion batteries, from their production and imbedded emissions, to safety, life-cycle and recycling, I think the use for Engine Free operation needs to be carefully assessed. The current battery technology does not provide sufficient capacity for any reasonable level of autonomy without significantly impacting the interior space and weight.
In addition, if installing large battery banks for Engine Free running, you may need to upsize the generators as the total amount of energy required is not diminished, it is just generated over a shorter period of time. You may also lose some efficiency gains due to the power required to keep the battery banks at optimum temperature.
A Hybrid Solution
The following example provides flexible modes of operation.
Fig 7. Fully Integrated Solution
A. Stationary – Hybrid GEN/BAT for electrical loads
B. Low Speed – Propulsion and electrical loads from Hybrid GEN/BAT
C. Cruise – Mechanical propulsion, Hybrid GEN/BAT electrical loads
D. Performance (Boost) – Combined mechanical and electrical propulsion/loads from Hybrid GEN/BAT
The main purpose of these modes provides operational flexibility to ensure the optimal engine load, performance and efficiency.
Fuel Saving and CO2 Reductions
Whilst we now know fuel can be saved by running diesel engines at optimal loads, the more difficult question to answer is; by how much?
One DNV study ‘Electrical Energy Storage For Ships, published in 2020’ suggested that the ‘fuel saving potential’ for yachts was around 5 – 10%. Engine manufacturers and yacht builders tend to be a little more “optimistic” with the potential savings and benefits often using emotive words to describe their benefits.
Where you measure the ‘delta’ from matters, as using the extremes will result in significant differences in SOFC, but may not reflect the real-World use – the time the engines spend at least efficient load may have very limited effect on overall consumption.
It is important not to focus on the headline figure, but to evaluate the potential savings across a range of speed and load scenarios that are expected with the yachts use. The engines technical files will help identify the real savings.
Is It Worth It
The evidence confirms that a well-designed ‘Hybrid’ system can have a positive impact today in terms of more efficient yachts and reduced fuel consumption. According to the IMO fuel coefficient, every ton of MGO/MDO emits 3.206 tCO2. So, on that metric alone, the answer would have to be yes.
Unfortunately a ‘Hybrid’ yacht will be more expensive which no doubt affects more widespread use. When viewed purely on a cost/benefit basis, it may be hard to justify the extra cost against the potential fuel savings, and reduced operational costs due lower engine hours and extended maintenance intervals. Depending on use, the break even point may be a many years away and lay outside the envisaged ownership timescale. So as long as it’s an ‘option’ from builders cost will probably trump environment.
In the evaluation process, it worth considering the cost of diesel fuel may increase in the future due to carbon tax, and renewable fuels such as HVO (drop-in diesel) will be significantly more expensive. So, the additional cost today, may be sound investment for the future?
Finally, whatever energy is used in the future, it will likely be less energy dense than diesel fuel, and certainly more expensive. This means power management and efficiency will become even more critical and Hybrid technology will remain a fundamental component, especially in mixed energy solutions.
There have been several concepts, and a good many articles and discussions relating to the use of solar panels on superyachts. And, as a zero-emissions energy source, this would seem to be an ideal technology to reduce or replace a yachts reliance on fossil fuels. You could have large arrays of panels on the superstructure or build them into sails to provide all the yachts energy…but could you?
Like many alternative energy solutions, away from the sensational headlines, it’s only when you look at the details do you begin to understand whether they are practical solutions or not.
In this piece I will shed some light on the use of solar panels on superyachts.
Using a 65m yacht as an example, I will assess the energy required from generators for a 24 hour period and the area of solar panels that would be required to generate this energy.
Sunlight As Energy
Studies suggest that the amount of sunlight that strikes the earth surface in 1.5 hours is sufficient to handle the Worlds entire energy consumption for 12 months. It is important to understand that although this solar radiation bathes the entire World it is dependent on time, date and location.
This is the monthly variation due to the sun’s declination, but there is also the diurnal variation due to the elevation of the sun from sunrise to sunset, as shown below.
Of note, the total radiation (Global) is based on Direct and Diffused radiation e.g. reflected.
Taking the monthly figures, the average daily amount of energy is therefore:-
July 6.6 kWh/m2
January 1.56 kWh/m2
Much like a stabilised VSAT or TV antenna depends on pointing directly at the satellite for the best signal, the same is true for solar radiation; the highest levels of insolation are when the sun’s rays are perpendicular to the plane – hence the improvement in solar cell performance with systems that track the sun both in azimuth and elevation.
For those projects that have suggested using solar panels on sails, the angle of the sails relative to the sun’s rays will impact heavily on the energy generated. Underway, the wind is unlikely to allow for the most optimum angle and, at anchor if windy, you would need a method of ‘stalling’ the sails to achieve the best angle.
Solar Panel Efficiency
But I have seen powerful solar panels rated at 500-550Wp!
This is true they are available, but panels of that power are approx. 2.2m2 and power rating is the peak performance based on the Standard Test Condition (STC).
The STC is based on horizontal solar radiation of 1000W/m2 at an internal cell temperature of 25°C. Efficiency is measured by how much of the solar radiation is converted into electrical power and currently the best panels have an efficiency rating of 21%.
This means under STC conditions the best 1m2 panel would produce 210Wp but, of course, as can be seen from the graphs above, solar radiation is not constant. And, along with seasonal and diurnal variation, a solar panel is also affected by angle of incidence and other factors that can reduce efficiency, such as system losses, contamination on the surface and temperature.
Air temperature has a major effect on the cell temperature, and higher or lower cell temperature will either reduce or increase the power output by a specific amount for every degree above or below 25°C (STC). This is known as the power temperature coefficient (PTC) which is measured in %/°C.
As an example, monocrystalline panels have an average PTC of -0.38% /°C, while polycrystalline panels are slightly higher at -0.40% /°C.
In general, cell temperatures run approx. 25°C above the ambient temperature. So, on a summer’s day with air temperature of 30°C you could see an approx. 11% reduction in efficiency of a Monocrystalline panel.
Daily Solar Energy Example
Knowing the efficiency of a solar panel enables us to do some basic calculations on daily energy produced from a 1m2 solar panel in July and January for Monaco.
Average daily solar radiation is 6.6kWh/m2
Total energy produced 1.39kWh/m2 per day
Average daily solar radiation is 1.56kWh/m2
Total energy produced 0.33kWh/m2 per day
How Much Energy is Required?
Taking a 65m yacht fitted with 200kW generators and, assuming with ‘guests-on’ will require around 4500kWh/day for the non-propulsion such as air-conditioning, stabilisers, water-makers, refrigeration, galley, laundry, water heaters, av/it., etc. This will be less ‘guest-off’ with good power management practices employed by the crew.
On this yacht the flat surfaces available for solar panels is approx. 407m2.
From the above, in Monaco in July, if you wanted to generate the energy from solar panels alone you would need approx. 3,240m2 of panels – approx. 8 x available area.
In addition, you would need and a battery bank of approx. 2.8MWh (only 80% useable due to battery cycling) for the hours when the sun is not shining.
This is assuming maximum efficiency and does not include any de-rating due to shade, cloud, rain, contamination on the panel surface or high air temperature, all of which impact efficiency and final energy generated.
And, in January…well you can work that out!
The Potential of Solar Panels
As can been seen given the variables that effect energy produced and the large surface area required, it would not be a practical solution to replace diesel generators with solar panels – not for large yachts anyway. However, they could be used as a part of a hybrid solution to reduce fuel consumption and CO2 and other exhaust gas emissions.
With the above example 407m2 x 1.39kWh/m2 = 565kWh or approx. 3 hours of generator use. This is a useful saving especially if combined with batteries and power management systems that can use that energy to help with generator efficiency. But, don’t forget, season and location will have a large effect on this number.
The challenge on any superyacht will be finding sufficient flat surfaces and the issue of heat and efficiency. New panel technologies are in development with higher efficiencies, possibly up to 50% and this will help the adoption of solar panels in the energy mix but, by themselves, do not offer a replacement of fossil fuels on superyachts.
Although the primary environmental concern challenging our industry is C02 and other emissions generated from burning fossil fuels, there are other vectors such as sewage and grey water that can also have an impact.
Whilst on the larger yachts the new treatments plants take care of both, producing effluent that can be clean enough to use as wash down water, smaller and/or older yachts may not be so well equipped, or have inadequate black/grey holding tanks. Grey water is often simply discharged overboard.
For those of us who have had the ‘pleasure’ of sticking their head into a grey water tank, we are only too aware of the odious and putrid soup that is contained within, in fact, I suggest many crew would rather inspect a sewage tank than a grey water tank such is the assault on the senses. And, given these sensory observations, and the impact grey water can have on tank coatings, why is grey water treated essentially as a harmless liquid?
Whilst the discharge of sewage (black water) is mostly regulated under the International Convention for the Prevention of Pollution from Ships (MARPOL) Annex IV and other national legislation such as United States Environmental Protection Agency (EPA) Clean Water Act (CWA) grey water from ships and yachts is discharged untreated directly into the sea. On yachts, this is very often in close proximity to the coast, beaches, ports and marinas, where there are swimmers or other recreational water users and where it has the potential for the greatest impact on the marine ecosystem.
So what is grey water?
*If using mobile phone, swipe or rotate screen to see the full table.
Grey Water Definition
Annex V Reg 1 Definitions
4. Domestic wastes means all types of wastes not covered by other Annexes that are generated in the accommodation spaces on board the ship.
Domestic wastes does not include grey water.
1.6.1 Dishwater means the residue from the manual or automatic washing of dishes and cooking utensils which have been pre-cleaned to the extent that any food particles adhering to them would not normally interfere with the operation of automatic dishwashers.
1.6.2 Grey water means drainage from dishwater, shower, laundry, bath and washbasin drains. It does not include drainage from toilets, urinals, hospitals, and animal spaces, as defined in regulation 1.3 of MARPOL Annex IV (sewage), and it does not include drainage from cargo spaces. Grey water is not considered garbage in the context of Annex V.
*Note: if in-sink macerators drain into grey water tanks, then the contents and discharge of that tank will need to comply with Annex V.
Clean Water Act, 33 U.S.C. 312(a)(11)
Galley bath and shower
Coast Guard regulations, 33 CFR 151.05
Drainage from dishwasher, shower, laundry, bath, and washbasin drains and does not include drainage from toilets, urinals, hospitals and cargo spaces.
So, whilst grey water is well defined, what is less well understood is that untreated grey water contains many undesirable pathogens, organic matter, chemicals and micro plastics (the microfibres that are shed during washing of man-made fabrics) often at levels that can be higher than domestic effluent from sewage treatment plants, and can have an impact on human health and the marine ecosystem.
One of the largest studies on grey water was done by the EPA following a petition in 2000 from Bluewater Network who represented 53 environmental organisations who wanted the EPA to take regulatory action on cruise ship pollution. The report – Draft Cruise Ship Discharge Assessment Report (EPA842-R-07-005) – was published in 2007 and covered sewage, oily bilge water, solid waste, hazardous waste and grey water. And, whilst there are significantly more crew/passengers on cruise ships and waste volumes greater, the sources and treatment are very similar to the superyacht industry.
From that study they list common sources and characteristics of grey water in the table below.
Automatic Clothes Washer
bleach, foam, high pH, hot water, nitrate, oil and grease, oxygen demand, phosphate, salinity, soaps, sodium, suspended solids, turbidity
Note: recent studies also suggest micro plastics from man-made fibres are also contained with the waste water.
Automatic Dish Washer
bacteria, foam, food particles, high pH, hot water, odor, oil and grease, organic matter, oxygen demand, salinity, soaps, suspended solids, turbidity
Sinks, including kitchen
bacteria, food particles, hot water, odor, oil and grease, organic matter, oxygen demand, soaps, suspended solids, turbidity
Note: if food waste from in-sink macerators is draining into grey water tanks this changes the grey water to food waste and therefore discharge must comply with MARPOL V.
Bathtub and Shower
bacteria, hair, hot water, odor, oil and grease, oxygen demand, soaps, suspended solids, turbidity
Source: ASCI 2001
Of course, the quantity and quality of grey water varies considerably depending on many factors, such as the number of crew and passengers, the various types of detergents and cleaning products used, personal grooming and hygiene products used by the crew and passengers, and various filters and fat traps if installed.
The EPA study, combined with findings from a previous study by the Alaskan Department of Environmental Conservation – Alaska Cruise Ship Initiative in 2001, found a range of readings of various analytes. A sample of which are found below.
Untreated Domestic Water
10,000 – 100,000
Biological Oxygen Demand (BOD 5 day)
110 – 400
Chemical Oxygen Demand
250 – 1,000
66.9% between 6.0 and 9.0
Between 6.0 and 9.0
Totals Dissolved Solids (TDS)
Total Suspended Solids (TSS)
100 – 350
Ammonia – Nitrogen
Total Kjeldahl Nitrogen
20 – 85
*MPN – most probable number
Untreated grey water contains many pathogens and, in addition to those listed above, can also include, Salmonella, shigella, hepatitis A and E, and gastro intestinal viruses (national Research Council, 1993). Pathogens can pose danger to human health by contact or ingestion of contaminated water, or by consuming shell fish which feed by filtering water.
The 1986 EPA Quality Criteria for Water, commonly known as the ‘Gold Book’, references pathogen indicators and has defined water quality standards based on two activities of import to yachting: marine water bathing and, shellfish harvesting.
From the samples of untreated grey water analysed in the study, the average fecal coliform contamination exceeded the standard of 43 MPN/100mL for shellfish harvesting and, the average enterococci contamination exceeded the standard of 35 MPN/100mL for marine water bathing.
Although not a major indicator in this study, chlorine is used on yachts in a variety of applications including sanitising fresh water tanks, the discharge of which is generally pumped overboard, often via the grey water tanks, so levels must be carefully controlled so they do not exceed recommended limits.
Studies have found that chronic affects to the marine biota such as poor reproduction and health can be observed at concentrations above 230mg/L with acute effects, severe illness or death, at concentrations exceeding 860 mg/L.
Organic matter from the grey water acts as food for water borne bacteria. The more food available, the greater the number of bacteria decomposing the waste and using oxygen in the process. Nitrates and phosphorous also contribute to high oxygen demand by providing nutrients for plants and algae to grow quickly, contributing to organic waste when plants die and decompose.
Reductions in oxygen level can be harmful to aquatic species and can, in extreme cases, create ‘dead zones’ where no fish or other organisms can live.
Suspended solids can affect the clarity of the water and in turn adversely affect the photosynthetic activity of marine biome.
This is a more recent and topical concern relating to plastics entering the food chain, consumption by humans, and the longer term environmental and health impacts.
A number of studies have shown that during machine washing of man-made clothing significant numbers of tiny fibres are released into the waste water; and, in the case of yachts, into the grey water tank and eventually into the sea.
One such study is ‘The release of microplastic micro fibres from domestic washing machines: Effects of fabric type and washing conditions’ (Elsevier: Imogen E. Napper, Richard C. Thompson).
This study examined the release of textile fibres during machine washing of clothes from three commonly used fabrics; polyester, polyester-cotton mix and acrylic. The results showed that laundering 6kg of synthetic material could release between 137,951 – 728,789 fibres per wash, ranging in size between 20 𝜇m and <5mm. Given the load on most laundries and, composition of the fabrics washed, one can see the potential for a significant number micro plastics being discharged into the sea on a daily basis.
It is important to note that when grey water is discharged into the surrounding sea it mixes with the sea water and dilution takes place. This effect can be affected by factors such as discharge rate, salinity, water temperature, wind, currents and, of course, a yachts movement.
The Alaska Department of Environmental Conservation (ADEC) concluded that dilution factor would range from approx. 5 to 60 and occur between 1 and 7 meters from the ship (ADEC, 2004). The EPA report suggests that the initial dilution estimated by ACSI and ADEC for a vessel at rest would not likely be great enough for untreated grey water to meet the ‘Gold Book’ standards for fecal coliform and enterococci
From tests conducted by the EPA, it was shown that the dilution effect, due to the movement of a vessel and the mixing by their propellers, for a ship underway between 9.1 and 17.4 knots was a factor of between 200,000:1 and 640,000:1 immediately behind the vessel and, based on those results all ‘Gold Book’ standards for water quality, apart from fecal coliform, would be met.
From this it can be seen there are significant benefits in only discharging when underway and away from the near shore.
Apart from yachts that have advanced waste treatment systems that treat both grey and blackwater compliant with MARPOL IV 9.1.1 and the guidelines in MEPC.227(64) most yachts will be discharging untreated grey water from their holding tanks, often with food waste contrary to MARPOL V, whilst static, directly into the sea. The effect of this can be observed in busy marinas and crowded anchorages on windless days when there is little water movement or seabed disturbance and the water takes on a milky and/or scummy appearance – the difference in water clarity around Cala de Volpe in and out of season is quite striking.
Furthermore, the grey water has the potential for human health risk – depending on contamination levels – especially for those engaging in activities such as swimming, jet ski, wake-boarding, or any other activity where they may ingest seawater or have contact via an exposed scratch or wound. There are also short and long terms considerations related to the marine ecosystem such as algae blooms, bacteria in shellfish, and the introduction of micro plastics into the food chain.
Whilst the issue surrounding grey water applies to commercial shipping as well, due to their sailing and trading patterns they tend to have little impact on inshore waters – as can be seen from dilution effect underway. For cruise ships, if they do not have suitable onboard treatment of grey water, the Cruise Lines International Association (CLIA) members voluntarily agreed to limit the discharge of untreated grey water to when they are underway at not less than 6 knots and at least 4 nm from the nearest land and not to discharge grey water when in port.
What can we do?
I outline some of the steps could be taken to reduce the impact of grey water discharges.
As per CLIA, no grey water discharge closer than 4nm from nearest land, underway at not less than 6 knots
No discharge of grey water in port if facilities available – marinas have work to do here?
Where available, discharge grey water to suitable reception facilities e.g. barge or ashore
On new builds, increase size of holding tanks to more practical sizes based on ‘practical’ use of yachts, so discharge can be better managed – including smaller yachts
Install filters to remove micro fibres from washing machines
Use ‘environmentally friendly’ cleaning and personal hygiene products – not just ‘ECO or Green’ labeled as these are often-abused and misleading descriptions – carefully scrutinise such claims and check if they have been independently assessed and verified
On new builds specify and install only black/grey water treatment plants
On refits, consider updating your treatment plant and include grey water
Consider dosing grey water with additives that reduce pathogens and/or organic matter
Avoid using in-sink macerators if the pulp discharges directly into grey water tanks – instead, bag, store and dispose as per MARPOL V
Installation of fat traps
Some of the above does not require major expense, just a change in operational procedures and, of course, education costs nothing.
The quality of our oceans, and its health are fundamental to yachting – it is the ‘playground’ from which we experience so much pleasure. With our intimate connection to the to the sea we have a responsibility to minimise our environmental impact, protect the long term health of our oceans, and to ensure that future generations get to experience the same pristine seas and diverse marine life that we have all enjoyed.
I was prompted to write this because of the increasing restrictions in France due to environmental concerns and the impact anchoring has been having on the sea grass/Posidonia. This means that in many places along of the French coast, yachts will have to anchor in water >30m depth.
Although the French rules have perhaps highlighted this, it is not the only place where anchoring in water deeper than 30m is required; other places include Monaco, Capri, the Amalfi Coast, some anchorages in Croatia, Greece and Turkey, the fjords in Norway and Chile and, some of the Caribbean islands – it is not uncommon.
With that in mind, and my own experience of the yachts I have run, I ran a short survey on LinkedIn to gauge how much chain yachts carry.
Although not a huge response, the results were sufficient to mirror my own experience of the amount of chain some yachts carry – in some cases, totally inadequate.
The results to “how many shackles do you carry per anchor?”
Less than 6 shackles – 18%
7 shackles – 18%
8 shackles – 33%
More than 9 shackles – 30%
Rule of Thumb
Of course, there are several ‘rules of thumb’ to help determine how much chain cable is laid depending on the depth of water, among other factors such as type of seabed, weather, current, length of stay, etc. Two such examples are: –
The International Association of Classification Societies (IACS) – length of chain in Metres = ratio 6 – 10 x Depth of Water in Metres.
For 30m this would be a minimum of 180m or just shy of 7 shackles.
The Admiralty Manual of Seamanship uses a formula – number of shackles = 1.5 x √Depth of Water in Metres.
For 30m this would be a minimum of just over 8 shackles.
With the above figures, if you err on the side of safety, just under 40% of yachts who responded may not have sufficient chain cable to anchor in water >30m depth and, at 35m depth, only 30% of yachts would have the recommended amount of chain. How this compares to the total fleet would be very interesting.
Interestingly, the RYA recommendation is for a minimum of 4 x Depth. For 30m depth only 4 shackles – approx. half of IACS and The Admiralty recommendation. This may be fine for recreational boats, but for superyachts this seems at odds with both IACS who test and approve anchoring arrangements for ships and superyachts, and the experienced seafarers of the Admiralty.
As RYA qualifications are inherent to Yacht Deck Officer training and certification, has their ‘rule of thumb’ become the standard that most superyacht crew use – again an interesting question!
There is no doubt IACS and The Admiralty are a more qualified authority when it comes to anchoring of ships and large yachts and in my opinion captains would be wise to use their ‘rule of thumb’ rather than the RYA.
The Mysterious Equipment Number
Until I did my Master Unlimited CoC, I never took time to consider how the size of anchor and length of chain were determined for a given vessel. That’s when I learnt about the Equipment Number (EN).
Most superyachts are Classed by one of the IACS members such as Lloyds, DNV GL, ABS, RINA, etc., and they use common rules to determine the mooring equipment. This is based on the EN which is calculated for every Classed vessel – the formula is as follows: –
EN = △ ² ⁄ ³ + 2 BH + 0.1A
△ = moulded displacement in tonnes to Summer Load waterline
B = moulded breadth, in metres
H = effective height, in metres, from Summer Load waterline, to top of uppermost house
A = area, in square metres, in profile view, of the hull, superstructure and houses above Summer Load waterline.
The resulting EN is used in a table that details the number and mass of the anchor, chain length, diameter and grade, as well as towing and mooring lines.
Excerpt from Equipment Table – note ‘Total Length’ of chain is normally split equally between the two anchors.
It is important to note that the EN and anchor equipment is based on the following assumptions and limitations:-
Temporary mooring in harbour or sheltered waters
Current velocity: max 5 Kn
Wind velocity: max 48 Kn
Length of chain paid out, scope 6 -10
Good holding ground
The effect of waves is important – a significant wave height of just 2 metres would reduce the equivalent max current and wind velocities as follows:-
Current velocity: max 3 Kn
Wind velocity: max 21 Kn
A significant reduction in the holding power.
As most yachts use high holding power anchors (HHP) the rules also allow their mass to be reduced to not less than 75% of the table value.
Bitter End – Caution!
It is also important to know that the pin securing the bitter end to the chain locker is designed to be sacrificial and break at a load between 15% – 30% of the minimum breaking strength of the chain cable – it is designed to fail to prevent structural damage to the vessel.
It should be a fundamental part of the yachts risk assessment and procedures that, in the event of a runaway chain, the mooring team evacuate to a safe area as the flailing end of an anchor cable can have devastating effects – as was sadly experienced on Ocean Victory.
The anchor and mooring arrangements need to be carefully designed for the risks involved; unfortunately, some yachts, especially those with enclosed decks, place the windlass operator in harm’s way and do not provide safe egress in the event of a failure. Like many operational aspects of yacht design, work is still required to improve safety.
A Guide to Anchoring
The video ‘Anchor Awareness’ produced by DNV, GARD and The Swedish Club, although based on commercial ships, is also valid to larger yachts and is a useful resource that helps demonstrate anchor procedures and safe practice and is well worth a watch – especially for junior officers and deckhands who may be part of the mooring team.
Can be accessed by taping on the image below.
This piece was not meant as a guide to anchor best practice, but to try to assess if yachts carried sufficient chain for the intended depth, and help fill in some of the knowledge gap that may be missing from the yacht syllabus.
I hope it imparts a better understanding of how anchor and chain cable size and length are determined for yachts. And, importantly, the amount of chain paid out relative to depth that is recommended by authoritative bodies.
This knowledge may result in more secure anchoring and the provision of chain more appropriate to the expected use, water depths and conditions that may be encountered.
The reason for this question is that it doesn’t take much to realise that being able to switch your yacht from fossil fuel to green fuels in the future will have a positive impact on use, cost, and asset value.
Whilst these concerns and the transition away from fossil fuel seems to be far away, the impetus is growing and the reality is that when you take into account the design and build cycle along with the lifetime of a superyacht, you begin to understand why this may be an important consideration for anyone investing in a new build today.
Indeed, Lurssens recent announcement of a project using methanol and fuel cells may represent a paradigm shift for the industry. Though there are still questions about the availability of green methanol and storage and bunkering, this is probably the only superyacht in build that has the potential to adapt to a zero emissions future.
From discussions with other shipyards, it is clear that the environment is becoming an important consideration for some owners, and the pressure to act will only become more intense in the coming years.
The current narrative seems to be that ‘hybrid’ or ‘diesel electric’ (propulsion from electric motors) will allow you to simply remove the generators, replace them with a stack of fuel cells and then load up on green energy. On the surface these seems to make sense, however I think reality may be a little different.
When you look more deeply at the how, the challenge will not come from the replacement of the generators, it will come from the availability and choice of the green energy carrier that replaces the diesel fuel.
Currently hydrogen, methanol and ammonia seem to be the leading fuels in the drive to zero emissions shipping. LNG and biofuels also provide a useful pathway that helps reduce emissions but are unlikely to be the long-term solution.
The production of green ammonia or methanol, also known as ‘e’ fuels, require hydrogen produced via electrolysis using nuclear or renewable electricity and synthesis with air (e-ammonia) or CO2 (e-methanol). It is a very energy intensive process and methanol also depends on the supply of green CO2 e.g. biomass or direct air capture (DAC).
Due to the amount of energy required to produce these fuels and supply chain costs, these fuels are likely to be more expensive than today’s diesel. Technology and innovation in all its forms will still be necessary to reduce energy consumption.
Worth noting is that hydrogen, ammonia, and methanol, can be used in internal combustion engines (ICE). For example, the Ro-Ro/Pax carrier, Stena Germanica was successfully converted to run on methanol. This could provide another pathway for us; though I don’t know if these ‘gas’ or ‘dual fuel’ ICE’s are suited to superyachts? Maersk has also announced the building of a ship to run on methanol, whilst acknowledging that they are not entirely sure of fuel supply or infrastructure – I think it demonstrates a leadership that may help break the supply/demand impasse and drive change.
The major challenge with all these fuels for yachts, where space and aesthetics – a cryogenic hydrogen tank on the aft deck would not be ideal – are major factors, is that they are less energy dense than diesel, require more volume for the same amount of energy, along with special storage and enhanced safety due to the nature of the fuels e.g. flammable and toxic.
More information an be found in The International Maritime Dangerous Goods (IMDG) Code, International Code of Safety for Ship Using Gases or Other Low-flashpoint Fuels (IGF Code) and IMO MSC.1/Circ.1621 Interim Guidelines For The Safety Of Ships Using Methyl/Ethyl Alcohol As Fuel.
This excellent diagram of Volumetric and Gravimetric energy of various fuels from DNV-GL – Comparison of Alternative Marine Fuels, Report No: 2019-0567, Rev. 3, clearly highlights the energy differences.
Energy densities for different energy carriers (inspired by /49/ /72/ and /73/ of the report). The arrows represent the impact on density when taking into account the storage systems for the different types of fuel (indicative values only)
Hydrogen, due to the storage requirements, compressed or liquid, probably excludes its use directly as a marine fuel on superyachts though, as with shipping, it may be well suited to coastal cruising. Much more likely, as with the Lurssen project, is that methanol or ammonia is used as the energy carrier and converted back into hydrogen using reformers onboard if fuel cells are used.
The resultant hydrogen would then be used in Proton Exchange Membrane (PEMFC) or High Temperature Proton Exchange Membrane (HT-PEMFC) fuel cells. HT-PEMFC are less critical on the purity of the hydrogen and the heat can be used to improve the overall efficiency – though, to date, as an industry we have not been very energy efficient with the use of waste heat from engines or generators.
Although solutions for the storage, ventilation, safety and bunkering of methanol and ammonia will no doubt be found – it’s already carried onboard ships either as a fuel or cargo – how this is integrated into the hull of a superyacht may have some significant impacts on space, layout and, of course, range.
I think some caution is required before promoting the use of ‘hybrid’ or ‘diesel electric’ as ‘future proof’ solutions. We need to be able to demonstrate how this would work, the practicalities and impact on cost, safety, use, space and range to name just a few considerations. This will be crucial to the future growth of the industry as yacht owners and their advisors will need to weigh these factors in their decision-making process.
Finally, Lurssen and their visionary customer, may have found one pathway that helps answer the question. That is a real benefit to the future of the industry.
It could be suggested there is too much information available on COVID-19 and the pandemic; including, an almost infinite number of articles and commentary on the internet, numerous Circulars and Guidance from the IMO and, publications from the International Chamber of Shipping (ICS) such as Coronavirus (COVID-19) Guidance for Ship Operators for the Protection of the Health of Seafarers (version 3.0 29th September 2020).
This excess of information can be confusing and, also as suggested in Tom Nichols book “The Death of Expertise” result in a tendency to trust in the internet to make us ‘experts’ in all manner of subjects and, resist or even ignore, advice from those with a deep understanding and experience of the subject matter, including COVID-19 – this can lead to poor outcomes.
With the absence of a collective response from the industry, it has been left to individual yacht management companies and/or captains and crew to wade through the mass of information, try to assess its quality and efficacy, and then develop and implement their own protocols and procedures in response to the virus. And, whilst some of these are well thought out and effective, others on deeper analysis, are perhaps like the ‘Swiss Cheese’ risk assessment analogy, have holes for the virus to pass through.
So, it was a great relief to come across the “Recommendations from the Healthy Sail Panel.” This is the first document I have seen from a related industry with a well-researched and holistic approach to the prevention, protection and mitigation of COVID-19, in an easy to follow format.
The Healthy Sail Panel is a collaboration between Royal Caribbean Group and Norwegian Cruise Line Holdings Ltd who put together a panel of World leading experts to help inform and find a new pathway back to the “new normal” of sailing. The resulting research and recommendations are broken down into 5 key focus areas, with over 70 recommendations, many of which are applicable to yachting.
The key focus areas are: –
Testing, Screening and Exposure Reduction
Sanitation and Ventilation
Response, Contingency Planning and Execution
Destination and Excursion Planning
Mitigating Risks for Crew Members
It is well worth downloading and reading. I suggest you also follow up on some of the footnote references.
COVID testing is one of the subjects with references in the footnotes. Further reading clearly highlights the value of testing for screening and diagnosis but, like the use of electronic aids to navigation, you have to be aware of the limitations, errors and accuracy.
I was certainly confused by the various tests; Rapid Antigen, PCR, Antibody, etc., their effectiveness for screening, diagnosing present and past COVID infection. The US CDC footnote reference in the Healthy Sail Panel certainly helped my understanding, along with the infographic below – found on the Nature website in their article “Fast coronavirus tests: what they can and can’t do.”
It became clear that, amongst other factors, the timeline of infection has a big effect on the various tests and why caution is required – especially with the Rapid Antigen tests that may be used by yacht crew.
Indian Ocean and Caribbean Passage
As many yachts and crew are readying themselves for passages to the Caribbean, Indian Ocean or further afield, I thought it was also worth considering this in the context of COVID-19 and posing the following question: –
“Should you self-isolate the yacht and crew and test before departing?”
Clearly, the time taken in transit is likely a suitable quarantine period for destination arrival purposes. However, the reason I pose the question is that given that most yachts will be departing from countries/areas with high rates of infection, and crew will have been enjoying shore leave and their time in port, what happens if a crewmember is infected, but tests negative (if tested) and is asymptomatic prior to departure?
Once underway and symptoms present, not only would there be concerns of further infections amongst the crew, and medical treatment if severely affected, there would also be concerns about at the port of destination; would the port allow the yacht to berth and what are the reception and medical facilities for any infected crew?
The same goes for ‘crossing crew’ do you bring them in early and quarantine (onboard in single cabin) and test prior to departure?
Clearly, no captain wants to restrict well-earned shore leave but, then again, it is important to avoid any crewmember being infected and becoming a medical emergency and/or a vector for further transmission, especially on a long sea voyage, so it makes sense to try and prevent this outcome.
I’d be interested to know how yachts and management companies are dealing with this. Some considerations:
What methods are in use for mitigating the risk of infection prior to departure
Has the port authority of your arrival destination been contacted and what is their policy in the event of an infected crewmember on an arriving yacht
Do the hospitals have the facilities and capacity to handle a COVID-19 patient
Are there any additional medical supplies and PPE above ‘Medical Scales’ that may be recommended to carry
The above, departs slightly from the main reason for this post but, for those about to embark on a lengthy passage, it’s something worth thinking about?
As always at OnlyCaptains, or goal is to share knowledge and help inform. Hopefully, the Healthy Sail Panel offers some useful information on COVID-19 that may help with your own procedures. And, perhaps it might be used as a reference by industry associations such as MYBA, LYBRA, IYBA, in a collaborative effort to create our own yachting recommendations. These would not only be of value to captains, crew and yacht management, they would also help to instil confidence in owners and charterers through the knowledge that industry accredited measures were in place to protect them whilst onboard.
Last week, I attended the Yacht Cub de Monaco: Capital of Yachting Experience. It was a very well organised and attended event, with some very interesting presentations and discussions.
It was also the launch of the Yacht Club de Monaco Superyacht Eco Association (SEA) INDEX. Supported by Nobiskrug and Credit Suisse, this is an important initiative with a goal to benchmark yachts in terms of their CO2 environmental performance. And, whilst there are other emissions, CO2 is by far the largest greenhouse gas (GHG) of importance and the one most visible in the public eye.
The principle is that it uses the IMO’s Energy Efficiency Design Index (EEDI) formula with a few changes to make it more specific to yachts.
The SEA INDEX is the first tool designed to assess and compare the efficiency of a yachts design and its environmental impact in terms of CO2, with a transparent and easy to understand rating system. Stars are awarded from 1 (lowest rating) to 5 (highest rating) depending on where a yacht sits above or below the rating bands relative to the baseline of sampled yachts.
Image: Courtesy of the SEA INDEX
The data from approx. 130 yachts of various length and displacement was sampled and their data entered in order to develop the initial baseline – there are now over 200 yachts.
It uses max power and speed, which may seem excessive, but a metric was required and, if you consider this as the ‘maximum emissions potential’ of a yacht, by using the same set of data points for all yachts, it provides a ‘standard’ for comparing their designs. For example, on comparable sized yachts, a more efficient hull will require less power for the same speed, and more efficient HVAC and hotel systems power management, will require smaller generators, both of which will result in reduced emissions and a higher INDEX rating.
And, as new designs and engineering innovations are introduced into yachting, the SEA INDEX will help highlight the improvements being made.
Of course, actual emissions depend on many variables that are affected by an owner and the operational profile of a yacht – these are hard to assess in any consistent or meaningful way. If we had recorded all yacht activity and consumption over the last 10 or 20 years, we would be able to draw a curve of standard deviation and have an idea of what might be described as ‘average use’ on which to make comparisons. Unfortunately, we don’t have this information, and this is perhaps the flaw in all such tools, so the only true account of a yachts CO2 emissions has to be calculated from their fuel consumed.
The factor the IMO use for CO2 emissions from MGO is 3.206, this means for every 1,000t of MGO used, 3,206t of CO2 is generated so it is easy to calculate your CO2 from fuel.
Any design efficiency gains, and improvements that can be made in the operation of the yacht, such as running at lower speed, managing power, switching off unused lighting and equipment, etc., will reduce the power required, fuel consumed and emissions.
In combination with efficiency gains, Carbon offsetting is one way to mitigate a yachts emission. Though, as I have written in a previous piece Superyacht Carbon Offsetting great care is required to select one that is fit for purpose.
But, it’s not just the amount of CO2 that is an important consideration. Looking to the future, it is very likely that shipping, like other industries, will be impacted by Market Based Mechanism’s (MBM) to drive forward the transition to a greener future, and these will have cost implications.
The IMO by 2023 will introduce their new framework for the reduction of GHG emissions from shipping and it could include a carbon tax. The EU in a recent plenary session of parliament, agreed that shipping should be included in the EU Emissions Trading Scheme (ETS) possibly in 2021and include vessels less than 5000gt. Trafigura, one of the World’s largest ship charterers, published on 25th September “A proposal for an IMO-led global shipping industry decarbonisation programme” calling for a $100 – $200 tax per ton of CO2 on shipping as the only way of driving the necessary industry change.
As further evidence of the direction of travel for CO2 emissions for business, Swiss Re made this announcement on the 15th September 2020:
“Swiss Re steps up its internal carbon levy to USD 100 per tonne as of 2021 and will gradually increase it to USD 200 per tonne by 2030”
Any such taxes or levies imposed on CO2 emissions will increase the cost of yacht ownership.
On top of that we have Environmental Governance and Sustainability (EGS) targets that are becoming ever more prevalent, especially in investment and finance. The Poseidon Principles is just one initiative, launched the 18th June 2019, “major shipping banks will for the first time integrate climate considerations into lending decisions to incentivize maritime shipping’s decarbonization” their goal is to work towards the IMO 2030 and 2050 reductions in GHG by ensuring that their loan books are aligned with those targets – finance will become harder for vessels that fail to meet efficiency improvements and GHG reductions.
Could similar lending rules apply to yachts in the future, how would that affect the value of older less efficient yachts?
Whilst it is not yet clear how taxes and regulations will be imposed in the future, what is clear, is that yachting is unlikely to escape their embrace. And our intimate connection to the sea and the environment places additional responsibility on the industry to protect the health of our oceans and planet. The SEA INDEX is the first of many important tools, including those from the Water Revolution Foundation, that will help us to understand our environmental footprint and drive the necessary change that puts us on a pathway to a sustainable superyacht industry.
Like any instrument that is reliant on data; the more yachts that participate, the more refined and accurate the SEA INDEX will become – I would call upon all Captains to get involved.