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RUSH YACHTS GREEN PROPULSION


Probably the most talked about topic when it comes to creating a more sustainable future for the marine industry, is propulsion. We have all seen the incredible progress within the automotive industry over the last decade with the develop of hybrid and electric cars. You only need to look at Tesla’s popularity to see how people’s views on electric cars have changed. Technology is constantly improving, infrastructure for fast charging is growing and the cost of these cars are becoming more and more in line with their diesel or petrol equivalent.


When we first started with Rush Yachts, our brief was entirely focused on creating the most practically green boat possible, taking the vessels full life cycle into consideration. When we talk about practically green we mean that the boat is designed, engineered and built as green and as sustainable as possible without having to compromise in the vessel performance. Performance to us relates to the vessels speed, handling, longevity, quality, and reliability. Our first major focus was to find or engineer a fully electric solution with the same performance and cost characteristics of its diesel counterpart. This was unfortunately an impossible task and we will tell you why:


Technology vs Performance


There is no getting away from it, but the marine industry is 10 years + behind the automotive. Where the automotive industry has seen stricter emission regulations, forcing manufacturers into investing tens of millions of pounds into R&D projects, the marine industry has been left in the dark ages. Electric propulsion in boats is not governed by environmental rules and regulations but of peoples and companies own attitudes to the environment. This doesn’t really have the same overall effect! The other big stumbling block is that the small boat segment of the marine industry is much smaller when compared to the overall automotive and therefore doesn’t attract the same sort of financial commitment to R&D projects.


Electric propulsion options for yachts have certainly developed considerably over the last few years and every month there are fresh releases with more advanced batteries (charging time, storage capacity for size and weight), more efficient motors and cheaper and more cost-effective electric and hybrid solutions.


The first thing we considered with the Rush 39 was the speed and range (without having to refuel all the time) an owner would expect for a day boat/superyacht tender. We looked at what was popular within this particular type of boat and establish that a 40 knots top speed, cruising speed of 30 knots and a range of around 800km at cruising speed was a benchmark specification. We then jumped into our research into the electrical options and within a couple of days felt very deflated about the whole situation! It was clear that those sorts of performance requirements were well out the question, so what could we offer if we went full electric?


After spending a large amount of time talking to various manufacturers of full systems and also manufactures of individual components that we could then look at integrating together, concluding all the latest technology advancements the best we could offer was a 20 knots top speed, cruising speed of 11 knots with a range of around 40km at cruising speed. A significant drop in performance values, values that we felt were too significant for the type of boat we wanted to build and the type of boat our clients wanted.


Speed and range were one thing, but the overall control and integration side was another stumbling block. Take Volvo Penta for example, with their IPS drive which can be controlled through a joystick giving the user full control of how their boat manoeuvres. This level of performance and usability has taken many years to create and perfect to what it is now but is something that is now expected within our market sector. Companies offering marine electric propulsion are essentially starting from scratch, with this level of control and usability taking years to develop and perfect to a fully function product.


Cost


When we were looking through the various full electric routes an immediate topic of conversation was cost. We took diesel options as a base point, which contains manufactures who have spent years perfecting performance characteristics, developing process, distribution networks etc. all to bring the overall cost to the end user down to a competitive price.


Electric propulsion is starting from a relatively new starting point. Completely new products, technologies and processes all take time and money to develop, market and then manufacture. All the advancements are big steps forward and therefore require significant financial backing and time to achieve. When stripping back the performance side and just looking at raw figures, comparing our original specification diesel with electric you are looking at a considerable increase in price. Electric motors and engines end up being pretty similar costs but then you need to buy the battery bank. For the above mentioned performance, you need around 200kW of battery performance and when it costs around £900 per kW of battery storage the electric propulsion route starts getting very expensive (£180,000).


Infrastructure


Jumping back to the automotive industry, fast charging infrastructure have been heavy invested in worldwide and in the UK alone we have over 35,000 stations with the majority of these being fast (≈7kW) or rapid charging (≈50kW) sites. Having this infrastructure in place is a key component for the quick and sustainable growth of the electric/hybrid sector of the automotive industry.


Fast/rapid charging options in marinas are incredibly limited. If you have a full electric boat that has a battery capacity of 200kW, even with a rapid charger its going to take well over 3 hours to charge and that’s all dependant if you can find one! There are however a few companies who are doing a fantastic job of starting to create the necessary infrastructure. Along the south cost of France, Vita Power are installing several 150kW charging stations providing the required infrastructure to make electric propulsion a viable option. This is just one company looking to make a difference, but to get the infrastructure set up properly, these charging locations need to be in every marina worldwide.


Hybrid


Something we also considered during the design and research/development phase of the project was hybrid propulsion. Hybrid propulsion is a very diverse term and in respect to the marine industry can be set up in several different ways. Some examples:


· Electric motors driven by a battery bank with a generator providing the power for the batteries


· Combination of diesel propulsion with an inline electric motor that uses the electric power for slow speeds and diesel propulsion for higher performance (we would call this conventional hybrid)


· Combination of both a form of diesel propulsion and electric propulsion. These two propulsion methods are independent of each other with the electric propulsion being used for slow speeds and diesel propulsion for higher performance


We looked at all these options and came up against some limitations. Within the superyacht industry, hybrid solutions are the way to go if, as an owner, you are looking to improve the sustainability and reduce the long-term costs of your yacht. There are also new regulations with Tier III engines meaning that a conventional diesel solution is only accepted by the regulators with considerable add ons. This type of hybrid propulsion has become very popular and a big factor of this popularity is that big manufacturers have developed excellent and viable hybrid solutions to the new regulations. With our size boat there is very little development from manufactures for hybrid solutions. 39ft is right on the limit of electric being a potential solution and conventional diesel. This means that hybrid solutions are generally expensive, complicated, lacking in overall performance and in some cases don’t actually give the propulsion system a greener, more sustainable solution.


Where We Got To!


It is a question that we have been asked many times, if you are building a green boat why aren’t you using electric prolusion? I hope the above has given some substantial reasoning to why our first choice isn’t electric propulsion! The Rush 39 is designed to be very flexible for propulsion options. We have left enough space midships and on centre line for a considerable battery bank and the transom has been designed so that if a client wanted electric propulsion with either stern drive or jet drive we could easily accommodate this. If the intended use for the boat fits within the performance characteristics of electric or hybrid propulsion then we would be incredibly excited to offer a full electric or hybrid package.


So we were back to a conventional diesel propulsion method looking at ways we could make this more “green” or make gains into fuel consumptions. There are several factors that can be considered in improving an engines fuel efficiency (hull below water design, weight of boat, introducing foil technology, etc.). All of these play a considerably role and you will see through the rest of these articles how we have looked at each individual component to maximise the overall fuel efficiency.


We then came across a company called Integrel Solutions, who, without dumbing down their solution have essentially created a super alternator that retro fits to your conventional marine diesel engine. The software runs the engine at a more fuel efficient rate, with the excess power not needed for propulsion going through a charger and to a battery bank. From their various research projects, this can save an owner 25% in fuel usage. This is an incredibly tidy add on solution to maximising the overall fuel efficiency of your boat and one that we are a particular fan of.


Something else that tied in well this solution was that an owner could sit at anchor without any discomforts of the noise, smell or vibration from a diesel engine required for the house loads with a suitably sized battery bank. The Rush 39 is sized with a 20kW battery bank giving a 10-hour period where the house loads of the vessel can be run purely from electric energy. With a 9kW Integrel generator fitted to each main engine, the batteries can also be fully recharged in a little over an hour.


Conclusion


We are incredibly supportive in moving the marine industry towards a more sustainable future and fundamentally propulsion, in particular electric propulsion is undoubtedly one the most feasible way to make a big step towards sustainability. Companies like Torqueedo and Vita-Power have done fantastic work on creating and then constantly developing their products, all of which are creating viable options for full electric propulsion. There are many instances where electric propulsion is in full use and for its application is just as effective as conventional diesel or petrol but with no environmental impact. In city ferries and smaller sailing yachts are great examples where electric propulsion is working perfectly and over the coming years the range of feasible marine markets for electric propulsion will only continue to grow.


In 2019 the UK government launched a Clean Maritime Plan with an aim to transit to zero emission shipping in UK waters by 2050. One of the key milestones along this path is that all new vessels being ordered for use in UK waters are being designed with zero emission propulsion capability. This is general terms relates to alternative fuels, non-fuel propulsion (electric, solar etc.) and some energy efficient options. The government have pledged millions of pounds to innovation and R&D projects to allow this to happen with some large grants issued in 2020 to support this vision (Artemis Technology is a great example). There are many other areas of focus within the Clean Maritime Plan such as infrastructure and the potential to review regulations which I am sure we all agree with is something that will make a big difference in how quickly this aim is achieved.

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