Story • 4th April 2022
The Sustainable Oyster Part 2

The need for a greener, more sustainable future is no longer up for debate. Yet taking the next step isn’t always straightforward when it comes to sailing yachts. In the second part of our sustainability series, Matthew Sheahan asks the experts about hydro and solar power generation and energy storage.

If the number of hydro-generator units fitted to bluewater cruisers is anything to go by, the case for green power has been made. The sustainability message is sweeping through the cruising world and not having some form of green power generation is fast becoming the exception.

And perhaps it’s hardly surprising, particularly for the blue water cruising community for whom the principle of generating and harvesting power on the move suggests an easy and efficient win.

As we reported in the previous edition of Oyster Life, storing electrical energy is also going through a revolution, with the benefits that are available with lithium-ion battery banks becoming better understood. Here, the ability to use more of the batteries’ overall capacity while also being able to charge considerably faster than with conventional lead acid batteries, reduces the hours that are required by a conventional internal combustion engine generator. In addition, lithium-ion batteries have a significantly longer life. So, what’s not to like?

Nothing, according to the lead 565 project manager, “The move towards lithium-ion is well underway,” he says. “Across the seven 565s that I’ve project managed, only one had lead acid batteries.

“The various Watt & Sea hydro-generator models are becoming a popular option on bluewater cruisers. The feedback we get from owners supports the initial analysis we carried out, which pointed to being able to generate 365 Amps/day on passage where the speed was around 8 knots. In simple terms that would mean that most boats would only need to run their generator for one hour per day. This would mean a transatlantic crossing could be completed on just 20 hours generator time.”

To complement the technical studies ashore, the lead project manager has first-hand experience as to what this might look like in reality, having been a professional skipper for many years. One of the boats he ran was Oyster 625/01 Blue Jeannie.

“Whereas previously, owners were looking to reduce their generator hours to bring down the cost of servicing, now it’s also about reducing their carbon footprint, so there is a strong incentive to take a much closer look at the alternatives,” he continues. “With conventional lead acid batteries and with a 200 hour service interval, we were servicing the genset every month on ‘Blue Jeannie’. Admittedly, she was operated as a charter boat and so the onboard services were used pretty heavily.

“But compare that to the 625 Bubbles that had a solar panel on her bimini, Watt & Sea hydro-generator and lithium-ion battery bank, when she came in for a re-fit after five years, having been used by her owners for nine months of the year, she had just 500 genset hours. The fact is that there is a lot that can be achieved straightaway.”

And therein lies the clue to the next step in the green power conundrum. Hydro generation may be efficient, but even the best systems won’t necessarily keep up with demand and when boats are at rest, hydro is no longer an option. Here, solar is the next area to consider as it can supplement hydro underway and continue to deliver charge when the boat is at rest.

Mark Durham, Oyster’s Director of Service Operations in Palma, has worked closely with a growing number of owners who have been keen to embrace solar power. Among them, Trevor Hill who carried out a detailed study on his Oyster 725 Intrepid and went on to produce an advanced solar power system.

“The results from the study led Trevor to specify twelve solid Solbian panels to be mounted on a custom carbon bimini,” explained Durham. “In previous studies, a typical battery bank would be 1,000Ah, but aboard ‘Intrepid’ the capacity has been more than doubled at 2,400Ah.

“The solar power panels account for 13m2 of space and generate 2,174 Watts which is connected via four solar regulators to the primary 500Amp DC Bus. From there, three 24/4000 inverters create 12,000 Watts of power for the primary 110Amp AC Bus which is used for the yacht’s main AC load, including watermarking and air-conditioning.”

Using solid solar panels was a significant undertaking, not only is it a large structure that needed to be skilfully incorporated into the existing yacht superstructure, but it was a costly exercise too.

For some, the high costs associated with a fixed structure and rigid panels could put solar power out of reach. But, as Durham points out, using flexible solar panels combined with hydropower is becoming a popular and more affordable approach.

Whereas previously, owners were looking to reduce their generator hours to bring down the cost of servicing, now it’s also about reducing their carbon footprint, so there is a strong incentive to take a much closer look at the alternatives
Oyster Project Manager
watt and sea pod oyster

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Flexible panels may not be quite as efficient as fixed ones, but in some cases, they have advantages, particularly if you don’t want or need to use them all the time. “There’s also no doubt that as more systems get installed, the knowledge is permeating out and the systems are becoming more efficient and more adaptable,” he said. “We have had a number of Oyster 575 owners who have gone for flexible Solbian panels. Some were sceptical to start with as to whether the system could really deliver, but by the time they reached the other side of the Atlantic, they were converted.

“There are a number of developments and tips that are helping to improve the systems. One of the biggest is the way in which solar panels are connected. A common limitation has been that when one panel is in shade, the whole system doesn’t supply a charge. But if panels are wired individually, the system continues to supply current even if some panels are in shade. We also put additional battens across the bimini to help support the panels and avoid hardpoints which can cause delamination.

“Combined with a better understanding of how to operate the panels and their charging systems, we’re regularly seeing 23Ah being generated aboard the 575s. This, combined with a set of four lithium-ion Mastervolt MLi 24/5500 200Ah batteries, means that owners are hardly having to use their gensets at all and a 5kW inverter allows them to run the aircon overnight. The most important point though is that the on-board power generation and storage systems provide a knock-on effect elsewhere throughout the boat, such as moving to an all-electric hob and oven.”

Richard Gibson, Oyster’s Sales Director, is also Head of Sustainability at Oyster. From his frontline position, he needs no convincing that sustainability is gaining momentum. But he is also clear that the developments so far are essential building blocks and that there is plenty more to come.

“The move to more sustainable solutions is gathering pace now which is exciting,” he says. “Modern hydro and solar power systems are now delivering increasingly impressive outputs and are proving reliable. The ability to reduce reliance on a combustion engine on a true go-anywhere bluewater cruiser is a reality today, but it is also an area that we continue to work on and develop. Add to that, the demands of creating a robust, safe yacht, with systems to match, that can deliver rewarding world cruising and it is easy to see the scale of the task.

“So, as the performance and reliability of hydro, solar and lithium-ion power make for increasingly efficient systems, the future for more sustainable blue water cruising looks brighter with every season.”

solar bimini intrepid v2
intrepid sailing hard top bimini

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