vas
Well-Known Member
cue UMA
Solar Catamarans
- Thread starter Rwc13
- Start date
dunedin
Well-Known Member
Sailing Uma doesn’t come close - tiny little battery pack, very small range and on their third OceanVolt saildrive in a few years. This proposed cat has a claimed battery pack over 10 times the size
PS. And probably cost 100 times less, as much less ambitious and much I think provided FoC for publicity
Rwc13
Well-Known Member
Hi Dunedin, thanks again for this helpful response. The plan would be to only use the generator exceptionally or in emergencies.
It’s like all these things, I guess you have to look at the specific circumstances of proposed use before concluding on how viable it will be as a solar catamaran, and I really didn’t provide this context.
A typical day cruise is likely to involve no more than 4 hours of sailing, at an average speed of 7kts. There will be several stops for swimming, snorkelling, SUPing etc, and then a long stop for lunch. The cat will do no more than three trips a week, and will start each trip with full batteries, mostly from sitting in the sun all day between trips, but with some top up where necessary from the marina shore power which has a significant and growing zero-emissions content - shore power here is included in the annual marina berth fee. While stationery for, probably, 4 hours of the cruise, the solar array will be recharging the batteries, and my understanding is that full batteries plus recharging both whilst cruising and stationery will be more than enough to mean no requirement to use the generator. I am waiting for some additional details on domestic services energy draw to evaluate and hopefully confirm this. There will be no hot catering on the cruise so no use of hob or microwave.
There is already several of these catamarans operating in the charter sector on a similar basis around Europe, and most of those have not even specified a generator…..it is only my preference to have a back up plan and also our potential private use that is causing me to specify this.
Concerning the virtue signalling comment, I see a lot of people make such observations about electric cars so no surprise to see it emerging here too. Yes, there is obviously an environmental costs to building such a boat, but I’m doubtful it is significantly different to building any traditional powerboat. Yes, some of these costs arise from different sources to a traditional boat, eg the batteries, and of course everybody focuses on those and the potential environmental significance.
But I’m in the camp that this is a long journey to a lower/zero emissions future, and unless we invest in alternatives to fossil fuels now, we won’t start let alone complete the journey. Nobody is saying that the current technology is the destination, but surely you have to start some where, ie with a less than perfect solution to continue to invest in the technology to improve it and reduce the environmental impact over time. As we know, once new technology gets a foothold in the market, its pace of evolution accelerates. So whilst it is true that some adopters might be virtue signalling, writing off all such investments, both manufacturer and consumer, seems more than a little trite.
Personally, I have been a petrolhead for as long as I can remember. I still have a petrol v8 in the garage for occasional pleasure, but a Leaf has become our daily local car. That was a choice between a used (already built) electric car versus a used diesel petrol car, and since electric cars are generally cheaper and petrol and diesel prices amongst the most expensive in Europe here in Portugal, that was an economic as well as environmental decision.
The catamaran decision is similar, we have a holiday rental business here and so a strong existing market to sell cruises to at a rate of 2-3 a week. The ongoing running costs of a solar catamaran are predicted to be tiny compared to a traditional powerboat. And there is definitely a growing market for “eco-tourism” at a premium price here. So, subject to getting comfortable about the the solar catamaran being more or less self-sustaining for its intended charter use, we will invest and see how we get on.
And I remain very grateful for the input this forum has already provided in helping me to better understand and now assess this.
dunedin
Well-Known Member
Makes sense. The key thing with electric propulsion, as well as “do the maths”, is having a clear “use case” - ie knowing how you plan to use the vessel, which you obviously do (though your original posting by contrast was somewhat sparse in content - I thought perhaps it was a fishing pontoon boat for a lake you might be considering
)Definitely worth still doing the maths on domestic & a/c power demand, but sounds an easy “Use case” in terms of propulsion - modest trips close to marina shore power.
Whether it makes any economic sense is a different question, and one only you can answer - but I guess there are marketing advantages in running a “green” trip boat. I would still prefer one with a mast and sails, but not for all.
vas
Well-Known Member
agree with Dunedin above,
not sure numbers match, best if you ask them to state CLEARLY consumption at different speeds (assume no tides) Knowing 4kn and top speed is not extremely helpful, in theory it should extrapolate almost linearly, but who knows what's actually happening...
7kn X4h 28nm what's the consumption going to be? wont be far from emptying a 150kWh bank if a couple of fridges are on, a plotter et al.
Not to mention that a 150kWh bank is not to be USED in total! you'd expect a 10-15reserve at the bottom (ideally 20) and a 5-10 on top, so if you want the batteries to last you'll calculate max 150X0.8= 120kWh sounds harsh and it's your money, but that's how lithium works afaik.
I'd suggest to forget getting the desalinator option unless you run the generator, but considering the time spent on the dock it's more money wasted imho. Or rather, ask them how many kWh does the desalinator consume to fill the tanks, then you decide yourself.
Day cruising back to base in the evening you should be OK.
tbh I really cannot believe that they offer them without a generator as standard!
apologies if I sound harsh, in my view you don't have the real picture, What you wade through is 80% marketing 20% real, got to find the other 80% and evaluate the cost/benefit of the various options mentioned.
vas
Well-Known Member
imho, UMA is in a much better state than this cat, when the going gets tough, they lift their sails and they are fine.
This one is stuck at 4kn with a 10kva geny working it's balls off. Come against some tide and you're in trouble...
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