Boat propulsion. Is electric actually green?

[Snowgoose-1]

No. Plenty of research and experience says not. The big advantage of hybrid is that it can support high electric consumption for domestic use while still providing propulsion. There are 2 basic types of hybrid, serial and parallel. The former uses electric only for propulsion so the energy must be provided by either an ICE such as a generator, renewable such as solar or regeneration or from shorepower, The latter incorporates a generator/motor into an ICE so that propulsion is by the engine or the electric, individually or together.

They start to become viable in larger boats over 45' or so (a bit smaller for multihulls) where you have the space to fit them, space for solar arrays and speed potential for useful regeneration. Serial have been around for a long time in both commercial and leisure applications, particularly large ocean sailing multihulls and charter vessels like the Dufour Atoll range. That however proved not viable because of the increased initial cost and particularly higher maintenance cost.

Parallel has also been around for getting on for 20 years but has failed to make any progress in the medium size sector (10-15m sailing yachts). The positives are silent short range motoring (typically 2 hours), higher generating capacity, either using the ICE motor alone, or exploiting the "spare" output of the engine when being used for propulsion. Downsides are roughly double the cost of the basic ICE and the need for a large 48v battery bank to provide sufficient energy storage for the 2 hours silent motoring, sophisticated electronics to control the combination of mechanical propulsion, electrical propulsion and power generation and the limited regeneration under sail - a combination of lack of speed on smaller boats and the inefficiency of a propeller designed for mechanical propulsion.

Various manufacturers have offered parallel systems including Yanmar and Nanni but have failed to find buyers. The only active company is Hybrid Marine hybrid-marine.co.uk who initially aimed at just this market with a serial system, but switched to parallel because they could not find takers in the sailing boat market for the reasons given above. As you will see from the website their target markets are canal boats and the larger boats as I described above.

So great idea as it seems to meet many sailors' wish list (including mine) but does not work in reality. Unsurprisingly no new boat production builder in the small to medium sector has adopted hybrids although many builders of custom and semi custom larger boats and multihulls have - but mainly to exploit the power generation potential rather than the short range silent running. That is just a side benefit.

Interesting. Thanks.

 

[dunedin]

They were asking about using a little power while sailing. Nothing to do with diesel at all.

That's just conventional "motor sailing", not "hybrid propulsion" in the commonly accepted terms (which is a combination of electric and/or ICE elements).

 

[Chiara’s slave]

That's just conventional "motor sailing", not "hybrid propulsion" in the commonly accepted terms (which is a combination of electric and/or ICE elements).

Well, if your propulsion is fully electric, and you’re motorsailing with it….. It would certainly work for us, we can get a big increase is speed with very little throttle, due to increasing our apparent wind. The question is, how long for. Plus we have to have enough power left to get back through the harbour to our mooring, for which we need more power than we’d use motorsailing. A couple of Kw would see a decent increase in light wind speed, but doing 4kn against the tide in the river is always going to need the taps opened a bit more. Weight wise, our outboard and some fuel weighs about 60kg. So, if the drive leg is 10kg or thereabouts, we’d break even on weight with 50kg of battery. Which gets us 8kwh. That’s 2 hours of motoring through the harbour, full to empty. So if we don’t want to kill the battery in double quick time, about 80 mins at the equivalent of half throttle on our current outboard, or about 20 mins of full throttle. Cost, about 50% more than replacing the outboard. Can we live with the range and the cost? Maybe not yet.

 

[lustyd]

That's just conventional "motor sailing", not "hybrid propulsion" in the commonly accepted terms (which is a combination of electric and/or ICE elements).

Kind of silly to ignore someone's actual question because you disagree on a term though. It seemed pretty clear what they were asking, and it was a sensible question with a sensible answer given that people have done it and demonstrated the vale.
It's entirely irrelevant whether the person asking knew or didn't know it's called motor sailing, or that they didn't know we usually use hybrid to mean hybrid engine. Their question was perfectly clear that they meant hybrid electric/sail and I'm sure you did know that but chose to ignore it for some reason.

 

[Tranona]

Kind of silly to ignore someone's actual question because you disagree on a term though. It seemed pretty clear what they were asking, and it was a sensible question with a sensible answer given that people have done it and demonstrated the vale.
It's entirely irrelevant whether the person asking knew or didn't know it's called motor sailing, or that they didn't know we usually use hybrid to mean hybrid engine. Their question was perfectly clear that they meant hybrid electric/sail and I'm sure you did know that but chose to ignore it for some reason.

As ever you are being selective. The post did NOT ask a question about "motorsailing". The question was specifically about hybrid. Read the first sentence which actually had a question mark at the end so there can be no misunderstanding.

The second sentence about using a motor (unspecified type) to assist sailing was a statement NOT a question.

So I was somewhat puzzled by your mention of Uma - other than knowing that you bring them in frequently when there is a discussion on alternative methods of propulsion as if they are the answer to all the questions.

I gave a response to the question by offering an explanation together with real world examples as to where and why hybrids have gained limited and specific acceptance.

 

[lustyd]

You must be reading a different post to me, or are just being obtuse.

I love the idea of adding an extra couple of knots under sail when necessary. Unlike cars, we can often make use of extra apparent wind too.

Very clearly talking about using power while sailing to create more apparent wind while not using full power. Therefore the hybrid they are talking about is very clearly motorsailing. Even in near zero wind you'll get more range from electric with your sails up due to the apparent wind generated. Snowgoose could see that, I can see that, but for some reason you're still grinding the same tired axe and trying to push your agenda.

It's not helpful, you could have answered their question in a thousand ways to help them understand it was "just" motorsailing but you chose to argue instead. You have a lot of knowledge to offer the forum, it would be great if you could do it in a more constructive way.

 

[dunedin]

You must be reading a different post to me, or are just being obtuse.



Very clearly talking about using power while sailing to create more apparent wind while not using full power. Therefore the hybrid they are talking about is very clearly motorsailing. Even in near zero wind you'll get more range from electric with your sails up due to the apparent wind generated. Snowgoose could see that, I can see that, but for some reason you're still grinding the same tired axe and trying to push your agenda.

It's not helpful, you could have answered their question in a thousand ways to help them understand it was "just" motorsailing but you chose to argue instead. You have a lot of knowledge to offer the forum, it would be great if you could do it in a more constructive way.

Keep digging if you like, but running your motor whilst sailing (ie motor sailing) does NOT increase the range - if there is enough wind to sail then switching the engine off and sailing a couple of knots slower gives infinite range. Motor sailing only speeds you to the destination.
With an efficient sailing boat there is almost no motor sailing mode that wouldn’t be more energy efficient as sailing only.
If there is 5 knotts of wind then sail. If less than 5 knots then the apparent wind goes pretty much dead ahead so have to furl the jib. Clearly it is different in slower boats with smaller rigs which need over 19 kts true wind speed to make any realistic progress, or can’t make a decent angle to windward.

 

[Tranona]

You must be reading a different post to me, or are just being obtuse.



Very clearly talking about using power while sailing to create more apparent wind while not using full power. Therefore the hybrid they are talking about is very clearly motorsailing. Even in near zero wind you'll get more range from electric with your sails up due to the apparent wind generated. Snowgoose could see that, I can see that, but for some reason you're still grinding the same tired axe and trying to push your agenda.

It's not helpful, you could have answered their question in a thousand ways to help them understand it was "just" motorsailing but you chose to argue instead. You have a lot of knowledge to offer the forum, it would be great if you could do it in a more constructive way.

No, I am not reading a different post. In fact your post#217 quoted the original which had the specific question about hybrids, which you ignored. The sentence about using power to aid sailing was NOT a question but a statement.

The thread is about alternative methods of propulsion and post#215 clearly asked if hybrid was the answer. Cannot see how you could not understand that.

The discussion about using power to aid sailing is unconnected with the source of the power. - the increase in range by using a mix of sail and motor applies equally to diesel or electric power.

I have no agenda other than contributing to the discussion by, as in this thread, drawing attention to published research or other material on the subject. This research is particularly useful as its objective is not to push an agenda but to inform its members of what are seen to be the issues relating to decarbonisation that might affect them. Inevitably the data given in many cases leads to logical conclusions, although the assumptions made and the methodology used leaves plenty of room for discussion and dissent as can be seen from many of the responses here.

 

[lustyd]

does NOT increase the range

The people who have sailed around the world for 8 years on an all electric yacht would seem to disagree. How many years have you sailed on your all electric yacht?

 

[dunedin]

The people who have sailed around the world for 8 years on an all electric yacht would seem to disagree. How many years have you sailed on your all electric yacht?

It’s simple physics - sailing without the motor providing drive gives a longer range than sailing with the motor providing propulsion. Even better if you can sail at 7-8 knots as with the right kit you will start to generate some power.

Which specific “people“ are you referring to, as I possibly already have the technical specifications of their setup?
Careful with YouTube examples, as unless they cover the specifications and the “maths” then often misleading. Sailing Uma were better than most in terms of the specifics, but if I recall correctly claimed to have never motored for longer than 30 minutes at a time.

 

[Tranona]

The people who have sailed around the world for 8 years on an all electric yacht would seem to disagree. How many years have you sailed on your all electric yacht?

Absolutely nothing to do with the propulsion being electric. Under the scenario you/they quoted the sails are assisting the motor so obviously the motor is using less power and therefore fuel/energy and the range for any given amount of storage capacity (fuel in the tank or watts in the battery) will be greater.

Not sure why you constantly cite that source as although they have a large following they are not doing anything out of the ordinary except demonstrating the limitations of electric power and to an extent how they can be mitigated by technological developments. Interesting that the supplier of their propulsion unit has made little inroads into the sector that Uma represents, much as I am sure they would like to. Oceanvolt, like all the other players in the electric and hybrid market concentrate their efforts on the market segments where their products offer something of value to the buyer.

 

[Sea Change]

Running an electric motor at low power to gain a useful boost in speed sounds very civilised and efficient, whereas running your diesel at just above tickover is not efficient or particularly good for the engine.

 

[Tranona]

That is correct, and some who do this sort of thing a lot fit a Bruntons propeller with variable pitch that will adjust the pitch automatically to load the engine even at low speeds. In this respect as you say electric power is better provided you can work within the limited amount of stored energy in the batteries. I would imagine in some circumstances with some boats that have large solar arrays you could probably match the consumption with the energy harvested from the sun. Perpetual motion!

 

[Sea Change]

That is correct, and some who do this sort of thing a lot fit a Bruntons propeller with variable pitch that will adjust the pitch automatically to load the engine even at low speeds. In this respect as you say electric power is better provided you can work within the limited amount of stored energy in the batteries. I would imagine in some circumstances with some boats that have large solar arrays you could probably match the consumption with the energy harvested from the sun. Perpetual motion!

I met a German couple who built a 50ft cat with electric drive. They could sustain 1.6kt from solar alone. But they had a lot of panels!

 

[Tranona]

I met a German couple who built a 50ft cat with electric drive. They could sustain 1.6kt from solar alone. But they had a lot of panels!

A bit more useful than the pu8blicity video demonstrating the regeneration of the Beta Hybrid in a 45' yacht where at 7 knots under sail it generates enough to boil water for a mug of tea bag tea.

Seriously though there is a lot of work going into improving regeneration and the use of solar to reduce the reliance on the diesel but inevitably it is limited to larger boats rather than the mass market that most of us inhabit. Does not come cheap though - the 25kW drive with Servoprop from Oceanvolt that claims over a kilowatt at 6 knots comes in at a cool £60k. some of this will of course trickle down over time but won't change the fundamentals until there is a step change in battery technology.

 

[Sea Change]

I wouldn't expect too much from regen. My Aquair, which is dedicated generator rather than an add-on to the engine with all the compromises that entails, is rated for about 24w, which is really a rounding error in the power budget of most boats today.

 

[dunedin]

I wouldn't expect too much from regen. My Aquair, which is dedicated generator rather than an add-on to the engine with all the compromises that entails, is rated for about 24w, which is really a rounding error in the power budget of most boats today.

Sailing Uma recorded 500W sailing at 7 knots average speed - but much less at lower speeds (negligible below 5 knots).
However that is with a very high tech Oceonvolt system with a variable geometry servo prop.
Would be much less on a typical DIY system without fancy prop. Plus need a fast enough boat to regularly average 7+ knots, including the extra drag caused by regeneration (probably negligible near hull speed, but more marked at lower speeds).
Hence why these serial hybrid systems are most popular on fast (and expensive) boats like Arcona, X-Yachts and performance cats.

 

[Tranona]

This is the Hybrid Marine take on regeneration with their parallel hybrid I referred to earlier. The graph says it all. With conventional propellers required for diesel propulsion the yield is around 50% of that Oceanvolt achieves with its similar size pod and Servoprop. The new 25kW claims around double that.

hybrid-marine.co.uk/index.php/hybrid-info/regeneration

 

[Chiara’s slave]

That is correct, and some who do this sort of thing a lot fit a Bruntons propeller with variable pitch that will adjust the pitch automatically to load the engine even at low speeds. In this respect as you say electric power is better provided you can work within the limited amount of stored energy in the batteries. I would imagine in some circumstances with some boats that have large solar arrays you could probably match the consumption with the energy harvested from the sun. Perpetual motion!

For people who only sail in the daytime, yes. We might be able to fit a Kw of solar, but we won’t. We would not need to run an electric drive that much, only in winds under 5kn. Even then, if we can get the kite up we probably wouldn’t.

 

[Tranona]

For people who only sail in the daytime, yes. We might be able to fit a Kw of solar, but we won’t. We would not need to run an electric drive that much, only in winds under 5kn. Even then, if we can get the kite up we probably wouldn’t.

I am surprised you have not already gone electric with one of the higher powered motors like the E Propulsion Navy range or a Torqeedo Cruise. Well suited for your boat as a direct replacement for your petrol outboard.