Real-life energy usage on electric/series hybrid narrowboat with solar and generator

[IanD]

There's a lot been said about this subject with lots of figures bandied around about how little (or much!) energy is needed/used by boats like this, so I thought I'd provide some actual numbers logged over the last year or so (50 days total cruising time) for my boat to counter some perhaps over-optimistic assumptions... 😉

 

-- boat is all-electric including cooking, also has washer/drier on board, has 2.1kWp of flat-mounted solar panels, 9kVA diesel generator, Victron Quattro 48/10000, diesel boiler

-- usage is more typical of "holiday boats" then long-term CCers, as can be seen by the 5hrs/day average cruising time (7hrs on the delivery trip!)

-- I typically cruise at about 3kW on most canals (less when passing boats, none in locks) -- faster than some other electric boats, but still slower than many (most?) diesel boats

-- most of the cruises were not in good weather (even the one in July was *lousy*, very little sun!)

-- I guess roughly half the evenings were spent onboard (streaming TV/laptops/lights etc using power), half in pubs

 

Here are some interesting/disappointing numbers from the results:

-- Solar yield (3.2kWh/day average) was quite a lot lower than I'd hoped for, predictions for more typical UK weather were 7kWh/day in summer and 4kWh/day in spring/autumn

-- Average drive power when travelling (cruising + moored boats + locks) was 2.3kW -- 11.7kWh/day at 5hrs/day, 1.3kWh/mile

-- Domestic energy use averaged 3.7kWh/day, dependent on activity and cooking/washing (2.0kWh-6.0kWh range), so about a third of propulsion power

-- Total energy use (solar+generator+shoreline) averaged out at 17kWh/day

-- Generator output is lower than expected (Quattro temperature derating + losses?) -- less than 5kW average, Quattro AC-DC charging efficiency around 88% (12% loss)

-- Generator running time averages out at a bit more than 50% of travelling time -- solar only provided about a fifth of total power demand overall, or a third on the best trip

 

The last point doesn't mean the genny is running for more than half the time I'm cruising, I usually run it in the morning while we're having tea in bed/breakfast and in the evening after we've gone to the pub -- respecting 8am-8pm hours, obviously (and it's pretty quiet). So most of the time (all day some days) we get silent cruising, which is the main point of going down this route.

 

I hope to be able to increase the (disappointing!) average generator output and speed up charging with better cooling of the electrical cabinet (adding a hot air exhaust fan to the cool air intake fan) but that's a job for this winter. A 48V DC generator would avoid these issues, but has other disadvantages (fewer available, more expensive, harder to control charging, no 230Vac backup if Quattro fails).

 

Of course all these numbers depend on boat and power usage; in more normal weather (especially summer) solar yield should be higher, propulsion power use will be lower for boaters who travel more slowly or for fewer hours per day, domestic power use will be lower for more frugal power-users -- and in all these cases the proportion of solar power will go up and generator use will go down. But for my use, given that average solar yield was less than average domestic energy use, only one trip out of the five would have any spare solar power left over to go anywhere without generator running.

 

It would obviously be helpful if other owners of similar boats could provide similar "warts-and-all" numbers -- say, averaged over a year rather than spot readings which can be way too optimistic -- to give a better idea of how all this varies with boat/power usage patterns, some of which will undoubtedly be quite different to mine... 🙂 

 

P.S. My logged travel times each day are usually very close to the ones calculated by Canalplan, which is why I used these for the calculation.

Boat energy consumption - Sheet1.pdf

Edited September 13 by IanD

[blackrose]

37 minutes ago, IanD said:

😉

-- boat is all-electric including cooking, also has washer/drier on board, has 2.1kWp of flat-mounted solar panels, 9kVA generator, Victron Quattro 48/10000, diesel boiler

Boat energy consumption - Sheet1.pdf 56.3 kB · 6 downloads

 

"All electric"? Is it really? What does the generator run on? 

[IanD]

11 minutes ago, blackrose said:

 

"All electric"? Is it really? What does the generator run on? 

Very funny. I'm sure you know what I meant (no gas -- or hydrogen, or nuclear power...), as would most sensible readers... 😉 

 

But just to make it crystal clear, I've added "diesel" before "generator" in the same line... 🙂 

Edited September 13 by IanD

[robtheplod]

It must be a little odd for a traditional boater when they switch to an electric boat. Usually you cruise to charge your batteries up, whereas on electric its doing the opposite?

[Naughty Cal]

So how much diesel has your generator used?

 

Struggling to really see the benefit of this system if I'm honest 

[ditchcrawler]

1 minute ago, Naughty Cal said:

So how much diesel has your generator used?

 

Struggling to really see the benefit of this system if I'm honest 

I think its silent boating 

[IanD]

33 minutes ago, robtheplod said:

It must be a little odd for a traditional boater when they switch to an electric boat. Usually you cruise to charge your batteries up, whereas on electric its doing the opposite?

You can do either, there's no link between when you need to generate the energy and when you need to use it because of the big battery bank and inverter. So you can choose to run the generator when is most convenient for you -- which since they're not completely silent is first of all when you're not there, then secondly when it'll bother you the least, and lastly when you want to cruise in silence.

 

You can also "mortgage the battery", if you want a silent day without any generator running at all then that's perfectly feasible and will typically use up less than half the battery capacity -- but of course any "energy debt" has to be paid back later, it has to come from somewhere.

 

All this applies to a series hybrid, parallel hybrids are more likely to charge while cruising due to the way they work -- I passed one last week doing just that, explaining why he was running the engine while travelling when I wasn't running the generator.

 

The real reason for putting the post up is I've seen lots of unrealistic assumptions made by people considering going down the hybrid route, usually underestimating power use (including things that take a bit of power all the time), ignoring inefficiencies (e.g. inverter/drive losses), overestimating solar yield, and generally being too optimistic compared to reality -- especially regarding how much of the demand can be met by solar power, especially outside sunny days in summer.

 

I found that in spite of trying to work out everything correctly I've seen lower solar yield and slower charging from the generator than expected -- the second one I can try and do something about, the first one is just the British weather nowadays... 😞 

 

But I still *love* cruising along with no noise except a gentle burble from the wash -- and even with the generator running it's quieter and with less vibration than any diesel boat I've even been on, including ones with extensive sound insulation and hospital silencers. Not a cheap way to get silent cruising, though... 😉 

 

19 minutes ago, ditchcrawler said:

I think its silent boating 

Which is exactly what I said, and have done so many times in the past. And everyone who has been on the boat agrees, as do many boaters (and non-boaters) I've passed. It completely transforms the experience of cruising along the canals, very much for the better -- you need to experience it to appreciate it.

 

Fuel consumption is lower than a diesel boat, depending how much power you can get from solar -- actually even with zero solar, fuel consumption is still lower because of higher efficiency because diesels are bad for this at the low power levels used on canals, even more so if run for battery charging.

 

But the saving in running costs is relatively small in the big picture, and I'd be surprised if it ever makes back the higher build cost in any boater's lifetime... 😉

 

To try and answer the question, I don't know exactly how much diesel my generator has used for propulsion because it also provides power for domestic use (and there's also diesel heating) -- but I calculate it's used 5.8l/day for all loads, which means 4.6l/day (5 hours cruising) for propulsion (and that's with only 20% of energy coming from solar).

Edited September 13 by IanD

[Ken X]

All good stuff and interesting to see how the the real figures varied from the predictions.  Do you envisage any changes in equipment or configuration in the near future to improve the systems or not?  I guess it may take a year or so to really develop some base lines.  I am wondering how you generate your hot water?  Do you have a variety of power sources depending on whether you have surplus electricity, or need to run the generator which I am assuming is water cooled?

 

I wonder whether improvements in battery and solar panel technology will bring better returns in future years as the systems mature.

[nicknorman]

Interesting. Personally i have no desire to own an electric car, even less an electric boat - I think I just like throbbing things and burning fossil fuels! But still interesting.
Do you have an idea what the energy efficiency of the battery set up is? (Not the charge efficiency, which will be close to 100%). This will depend on how fast you charge and discharge, but it would be interesting to compare that with the energy saved by using an efficient generator running optimally vs (as you say) a large diesel engine running rather slowly.

[IanD]

41 minutes ago, Ken X said:

All good stuff and interesting to see how the the real figures varied from the predictions.  Do you envisage any changes in equipment or configuration in the near future to improve the systems or not?  I guess it may take a year or so to really develop some base lines.  I am wondering how you generate your hot water?  Do you have a variety of power sources depending on whether you have surplus electricity, or need to run the generator which I am assuming is water cooled?

 

I wonder whether improvements in battery and solar panel technology will bring better returns in future years as the systems mature.

The generator is connected to one coil in the calorifier, the diesel boiler to the other. Whenever the genny is running the water heats up, typically by about 25C/hour so pretty fast -- see temperatures over a week. If I don't run the generator for a day or so I turn on the diesel boiler for a bit which heats the water at about the same rate. There's also an immersion heater which dumps excess solar power into the water, but this has never done anything when I'm out on the boat, only when moored for long periods so the solar pushed the batteries up to 100% SoC.

 

Battery technology isn't going to help with any of this except to bring costs down. Solar panels are currently close to the practical limit (about 22% efficiency) for silicon, if multilayer ones (e.g. silicon+perovskite) hit the market with low enough cost and long life these could push that up towards 30% but they're not there yet.

 

 

33 minutes ago, nicknorman said:

Interesting. Personally i have no desire to own an electric car, even less an electric boat - I think I just like throbbing things and burning fossil fuels! But still interesting.
Do you have an idea what the energy efficiency of the battery set up is? (Not the charge efficiency, which will be close to 100%). This will depend on how fast you charge and discharge, but it would be interesting to compare that with the energy saved by using an efficient generator running optimally vs (as you say) a large diesel engine running rather slowly.

 

The generator itself is about 25% efficient, allowing for the measured 12% inverter loss (230Vac-48Vdc) this means 22% efficiency for charge into the batteries.

 

A typical marine diesel on a narrowboat is about 20% efficient (or less!) at the low loads used for battery charging (or cruising), 12V alternators are typically only about 55% efficient (which is why they get so hot), so for battery charging about half the efficiency of a generator. 24V alternators are a little bit better (60%?), but not much.

 

For propulsion only the gap is smaller; allowing for realistic losses in motor controller/motor (10%?) the efficiency from fuel to prop for a hybrid is also about 20% when cruising so similar to a diesel. However the difference becomes bigger when going more slowly past moored boats, end even more so in locks comparing an idling diesel to electric drive. Then there's the power from solar which means not all the energy comes from running the generator.

 

Depending on running hours and speed and amount of sunshine the net result is typically a fuel saving of between a third and a half compared to a diesel (the Ortomarine trials bear this out), but it can be bigger than this in summer and with fewer hours travelling -- in theory all the way to 100% saving if solar-only is sufficient, though I have never seen this.

Edited September 13 by IanD

[Onewheeler]

Interesting data. For me the appeal is that if shore power ever becomes widely available (a forlorn hope in the UK, maybe halfway there in France) an overnight charge should be able to make the generator redundant,oir at least permit a smaller unit.

[IanD]

Just now, Onewheeler said:

Interesting data. For me the appeal is that if shore power ever becomes widely available (a forlorn hope in the UK, maybe halfway there in France) an overnight charge should be able to make the generator redundant,oir at least permit a smaller unit.

Indeed, an overnight charge (16A socket) would easily get back to 100% SoC -- but if you miss one then 2 days without a charge would be pushing it, so unless they're frequent enough you'd still need a generator, unless you're willing to wait -- maybe for days! -- for enough sun to shine... 😉 

 

Chances of such a network happening in the UK -- zero at present, and no credible plan for the future... 😞 

[Momac]

Are you able to estimate  your diesel use in litres divided by the hours spent travelling ?

 

 

 

[IanD]

18 minutes ago, Momac said:

Are you able to estimate  your diesel use in litres divided by the hours spent travelling ?

 

I did that a few posts back, it came out to about 0.9l/hour for propulsion. That's with an average of 9 furlongs between locks in old money, or 8 locks per 5-hour day... 😉 

 

A typical diesel (e.g. Beta 43) is about 1.5l/hr when cruising, 1.1l/hr when passing moored boats, and 0.8l/hr when idling (locks) --depending on how much time you spend doing each, something like 1.2-1.3l/hr is a reasonable guess.

 

So about 30% less fuel, and that's with 80%/20% power split between generator and solar, which is unusually low solar yield -- others have reported a 50% fuel saving (see Ortomarine trials).

Edited September 13 by IanD

[Momac]

And presumably you start from your home mooring with a full battery off shore power so I would expect that gives you some saving over a diesel engined boat at least for the first part of the journey (as per a plug in hybrid car).

Plus you have the advantage of using no energy when in neutral compared to a diesel.

 

What does a diesel engined boat of the same size use in fuel per hour travelling?

 

 

[IanD]

Just now, Momac said:

And presumably you start from your home mooring with a full battery off shore power so I would expect that gives you some saving over a diesel engined boat at least for the first part of the journey (as per a plug in hybrid car).

Plus you have the advantage of using no energy when in neutral compared to a diesel.

 

What does a diesel engined boat of the same size use in fuel per hour travelling?

 

 

I just answered that... 😉

 

Yes you start off full and can run down over the last day or two, bollard power is about half the cost and doesn't make any noise -- if we just nip out from the marina for a couple of days I probably wouldn't run the generator at all...

[hider]

27 minutes ago, Momac said:

And presumably you start from your home mooring with a full battery off shore power so I would expect that gives you some saving over a diesel engined boat at least for the first part of the journey (as per a plug in hybrid car).

Plus you have the advantage of using no energy when in neutral compared to a diesel.

 

What does a diesel engined boat of the same size use in fuel per hour travelling?

 

 

My boat, 50', with its old BMC 1.8D averages 1.16 litres an hour but its hard to judge as it is only between fill ups that I can guess at consumption. It includes tickover in locks etc. and running light and fast battery charging.

[IanD]

32 minutes ago, hider said:

My boat, 50', with its old BMC 1.8D averages 1.16 litres an hour but its hard to judge as it is only between fill ups that I can guess at consumption. It includes tickover in locks etc. and running light and fast battery charging.

That stacks up with the slightly higher figure I came up with for a 60' boat with a Beta 43, which is the diesel I would have used if I hadn't gone hybrid.

 

Either way, the fuel saving is interesting and nice to have but not really a compelling reason for going hybrid, the cost saving is too small compared to the higher upfront cost.

Edited September 13 by IanD

[n-baj]

Interesting post, I’ve always been interested in electric hybrid boats and if I get the opportunity to talk to the owners of one I ask them questions about their set up.

 

I am intrigued with what you do with the waste heat from your diesel generator. You said that the generator heats up the water and I guess you have a skin tank to take away the rest of the heat like in a standard diesel engine set up but have you considered plumbing in your radiators to your generator cooling system so if you’re feeling a little chilly your generator is doing the job of your diesel heater but it is also generating electricity?

Assuming your radiator are of sufficient size there’s the possibility of using close to 100% of the energy contained in diesel (I know it will not be 100% due to inefficiencies in generating electricity, heat coming from the generator, etc) and in the process making the diesel heater redundant. Yes in summer it’s too hot to have the heating on but if you use your boat in March/April and September/October then this would be a nice feature.

 

I spoke to the owners of nb Ampere when they went through standedge tunnel on the same day as me last year and they had a set up where their generator heated the cabin. Their set up was perfect for the hnc as 90% of my engine running was in idol in locks and lock landings whereas they would just run the generator for an hour in the morning for heating and hot water and that’s them set for a day locking. I was envious of their system but personally I cannot justify the cost.

 

many thanks.

[Paul C]

If we had a "long hot summer" (ie, very sunny, not the miserable one we've had this year) would it have made a noticeable difference?

[Tacet]

It's very decent of IanD to post the real life, year long, figures in the circumstances.  One suspects others are more selective to justify their decisions.

 

The solar energy looks to be the major disappointment but Ian has undoubtedly achieved his principal aim of silent cruising.

[IanD]

37 minutes ago, n-baj said:

Interesting post, I’ve always been interested in electric hybrid boats and if I get the opportunity to talk to the owners of one I ask them questions about their set up.

 

I am intrigued with what you do with the waste heat from your diesel generator. You said that the generator heats up the water and I guess you have a skin tank to take away the rest of the heat like in a standard diesel engine set up but have you considered plumbing in your radiators to your generator cooling system so if you’re feeling a little chilly your generator is doing the job of your diesel heater but it is also generating electricity?

Assuming your radiator are of sufficient size there’s the possibility of using close to 100% of the energy contained in diesel (I know it will not be 100% due to inefficiencies in generating electricity, heat coming from the generator, etc) and in the process making the diesel heater redundant. Yes in summer it’s too hot to have the heating on but if you use your boat in March/April and September/October then this would be a nice feature.

 

I spoke to the owners of nb Ampere when they went through standedge tunnel on the same day as me last year and they had a set up where their generator heated the cabin. Their set up was perfect for the hnc as 90% of my engine running was in idol in locks and lock landings whereas they would just run the generator for an hour in the morning for heating and hot water and that’s them set for a day locking. I was envious of their system but personally I cannot justify the cost.

 

many thanks.

 

The generator and the heating are two separate closed circuits to avoid problems with interaction/fighting between the two; the generator cooling circuit goes to one calorifier coil and also a skin tank, the heating (Bubble diesel boiler) is like a home CH system (with Nest controller), with motorised valves to steer the output to either hot water (second calorifier coil) or heating (radiators) or both.

 

As you say, it would in theory be possible to also use the generator to run the heating by linking the two systems, but making sure this all works without screwing up the diesel boiler (or generator cooling) isn't trivial when you have two heat sources (generator and boiler), four heat sinks (two calorifier coils, radiators, and skin tank), two controllers (Nest and Cerbo), two pumps (CH and generator cooling), and need to to able to run the generator with or without heating up the radiators -- I can see things going wrong during operation which would be difficult to debug.

 

There's also the practical point that when you need/want to run the generator and when you need/want heating often don't coincide -- with my usage pattern most heating is needed in the evening, when you don't want to run the generator (or can't after 8pm).

 

36 minutes ago, Paul C said:

If we had a "long hot summer" (ie, very sunny, not the miserable one we've had this year) would it have made a noticeable difference?

Yes, and that's exactly what I was hoping for by going out in July. But the weather was so horrible we cut the trip down from 3 weeks to 2 and came home... 😞 

 

22 minutes ago, Tacet said:

It's very decent of IanD to post the real life, year long, figures in the circumstances.  One suspects others are more selective to justify their decisions.

 

The solar energy looks to be the major disappointment but Ian has undoubtedly achieved his principal aim of silent cruising.

 

The low solar yield was disappointing but not unexpected given the unusually bad weather, especially in our July trip. The lower charging currents were not expected and I'm looking into this.

 

I posted real year-long figures -- disappointing or not -- because it's important to be honest about things like this, not pretend that everything's rosy even when it's not.

 

The silent cruising is great when it happens (i.e. a lot of the time), but would be better still with shorter generator running times... 😉 

 

(not that it's noisy, but it's still noisier than when not running -- and it's running for longer than I planned/expected)

Edited September 13 by IanD

[Tacet]

13 minutes ago, IanD said:

 

The generator and the heating are two separate closed circuits to avoid problems with interaction/fighting between the two; the generator cooling circuit goes to one calorifier coil and also a skin tank, the heating (Bubble diesel boiler) is like a home CH system (with Nest controller), with motorised valves to steer the output to either hot water (second calorifier coil) or heating (radiators) or both.

 

As you say, it would in theory be possible to also use the generator to run the heating by linking the two systems, but making sure this all works without screwing up the diesel boiler (or generator cooling) isn't trivial when you have two heat sources (generator and boiler), four heat sinks (two calorifier coils, radiators, and skin tank), two controllers (Nest and Cerbo), two pumps (CH and generator cooling), and need to to able to run the generator with or without heating up the radiators -- I can see things going wrong during operation which would be difficult to debug.

 

There's also the practical point that when you need/want to run the generator and when you need/want heating often don't coincide

A plate exchanger between the generator and central heating circuits keeps the systems separate at the modest expense of a circulating pump.

 

It worked very well for us on a standard diesel engine.

[IanD]

10 minutes ago, Tacet said:

A plate exchanger between the generator and central heating circuits keeps the systems separate at the modest expense of a circulating pump.

 

It worked very well for us on a standard diesel engine.

 

I agree that seems like it should work at first glance. But unlike a generator a standard diesel engine is not turned on and off on demand (and in relatively short bursts) by an external controller, and I guess in your case you also didn't have similarly (but separately) controlled boiler and motorised valves in the CH circuit. Getting two separately (and automatically) controlled systems to play together nicely -- even if only linked thermally by a heat exchanger, not sharing bodily fluids -- is by no means a trivial task, and after discussing this with Ricky I decided that the possible benefits were too small to justify the time and effort to make sure everything worked properly in a linked system.

 

Not saying it can't be made to work, but we decided against it. For example we often want the heating and hot water to come on before 8am so can't run a generator, and most commonly want heating after 8pm when the same applies. For other people with different systems and lifestyles a linked system might work very well... 😉 

Edited September 13 by IanD

[Naughty Cal]

4 hours ago, IanD said:

I did that a few posts back, it came out to about 0.9l/hour for propulsion. That's with an average of 9 furlongs between locks in old money, or 8 locks per 5-hour day... 😉 

 

A typical diesel (e.g. Beta 43) is about 1.5l/hr when cruising, 1.1l/hr when passing moored boats, and 0.8l/hr when idling (locks) --depending on how much time you spend doing each, something like 1.2-1.3l/hr is a reasonable guess.

 

So about 30% less fuel, and that's with 80%/20% power split between generator and solar, which is unusually low solar yield -- others have reported a 50% fuel saving (see Ortomarine trials).

So really it's a hell of a lot of initial outlay to save about 46p an hour in fuel? 

 

"Silent" cruising we have found from hiring day boats isn't all that silent. There was still mechanical noise and prop noise.