Proposed new accessible electric narrowboat.

[Matt Wardman]

3 hours ago, IanD said:

 

Looks good at first glance, but as usual the devil is in the details. The *minimum* airflow rate is something like 10l/s (maximum is 38l/s) which is *way* too high for a boat, especially a narrowboat.

 

The implication is that the intended use is for large kitchen/bathroom/wetroom extractor fans, to stop them sucking lots of heat from the inside to the outside when there's a *lot* of air being moved -- which is absolutely a good thing for that application, but not for background air exchange in a small living space like a narrowboat.

 

 

To comment on these numbers.

According to me (I did some approx. calculations using a heat /ventilation model right near the top of the thread) a narrowboat interior is approximately 2m x 2m x 12m = 48 cubic m, which is 48,000 litres.

 

So for one air change per hour (ach) via ventilation (for a lowish level of ventilation), we need 48,000 litres / 3600 seconds, which is 13.33 litres per second.

So 10 l/s gives 0.75 ach, or the 6l/s of the low-trickle setting (High trickle = 9l/s, Boost = 15l /s) on the Heat Recovery extractor fan I have mentioned elsewhere on thread gives 0.45 ach.

Both seem to me to be not unreasonable rates of ventilation to keep a living space comfortably fresh, and are not much different from eg figures in the Building Regs. I would quote a number from the Boat Safety Scheme, but they have not yet considered mechanical ventilation afaics.

I'll definitely say that both God and the Devil are in the Details *, as always.

 

Of course other factors apply - such as a boat being opened up in the day, and closed down to help warm it up at meal times or autumn evenings, but when closed down I'd say that such ventilation is a reasonable level of throughput. And types of appliance such as solid fuel burners etc being often present, and the need to consider Carbon Monoxide and Carbon Dioxide.

 

I'd argue that as NBs are smaller spaces with a KitKat-like form factor where the floor is below the entry level, probably a higher level of ventilation in terms of ach than a normal house would be appropriate.

 

Matt W

 

* With apologies to Mies van der Rohe, who left the Devil out of his aphorism.

The post I referenced:

 

Edited December 29, 2023 by Matt Wardman

[agg221]

9 minutes ago, Alan de Enfield said:

 

If I'm understanding correctly & I've got the maths the 'right way around' thats 225 amps at 12v (225Ah per day)

 

How are the batteries going to be recharged and that 225 amps replaced as you don't have a generator, or, an engine, and their are no 'hook-ups' canalside ?

I think we are somewhat at cross-purposes here.

 

I think you are still considering the OP's proposition of a fuel-free narrowboat, which I think everyone is in agreement is not achievable.

The thread has moved on to consider the art of the possible - how much can you reduce energy input requirements, using what approaches and, for each individual approach, how much would  that reduce energy requirements and what would it cost? This is effectively the watered-down question of 'how close to a fuel-free narrowboat can you currently get?' In this case, I presume a dedicated genset would be used, with solar when available, and hook-ups in marinas or a permanent mooring as a preferred option when available.

 

Although there are disparaging comments that a thought exercise such as this is effectively a waste of time, I see it as useful as it defines what is currently possible and what the potential impact of emerging technologies will be.

 

Alec

Edited December 29, 2023 by agg221

[Alan de Enfield]

6 minutes ago, agg221 said:

I think you are still considering the OP's proposition of a fuel-free narrowboat, which I think everyone is in agreement is not achievable.

 

You are correct that is the scenario I am working on - whilst 'we' all agree it is not achievable I have yet to see an acknowlegement of this from the OP.

 

If he still thinks it can be done he needs to work out how he is going to power his systems.

[Matt Wardman]

4 hours ago, MtB said:

 

Thanks, but I can see any efficiency calculations on that data sheet. Just unsupported assertions of up to 94% efficiency. Is this the data sheet you meant? 

https://www.blauberg.co.uk/en/amfile/file/download/file/3023/product/6167/

 

My gut feeing is this is a semantics problem, as so often is the case. I think a 100% efficient heat exchanger will recover 50% of the available heat in the outgoing air, for the reasons I stated earlier. Nowhere in the link can I see a claim that 94% heat in the outgoing air is recovered.

 

Just an un-defined 'efficiency' figure of 94%, which isn't the same thing at all as "a MVHR unit will be installed which are available to recover 90% of heat."

 

I think it is dishonest marketing as the writing is always arranged to lead the reader to the assume they mean what you wrote, when they didn't actually say that. 

 

 

 

I think there's something in that, and also that there are many different types of heat exchanger (eg 'counter flow, concurrent flow, cross flow and hybrids of those types such as cross counter flow and multipass' *).

 

I think here be a rabbit hole, which probably ends at an Appendix in an ISO or British Standards document.

 

I expect that there will be approved methods of making such calculations, which allow comparisons, and approved ways of doing measurements under standard conditions. 

And that in practice we will find a benefit, but just *how* big the benefit is will depend on other aspects of our environment, such as (for example) just how good the air seals are around our window frames. eg if only 80% of the air from our living space exiting via the MVHR system, then the system will work efficiently on air it gets at, but leakage elsewhere will degrade performance of the overall system which includes all the leaks.

 

* I can see how those concepts are all different categories, but I got the words from here:

https://www.thermopedia.com/content/832/

========================

Bah humbug the autosec merged my comments.

MVHR in Houses and Efficiency etc.
 

On MVHR, here is a recentish shortish 2020 Passivehaus Trust paper on MVHR for anyone wanting to pursue the subject a little further.

 

They emphasise that in their analysis such systems deliver a desirable living environment in addition to energy saving. My personal anecdote on this is that if I am in a very high humidity environment I start coughing.

We need to keep in mind that a) PHT are authoritative but also advocates and b) That applying insights from house to boat and vice-versa needs care.

This paper has shown that previous analyses indicating that MVHR systems should only be installed in properties with an air permeability of 3 m³/m².hour @50Pa or less are based on outdated information and flawed assumptions using a modelling system which was never intended to be used to compare ventilation systems.

 

A modern MVHR system will result in significantly lower CO2 emissions at any reasonable level of air permeability. However, an MVHR system’s primary function is ventilation and, in this capacity, it is far more effective at providing a good quality indoor air environment – regardless of external conditions – than natural ventilation.

 

There is no clear up-to-date evidence behind the rule of thumb that says MVHR is inappropriate for dwellings with air permeability above 3m³/m².hour @50Pa. This analysis has shown that MVHR systems result in improved ventilation and lower carbon emissions for all levels of airtightness.

 

There is a compelling case for MVHR systems to be fitted in all new dwellings and to be strongly encouraged in retrofits where significant reductions in energy demand are being targeted.
https://passivhaustrust.org.uk/UserFiles/File/research papers/MVHR/2020.04.27-The Case for MVHR-v7 new cover.pdf

Edited December 29, 2023 by Matt Wardman

[ditchcrawler]

7 hours ago, Matt Wardman said:

(BTW imo perhaps don't put a HR extractor fan in a shower room, since the incoming air is *always* slightly cooler than the air already in the room, so your beloved-coming-out-of-the-shower will be subjected to an airflow that feels cold, on top of the perceived cold caused by water evaporation from skin, and you may receive the appropriately vigorous customer feedback.)

 

I would have thought it would also have lots of condensation problems in the heat exchanger as the very warm wet air is cooled down by the cold air coming in on the other side of the exchanger. a lot more than any other part of the house  

[IanD]

20 minutes ago, ditchcrawler said:

I would have thought it would also have lots of condensation problems in the heat exchanger as the very warm wet air is cooled down by the cold air coming in on the other side of the exchanger. a lot more than any other part of the house  

That'll be why they have condensate drains then, it's how they're designed to be used...

[Willonaboat]

5 hours ago, IanD said:

Which is just over 0.2kWh/day. So it needs to recover about 0.8kWh/day to make the heat/electricity costs balance out, assuming the power comes from a generator. If the power comes from an engine alternator charging batteries (~10% efficient), it needs to recover about 2kWh/day to break even.

 

 

How about assuming the power comes from solar, Ian (I have a widebeam, don't forget). Because with over 6kw on the roof, half of which will be at a negligable angle towards the sun (~3 degrees tilt) so not producing anything worthwhile in December, but the other half tilted at anything up to ~85 degrees in winter, I estimate that the MVHR electrical power will be met by solar even in winter *most of the time* and for the worst months (Dec, Jan) I am likely to be on shorepower for at least some of that time but with solar power generated prioritised via programing over shorepower. But this is my set of circumstances and use case, not necessarily yours or anyone elses.

 

Edited to add: I estimate the saving to be approx 180 watts (of heat) per hour, or approx 4.3kw (of heat) per 24 hours. This is based on a spreadsheet calculation that I did over a year ago but having just looked at it I can't recall how the hell I did it. It made sense at the time, honest Guv. All I can say is, the heat loss calulations have so far proved to be in the right ball park based on what we are experiencing in real life, so I'm buoyed with confidence that I'm not going to be a million miles out when everything is installed as planned. But remember, this is for a widebeam, not a narrowboat, so your circumstances and calculations will no doubt yield different results.

Edited December 29, 2023 by Willonaboat

[Matt Wardman]

50 minutes ago, ditchcrawler said:

I would have thought it would also have lots of condensation problems in the heat exchanger as the very warm wet air is cooled down by the cold air coming in on the other side of the exchanger. a lot more than any other part of the house  

 

For a through the wall unit like that the standard install is to incline the hole in the wall slightly so that any condensation runs outward and drips off the end.

 

I go a little further and put a section of soil pipe set in the wall projecting slightly away from the surface on the outside 1) to protect the fabric and surface of the wall just in case any moisture does manage to condense on the pipe, and 2) so that the unit can be taken completely out from the inside to be maintained or replaced. It leaves a tiny gap between the unit and the piece of pipe which can be siliconed.

Edited December 29, 2023 by Matt Wardman

[Tony Brooks]

3 hours ago, Matt Wardman said:

 

To comment on these numbers.

According to me (I did some approx. calculations using a heat /ventilation model right near the top of the thread) a narrowboat interior is approximately 2m x 2m x 12m = 48 cubic m, which is 48,000 litres.

 

So for one air change per hour (ach) via ventilation (for a lowish level of ventilation), we need 48,000 litres / 3600 seconds, which is 13.33 litres per second.

So 10 l/s gives 0.75 ach, or the 6l/s of the low-trickle setting (High trickle = 9l/s, Boost = 15l /s) on the Heat Recovery extractor fan I have mentioned elsewhere on thread gives 0.45 ach.

Both seem to me to be not unreasonable rates of ventilation to keep a living space comfortably fresh, and are not much different from eg figures in the Building Regs. I would quote a number from the Boat Safety Scheme, but they have not yet considered mechanical ventilation afaics.

I'll definitely say that both God and the Devil are in the Details *, as always.

 

Of course other factors apply - such as a boat being opened up in the day, and closed down to help warm it up at meal times or autumn evenings, but when closed down I'd say that such ventilation is a reasonable level of throughput. And types of appliance such as solid fuel burners etc being often present, and the need to consider Carbon Monoxide and Carbon Dioxide.

 

I'd argue that as NBs are smaller spaces with a KitKat-like form factor where the floor is below the entry level, probably a higher level of ventilation in terms of ach than a normal house would be appropriate.

 

Matt W

 

 

 

 

I see something that may be a problem in a typical narrowboat in that for the heat exchanger box not to suck just warmed up and delivered fresh air back out again the old air intake and the fresh air delivery probably needs to be on opposite ends of the cabin space. The p iece I found suggests 6"  diameter pipes, and they will not be so easy to install in an unobtrusive manner. maybe square/rectangular ducting could be used, but it would still be intrusive. I fear ducting length might have a detrimental effect on air flow or fan power rating.

 

This is not to say it won't work, but the practicalities for NARROW BOAT insulation do not seem to have been considered yet.

Edited December 29, 2023 by Tony Brooks

[Matt Wardman]

2 hours ago, Tony Brooks said:

This is not to say it won't work, but the practicalities for NARROW BOAT insulation do not seem to have been considered yet.

 

Agree that's important, and I probably put it under careful planning, homework and sweating the design detail. Incorporation of units into the space needs thought.

 

For a narrowboat, one thought could be for a type of "not full MVHR" as I have used effectively in renovations of older houses.

 

I think an airflow from one end to the other end is fairly clearly the option for a narrowboat (though from the middle to both ends is another possibility).

 

I would perhaps put an extractor unit (probably 12V Supply Heat Recovery) in the kitchen end, so that food smells go out rather than permeate into the bedrooms etc, then an input unit at the other end. 

 

Wrinkles could be a filter on the input - possibly activated carbon to keep the smells from other narrowboats out, humidistat or timer control of one or both units, and possibly an on/off switchable heater (say 300W) on the input unit to give an option for a low heat when required at certain times of the year or to warm up the boat a little in the morning or at bedtime. 

 

Through room flow could be facilitated either by door gaps (ie shave the top or bottom of the inside doors) or via soundproofed inter-room vents.

 

For a full MVHR and a narrowboat sized space I think 100mm or rectangular 110mmx54mm ducting would be suitable.

[David Mack]

3 hours ago, Willonaboat said:

Edited to add: I estimate the saving to be approx 180 watts (of heat) per hour, or approx 4.3kw (of heat) per 24 hours.

It's 180 watts whether it lasts a second, a minute, an hour or all day! And it will save you 4.3 kWh per 24 hours!

[IanD]

6 hours ago, Willonaboat said:

 

How about assuming the power comes from solar, Ian (I have a widebeam, don't forget). Because with over 6kw on the roof, half of which will be at a negligable angle towards the sun (~3 degrees tilt) so not producing anything worthwhile in December, but the other half tilted at anything up to ~85 degrees in winter, I estimate that the MVHR electrical power will be met by solar even in winter *most of the time* and for the worst months (Dec, Jan) I am likely to be on shorepower for at least some of that time but with solar power generated prioritised via programing over shorepower. But this is my set of circumstances and use case, not necessarily yours or anyone elses.

 

Edited to add: I estimate the saving to be approx 180 watts (of heat) per hour, or approx 4.3kw (of heat) per 24 hours. This is based on a spreadsheet calculation that I did over a year ago but having just looked at it I can't recall how the hell I did it. It made sense at the time, honest Guv. All I can say is, the heat loss calulations have so far proved to be in the right ball park based on what we are experiencing in real life, so I'm buoyed with confidence that I'm not going to be a million miles out when everything is installed as planned. But remember, this is for a widebeam, not a narrowboat, so your circumstances and calculations will no doubt yield different results.

It's only fair to assume the power to run it comes from solar if you have enough solar power to meet all the boats needs, which is unlikely in winter even with a widebeam -- which is when you'll need heating and really want to avoid losing warm air through ventilation, and power is in short supply.

 

If you have to get some (or all) electrical power from a generator or running an engine, that's where every extra watt to run the added heat recovery load has to come from.

 

If you're plugged into shorepower the results are likely to be very different -- but in this case power isn't in short supply anyway, unlike when away from home.

 

I'll believe it's a workable idea on a narrowboat when a proper heat/power audit (including ventilation) shows that it is, and that it makes enough difference to heating requirements to justify fitting it. My suspicion is that it won't, but I'm perfectly happy to change my mind given evidence rather than speculation 🙂

 

It's got a much better chance of working on a wideboat with much more solar, lower surface area to volume ratio, and the possibility of fitting much thicker insulation -- but that's not the OP's target...

Edited December 29, 2023 by IanD

[Matt Wardman]

Can I ask for some help - what do I call the various spaces in a narrow boat, wider boat etc? This is for if I create some sort of power consumption spreadsheet model at the end.

 

In a house I would be talking about Kitchen, Living Room 1, Living Room 2, Study, Hall, Downstairs Bath, Bed 1, Bed 2, Bed 3, Upstairs Bath and so on.

 

Is there a list which covers the various spaces in a canal/river boat. I am thinking perhaps Galley, Saloon, Cabin 1, Cabin 2, Cabin 3 (in a long, wide barge?), Bath/Shower, Corridor (or perhaps Circulation Space).

 

I could just do Room 1 -> Room n, but it is perhaps better to get it roughly right if that is straightforward.

 

(I have some think-posts still to do on a few aspects, but TBH I'm not up to thinking on January 2nd so I'm doing something easier 🙃).

All comments are most welcome.

Edited January 2 by Matt Wardman

[BoatinglifeupNorth]

Keep it simple, on a typical layout Narrowboat from the bow(front) doors, Saloon, Galley, bathroom, bedroom, engine area, rear doors to stern deck.

 That’s in a Traditional hull design.

 There’s various layouts and hull designs, Semi-Trad, Cruiser, reverse-Layout also various lengths. I would just stick with the traditional layout for a 57ft Narrowboat.

 You’ll now get people saying, we’ll I’ve got a X/Y design, width & length.

 The common size is 57ft length, 6ft 10’ for Narrow and 10ft 6” for a widebeam.

 Keep it so people can understand and not massive rambling too technical posts as most will just switch off and the few tech heads/“figures show” posters will fill the Thread with their opinions and long winded threads and people will get bored with it. Also start a new Thread and Title and put it in the relevant “Boat Building/Technical” section, not “New to Boating/General” and I’m sure if you PM @Jen-in-Wellies she’ll highlight it in the relevant section if your research is helpful to most.👍

  

Edited January 2 by BoatinglifeupNorth

[IanD]

11 minutes ago, BoatinglifeupNorth said:

Keep it simple, on a typical layout Narrowboat from the bow(front) doors, Saloon, Galley, bathroom, bedroom, engine area, rear doors to stern deck.

 That’s in a Traditional hull design.

 There’s various layouts and hull designs, Semi-Trad, Cruiser, reverse-Layout also various lengths. I would just stick with the traditional layout for a 57ft Narrowboat.

 You’ll now get people saying, we’ll I’ve got a X/Y design, width & length.

 The common size is 57ft length, 6ft 10’ for Narrow and 10ft 6” for a widebeam.

 Keep it so people can understand and not massive rambling too technical posts as most will just switch off and the few tech heads/“figures show” posters will fill the Thread with their opinions and long winded threads and people will get bored with it. Also start a new Thread and Title and put it in the relevant “Boat Building/Technical” section, not “New to Boating/General” and I’m sure if you PM @Jen-in-Wellies she’ll highlight it in the relevant section if your research is helpful to most.👍

  

And when you're working out what will fit inside, use realistic figures for the internal width.

 

For example, my narrowboat (with good sprayfoam insulation, not extra-thick like you're proposing) is 6'1"/185cm wide at floor level, but narrows to something like 165cm at gunwale level (upper cabin walls step inwards by about 10cm per side) and 145cm at roof level due to the tumblehome of the sides of the cabin (inward slope about 10cm per side) -- the last two numbers are guesstimates, I haven't measured them.

[BoatinglifeupNorth]

8 minutes ago, IanD said:

And when you're working out what will fit inside, use realistic figures for the internal width.

 

For example, my narrowboat (with good sprayfoam insulation, not extra-thick like you're proposing) is 6'1"/185cm wide at floor level, but narrows to something like 165cm at gunwale level (upper cabin walls step inwards by about 10cm per side) and 145cm at roof level due to the tumblehome of the sides of the cabin (inward slope about 10cm per side) -- the last two numbers are guesstimates, I haven't measured them.

You see what I said, people will come on with my boat is Y&X not X&Y, it will be difficult to get accurate figures that will be workable with every build/boat.

 Let’s see what @Matt Wardman produces, hopefully in a new thread in the relevant section and hopefully it will be of use to some people. Then all the Tech heads can have their say with their opinions and technical advise.

 

[MtB]

6 hours ago, Matt Wardman said:

All comments are most welcome.

 

As BLUN said, start a new thread asking this. 

 

Lots of people will miss your question as it is piggy-backed into a thread on a different subject, which people are broadly bored with now. 

[Matt Wardman]

Cheers.

 

I'll take the advice, and start another thread in a few days.

In the meantime, thanks to everyone who has commented on my posts - most enjoyable.

And best wishes to anybody bobbing up and down or stranded at the end of a flooded pontoon because of all the extra water.