Proposed new accessible electric narrowboat.

[Willonaboat]

21 minutes 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 to the assume they mean what you wrote, when they didn't actually say that. 

 

 

 

"Heat recovery efficency: Up to 94%"

 

Details on the middle graph on page 4.

 

[Alan de Enfield]

8 minutes ago, Willonaboat said:

"Heat recovery efficency: Up to 94%"

 

Typical marketing speak (and I speak as a Marketeer, a Post Graduate Degree in marketing and member of the Institute of Marketing)

 

That comment could mean that if they achieve (say) a 50% efficiency it is within the stated parameters of UP TO 94%

Edited December 29, 2023 by Alan de Enfield

[Willonaboat]

7 minutes ago, magnetman said:

Also someone looking to have an accessible electric Boat based in London may not ever get to narrow canals in the first place. 

 

I would be looking at something a bit wider myself. Not a big fat horror box but something like 9ft beam. It may seem a pointless width for a Boat but it gives more space than a narrow and one does not receive endless streams of abuse from Harold Shipman beard,-wearing owners of narrow Boats. 

 

 

May I, with a high degree of bias, suggest 10' 6" beam with a chined hull as the sweet spot between asthetics, space and practicality?

[MtB]

7 minutes ago, Willonaboat said:

 

"Heat recovery efficency: Up to 94%"

 

Details on the middle graph on page 4.

 

 

My point exactly. No definition of what "recovery efficiency" actually means. 

 

 

[magnetman]

Thats about right. One of my Boats is 10ft7 wide and the other is 9ft wide. Both of them have Boat shaped hulls. 

 

So yes. 

[Willonaboat]

1 minute ago, Alan de Enfield said:

 

Typical marketing speak (and I speak as a Marketeer, a Post Graduate Degree in marketing and member of the Institute of Marketing)

 

That comment means that if they achieve (say) a 20% efficiency it is within the stated parameters of UP TO 94%

 

This really is like pulling teeth. Look at the spec sheet. Look at the graph. Or don't.

[magnetman]

Anyone doing electric, if they can get away from it being narrow, is very well served having a sensible underwater shape.

 

[Alan de Enfield]

4 minutes ago, Willonaboat said:

 

This really is like pulling teeth. Look at the spec sheet. Look at the graph. Or don't.

 

I did - the figures quoted of ~80 - 92% are under specific conditions - kitchen and a wet room (both very high humidity) and a rate of exchange which would never be found on a NB.

 

A NB is pretty much a single room.

Edited December 29, 2023 by Alan de Enfield

[IanD]

2 minutes ago, Alan de Enfield said:

 

I did - the figures quoted of ~80 - 92% are under specific conditions - kitchen and a wet room (both very high humidity) and a rate of excvhange which would never be found on a NB

Actually the efficiency is highest at lower air exchange rates -- the problem is that even these are far too high for living accomodation use in a narrowboat.

[MtB]

4 minutes ago, Willonaboat said:

 

This really is like pulling teeth. Look at the spec sheet. Look at the graph. Or don't.

 

Ok lets get into detail. For simplicity, what would, say "100% heat recovery" mean to you? 

 

Would it mean for example, on a freezing cold day, the inside air at 20c is being blown out and replaced by incoming air which has raised up to 20c by our imaginary 100% efficient heat exchanger?

 

Or something else?

 

I'm really keep to understand this. Humour me if necessary, please!

 

 

 

 

[IanD]

7 minutes ago, Willonaboat said:

 

May I, with a high degree of bias, suggest 10' 6" beam with a chined hull as the sweet spot between asthetics, space and practicality?

Indeed, the main reason for choosing a narrowboat is if you want to be able to explore the narrow canals (and get from the northern to the southern canals, because there's no wide link). If not, a wider boat offers much more usable living space, and more opportunities for thick insulation 🙂

[Willonaboat]

27 minutes ago, IanD said:

Actually the efficiency is highest at lower air exchange rates -- the problem is that even these are far too high for living accomodation use in a narrowboat.

 

Correct - highest efficiency at lower air flow rates. Hence, the statement on the spec sheet and as shown by the graph, "heat recover efficiency: up to 94%". I accept that the minimum air flow on this unit might be too high for a narrowboat. As I said, other units are available with lower air flow rates.

 

 

21 minutes ago, MtB said:

 

Ok lets get into detail. For simplicity, what would, say "100% heat recovery" mean to you? 

 

Would it mean for example, on a freezing cold day, the inside air at 20c is being blown out and replaced by incoming air which has raised up to 20c by our imaginary 100% efficient heat exchanger?

 

Or something else?

 

I'm really keep to understand this. Humour me if necessary, please!

 

 

Try here (or google) https://www.architecturelab.net/how-heat-recovery-systems-work/

 

Another benefit of MVHR units that hasn't yet been mentioned are the in-built filtration systems (some better than others) which filter incoming air to varying sizes of particulates. Some of the better models allow for fine(r) filters to be used.

 

Edited December 29, 2023 by Willonaboat

[MtB]

5 minutes ago, Willonaboat said:

 

Correct - highest efficiency at lower air flow rates. Hence, the statement on the spec sheet and as shown by the graph, "heat recover efficiency: up to 94%". I accept that the minimum air flow on this unit might be too high for a narrowboat. As I said, other units are available with lower air flow rates.

 

 

 

Try here (or google) https://www.architecturelab.net/how-heat-recovery-systems-work/

 

 

Clearly you are avoiding the question I'm asking. 

 

Never mind. 

 

 

[IanD]

9 minutes ago, Willonaboat said:

 

Correct - highest efficiency at lower air flow rates. Hence, the statement on the spec sheet and as shown by the graph, "heat recover efficiency: up to 94%". I accept that the minimum air flow on this unit might be too high for a narrowboat. As I said, other units are available with lower air flow rates.

 

 

What still matters most is how much heat will actually be recovered at low (narrowboat-appropriate) air exchange rates, and how this compares to all the other sources of heat loss on a narrowboat.

 

Also how much "high-grade power" (electricity) is needed to run it compared to how much "low-grade heat" (from heating system) is saved -- low-grade heat (e.g. from burning diesel or HVO at ~85% efficiency) is a lot cheaper than high-grade electrical power (e.g. from a generator at ~25% efficiency).

 

This is one reason that heat pumps on a boat (instead of a CH boiler) are not as attractive as they might at first appear -- you need to look at the bigger picture, especially where the energy is coming from. If you're plugged into shoreline (with getting on for 50% renewable grid power in the UK) then the picture is very different e.g. for liveaboards which spend most of their time in a marina.

Edited December 29, 2023 by IanD

[Willonaboat]

17 minutes ago, IanD said:

 

What still matters most is how much heat will actually be recovered at low (narrowboat-appropriate) air exchange rates, and how this compares to all the other sources of heat loss on a narrowboat.

 

Also how much "high-grade power" (electricity) is needed to run it compared to how much "low-grade heat" (from heating system) is saved -- low-grade heat (e.g. from burning diesel or HVO at ~85% efficiency) is a lot cheaper than high-grade electrical power (e.g. from a generator at ~25% efficiency).

 

This is one reason that heat pumps on a boat (instead of a CH boiler) are not as attractive as they might at first appear -- you need to look at the bigger picture, especially where the energy is coming from. If you're plugged into shoreline (with getting on for 50% renewable grid power in the UK) then the picture is very different e.g. for liveaboards which spend most of their time in a marina.

 

At the 15l/s air flow setting (it can be configured lower with the S-14 controller) the unit I linked to draws 9 watts. Or about 4.5a/h per day from a 48v battery bank

[IanD]

7 minutes ago, Willonaboat said:

 

At the 15l/s air flow setting (it can be configured lower with the S-14 controller) the unit I linked to draws 9 watts. Or about 4.5a/h per day from a 48v battery bank

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.

 

At typical narrowboat airflows (pretty low!), how much energy per day do you estimate it will recover? How does this compare to heat loss through other sources? (e.g. through roof/cabin/hull)

 

The numbers should make it obvious whether it's worth doing or not -- ignoring the cost of the installation (how much?), which I suspect will more than wipe out any energy savings...

Edited December 29, 2023 by IanD

[Rishworth_Bridge]

Perhaps I can throw a couple of curved balls relating to boat heating and a comment about batteries/charging.

1. Is it possible to address the problem of icing of water-source heat pump sources by using a propeller (think gentle bow thruster) to blow canal water continuously over (internally-mounted) input coils?
2. In a boat equipped with a heat pump would it be simpler to recover heat from stale warm air by passing it through an air/water heat exchanger in the heat pump input system?
3. The next big step in electric propulsion, long promised but yet to arrive, is the solid electrolyte battery. These are said to be in an advanced stage of development, with Toyota in particular, suggesting for some years that they would have them in their cars by now. This hasn't happened but, if projected figures are correct, when they do the energy density should be high enough for the battery volume we have in Ampère (about a cubic metre) to support our (fairly gentle) regime for a week, making managing without a generator at least a theoretical possibility. However, this is a 2-edged sword. Currently, a 16A overnight plug-in is sufficient for a couple of days, meaning that a 32A one should suffice for 4 days. Both of these would be possible using our existing inverter/charger with power at sensible prices governed by the electricity resale regs. However, if it becomes necessary to double this charging rate again we get into fast chargers, to which the regs do not apply, so could finish up paying more for our power (as with cars) than we would burning HVO in our generators.
4. Incidentally, the Thames has, in theory, enough charging points (at locks) for a boat like ours to manage without using the generator, though about half were out of action when we were last there.

[Alan de Enfield]

17 minutes ago, Rishworth_Bridge said:

Both of these would be possible using our existing inverter/charger with power at sensible prices governed by the electricity resale regs. 

 

As a reseller of electricity (caravan park) which has controlled resale prices, we were informed by Ofcom that electricity supplied by us for the charging of EVs does not fall undeer the resale legislation as we are free to charge whatever we like. The Government made this decision to allow for the costs of the necessary infrastructure to be recouped.

 

I would not base your 'economic plans' for charging electric boats on the assumption that you will get 'domestic' rates of electricity. You may well, by default, if you plug into the standard bollard, but if moorings for electric boats become the norm you may well find that you are paying a premium for the pleasure.

[magnetman]

They would have to charge a premium otherwise the service would not be available very often because of too much demand. 

 

I'm not sure how it works on the Thames lock electric points. I know one has to pay an EA mooring fee which is about £10 for 24hrs.

 

I think you pay a bit extra to get a certain amount of electric. Whether the EA could look at charging more for the electric is an interesting question but I think its only a 16 amp supply. 

 

 

 

 

So hypothetically if it was 16A outlet thats 3Kw and you moored for 12hrs so 36Kwh for £10 plus lets say £0.25 so another £9 on the electric. 

 

So that would be £20 to go for 10 hours motoring? 3mph

 

30 miles for £20? 

Edited December 29, 2023 by magnetman

[Rishworth_Bridge]

1 minute ago, Alan de Enfield said:

 

As a reseller of electricity (caravan park) which has controlled resale prices, we were informed by Ofcom that electricity supplied by us for the charging of EVs does not fall under the resale legislation as we are free to charge whatever we like. The Government made this decision to allow for the costs of the necessary infrastructure to be recouped.

 

I would not base your 'economic plans' for charging electric boats on the assumption that you will get 'domestic' rates of electricity. You may well, by default, if you plug into the standard bollard, but if moorings for electric boats become the norm you may well find that you are paying a premium for the pleasure.

Thanks for that Alan. Presumably you have to have dedicated EV chargers to make differentiation possible. At the moment marinas seem to be covered so it's probably something that hasn't received much thought - yet. I don't expect to get the use of charging facilities for free as I recognise that there are costs involved to the provider but should prefer that to take the form of a reasonable mooring charge (£2-5 per night rather than the £15-20 which seems to be the norm in marinas nowadays) with the actual power still supplied at cost.

 

Referencing Magnetman's comments on the Thames. There doesn't seem to be a single system. Some places charge a fixed amount with power included while others charge for it separately. Overall, cost tends to be £10-15, which isn't bad compared with using marinas but equally isn't really competitive with using the generator, though we do it to be that bit greener. We try to arrange to plug-in when we want to float the batteries as doing so using the generator is very inefficient.

[Alan de Enfield]

10 minutes ago, Rishworth_Bridge said:

Thanks for that Alan. Presumably you have to have dedicated EV chargers to make differentiation possible

 

That is the only practical way that I can see it being achievable. We have not gone down that route yet - it cost us £20,000 to get a pole mounted upgraded transformer installed which doesn't have a great deal of spare capacity when the vans are in use. There is no way I'm going to spend another £20k+ upgrade just to be able to charge an 'odd' electric car.

If they want to charge the car then they can use a 'granny lead' thru a window and get the benefit of 'cheap' electricity but have to put up with it taking many hours to charge, or, they can drive around and find a supermarket charger and pay whatever they charge.

[MtB]

55 minutes ago, Rishworth_Bridge said:

Is it possible to address the problem of icing of water-source heat pump sources by using a propeller (think gentle bow thruster) to blow canal water continuously over (internally-mounted) input coils?

 

And I'll bung another curved ball over to you!

 

Did you know permission (i.e. a licence) from CRT is required to abstract heat from the canal?

 

 

 

 

[Rishworth_Bridge]

Certainly didn't, though I can see that it might be an issue for canal-side properties. (The only property I know of using such a system is on CRT's Kennet) Can you quote chapter and verse for boats, please?

[agg221]

2 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.

 

At typical narrowboat airflows (pretty low!), how much energy per day do you estimate it will recover? How does this compare to heat loss through other sources? (e.g. through roof/cabin/hull)

 

The numbers should make it obvious whether it's worth doing or not -- ignoring the cost of the installation (how much?), which I suspect will more than wipe out any energy savings...

Recognising that this thread has drifted away from the OP's narrowboat question on to boat insulation in general, so @Willonaboat will exceed the figures calculated below, this is actually a very simple calculation to answer:

 

Assume a cabin volume of 15x2x2m for a narrowboat, ie 60m3

Assume 'normal' air with a specific heat capacity of 1.012J/g-1K-1

Assume sea level air density of 1.204kg/m3 at 20degC

Assume you are using the air exchange system to replace standard vents

Assume you are heating the inside air to 20degC and the outside air is 0degC

Assume you are aiming for the recommended minimum of 0.35 air changes per hour

Assume you achieve 'real world' efficiency of 80% on the heat exchanger system (total efficiency)

 

The boat contains 60x1.204=72kg of air

The energy required to raise its temperature from outside to indoor temperature is 72x20x1.012=1.5kJ=0.41kWh

The energy recovered from a full air change by the recovery system is therefore 0.41x0.8=0.33kWh

The energy recovered per day is 0.33x0.35x24=2.7kWh

 

These figures are of course also compared against your worst case generation efficiency of 10%. In practice, as I am sure you know, if you are aiming for efficient electrical generation you would use a dedicated system, and you would also recover the thermal energy to achieve heating and hot water, but it still works, on a narrowboat, with the least efficient charging system possible.

 

You can disregard other sources of loss, since this is an independent source of loss, ie you will need the same additional heat input to replace conductive losses irrespective of the venting system.

 

Alec

Edited December 29, 2023 by agg221

[Alan de Enfield]

29 minutes ago, agg221 said:

The energy required per day is 0.33x0.35x24=2.7kWh

 

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, its dark and has not stopped raining for days, you don't have a generator, or, an engine, and their are no 'hook-ups' canalside ?

 

All that assumes that you do not have any other electrical consumption (propulsion, cooking, lighting, heating, pumps etc etc)

Edited December 29, 2023 by Alan de Enfield