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?

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.

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

... and flattens your battery alarmingly fast! It's more than you would use for cruising. If the weather isn't excessively cold we often run a couple of fan heaters in the morning instead of lighting our oil stove but do so at the same time as running the generator to avoid charging losses.

I understand that the provenance of the HVO currently sold in the UK is sound - waste oils and fats, etc. I share your concerns about potential conflict with food supplies if/as demand increases.

I have come rather late to this discussion but should like to offer a few thoughts, some based on 8 years' experience, some more blue sky. I should appreciate input from members who might have more detailed knowledge than I. As I haven't read the whole thread I apologise if I am re-covering ground already covered. I don't believe that any boat doing more than token cruising can be 'carbon based fuels free' at this point in time. My approach favours incremental improvement so I'm happy to retain my diesel generator, taking steps to minimise its use while waiting for the day when I can take another tanker delivery of HVO. (We managed one in 2020, shortly before Crown realised the complexities of the then subsidy/tax situation.) When trying to assess your power requirements don't believe the fanciful claims made by people wanting to sell boats with large solar arrays. Assume that you will need 1 kWh/mile for cruising (it will probably be a bit less) and add in your domestic requirements (fairly straightforward). Then see if it adds up, remembering that, unless you spend a lot of time tilting and pointing your panels, you will get a maximum of 50% of their nominal output in the UK, something often forgotten (conveniently ignored?) by solar advocates. Having said that, power from rigid panels works out considerably cheaper than that from a diesel generator so is worth having on the basis of 'every little helps'. Power from flexible panels tends to be more expensive than diesel. Our experience, and that of other longer-term users, is that (semi-)flexible panels are damaged by heat so are not very durable. Ours died after about 3 years and there are lots of reports on the Internet of others not lasting more than 5. Most of their most vocal defenders haven't even got 3 years experience yet. If you must use flexible panels try to arrange some sort of cooling, possibly using the hybrid panels now becoming available to allow you to circulate cooling water. There can be little doubt that a water-source heat pump will be more efficient than an air-source one, though I would hesitate even to try to calculate how large the skin tanks to support one would need to be. Years ago, when radiant electric ceiling heating was popular for the bedrooms of new-build houses with electric underfloor heating downstairs, I did some development work on it. Our findings then, seemingly still accepted, were that the system needed 20-25% less energy to provide comparable comfort. (For anyone unfamiliar with such systems, this is because the radiant heat keeps people warm while the air temperature remains lower than in a convection-based system so losses are less.) Nobody would consider using direct electric ceiling heating on a narrowboat but wet systems, using 'capillary matting' are readily available and will run happily on the sort of 30-40 degree output temperatures at which heat pumps work best. We have underfloor heating (using waste heat from our generator) in our boat but, like most boats, the floor area is relatively small so 500W is about the most we can obtain. However, the ceiling area is 3-4 times as large, giving the potential for up to 2 kW, probably, given the higher efficiency, enough to provide comfort in all but the most extreme weather. With a bit of luck a water-source pump would give about 400% efficiency so the power requirement would be more like 0.5 kW than the 1 kW previously suggested. The only problem I can foresee is that ceiling heating works best if the ceiling is a bit higher than is usual in a narrowboat, a minimum of 2.25m often being suggested. Maybe OK for vertically challenged boaters with Tyler-Wilson shells but not so good for my 6'2" in a Roger Farringdon! Capturing waste heat from showers, sinks - and even loos - might be possible, if a bit complex. The subject of double glazing has come up a few times. We started with typical, thin (12mm) panels, upgraded those to 18mm and then again to what are called 'warm edge' units (again 18mm). As most of the heat lost through double-glazed panels is at the edges and, given the small size of boat windows, there is a lot of 'edge', these were a big improvement - until they started to fail. We only have 8 or 9 (of 22) still sound after 3½ years (and that after 3 were replaced under warranty). Without going into detail, the problem arises from where and how the desiccant is stored. Not sure if this failure rate is normal or whether our local glass company just buys from a particularly careless manufacturer. The one panel which came from another manufacturer is one of those which is still OK but that's hardly statistically significant. Over to you.

I can only say that I am amazed.

We have done Crick 3 times as a show-boat, living aboard on each occasion. Having 100+ people through your boat each day is utterly exhausting but their comments can be both interesting and rewarding. The main practical requirements are an early start so that all your personal stuff can be stowed away before the hordes descend and a stock of ready meals as you will be too kn*****ed to cook afterwards. Didn't things like the white boat in the pictures use to be called 'Houseboats'? Not intended to be moved.

Almost all the figures I use are from specifications as I don't have the equipment to undertake independent measurements. I have always assumed that the problem with Vicprop and similar sites is that they are set up for diesels, which have significantly lower torque at maximum revs than at (approx) 2/3rds maximum. As props are basically sized for maximum rpm, it specifies them on the basis of this reduced torque. A Beta 43's torque at maximum revs, when I assume that it is putting out its full 43 hp, is just under 110 Nm - less than 75% of ours - though there is an interesting mathematical mismatch here. Power = revs*torque = 2,800 *110/1000 = 25.5kW = 34 hp. What happened to the other 9? Not sure where I got this idea from but isn't there a torque^2 factor somewhere in propeller theory? If so, we would sit at 185% of the Beta 43, close enough to the double I had observed. As for reaching 1,000 rpm, we didn't monitor it closely as we were principally watching a rather dodgy speedo app to check that we could reach 6 mph. However, we certainly got damned close, too close to account for the discrepancies we are discussing.

Data entered for Ampère. all units as required. Length: 55 Beam: 6.5 Draft: 2.5 Displacement: 51500 Engines: 1 HP: 20 RPM: 1000 Gearing: 1 Bearings: 1 Speed: 5 (won't allow 5.2) This then comes back with 18.2" x 11.3" for a 3-bladed prop, suggesting at the same time that this will achieve 5.65 knots (6.5 mph). Upping the power to 40 hp produces the suggestion of 20.9" x 13.6" and a maximum speed of 7.13 knots (8.2 mph). We didn't investigate the maximum speed with our original, 19" x 12" prop as we were never in suitable water but can say that with our current 20" x 14" we can just about achieve our target 6 mph.

I need more time to thinks about some of your points Ian but I would say that I wouldn't trust Vicprop as far as I could throw it. If you feed the correct figures for Ampère into it it suggest an 18" x 11" prop. That would almost certainly not even give the 6 mph maximum speed requested. On the recommendation of Crowthers we originally fitted a 19" x 12" prop and were clearly under-propped. After our engineer gave them more information about our motor's characteristics they upgraded their recommendation to our current 20" x 14". This is much better but still revs so freely that I suspect we could go slightly larger still and still reach maximum revs. To get a sensible suggestion from Vicprop you need to tell it that you have double the power you actually have. Inputting 40 hp instead of our actual 20 produces a 21" x 14" recommendation, slightly bigger than what we have. Putting numbers into your tip-speed equations, we score 20,000 and 0.7 which I think agrees that we are likely still to be slightly under-propped. Only the £1,000 cost of doing so deters me from trying a larger prop.

I'm not going to get into a detailed discussion with you, if only because I'm not an engineer so have only a qualitative understanding of the subject, but we have had this discussion within the Sustainable Boating Group (where we have a couple of engineers) and the conclusion seemed to be that it isn't the torque required to turn the prop which matters - you can easily do it by hand at zero revs - but that required to accelerate it instantaneously from 0 to 400 rpm when drive is engaged. I can't remember the acceleration formula but the torque requirement is much greater. An electric motor winds the speed up relatively gently so, as well as probably having more torque available, the demand is not so great. On the subject of propeller efficiency I offer two comments. Working backwards from our overall performance by removing the 'stopped' and 'diesel efficiency' savings suggests that we benefit by about 30% from our larger prop. That said, while the 'stopped' saving can be calculated quite accurately, the 'diesel efficiency' one is only an educated guess based on generic diesel engine consumption curves so I wouldn't argue too hard. However, as propeller slippage (at 3 mph in open water) seems to vary from less than 40% for Firecrest (about 45% for us) to about 60% for boats with typical diesel installations it is hard to believe that the benefits of larger propellers aren't more than 10-20% unless there are compensating factors elsewhere in the overall efficiency equation. I can see that greater grip might require more power and that might be self-compensating, though I'm having a similar discussion with a retired aero engineer who provided me with an overall efficiency equation which contained the figure 0.5 for propeller grip (1-slippage, I assume). I'm still waiting for an answer to my question about what happens if this is changed to 0.4 or 0.6.

Thanks Ian. I believe that my comments about propellers are justified. We chose to have a deep draft (30") for aesthetic reasons so had no problem fitting a 20" prop. However, the most efficient current boat of which I know (Firecrest - they have speed/power curves in their blog) is only 24" draft and has a smaller, 4-bladed prop. The new eco-boat to be exhibited at Crick (by Cadal Craft) actually has a parallel hybrid (for reasons to do with taking it to the Continent) with 3:1 reduction. However, reduction gearing doesn't get you away from the fact that diesel torque starts low, increases to a maximum at about 2/3rds maximum revs, and then falls again. I can't be sure but suspect that even with 3:1 reduction a 2 litre diesel wouldn't be able to start our prop. Given that most of the electric motors offered for (inland) boats run at about 1,500 rpm (ours is 1,000), much the same as diesels with 2:1 reduction, they have to be fitted with diesel-sized propellers so don't max out their potential. If I were doing a new installation, I would be tempted to gear down a 1,500 rpm motor by something like 2:1 and then fit the biggest prop I could, bearing in mind that, as well as increasing the number of blades, pitch can be substituted for diameter, albeit with some loss of efficiency. Given the torque characteristics of diesels I've always wondered why strategies used elsewhere, or in one case previously on boats, aren't used. This case is a bl**dy big flywheel, the inertia of which would help accelerate the prop to the point where the diesel could cope. This was common in diesels of 40+ years ago but has been engineered out as engine speeds have increased. The second is a clutch, used in almost all road vehicles to overcome exactly the same problem; I used to have a motorbike with a centrifugal clutch, something which might work well on a propeller. Finally there is the "mild hybrid" option where an electric motor assists a smaller diesel, much like the modern London buses in which an electric motor gets them rolling before the diesel takes over. All these would permit the use of smaller, less thirsty engines (20 hp instead of 40?), though only the last could assist at maximum revs. And that's before we get onto continuously variable gearboxes! We don't have any solar at the moment. We had 4x100W of flexibles fitted from new but they failed prematurely (not uncommon with flexibles) and, as the power from them would have cost about double that from our generator even if they had lasted 10 years, we didn't replace them immediately. We are about to have another shot with 2x215W of rigids, having finally found some that will fit in the spaces available on our roof without getting in the way of poles, ropes, etc. Having said that, previous experience suggests that, unless we can improve the gain significantly by angling our panels, we will get only about 10% of a day's usage in mid-summer and very little in mid-winter, about 3-4% overall. That's hardly a game changer. However, solar can work very well for a boat which has room for more solar and/or doesn't cruise as much as we do. Take a look at Firecrest's blog for their experience.

A further thought about peterboat's comment. I thoroughly applaud the use of a 2nd hand generator. I bought a continuously-rated, 6 kVA, ex-standby unit with just 24 hours on the clock for £1,500 in anticipation of having Ampère built but was talked out of using it by our electrical engineer on the grounds that we needed something more powerful. I didn't discover until it was too late that our 8 kVA F-P has to be downrated to 70% (5.6 kVA) for "continuous running" so we would have charged marginally quicker (and been £12,000 better off) if we had stuck with the original. To be fair, this was his only significant misjudgement and his advice was invaluable in many other respects, leaving us with a boat which hasn't had a single electrical problem in 7 years. The original generator is still in Stockport if anyone wants one.

Not going to Crick. Done it 3 times as a show boat and that's quite enough. We'll be somewhere near Aylesbury.