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phasing out of fossil fuels - programme


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2 hours ago, Mike Todd said:

Is that correct? It assumes that there care fixed emissions regardless of load or at least a reducing proportion. Seems unlikely but I have not seen any data on it.

as much as what? momentum is a function of mass . . . 

The genny spins at 3000 rpm, even with no load according to the figures it doesn't use much more fuel at full load than light load so I am better loading it up and running it less

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23 minutes ago, cuthound said:

 

This logic doesn't really apply to diesel engines. Capacity is irrelevant as the CO2  comes from the fuel burnt and diesel engines can only burn the fuel the pump injects into them, which is the amount needed to support the load applied at the time.

 

This is the reason why canal boats all seem to use about 1.5 litres per hour at normal cruising speed, irrespective of engine size. Frictional and pumping losses account for the minor variations between engines.

I would think that serial hybrids will cut emissions by a quarter as long as you have plenty of solar. Small engines running hard are more efficient than large engines on very light load 

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26 minutes ago, peterboat said:

I would think that serial hybrids will cut emissions by a quarter as long as you have plenty of solar. Small engines running hard are more efficient than large engines on very light load 

 

Only because of the lower frictional and pumping losses of smaller engine, which I had already stated. If there is another reason for lower fuel consumption please provide evidence of this.

Edited by cuthound
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3 minutes ago, cuthound said:

 

Only becauseof lower frictional.and pumping losses. If there is another reason for lower fuel consumption please provide evidence of this.

It doesn't run when not needed, when I am in a lock no motor running, whereas nobody turns off the engine in a lock or when mooring up etc do they?

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Just now, peterboat said:

It doesn't run when not needed, when I am in a lock no motor running, whereas nobody turns off the engine in a lock or when mooring up etc do they?

 

I agree that any engine will produce less emissions if turned off in a lock, but you could do that with a conventional diesel if you wanted to.

 

Turning the engine off in locks is to do with the method of operation, rather than small engines being more efficient, which is what you said.

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My attention has only just been drawn to this thread and there is far too much to comment on everything. However, as the owner of an electric-drive boat (I don't like the term 'Serial Hybrid' as such systems lack the either/or characteristics of a hybrid) with 3 years of design, and 6 years of operating, experience under my belt I think I might be able to add a few facts about performance to what, unlike the technical contributions, appears to be mostly speculation.

 

The factor that seems to have been missed is the propeller. These 'slip' in water, meaning that each turn of the propeller only moves the boat forward by a proportion of its pitch, typically 10-50%. The larger the propeller and the slower it turns the greater this percentage will be and, as their torque characteristics mean that electric motors can turn larger propellers more slowly than diesels, this means that more thrust is available to the electric-drive boat.  This can be seen in a number of ways, the most obvious being the much lower power required for cruising. We, at 23 tonnes, get 3.3 mph from our 14" x 12" propeller using 2.25 kW @ 430 shaft rpm in open water. That's about 55% propeller efficiency. Lighter boats with similar drive systems report that they need between 1.8 and 2,2 kW in similar situations. This is to be compared with the 15-20 kW (less gearing losses) @ 700 rpm of a typical 40 hp diesel with 2:1 reduction and a 17" or 18" x 12" propeller. This (plus a couple of other factors) leads to the fuel efficiency that has already been mentioned by others. We use only about a third of the diesel through our generator that we would need for a diesel propulsion engine.

 

The other point on which I should like to comment is that of power in demanding situations. It is a fallacy that huge amounts of power are necessary. What matters when manoeuvring or going against a strong stream is thrust and, for the above reasons, the electric drive has plenty - as did working boats with large propellers driven by high torque diesels like Lister JP2s and Russell Newburys. The only reason for needing such high powered diesels is that they are driving propellers which are inefficient because they are too small and run too fast.

 

Finally, something to think about. While waiting for the hundreds of charging stations necessary to make plug-in boating viable the best option for powering a narrowboat  is likely to be a small (1 kW) fuel cell running 24/7 on Propane, with a modest bank of supercapacitors rather than batteries. This should give a fuel saving in excess of 80% relative to a diesel and be cheaper to install than the current type of electric drive as well as providing all the hot water and much of the space heating. The only problem is that nobody seems to want to supply suitable fuel cells in anything less than container loads. If anyone knows any different (Solid Oxide cell of approx. 1 kW) I'd like to know as I'll be first in the queue to fit one.

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3 minutes ago, peterboat said:

It doesn't run when not needed, when I am in a lock no motor running, whereas nobody turns off the engine in a lock or when mooring up etc do they?

I do when locking wherever possible.

Outboard powered with a pull start as well as electric,and switch off while setting the lock,bowhaul into the lock,do the necessary (some locks take forever to fill) restart with the pull start (saves wear and tear on the starter and battery) and carry on.

Saves fuel and pollution,and is nicer sitting on the lock beam in silence.

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43 minutes ago, cuthound said:

 

I agree that any engine will produce less emissions if turned off in a lock, but you could do that with a conventional diesel if you wanted to.

 

Turning the engine off in locks is to do with the method of operation, rather than small engines being more efficient, which is what you said.

Diesel engine generators are often called on to follow the load. That means that their output must be equal to the system load (or to the system load less the production of any other generators that might be on; this is called the net load). As the load may go up and down, so must the electricity generated. This is known as part load operation. Generally, the conversion efficiency is less at part load than at full load. Fuel consumption over the full range of operation is summarized in fuel curves. In these curves, fuel consumption is graphed against power. Figure 7 shows a typical example.

 

See image below for full explanation, however my boat requires 3.3 kw to cruise at 3mph which means the genny can produce that in just over half an hour. Also a hard working engine is cleaner and more efficient than a large engine just idling plenty on the net for it.

My own boat had a modern 2250 cc engine, most of the time it was just over idle, the genny is 460cc and always spinning at 3000rpm right in its maximum powerband so it running efficient and cleanly as its governor keeps it right for the load app;ied

3-s2.0-B012176480X003600-gr7.jpg?_
Edited by peterboat
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37 minutes ago, Rishworth_Bridge said:

My attention has only just been drawn to this thread and there is far too much to comment on everything. However, as the owner of an electric-drive boat (I don't like the term 'Serial Hybrid' as such systems lack the either/or characteristics of a hybrid) with 3 years of design, and 6 years of operating, experience under my belt I think I might be able to add a few facts about performance to what, unlike the technical contributions, appears to be mostly speculation.

 

The factor that seems to have been missed is the propeller. These 'slip' in water, meaning that each turn of the propeller only moves the boat forward by a proportion of its pitch, typically 10-50%. The larger the propeller and the slower it turns the greater this percentage will be and, as their torque characteristics mean that electric motors can turn larger propellers more slowly than diesels, this means that more thrust is available to the electric-drive boat.  This can be seen in a number of ways, the most obvious being the much lower power required for cruising. We, at 23 tonnes, get 3.3 mph from our 14" x 12" propeller using 2.25 kW @ 430 shaft rpm in open water. That's about 55% propeller efficiency. Lighter boats with similar drive systems report that they need between 1.8 and 2,2 kW in similar situations. This is to be compared with the 15-20 kW (less gearing losses) @ 700 rpm of a typical 40 hp diesel with 2:1 reduction and a 17" or 18" x 12" propeller. This (plus a couple of other factors) leads to the fuel efficiency that has already been mentioned by others. We use only about a third of the diesel through our generator that we would need for a diesel propulsion engine.

 

The other point on which I should like to comment is that of power in demanding situations. It is a fallacy that huge amounts of power are necessary. What matters when manoeuvring or going against a strong stream is thrust and, for the above reasons, the electric drive has plenty - as did working boats with large propellers driven by high torque diesels like Lister JP2s and Russell Newburys. The only reason for needing such high powered diesels is that they are driving propellers which are inefficient because they are too small and run too fast.

 

Finally, something to think about. While waiting for the hundreds of charging stations necessary to make plug-in boating viable the best option for powering a narrowboat  is likely to be a small (1 kW) fuel cell running 24/7 on Propane, with a modest bank of supercapacitors rather than batteries. This should give a fuel saving in excess of 80% relative to a diesel and be cheaper to install than the current type of electric drive as well as providing all the hot water and much of the space heating. The only problem is that nobody seems to want to supply suitable fuel cells in anything less than container loads. If anyone knows any different (Solid Oxide cell of approx. 1 kW) I'd like to know as I'll be first in the queue to fit one.

I am in my third year of electric now I am fitting the genny ready for constant cruising, in the past solar and the whispergen for domestic hot water/central heating electric has worked. The genny will heat water as well along with charging the both battery banks in poor weather.

The propeller was the hardest part I had a few to choose from and in the end cut my own down to get what I really wanted

Fuel cell wise no interest for me as calor charge an arm and a leg for the stuff and its still a fossil fuel although cleaner, full biodiesel suits me better as it is waste repurposed.

Glad that somebody else out there is as mad as me ?

Edited by peterboat
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7 minutes ago, peterboat said:

Diesel engine generators are often called on to follow the load. That means that their output must be equal to the system load (or to the system load less the production of any other generators that might be on; this is called the net load). As the load may go up and down, so must the electricity generated. This is known as part load operation. Generally, the conversion efficiency is less at part load than at full load. Fuel consumption over the full range of operation is summarized in fuel curves. In these curves, fuel consumption is graphed against power. Figure 7 shows a typical example.

 

I cant get the image to copy, however my boat requires 3.3 kw to cruise at 3mph which means the genny can produce that in just over half an hour. Also a hard working engine is cleaner and more efficient than a large engine just idling plenty on the net for it.

My own boat had a modern 2250 cc engine, most of the time it was just over idle, the genny is 460cc and always spinning at 3000rpm right in its maximum powerband so it running efficient and cleanly as its governor keeps it right for the load app;ied

3-s2.0-B012176480X003600-gr7.jpg?_

 

Yes that it what I said, engine capacity is largely irrelevant for diesel engines. It is always about half a pint of fuel (0.28 litres) consumed for every kWh generated.

 

I had a 41 year career in critical power and attened hundreds if not thousands of factory and site commissioning tests for diesel generators from 10kVA up to about 3MVA, where the fuel consumption against load was accurately measured using calibrated fuel flow instrumentation and calibrated load banks. All produced the graph show above.

 

Still waiting for the evidence that small engines are more efficient than larger ones, once frictional and pumping losses have been taken into account.

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3 minutes ago, cuthound said:

Yes that it what I said, engine capacity is largely irrelevant for diesel engines. It is always about half a pint of fuel (0.28 litres) consumed for every kWh generated.

 

 

I've always worked on :

 

Diesel engines using approximately 1 gal  (4.4 litres) per hour per 20 HP developed :

Fuel consumed is proportional to the power developed

Power developed is approximately proportional to the cube of the engine revs

Hence fuel consumed is proportional to the cube of the engine revs.

 

Consumption = C x RPM3

Where C = Max Fuel Consumption at WOT / RPM3

(Take revs as ‘single figures’ ie 2000 rpm as 2.0, & 2600 rpm as 2.6)

 

My engines are Ford 2725E engine & Max fuel consumption is 28 litres at 2600 rpm

Therefore C = 1.59

 

At 1000 rpm.                1.59 x 1.03 = 1.6 litres per hour

At 1100 rpm                 1.59 x 1.13 = 2.1 litres per hour

At 1200 rpm                 1.59 x 1.23 = 2.7 litres per hour

At 1300 rpm                 1.59 x 1.33 = 3.5 litres per hour

At 1400 rpm                 1.59 x 1.43 = 4.4 litres per hour

At 1500 rpm                 1.59 x 1.53 = 5.4 litres per hour

At 1600 rpm                 1.59 x 1.63 = 6.5 litres per hour

At 1700 rpm                 1.59 x 1.73 = 7.8 litres per hour

At 1800 rpm                 1.59 x 1.83 = 9.3 litres per hour

At 1900 rpm                 1.59 x 1.93 = 10.9 litres per hour

At 2000 rpm                 1.59 x 2.03 = 12.7 litres per hour

At 2100 rpm                 1.59 x 2.13 = 14.7 litres per hour

At 2200 rpm                 1.59 x 2.23 = 16.9 litres per hour

At 2300 rpm                 1.59 x 2.33 = 19.3 litres per hour

At 2400 rpm                 1.59 x 2.43 = 22.0 litres per hour

At 2500 rpm                 1.59 x 2.53 =  24.8 litres per hour

At 2600 rpm                 1.59 x 2.63 =  28.0 litres per hour

Edited by Alan de Enfield
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1 minute ago, Alan de Enfield said:

 

I've always worked on :

 

Diesel engines using approximately 1 gal  (4.4 litres) per hour per 20 HP developed :

Fuel consumed is proportional to the power developed

Power developed is approximately proportional to the cube of the engine revs

Hence fuel consumed is proportional to the cube of the engine revs.

 

I dont disagree, however diesels driving standby generators usually run at a constant speed.

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17 minutes ago, Rishworth_Bridge said:

My attention has only just been drawn to this thread and there is far too much to comment on everything. However, as the owner of an electric-drive boat (I don't like the term 'Serial Hybrid' as such systems lack the either/or characteristics of a hybrid) with 3 years of design, and 6 years of operating, experience under my belt I think I might be able to add a few facts about performance to what, unlike the technical contributions, appears to be mostly speculation.

 

The factor that seems to have been missed is the propeller. These 'slip' in water, meaning that each turn of the propeller only moves the boat forward by a proportion of its pitch, typically 10-50%. The larger the propeller and the slower it turns the greater this percentage will be and, as their torque characteristics mean that electric motors can turn larger propellers more slowly than diesels, this means that more thrust is available to the electric-drive boat.  This can be seen in a number of ways, the most obvious being the much lower power required for cruising. We, at 23 tonnes, get 3.3 mph from our 14" x 12" propeller using 2.25 kW @ 430 shaft rpm in open water. That's about 55% propeller efficiency. Lighter boats with similar drive systems report that they need between 1.8 and 2,2 kW in similar situations. This is to be compared with the 15-20 kW (less gearing losses) @ 700 rpm of a typical 40 hp diesel with 2:1 reduction and a 17" or 18" x 12" propeller. This (plus a couple of other factors) leads to the fuel efficiency that has already been mentioned by others. We use only about a third of the diesel through our generator that we would need for a diesel propulsion engine.

 

The other point on which I should like to comment is that of power in demanding situations. It is a fallacy that huge amounts of power are necessary. What matters when manoeuvring or going against a strong stream is thrust and, for the above reasons, the electric drive has plenty - as did working boats with large propellers driven by high torque diesels like Lister JP2s and Russell Newburys. The only reason for needing such high powered diesels is that they are driving propellers which are inefficient because they are too small and run too fast.

 

Finally, something to think about. While waiting for the hundreds of charging stations necessary to make plug-in boating viable the best option for powering a narrowboat  is likely to be a small (1 kW) fuel cell running 24/7 on Propane, with a modest bank of supercapacitors rather than batteries. This should give a fuel saving in excess of 80% relative to a diesel and be cheaper to install than the current type of electric drive as well as providing all the hot water and much of the space heating. The only problem is that nobody seems to want to supply suitable fuel cells in anything less than container loads. If anyone knows any different (Solid Oxide cell of approx. 1 kW) I'd like to know as I'll be first in the queue to fit one.

An electric drive boat with an onboard diesel generator is a series hybrid, that's the definition -- the fact it has a battery bank so the generator doesn't run all the time is also the case for a parallel hybrid.

 

Your assumption that a diesel generates 15-20kW at low propellor revs is wrong. It puts out just as much power as needed to turn the prop, if this is (for example) 3kW (like electric) then that's what it does. The fact that the engine *could* put out 15-20kW is irrelevant, there isn't enough prop load to absorb this.

 

The question about how much power is needed is exactly what I was asking, and no amount of talking about torque and low revs hides the fact that it's power -- not torque -- that pushes a boat along. A bigger slower prop might indeed be 10%-20% more efficient than a smaller faster one ( e.g. 55%-60% compared to 50%), but this doesn't make up the difference between 15kW/20bhp electric and a typical Beta 43 which has about 35bhp available at the prop allowing for gearbox and (high-current) alternator losses.

 

So either the 15kW electric boat is underpowered, or all the boats -- thousands of them -- with a Beta 43 or similar are overpowered. Which is it?

 

And if 20bhp is enough, why don't boat builders save cost and fuel by installing a Beta 25?

 

My view -- which others may disagree with -- is that the electric boat proponents are making a virtue out of a problem, which is that they want to use 48V to avoid HV regulations, and it's difficult to get past 15kW, so they say that this is plenty -- which it undoubtedly is under almost all circumstances. Except the rare occasions when it isn't, which is why builders install Beta 43s not Beta 25s...

 

(yes I know series hybrids have crossed the Wash and gone up rivers on 20bhp -- so when 

*is* all that extra power needed? Ribble link? Upstream on the Trent?)

 

This isn't just pushing numbers around sitting in a chair, it's what every naval architect does when deciding on an engine size -- the very first question is, how much power do I need?

 

And either there's a lot of wool being pulled over eyes by electric boat fans, or if they're right almost every diesel narrowboat built in the last 30 years or so has an engine almost twice as big as it needed to be... ?

 

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1 minute ago, cuthound said:

 

Yes that it what I said, engine capacity is largely irrelevant for diesel engines. It is always about half a pint of fuel (0.28 litres) consumed for every kWh generated.

 

I had a 41 year career in critical power and attened hundreds if not thousands of factory and site commissioning tests for diesel generators from 10kVA up to about 3MVA, where the fuel consumption against load was accurately measured using calibrated fuel flow instrumentation and calibrated load banks. All produced the graph show above.

 

Still waiting for the evidence that small engines are more efficient than larger ones, once frictional and pumping losses have been taken into account.

look at the graph my boat had a 40 kw engine doing 3.3 kws of work, I now have a 6 kw engine doing 6 kw of work and uses less fuel so its more efficient and cleaner.

Also look at the vehicle world small turbocharged diesels have replaced large diesels why because they are more efficient if they wernt they would not have bothered. The same is happening in the petrol world as well small 3 cylinder engines replacing large 6 cylinder engines.

Remember I worked on Jags at the start it was 4 to 6 litres now its 2 litres and they are faster as well

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19 minutes ago, cuthound said:

 

Yes that it what I said, engine capacity is largely irrelevant for diesel engines. It is always about half a pint of fuel (0.28 litres) consumed for every kWh generated.

 

I had a 41 year career in critical power and attened hundreds if not thousands of factory and site commissioning tests for diesel generators from 10kVA up to about 3MVA, where the fuel consumption against load was accurately measured using calibrated fuel flow instrumentation and calibrated load banks. All produced the graph show above.

 

Still waiting for the evidence that small engines are more efficient than larger ones, once frictional and pumping losses have Wbeen taken into account.

Consumption per kWh being independent of size is true for a fully loaded engine, like in a generator.

 

But this doesn't happen in a diesel-driven boat because of propellor loading. A Beta 43 is about 34% efficient at full power (9l/hour=33kW/2800rpm), 28% at 3.5l/hour=10kW/2000rpm, 19% at 1.5l/hour=3kW/1400rpm -- these aren't maximum engine power, they're what the prop absorbs. So efficiency drops off at lower rpm because the engine is nowhere near fully loaded.

prop.JPG

Edited by IanD
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7 minutes ago, IanD said:

An electric drive boat with an onboard diesel generator is a series hybrid, that's the definition -- the fact it has a battery bank so the generator doesn't run all the time is also the case for a parallel hybrid.

 

Your assumption that a diesel generates 15-20kW at low propellor revs is wrong. It puts out just as much power as needed to turn the prop, if this is (for example) 3kW (like electric) then that's what it does. The fact that the engine *could* put out 15-20kW is irrelevant, there isn't enough prop load to absorb this.

 

The question about how much power is needed is exactly what I was asking, and no amount of talking about torque and low revs hides the fact that it's power -- not torque -- that pushes a boat along. A bigger slower prop might indeed be 10%-20% more efficient than a smaller faster one ( e.g. 55%-60% compared to 50%), but this doesn't make up the difference between 15kW/20bhp electric and a typical Beta 43 which has about 35bhp available at the prop allowing for gearbox and (high-current) alternator losses.

 

So either the 15kW electric boat is underpowered, or all the boats -- thousands of them -- with a Beta 43 or similar are overpowered. Which is it?

 

And if 20bhp is enough, why don't boat builders save cost and fuel by installing a Beta 25?

 

My view -- which others may disagree with -- is that the electric boat proponents are making a virtue out of a problem, which is that they want to use 48V to avoid HV regulations, and it's difficult to get past 15kW, so they say that this is plenty -- which it undoubtedly is under almost all circumstances. Except the rare occasions when it isn't, which is why builders install Beta 43s not Beta 25s...

 

(yes I know series hybrids have crossed the Wash and gone up rivers on 20bhp -- so when 

*is* all that extra power needed? Ribble link? Upstream on the Trent?)

 

This isn't just pushing numbers around sitting in a chair, it's what every naval architect does when deciding on an engine size -- the very first question is, how much power do I need?

 

And either there's a lot of wool being pulled over eyes by electric boat fans, or if they're right almost every diesel narrowboat built in the last 30 years or so has an engine almost twice as big as it needed to be... ?

 

We are right but because most narrowboats are overpropped and can only develop 20 hp at 2000 rpm ?

I can assure you after years playing on the Trent my boat would have required far more than 50 hp to push the tide on the Trent more like 100hp would be required

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5 minutes ago, IanD said:

Consumption per kWh being independent of size is true for a fully loaded engine, like in a generator.

 

But this doesn't happen in a boat because of propellor loading. A Beta 43 is about 34% efficient at full power (9l/hour=33kW/2800rpm), 28% at 3.5l/hour=10kW/2000rpm, 19% at 1.5l/hour=3kW/1400rpm -- these aren't maximum engine power, they're what the prop absorbs. So efficiency drops off at lower rpm because the engine is nowhere near fully loaded.

 

See the graph's in @peterboat's  post above.

 

For a diesel engine driving a generator at a constant speed the fuel consumption is proportional to the load applied provided that the engine is being operated within its rating.

 

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3 minutes ago, peterboat said:

We are right but because most narrowboats are overpropped and can only develop 20 hp at 2000 rpm ?

I can assure you after years playing on the Trent my boat would have required far more than 50 hp to push the tide on the Trent more like 100hp would be required

The boats I've been on with Beta 43s -- presumably with the recommended 18" x 12" prop -- have been able to push well beyond 2000rpm at full throttle. A Beta 43 puts out 36bhp at 2000rpm (30bhp at prop allowing for gearbox/alternator losses) compared to 43bhp at 2800 rpm so the drop is nothing like as big as you said...

 

(maybe some other boats are more overpropped -- but don't see why, engine manufacturers seem to recommend about the right sizes from what I've seen)

 

Isn't your boat wide? In which case I can quite believe you'd need much more than 100hp on the Trent...

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19 minutes ago, IanD said:

Consumption per kWh being independent of size is true for a fully loaded engine, like in a generator.

 

But this doesn't happen in a diesel-driven boat because of propellor loading. A Beta 43 is about 34% efficient at full power (9l/hour=33kW/2800rpm), 28% at 3.5l/hour=10kW/2000rpm, 19% at 1.5l/hour=3kW/1400rpm -- these aren't maximum engine power, they're what the prop absorbs. So efficiency drops off at lower rpm because the engine is nowhere near fully loaded.

prop.JPG

The graph shows how inefficient diesels are in boats doesnt it?

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1 minute ago, IanD said:

The boats I've been on with Beta 43s -- presumably with the recommended 18" x 12" prop -- have been able to push well beyond 2000rpm at full throttle. A Beta 43 puts out 36bhp at 2000rpm (30bhp at prop allowing for gearbox/alternator losses) compared to 43bhp at 2800 rpm so the drop is nothing like as big as you said...

 

(maybe some other boats are more overpropped -- but don't see why, engine manufacturers seem to recommend about the right sizes from what I've seen)

 

Isn't your boat wide? In which case I can quite believe you'd need much more than 100hp on the Trent...

A lot of boats are over propped to give better fuel consumption, and quieter cruising my old narrowboat with 30 hp had a small prop and was horrible docked, blacked, bigger prop transformed it and it was 60 foot long, most narrowboats are over engined

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-- so when  *is* all that extra power needed? Ribble link? Upstream on the Trent?

 

I well remember an Easter cruise up the Shropshire  Union  which included the stretch where it runs almost due North on a long exposed embankment. There was a strong cross-wind blowing from the Welsh marches. The only way to proceed was to give the engine maxmum throttle, with the tiller held over and the boat at an angle to the direction of travel with the bow and stern only a foot or so from the opposite banks. Anything slower and we would have been blown against the tow path bank. Fortunately there  was nothing coming the other way. A real-life example of the principle of vectors and resultant forces I had been taught in applied mathematics. 

 

 

 

Edited by Ronaldo47
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3 hours ago, cuthound said:

 

See the graph's in @peterboat's  post above.

 

For a diesel engine driving a generator at a constant speed the fuel consumption is proportional to the load applied provided that the engine is being operated within its rating.

 

The spreadsheet numbers I gave were for a diesel driving a prop, not a generator.

 

As pointed out earlier, all generators tend to be similar efficiency when run at full rated power -- about 25% overall from tank to battery including all losses going by the comparative tests Victron did, for all sizes from 3kW up to 20kW IIRC.

 

And like a normal diesel, their efficiency drops off when they're not fully loaded, for exactly the same reason.

 

This efficiency plus the added losses in generator/controller/motor are why the fuel savings for a series hybrid are not as fantastic as sometimes claimed, even if the generator runs at full power for short periods.

 

The hybrid fuel savings are because of higher efficiency at the normal low power levels needed on canals (typically 3kW or less) and no power in locks, plus power from solar -- at full power a straight diesel is considerably more efficient, but this hardly ever happens on canals.

 

Don't get me wrong, I think series hybrids (I'm not going to call them electric boats...) are the future, but you need to take an unbiased view of their advantages and disadvantages, because they have both ?

Edited by IanD
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20 minutes ago, IanD said:

The spreadsheet numbers I gave were for a diesel driving a prop, not a generator.

 

As pointed out earlier, all generators tend to be similar efficiency when run at full rated power -- about 25% overall from tank to battery including all losses going by the comparative tests Victron did, for all sizes from 3kW up to 20kW IIRC.

 

And like a normal diesel, their efficiency drops off when they're not fully loaded, for exactly the same reason.

 

This efficiency plus the added losses in generator/controller/motor are why the fuel savings for a series hybrid are not as fantastic as sometimes claimed, even if the generator runs at full power for short periods.

 

The hybrid fuel savings are because of higher efficiency at the normal low power levels needed on canals (typically 3kW or less) and no power in locks, plus power from solar -- at full power a straight diesel is considerably more efficient, but this hardly ever happens on canals.

 

Don't get me wrong, I think series hybrids (I'm not going to call them electric boats...) are the future, but you need to take an unbiased view of their advantages and disadvantages, because they have both ?

I have read it's 29 to 32%, which is way better than the 19% that your graph shows for NBs at similar speeds and that's with a 65% loading on the genny. We also have other advantages in that the coolant can be used to heat water and run central heating which in normal electric production doesn't happen. I would think its fair to say with solar in the mix series hybrids have real potential for cutting emissions by a large amount and save plenty of dosh.

I will report my findings when this latest modification is finished but that's going to be a while for obvious reasons 

Edited by peterboat
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