Electric Drive: Who uses it?

[Dockhead]

Originally Posted by a64pilot

Another big reason why hybrid automobiles work is they enable the use of an Atkinson cycle engine, https://en.m.wikipedia.org/wiki/Atkinson_cycle
this engine has been around for more than 100 years but isn’t used in a regular automobile as it has a very poor ability to accelerate, low torque if you will.
However the electric motors will accelerate the vehicle nicely allowing the use of the Atkinson cycle engine. It’s the Atkinson cycle engine that gives good fuel economy at steady state highway speeds, not the hybrid system, that is largely dead weight at high, sustained speeds.
Newer cars have engines that emulate an Atkinson cycle and can operate as an Atkinson cycle at steady state and in the Otto cycle to accelerate. Different manufacturers have their own cute little names for it.

It's so cool that we've finally broken through to get beyond the old Otto cycle engines. I hope we'll see some more development of the old IC engine.

I don't think current Atkinson cycle engines quite match advanced highly pressurized common rail diesels, though -- like the BMW diesel in the 1 series. Which are not sold in the U.S. unfortunately.

So isn't it rather the regenerative braking, which is the killer app? I note that you can buy the Toyota Auris in the UK as either a turbo diesel or hybrid with the Prius drive train. The hybrid is much more efficient in town, but the turbo diesel is much more efficient in highway driving- like 10 miles (per Imperial gallon) more. That's a good comparison since it's exactly the same car.

I talked to a taxi driver somewhere who uses a Prius, and swears by it. In taxi duty it is much more efficient, plus -- the brake pads last forever!

[john61ct]

Yes, regenerative braking is a huge reason for EV / hybrid energy efficiency.

And lack thereof a huge reason the case for propelling boats via electricity is not there.

[seandepagnier]

Originally Posted by john61ct

Thanks for the reality check.

And Torqueedo makes great practical products, very energy efficient.

They are still not theoretically very efficient at all. 1000 watts to go 4 knots on a 15ft boat is not very good.

In the race to alaska, there was a 24ft catamaran that could be pedaled at 5 knots in sprint, or 3.5 knots for 3 hours by just one human. This is because of the very large carbon fiber propellor. This person is not producing muc more than 200 watts.

Originally Posted by john61ct

Yes, regenerative braking is a huge reason for EV / hybrid energy efficiency.

And lack thereof a huge reason the case for propelling boats via electricity is not there.

You can regen while sailing, so it is there.

[a64pilot]

An issue with Diesels in the US is it’s extremely difficult to pass emissions, and many if not most manufacturers cheat, cause they are allowed to. It’s not just VW. A favorite way to cheat is to claim engine is in self protection mode, which is allowed, however what defines the need to be protected is not, so normal operating temp can be defined as to need protection etc.

Another very real thing is fuel cost, back in the day of high sulphur Diesel, fuel cost was significantly less than cheap gas, now days Diesel is as much or more than a premium fuel or on average about .25c a gallon more than cheap gas.
So you have to get at least 10% better fuel mileage just to break even.

Ford, Mercedes, BMW and VW are all in court over cheating Diesel emissions, Is bet there are others.
The rules that were put in place to clean up the air have largely been subverted, and it’s not just lately either. Ever wonder how full size pickups and SUV’s meet CAFE standards? Why don’t you pay a gas guzzler tax on them?
They are exempt that’s why, but cars are not?

[Dockhead]

Originally Posted by a64pilot

An issue with Diesels in the US is it’s extremely difficult to pass emissions, and many if not most manufacturers cheat, cause they are allowed to. It’s not just VW. A favorite way to cheat is to claim engine is in self protection mode, which is allowed, however what defines the need to be protected is not, so normal operating temp can be defined as to need protection etc.

Another very real thing is fuel cost, back in the day of high sulphur Diesel, fuel cost was significantly less than cheap gas, now days Diesel is as much or more than a premium fuel or on average about .25c a gallon more than cheap gas.
So you have to get at least 10% better fuel mileage just to break even.

Ford, Mercedes, BMW and VW are all in court over cheating Diesel emissions, Is bet there are others.
The rules that were put in place to clean up the air have largely been subverted, and it’s not just lately either. Ever wonder how full size pickups and SUV’s meet CAFE standards? Why don’t you pay a gas guzzler tax on them?
They are exempt that’s why, but cars are not?

Major thread drift, but I really prefer driving a diesel, and wouldn't care if it cost more. If it's one of those high pressure common rail torque monsters. It's just an extraordinary feeling. It just feels and sounds good.

Kind of theoretical discussion, as what I drive these days is mostly a bicycle, or an Uber.

[Dockhead]

Originally Posted by boat_alexandra

They are still not theoretically very efficient at all. 1000 watts to go 4 knots on a 15ft boat is not very good.

In the race to alaska, there was a 24ft catamaran that could be pedaled at 5 knots in sprint, or 3.5 knots for 3 hours by just one human. This is because of the very large carbon fiber propellor. This person is not producing muc more than 200 watts.

Beware design parameters which assume ideal glassy water and no head winds.

Originally Posted by boat_alexandra

You can regen while sailing, so it is there.

It's an attractive idea, but unlike regenerative braking on hybrid cars, which works extremely well, regenerative sailing doesn't seem to have much practical value, at least according to those who have tried it. First of all, you need a fixed propeller, which is death to sailing performance. Then, you need enough wind that you don't notice (or don't mind) all the drag. I think it's pretty incompatible with a really good sailing boat, and for the boat to be really good sailing, it seems to me, especially upwind, is a far more effective way to reduce the consumption of fossil fuels.

[john61ct]

Lots of sailing boats have hydro power, works great, drag not a big issue for cruisers.

But the output per day of travel is the same scale as wind and solar, great for efficient House bank usage.

Not at all the scale required for any significant propulsion.

And OT here anyway it seems.

And nothing to do with brakes regen on land.

[Jim Cate]

Regen from braking in an automobile is good because it augments the desired effect:slowing the vehicle down. Regen while sailing is bad because it diminishes the desired effect: moving the boat via wind power.

Big basic difference IMO.

Jim

[hzcruiser]

Originally Posted by Corvidae

The trade off overall, is that instead of a motor sailor that would go wherever, whenever, almost entirely regardless of the weather, it's going to be a sailboat that has to pick and choose good tide and weather windows. And given the use I'm intending, that's just fine. The only reason I went with a MS is the space, the motoring ability wasn't important. Having two motors just negated the need for a bow thruster more than it gave any navigational advantage. Honestly I expect the only time I'll be using full throttle is trying to escape from shoals.

Hats off to you for giving this a go!



I'm also seriously contemplating to switch to electric if or when the old Perkins packs it in...



By then a bigger battery bank should be more affordable and a smaller generator can add some serious Amps when needed, otherwise it could be used to charge the batts on rainy days and maybe run the dive compressor as well.

[john61ct]

Do not make plans based on future drops in battery prices.

IMO increasing demand will keep them high.

BMS gadgets yes, but not the cells.

[hzcruiser]

Originally Posted by john61ct

Do not make plans based on future drops in battery prices.

I won't, John. Have already moved to mostly LFP with just two AGMs left in the house bank plus two LAs as starter batts. The LAs are fairly new but once they're EOL one of the house banks will provide the juice to start the engine. All properly monitored to avoid deep discharge, of course.

[KeelMe]

I spent a few years worth of free time designing a submarine. I finally finished and began sourcing distributors and pricing for all of the parts and tools needed. The cost of batteries alone derailed the whole project. I could have built four submarines for the cost of one battery bank.

Batteries have come down a lot in price and have technologically improved substantially since then. I may have to revisit my submarine plans and finally check off "#826 - Circumnavigate by Submarine" from my bucket list.

[Adelie]

Originally Posted by Dockhead

It's so cool that we've finally broken through to get beyond the old Otto cycle engines. I hope we'll see some more development of the old IC engine.

I don't think current Atkinson cycle engines quite match advanced highly pressurized common rail diesels, though -- like the BMW diesel in the 1 series. Which are not sold in the U.S. unfortunately.
....

I would like to see the Atkinson cycle combined with diesel and see how efficient that is. You trade power to weight ratio in exchange for efficiency.

I assume it is being worked on by not very hard because of the already low power to weight of diesel means it has more of a niche application.

[Dockhead]

Originally Posted by Adelie

I would like to see the Atkinson cycle combined with diesel and see how efficient that is. You trade power to weight ratio in exchange for efficiency.

I assume it is being worked on by not very hard because of the already low power to weight of diesel means it has more of a niche application.

Yes, but there is much less to gain with a high pressure diesel, which is much more efficient to begin with, and which doesn't have the pumping loss issue of Otto engines. Atkinson cycle with a spark ignition engine benefits hugely by moderating pumping losses at partial output regimes. Probably the biggest part of efficiency gain for spark ignition engines. No such benefit for compression ignition engines.

[a64pilot]

Respectfully pumping losses have nothing to do with the Atkinson cycle, entirely separate issue.
The modern pseudo Atkinson cycle engines have more pumping loss than a regular Otto cycle engine, the reason is that they simulate the Atkinson cycle by valve timing, they leave a valve open until well up on the compression stroke, before they close it, and of course pumping all that air through an open valve is pumping loss.

However the Prius and other such cars I’m sure have essentially zero pumping loss as the computer operates them at usually full throttle, but drawing them down in RPM so that the engine at full throttle produces just the amount of power required, and will vary RPM and not throttle to reduce or increase power output.

Actually if you look, you will find that the modern Diesel is dropping in compression rather markedly, and the modern gas motor increasing.
They will soon meet.
Rather odd place for this article, but read this
https://www.economist.com/babbage/20...ine-born-again