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Old 12-12-2018, 23:03   #1606
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Re: Oceanvolt Hybrid Motor

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Originally Posted by a64pilot View Post
Back in the 1070’s the Russians built a City bus that had a small diesel running a generator to charge a battery bank, and it had regenerative braking.
Idea was that a City bus spends most of its time sitting waiting for people to load and unload, then needs the BIG motor to accelerate int traffic where it then maintains speed for a short time, then slows of course and sits again.
It worked, and worked well, a little something like a 5 KW generator ran the City bus easily, and did substantially decrease fuel consumption.

Unfortunately it wasn’t successful because it couldn’t sustain high speeds for long at all, and I guess maybe busses need to be repositioned etc at times and need the ability to jump on the highway?
Actually a city bus is the ideal hybrid platform (and a lot of new ones are hybrid). As you mention, a typical day the bus probably averages 10-15mph needing substantial low end power for acceleration but very little sustained power for cruising speeds...plus you have lots of braking regeneration and idle time at stops where the batteries can be refilled.

5KW is probably a bit light on power unless you have a very big battery bank but dropping from a 300hp to a 50hp is probably viable.

Of course, this is a completely different use case from the typical displacement cruising boat where other than a few minutes at the start and end of a day, the motor is set per cruising speed and you continue on like that for hours.
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Old 12-12-2018, 23:10   #1607
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Re: Oceanvolt Hybrid Motor

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Originally Posted by john61ct View Post
Well that is exactly where EP stops making sense!

But there are those sailing, not on schedules, that plan to only use power for very short periods. If the case can be made that EP is practical / cost-effective at least for them, even for a heavy monohull, there's an entry point anyway.
If your use case is 30min to get in and out of port...yes EP is viable. That's was said a year or two ago on this thread and no one challenged it. If you are willing to accept drastic reduction in the motoring capability, you could have gone electric decades ago (the technology is essentially the same as an electric golf cart which has been around since the 50's)

Very few brand new cruising boats are bought with that kind of limitation in mind. Most new buyers expect to be able to motor for several hours at 80-100% of hull speed and have reserve power in the event of bad conditions.
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Old 12-12-2018, 23:15   #1608
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Re: Oceanvolt Hybrid Motor

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No one is saying "adding components" to an existing power-train. No one. The statement is a distortion of the discussion (accidental or otherwise).
Actually if you go back, you will find lots of prop changes put into the discussion to make EP sound better.

The issue with your idea of setting up the prop so the prop power matches up with the motor power at a lower power with the strawman 15kw EP system. You can do the exact same thing with a 15kw continuous rated diesel...you are demonstrating the effects of using different types of props and then claiming it shows EP is better...that's false equivalency.

Provide the performance specifications required and then you can design either motor type to meet it...with HP that is pretty close to the same.

Big difference is most EP proponents assume a normal cruising speed of 30-50% of hull speed and a peak of maybe 70-80% of hull speed. Then compare it to what people actually buy (and presumably want) of a cruising speed of 70-80% of hull speed and the capability of doing 100-110% of hull speed.

The problem is the EP proponents, lower the bar for EP and then point to a diesel system designed for a higher bar and say how bad the diesel is.
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Old 13-12-2018, 02:54   #1609
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Re: Oceanvolt Hybrid Motor

A lot of supposedly smart people are designing EP systems for boats. Don't you think if they could get a substantial reduction in fuel usage from the "more efficient" hybrid vs. mechanical they would promote the heck out of it? But they don't. They talk about magic HP, regen, solar, etc. as a way to reduce fuel usage.

You guys go ahead and design a system on your bar napkins. But unless you build it it's just talk. The actual builders of EP know the fuel/mile equation isn't in their favor which is why they don't promote it. And for EP to be a viable business they have to get the cost way down. But none of the technology they employ (except Li batteries) is new and low volume production. So they have a hard time making the business case that EP will ever be same or less expensive than mechanical.

Let's see:

EP costs more.

EP is less efficient unless maybe if you have solar and regen. For regen to be useful you have to sail in pretty rough conditions. And you need a much stouter rig because you are driving the boat plus the regen. Regen is horribly inefficient. I estimate it is about 10% or less efficient in terms of power from sails to electrical power produced. It was earlier stated that 5 knots gave less than 1kW regen.

EP is more complex and requires multiple skills to repair (electronics, high power wiring, mechanics). Dump a few gallons of salt water on your auxiliary engine. Are you afraid? No. Flush with fresh water and don't look back. Dump a few gallons on your EP system? Still not afraid?

EP makes some people feel good. Can't deny that benefit.
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Old 13-12-2018, 04:07   #1610
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Re: Oceanvolt Hybrid Motor

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Originally Posted by OldMan View Post
The prop still presents the same load to the EP motor, hence the EP has to expend the same KW as a direct drive ICE.



There is more than 5% loss in ICE driven EP, 5-15% in the alternator plus 5% in the EP motor....batteries are additional 4% (? in/out). Minimum loss is 13%.
Read carefully. The 5% is for DC electricity going through the pack to be used at a later time, not anything about overall losses.

I've been hand waving the total calculation because I hate using the data from the wrong engine, especially since the yanmar data above suggests the yanmar is ~20% less efficient than the Mercedes engine we do have data on (which is plausible since as I just realized yesterday it's a swirl chamber engine rather than direct injection like the Mercedes. I didn't think anyone was still making swirl chamber engines, but I guess the marine emissions requirements are less stringent.)

I guess the easiest way to make it make sense is to continue with the numbers we've had. 4 kW to the propeller probably means about a five knot cruise for a typical catamaran.

So with the Mercedes engine, the single speed fixed pitch system runs at 1800 rpm and burns 260 g/kWh, for a total of 1040 g/h, 1.25 liters per hour.

If the hybrid uses the peak output cycling operating strategy, it burns 206 g/kWh making 15 kW, then turns the engine off until the charge has burned off. 3090 g (3.7 liters) of fuel for 15 kWh mechanical.

Polar Power quotes 92% efficiency for their permanent magnet DC generator, so that 15 kWh mechanical work from the engine turns into 13.8 kWh of electricity.

If you assume motors of equal efficiency, that 13.8 kWh of electricity will eventually become 12.7 kWh of mechanical motion again.

Right now I only need 4 of those, though, so the other 8.7 kWh of motion (more accurately, the 9.5 kWh of electricity that will eventually produce them,) need to be stored in the battery, which is where the 5% came in. 9.5 kWh into the battery, 9 kWh back out, 8.3 kWh motion of driving the boat stored up and used later.

So one hour of running the engine ended up giving 12.3 kWh of total motion at 4 kW, 3 hours and 5 minutes of motion.

So the hybrid's effective fuel burn is 1005 g/h (3090/3.075), 1.20 liters per hour, with an overall efficiency of 251 g/kWh.

I'll admit I was expecting a bigger difference when I started, and a higher speed (fewer battery losses) or a more efficient motor (many are claiming more like 95%, allegedly) would make the case marginally better - but the concept comes across - losses in the hybrid system can be offset by improved engine efficiency for a large portion of the operating range.
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Old 13-12-2018, 05:28   #1611
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Re: Oceanvolt Hybrid Motor

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Originally Posted by saghost View Post
If the hybrid uses the peak output cycling operating strategy, it burns 206 g/kWh making 15 kW, then turns the engine off until the charge has burned off. 3090 g (3.7 liters) of fuel for 15 kWh mechanical.

Right now I only need 4 of those, though, so the other 8.7 kWh of motion (more accurately, the 9.5 kWh of electricity that will eventually produce them,) need to be stored in the battery, which is where the 5% came in. 9.5 kWh into the battery, 9 kWh back out, 8.3 kWh motion of driving the boat stored up and used later.

So one hour of running the engine ended up giving 12.3 kWh of total motion at 4 kW, 3 hours and 5 minutes of motion.

So the hybrid's effective fuel burn is 1005 g/h (3090/3.075), 1.20 liters per hour, with an overall efficiency of 251 g/kWh.

I'll admit I was expecting a bigger difference when I started, and a higher speed (fewer battery losses) or a more efficient motor (many are claiming more like 95%, allegedly) would make the case marginally better - but the concept comes across - losses in the hybrid system can be offset by improved engine efficiency for a large portion of the operating range.
I really appreciate people bringing real math instead of creative writing, empty statements "It can't be done" with no data, and FUD ("electrickery", "magic"...) to this discussion, thank you.

You are of the same mind as me, but I think there are a few more design considerations that improve our comparisons.

Direct Drive requires a transmission, EP does not. 3-15% losses according to Gerr.

Generator power matched to cruise load on a DC bus. Since a large percentage of the time we are cruising (as stated by both DD (direct drive) proponents and EP alike), match the generator(s) to the load at cruise. Why? Cycle it on when cruising and off when not, and you have zero battery loss. Related: Some LiFePO4 folks are claiming 98% efficiency on battery charging, but I haven't investigated those claims. If claims are real, you don't have to use this optimization, but I'd prefer to keep it because it's free, it only requires logic to implement, and it still would save 2% and battery life. Source: https://forums.energymatters.com.au/...topic6033.html

Ability to downsize the overall power requirement because we are not required to oversize. I have mixed feelings about this. DD folks point to it as a weakness because EP folks are choosing to target cruise instead of cruise + reserve. They also cry "not apples to apples", but that is silly. Ability to size correctly is a benefit that can be counted if the sizing is correct. But I have yet to find anyone who can tell me exactly how much reserve is required. To me (and maybe most EP folks) reserve is wasteful and hard to justify because you can't quantify it. How do I know if 10 or 20 or 50% more power is enough to save my bacon? How do I know that I can't save myself with my existing max cruise power? What do sailboats with tiny engines do for reserve? I would love some math on reserve power, I asked a while ago and no one answered. I will keep this in my calculations, but others don't have to (including DD folks who are used to having it and won't want to give it up regardless of whether it can be quantified, they feel good about it and that's worth something to them). It's important to note that this is not a large savings because the power requirement is still the same at cruise, so we are unlikely to save a large amount just due to engine sizing. Capital cost mostly, but we lose that in our generator because it's duty rating has to be higher (therefore bigger in any case) It might be worthy of calculating if it's 1 or 2%. It's not the largest savings by far however, therefore I list it last.


Not a factor, but a reminder that the costs of these new systems are still high, I don't think anyone is saving any money over the life of the system unless they have a design that incorporates a LOT of solar, wind, or sail regen and USE it. Today's buyers might get some efficiency, and are definitely buying a tool that allows them to be more green if they collect the "free" fusion energy all around us.
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Old 13-12-2018, 05:55   #1612
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Re: Oceanvolt Hybrid Motor

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Originally Posted by saghost View Post
I guess the easiest way to make it make sense is to continue with the numbers we've had. 4 kW to the propeller probably means about a five knot cruise for a typical catamaran.

Since actual KW used is a mystery to me, do you have any data that shows 4KW will push a typical catamaran @ 5kts?


I can achieve 5kts with each engine at 2000rpm, which is max 4KW each at the prop, i.e. total 8KW. As I mentioned earlier, I don't know actual KW as that would require precise fuel measurement.


It's also not clear me about SVReality actual usage in posts #1430 and #1441. I would be surprised if 15KW can push that boat @ 8.5kts (or the restated 7.9kts), but again, I don't have a basis to compare. I'm thinking he meant 15KW per OV for a total of 30KW. Can anyone clarify?
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Old 13-12-2018, 06:14   #1613
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Re: Oceanvolt Hybrid Motor

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I didn't get a chance to do this last night but started to do it earlier this morning. In doing so it seems I'm trying to achieve what bridaus is already doing with building his/her model.

bridaus, you're best placed to do this, in my opinion, are you able to clearly put your engines, motors, generators in terms of specs and perhaps start to build this system so we're all on the one page? Maybe it could be pasted into posts by those who are commenting on that model?

Just a thought that would help. I'll leave this now.

Cheers,

TP
Not yet, but I'm saving/sourcing data from this post and elsewhere and building it in a spreadsheet. I am not close to building or actually building like others are, so I also am interested in their real world reports on specific implementations (which could be good/bad/otherwise).

There is a lot of ground still not even covered here such as uncertainty, wear/efficiency over time of all systems, true USE by collecting real engine usage data (I suspect everyone thinks they run at cruise speed (by engine hours) way more than they really do), etc. It will take more time than we'll want, but I will attempt to do this, kind of already was... great idea.

-Brian
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Old 13-12-2018, 06:15   #1614
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Re: Oceanvolt Hybrid Motor

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Originally Posted by OldMan View Post
Since actual KW used is a mystery to me, do you have any data that shows 4KW will push a typical catamaran @ 5kts?


I can achieve 5kts with each engine at 2000rpm, which is max 4KW each at the prop, i.e. total 8KW. As I mentioned earlier, I don't know actual KW as that would require precise fuel measurement.


It's also not clear me about SVReality actual usage in posts #1430 and #1441. I would be surprised if 15KW can push that boat @ 8.5kts (or the restated 7.9kts), but again, I don't have a basis to compare. I'm thinking he meant 15KW per OV for a total of 30KW. Can anyone clarify?
No, I don't. Obviously different boat designs and even different loadings of the same type will produce different results. I was thinking of this post and remembering it wrongly.

As you'll see a couple posts down that thread the battery numbers in the cited post are wrong, so he gets 75 minutes at 6 knots from a rated 15 kWh discharge, which means about a 12 kW electrical load (no idea what the motor efficiency is on the lagoon - likely worse than today's but not sure how much.) So maybe 10-11 kW mechanical?

So for a Lagoon 420, 4 kW probably won't produce 5 knots. That actually wasn't the point of the discussion, just me trying to put it in perspective. And apparently failing.
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Old 13-12-2018, 06:32   #1615
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Re: Oceanvolt Hybrid Motor

I'd leave the boat out of theoretical discussions, because you can pick any boat (within reason) and it's equal for both cases. Same with variable pitch props, choice of prop, etc.

For real world comparisons, the boat (and all efficiency affecting details) are critically important to keep the same for a fair comparison. Even the anchor, for if one was dragging an anchor and one wasn't...
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Old 13-12-2018, 06:44   #1616
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Re: Oceanvolt Hybrid Motor

The Reserve Power for Safety issue

How much is "needed" is impossible to quantify as a generality.

No one can predict what you will encounter, the skillset of the captain in avoiding trouble is even more a variable than the "hull strength / build quality" or "RTW bluewater vs weekender hugging coasts" factors.

Plenty of sailors make do with zero "emergency power" it is true, but these days - just like camping discomfort in tiny cabins - that is much less mainstream.

In any case, I'm not clear if this factor weighs heavily in the cost / efficiency argument when comparing direct drive with hybrid-EP.

Any EP design that delivers the standard expectations of most modern big-diesel setups, throws the idea of alternative-energy being a significant source out the window,

so best to just eliminate that factor except for no-schedule trolling motor use cases.

Otherwise, comparing apples to apples, pick a number for Normal Cruising All Day and use that for the basis.

If you want to take into account a SHTF reserve power factor, just make sure it is the same for both sides of the comparison.
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Old 13-12-2018, 06:45   #1617
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Oceanvolt Hybrid Motor

Someone mused that transmissions are not needed for EP. Then why do some EP systems have a transmission if it is not needed?

Hint: electric motors have an upper torque limit even at zero RPM. Lots of people think the upper torque limit is infinite but it's not.
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Old 13-12-2018, 07:04   #1618
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Re: Oceanvolt Hybrid Motor

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Originally Posted by transmitterdan View Post
Someone mused that transmissions are not needed for EP. Then why do some EP systems have a transmission if it is not needed?

Hint: electric motors have an upper torque limit even at zero RPM. Lots of people think the upper torque limit is infinite but it's not.
No musing at all, some do, some don't. I'm sure the ones that do have it feel that the electric motor they've chosen is utilized better with it. If it's in, it gets counted in my calculations if they don't already include it in their system efficiency (but I think they do). The point is that it's not required to do forward/reverse or hit the right curve on the sfc graph.

Which system are you referring to out of curiosity?
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Old 13-12-2018, 07:23   #1619
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Re: Oceanvolt Hybrid Motor

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Originally Posted by john61ct View Post
The Reserve Power for Safety issue

How much is "needed" is impossible to quantify as a generality.

No one can predict what you will encounter, the skillset of the captain in avoiding trouble is even more a variable than the "hull strength / build quality" or "RTW bluewater vs weekender hugging coasts" factors.

Plenty of sailors make do with zero "emergency power" it is true, but these days - just like camping discomfort in tiny cabins - that is much less mainstream.

In any case, I'm not clear if this factor weighs heavily in the cost / efficiency argument when comparing direct drive with hybrid-EP.

Any EP design that delivers the standard expectations of most modern big-diesel setups, throws the idea of alternative-energy being a significant source out the window,

so best to just eliminate that factor except for no-schedule trolling motor use cases.

Otherwise, comparing apples to apples, pick a number for Normal Cruising All Day and use that for the basis.

If you want to take into account a SHTF reserve power factor, just make sure it is the same for both sides of the comparison.


Anything that simplifies the theoretical discussion without changing the results makes it easier for us all to get on the same page.
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Old 13-12-2018, 07:23   #1620
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Re: Oceanvolt Hybrid Motor

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Originally Posted by bridaus View Post
Not yet, but I'm saving/sourcing data from this post and elsewhere and building it in a spreadsheet. I am not close to building or actually building like others are, so I also am interested in their real world reports on specific implementations (which could be good/bad/otherwise).

There is a lot of ground still not even covered here such as uncertainty, wear/efficiency over time of all systems, true USE by collecting real engine usage data (I suspect everyone thinks they run at cruise speed (by engine hours) way more than they really do), etc. It will take more time than we'll want, but I will attempt to do this, kind of already was... great idea.

-Brian
Thanks Brian, I appreciate that. It will greatly benefit all of us, in my opinion, not just you and I.

To add to the system spec, and to address some of your further points, a list of assumptions can go along with the system spec. Such as uncertainty, time at optimum efficiency and so on. I can see you were already building it but I guess the biggest benefit for all of us comes in a shared understanding. Those assumptions can be challenged and the model updated; there's real value here.

I'm happy to help with the spreadsheet model, I've built a few of those, but I suspect you've built a few more. PM me if you want to chat further

TP
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