Electric Feasibility Study for an Owens

[CPseudonym]

This thread is for me to research the feasibility of converting my 1967 27' Owens Concorde to plug in electric propulsion power. Current power comes via 350 cid Chevy engine with Borg Warner velvet drive transmission(I believe a 1.34-1 gear ratio). Electric head, fridge and 2 burner cook top. 1 rather large (66"x32")solar panel can be fitted to the hard top without affecting the appearance of the boat. 3 additional while possible on the cabin top would affect the use and looks of the boat enough to be less desirable.

Our current use of the boat is mostly day trips of less than 30 miles out and back, however overnight and multi-day trips are in our future. Protected inland waterways with moderately slow tides are the norm rather than the exception in my cruising area. Assume no more than 3 days away from the dock. If longer trips are desired a small generator may need to be compromised into the equation.

I imagine the design will incorporate the use of LiFePO4 battery cells for power storage. The amount of storage needed will need to be determined. The horsepower of the motor would ideally provide for up to 10 kn of speed but 7 or less would be acceptable too. All interior and exterior lighting will be LED.

How close to reality are my expectations to the current state of electric propulsion and battery storage technology? For our purposes here let us assume future resale value is of no concern to me.

Thank you,

 

[rjtrane]

Do you have any current data on HP needed for the speeds for which you are looking? Any sea trial info? It's simple math once you determine your HP needs.
Most likely 5 knots will be a realistic speed. Since your boat is not designed to be truly efficient at slow speed, it may take a bit more power to go 5 knots. Assume you can go five knots in calm conditions with a 10 kw motor. 30 miles is 6 hours or 60 kw/ hours. At 48 volts, this is 1,250 amp hours for day-trip propulsion only. Assume you build your battery with 32 each, 700 ah cells for a total of 1,400 ah. Each cell is $770.00 from Balqon or about $25,000 with freight. Add a BMS (battery management system) for a couple thousand dollars and shore charger another several thousand, your investment for the battery is $30k.

We have 28 PV panels your size on Sunshine with a rated output of close to 6 kw. 4 panels will keep your refrigerator and pumps going, but not much else.

Finally, you have the motor. Good thing about a 10 kw motor and controller is they are not too costly - maybe around $10,000 depending on type and make. You won't need your gas motor or gear box. Hook up the motor directly to your shaft.

For overnight trips, a small 48v DC generator could recharge your battery overnight.

Total materials will be around $50k - $60k plus labor.

Any extra money you have in your budget spend on more battery. You cannot have too much.

Oh, and forget about 10 knots.

Note: my estimates are based on guessing you can use a 10 kw motor to get your 5 knots. If you have any powers curves for your boat, you can make a closer estimate on the size motor you'll need for the speeds you desire. Smaller would save you some money - larger would cost you more.

 

[Marin]

Craig--- You might want to start by talking to these folks. Electric Boats | Electric Launch | Elco Boats Some of their launches are in operation on Seattle's lake Union.

 

[CPseudonym]

Thanks for that link Marin, good stuff.

Reuben I posted the above "soft requirements" which I knew where way over the top to get the conversation started so to speak. What gave me the idea to do this was Mark's comments about the trimaran solar boat in another thread lacking aesthetics. Some folks, myself included appreciate a boat that looks like our idea of a boat. The possibilities are great so why not look at what is required to convert an existing boat of a design we like. Well I happen to like my Owens.

Your right of course, my planing hull is a very bad candidate for such a conversion Eric's Willard FD hull would be a better candidate IMO. But seeing how Eric didn't start this mess I threw mine into the ring. The horsepower curves are something I have to investigate further along with components. I threw the solar panel idea in more as a why not add one, not all of us have boats that lend themselves to being all solar such as yours.

This is one of those subjects that is difficult to understand fully until we use a tangible example. Ideally cats and tris are better candidates for electric but some of us are die hard mono hull lovers. A wise general once said you go to war with the army you have, not the one you want so that is what this thread is really about.

 

[deckofficer]

If your old Owens has a stern bracket for a small outboard for trolling, you can get some rough efficiency numbers that way, just remember the prop on a small outboard won't be pitched to allow full rpm because the Owens will be too much of a load. I'd be willing to bet if you roll your own with this motor Motor MotEnergy ME1003 Permanent Magnet DC Pancake Brushed Double Magnet at $589 has a cont. rating of 19.3 hp @ 72 VDC. This controller Controller Kelly KDH07500A 24-72 Volt 500 Amp Series or PM will do the job for $465, you should be able to pull it off for less than $20K.

Find out what speed you can live with for a consumption of 700 w-hr per nm. Might be as fast as 4 kt at 2800 watts. If you need 60 nm range for your outings, then 52.5 Kw-hr (for 80% DOD) would work. Size your solar to handle hotel loads at 12 volts and your propulsion bank will be 72 volts. (24) 700 a-hr cells will get you 54.6 Kw-hr bank at Balqon's clearance price of $560 per cell $13,440. Here is a LiFePO4 charger 20 amp for $465. http://www.cloudelectric.com/product-p/bc-sco7220.htm

The Balqon sale http://www.balqon.com/store.php#!/~/product/category=4218089&id=18005962

Motor $589
Controller $465
LiFePO4 $13,440
Charger $465

Under $15K if you roll your own.

Keep the trans because the smallest pitched prop might still be pitched too high for the electric motor.

 

[CPseudonym]

Quite frankly 30 miles would probably be more than sufficient. I do not have far to go in any direction to reach a great anchorage. That's just one of the things I love about the Delta.

72 volts DC is what I run in my Gem NEV. Finally, some battery technology I can relate to.

 

[deckofficer]

Do you feel comfortable rolling you own? By very rough estimates you might be able to cruise at 4 kt on 3.75 hp (2800 watts). The reason I picked a motor with a cont rating of 19.3 hp is that speed increases require a disproportionate increase in power. There will be times you will need or want to run at 8 kt instead of 4 kt, and that power increase would require going from 3.75 hp to 15+ hp. The motor and controller are rated to 400 amps for 1 minute due to thermal conditions, which is 38.6 hp. 200 amps cont rating, which will cover 15 hp. Remember, because of the torque of an electric motor, 15 hp electric rating would equate to much more than an ICE rating.

 

[CPseudonym]

I just noticed no BMS in your above system description George. Is there not one needed? I was under the impression one was mandatory.

 

[deckofficer]

Who is George? I don't use a BMS. I do a parallel bottom to top balance and use a cell logger with low alarm set at 2.95 volts on discharge and 3.5 volts high alarm for charging. Use an e-xpert to determine remaining capacity. Just stay away from voltage knees and you'll be fine, and that is easy to do on these cells because they have such a small voltage swing during discharge until the knee is reached.

 

[CPseudonym]

Sorry Bob, I'd blame my phone but that'd be a lie. Just a classic case of multi tasking brain spasm


Ok, that makes sense to me and explains the lack of BMS reference above.

 

[deckofficer]

When someone like Reuben designs systems for the masses, he has to protect the battery investment against careless operators, hence a BMS. You can employ one to be on the safe side, they are cheap insurance against a screw up, but to keep cells balanced which a BMS also does, I have found that if you balance before the install, then stay away from the voltage knees, they stay balanced. The alarm circuit on the cell loggers can always be used to activate a high amperage disconnect for the bank, thus removing it from further discharge and over charge.

 

[markpierce]

A sailboat seems more practical if one wants to go "solar." ... Batteries are "nasty" (chemicals, lead, lots of CO2 to produce) especially in the volumes needed for primary propulsion. Spending 50K to 100K for electric conversion would buy a lot of diesel fuel even at several times the current cost.

 

[deckofficer]

A sailboat seems more practical if one want to go "solar." ... Batteries are "nasty" (chemicals, lead, lots of CO2 to produce) especially in the volumes needed for primary propulsion. Spending 50K to 100K for electric conversion would buy a lot of diesel even at several times the current cost.

Just 5 years ago you wouldn't be able to recoup the cost of electric propulsion over the cost of diesel. At the current cost of solar around $1 per watt, combined with the recent drop in LiFePO4 prices, the return on say a converted PDQ 34 trawler would occur in under 25,000 nm. For a full time cruiser, that would be about 3 years of cruising, after that your almost cruising for free.

The time has come to give consideration to electric propulsion.

 

[markpierce]

If so cost effective, how come taxpayers need subsidize solar?

 

[deckofficer]

If so cost effective, how come taxpayers need subsidize solar?

It isn't that cheap due to domestic produced solar but rather China dumping to capture the market. That kind of competition will drive others to bankruptcy. But makes no difference, the result is the same, and that is cheaper propulsion than fossil fuel.

 

[markpierce]

Staying with a 1-to-4 gallon-per-hour diesel engine is the smart "non-move" at my life stage.

 

[RickB]

Remember, because of the torque of an electric motor, 15 hp electric rating would equate to much more than an ICE rating.

Bollocks.

Playing games with input power doesn't change the fact that boats are driven by output power measured at the propeller shaft. If your boat takes 15 HP to move through the water at 5 knots, it doesn't make one nanospeck of difference if that shaft is turned by an electric motor, a gas turbine, a squirrel in a cage, a steam turbine, or a diesel engine.

The metrics you guys use to develop interesting numbers for terrestrial vehicles simply don't apply to boats. A propeller doesn't act on the water like a tire on pavement or train wheel on a rail. The availability of high torque at low speed doesn't count for much in a fluid medium unless acceleration is your primary interest and I suspect few here are driving ship assist tugs, ferries, or drag boats.

 

[FF]

"If so cost effective, how come taxpayers need subsidize solar?"

Because solar folks bundle cash into 1/2 million dollar chunks for democrat elections and get paid back 1000-1 .

Similar questions have been asked on this , link for a decade.

http://www.boatdesign.net/forums/hybrid/solar-powered-cat-again-46834.html

They have a great search function.

 

[RT Firefly]

 

[sunchaser]

Craig

Feasibility Studies always have section called Risk and one called Economics. For Risk, think clearly and ask your insurer. For Economics add a contingency of at least 50 percent.

Ask Bob to give an estimate to Lump Sum the entire job through acceptable turnover to the client and see what the real cost is if contracted out. If not Bob I would assume he knows of an experienced company to Lump Sum EPCM the job through Completion.

BTW, the terms I have capitalized are well defined in Feasibility Study efforts. It is necessary with new endeavors to smoke out the real costs and issues and get beyond the hype. Feasibility Studies can be done on a small scale too, the pencil just needs to sharper.

Last but not least, props move boats as was just stated by the smartest marine engineer on TF.

 

[CPseudonym]

This is all great stuff and what this thread is about, real numbers to compare to. I am interested in not just the good, but the bad and ugly as well.

 

[CPseudonym]

Bollocks.

Playing games with input power doesn't change the fact that boats are driven by output power measured at the propeller shaft. If your boat takes 15 HP to move through the water at 5 knots, it doesn't make one nanospeck of difference if that shaft is turned by an electric motor, a gas turbine, a squirrel in a cage, a steam turbine, or a diesel engine.

The metrics you guys use to develop interesting numbers for terrestrial vehicles simply don't apply to boats. A propeller doesn't act on the water like a tire on pavement or train wheel on a rail. The availability of high torque at low speed doesn't count for much in a fluid medium unless acceleration is your primary interest and I suspect few here are driving ship assist tugs, ferries, or drag boats.

This has been a major stumbling block to my understanding this from the very begining. HP is HP and boats are driving 'uphill' so to speak all the time. Part of the reason you dont find 5 speed transmissions in boats. I see where an electric motors inherent torque is an advantage but that still doesn't rule out the obvious, it's still HP doing the work. Minimum surface boats such as cats and tris have obvious advantages but the subject is converting my Owens, a mono.

I suppose calculating the hull speed and then finding the horsepower required to push it just below that speed are the next 2 things I need to do in order to get a better picture of reality.

I'm compelled to give you guys a bit of personal background to perhaps understand my facination with this subject better. I have been driving an electric vehicle daily for 3 years and really enjoy it. It has limitations as it only drives 25 MPH with 30 miles range but have found living within those limitations quite a bit easier than some might invision.

 

[AusCan]

The economic advantage of solar may or may not be there, depending on how you use your boat. IMO in most cases, it isn't ther yet - but its getting closer every year.

But really - who owns a trawler for economic advantage? All boats are an economic disadvantage unless you make your living from it.

What I love about projects like what Craig, Rueben and Bob are into, is that it pushes the boundaries. It's not just restoring old technology (nothing wrong with that), but it seeks to improve on a thousand+ years of boatbuilding design.
Successful or not, how can anyone knock that? As a bonus, it may leave a few gallons of diesel for future generations.

I congratulate you guys for your efforts!

 

[rjtrane]

I was just thinking that a good candidate for conversion to electric propulsion would be a 30' Scout (Elco replica). She is a more aesthetically-pleasing platform with plenty of fore-deck and canopy for solar panels. I recall from her sea trials that she uses minimal fuel (ie. HP) at lower speeds.

Regarding the Owens - why not convince a good friend to tow you on a calm day with an adequate scale in line with the tow rope. Measure the pounds of resistance at a variety of speeds creating an empirical HP/Speed curve. A naval architect will be able to translate the pounds into HP for sizing the motor and battery. This should not be too difficult to execute with some planning.

One of the most attractive aspects of cruising an electric boat is the absence of noise and fumes. A well-equipped cruiser that spends significant time on the hook, will run a generator from time to time - sometimes daily - sometimes continually (for air conditioning). Not having to do this can increase the intangible pleasures of anchoring out - especially in crowded anchorages. Cruising yachts, by their very nature tend to be expensive - and choosing the best personal return for one's dollars is certainly an individual's choice. Many buyers of hybrid cars do so not to save money - but to use less gas. Rather than buy a Prius, one could buy an equally well-equipped Hyundai for significantly less and use the savings to buy gas for the length of ownership. But most Prius owners feel good about their return on investment.

Since this is a trawler forum and not a sailing one, I am curious why suggesting a sail boat as an alternate to an e-boat keeps being raised. Usually accompanied with comments such as how does a solar boat do at night? My suggestion is to reverse the situation - how does a sail boat do in a calm? Along the ICW? Going under bridges? Through crowded anchorages? Sail has its limitations just as electric propulsion just as diesel and gas. They're just different. Having lived aboard a sail boat, done some ocean passages and built over 300 of them, I feel I can speak with a modicum of experience.

 

[rjtrane]

I was thinking the other day that a good candidate for electric propulsion would be a 30' Scout (Elco replica) - she is aesthetically pleasing while having plenty of fore-deck and canopy space for a PV array. From original sea trials I recall that she used minimal fuel at slow cruising speeds - about 6 knots.

Regarding the Owens - perhaps you could convince a friend to tow your Owens with a suitable scale mounted in-line with the tow rope (see attached photo). A naval architect could take the speed/pounds data and convert to speed/HP curve. Armed with this empirical data, you could then easily determine the amount of e-power and battery that would meet your needs.

 

[CPseudonym]

I agree the Scout would make a great candidate. Love those classic lines.

Towing with the scale or force gauge is something I'll try arranging.

 

[deckofficer]

Bollocks.

Playing games with input power doesn't change the fact that boats are driven by output power measured at the propeller shaft. If your boat takes 15 HP to move through the water at 5 knots, it doesn't make one nanospeck of difference if that shaft is turned by an electric motor, a gas turbine, a squirrel in a cage, a steam turbine, or a diesel engine.

The metrics you guys use to develop interesting numbers for terrestrial vehicles simply don't apply to boats. A propeller doesn't act on the water like a tire on pavement or train wheel on a rail. The availability of high torque at low speed doesn't count for much in a fluid medium unless acceleration is your primary interest and I suspect few here are driving ship assist tugs, ferries, or drag boats.

Your right hp is hp regardless of what is producing it. The difference comes when trying to reach an rpm for a given hp. 9.9 hp outboards come in two configurations, standard and high thrust. High thrust just means the prop is pitched shallow to allow the gas engine under the load of a 7000 lb sailboat to reach its rpm range that produces those 9.9 hp, around 5500 rpm. It trades speed through the water with that lighter pitch because the gas engine does not produce enough torque at lower rpm. If you were to take static bollard pulls on a 4 hp electric vs a 9.9 hp gas, you would see through the pull that the electric would match (or exceed at very low rpm) what the gas engine was doing, so it is fair to say that a 4 hp electric has the same propulsive pull as a 9.9 gas, and that is what you as an operator depend on.

The same does apply to cars, trains, and boats. The diesel in a train at its rated rpm for hp does move the train, but could never get it started from a standstill because if it was direct coupled the diesel would stall under the load. The last ship I was on had the task of holding position over oil wells during all conditions and currents. This could never be done with the weak kneed torque of a diesel at low rpm. I had (7) Cat diesels, each rated at 4.6 Mw @ 900 rpm producing the electricity needed to power (6) 5000 hp electric thrusters. Through the entire rpm range the electric motors were doing a job the diesels with their torque curves couldn't.

For the few of you that have had the pleasure to do tight maneuvering in a current plagued marina know how precise you can handle your vessel with electric propulsion. No clunking in and out of gear, able to change prop speed quickly, and being able to choose as slow a prop rpm as you want, not dictated by the diesel's need to idle at 600 rpm. Reuben knows this feeling, I'm surprised he hasn't mentioned that in tight situations he has full linear control of his boat in a very precise manner. You have to try it to believe it.

 

[RickB]

I had (7) Cat diesels, each rated at 4.6 Mw @ 900 rpm producing the electricity needed to power (6) 5000 hp electric thrusters. Through the entire rpm range the electric motors were doing a job the diesels with their torque curves couldn't.

I guess I should have added DP vessels to the list of those that normally operate at low speed and require frequent and rapid thrust changes to facilitate maneuverability.

The only time(s) electric propulsion has proven effective in what might be defined as "cruising" vessels is the very first installation which was chosen because there was no other way to power astern, during wartime when reduction gear production was limited to warship propulsion, a few coastwise product tankers because they commonly as much power to offload as they do to travel at sea speed, and cruise ships which spend the majority of their lives at zero speed with an enormous hotel load.

It appears this discussion provides readers with a glimpse behind the doors of the MEMMS.

 

[deckofficer]

Rick,

The only real issue to cruising with electric propulsion is competing with the energy density of fossil fuel. Reuben has addressed that by having a daily trickle of energy being produced via solar and storing for night time propulsion. If a clunky, heavy cat like the C60 commercial ferry can cross the Atlantic on just 10 Kw of solar panels, does that not prove the concept viable? transatlantic21: The world's first crossing of the Atlantic on a solar boat

How about a purpose built, light weight cat that has 8000 nm on just 8 Kw of solar?
Boat - SolarWave

I could take Reuben's boat Sunshine with just 6 Kw of solar and circumnavigate. Granted it would take a bit longer to do so than in a fossil fueled boat, but at 27,000 nm the fossil fuel boat would burn through over 13,000 gallons of diesel.

The name of the game is hull(s) efficiency and light weight. My personal best is 32 w-hr per nm. With LiFePO4 that equates to 80 nm on 60 lb of batteries.

 

[RickB]

The only real issue to cruising with electric propulsion is competing with the energy density of fossil fuel.

So who is competing? I am just saying that it is silly to imagine anyone can convert an existing "trawler" (or any other powerboat for that matter) into a solar powered or hybrid vessel and save money or energy, or increase propulsive efficiency and still maintain the utility and versatility of the original boat.

It may be great fun to debate the pros and cons of various bits of hardware but trying to justify it as a means to save fuel or money is more than just a stretch.

With enough cash and time, anyone can build, convert, or install pretty much anything available and given enough time and more money, go around the world a few times with it but leading people to think that is somehow more efficient or better than knocking around the San Juans or the Keys in a Lehman powered trawler is specious. If economy and efficiency are the real goals, build a raft. There is a current going your way somewhere ... eventually.