Electric Ferry

Hi guys,

We are working on an electric ferry but I have come up against a road block of sorts. It revolves around the charging of the vessel. We would like to auotmate this system so the ferry automaticall couples to shore power each time it docks and has the potential to take on energy. My problem is I haven't been able to find any suitable connectors to do this. I want to ask if anyone out there on this great website has seen or used such a connector before? We are talking about the ability to hand 600VAC, 200 amp service and be reliable enough to manage over 80 connections a day plus be suitable for the marine environment. I will appreciate any help I can get on this. Only so much time you can search the internet for this stuff.

Regards,

Christian

 

I believe that your best bet is the inductive charging - http://en.wikipedia.org/wiki/Inductive_charging. This company, for example, produces inductive chargers for automotive use: http://www.pluglesspower.com/unleash/ . Pdf brochure here: http://www.pluglesspower.com/unleash/images/Plugin_2011_brochure.pdf

Since your requirements call for a rather intensive power transfer (120 kW), way above what is used for automotive battery charging, you might not be able to find an off-the-shelf solution for your needs (I haven't checked this). However, it should not be too difficult to design an inductive plug for marine use and optimized for your specific needs.

One advantage of this type of chargers is that, since they don't require direct contacts between conductors, the whole system can be made perfectly sealed, waterproof and with minimal risks of electrocution. A disadvantage is that a certain percentage of energy will be lost due to inductive losses, so the transmission efficiency is typically between 85-95%.

The following pdf contains some more info on inductive chargers currently under development for a use in automotive industry: http://etecmc10.vub.ac.be/publications/evs18gm.pdf


Cheers!

 

How about something based on a contact shoe like is used in electric streetcars, here just one version: http://en.wikipedia.org/wiki/Contact_shoe#Contact_shoe

Should be able to take the power and repetitive contact, and could be customized to less challenging non mobile applications..

Porta

 

That depends on the service (maintenance) available in your area.

What part of Canada are you in?

-Tom

 

I was thinking the same as Portacruise. You can take any amount of current through such a setup and it can be rigged up very high above the boat and away from any ferry passengers.

Also, think of electric bumper cars... they use the shoe as well.

 

I'm not an expert at anything really exept how to talk about things I know nothing about.

The crucial thing would seem to me the amount of time you are in dock versus the amount of time in transit. Can you transfer enough power to the batteries in that time? Good battery life normally requires a trickle charge about the same time charging as working. The only experience I have is electric forklifts and boomlifts.

Also some batteries like to be fully discharged before recharging, although I think later technology has overcome this problem.

So even with a fast charge you would require more power to charge equaling bigger installation cost.

Maybe best not to reinvent the wheel and think along the lines of battery powered equipment that requires a change of battery so somewhere along the route you have a battery change station.

This then requires a smaller battery charger and where charging can equal time used. The batteries would be heavy and require mechanical means to change. An emergency power unit would also be necessary if the batteries went flat.

 

A proximity switch can be used to deactivate the streetcar contacts on the charger side for additional safety, so there in no shock hazard at intervals between charges.

"Dump charging" would be the way to go and just about all battery chemistries except SLA of the lead type have versions that can be charged in as short as 15 minutes from 0% to 80% without damage. This is old technology which has been used in EV drag racing to quickly charge between runs. The last 20% may need to go in slowly for some types to prolong cycle life but doesn't have to be done every cycle. Fully discharged requirement is only used for older nicad systems, AFAIK.

Dump charging is more practical than changing out tons of batteries several times a day. The dump can be done from a huge bank of stationary batteries that have been trickle charged overnight when power rates are much lower. It has been proposed as a method for quickly filling electric cars without exceeding the instantaneous capacity of the grid.

P.

 

No off the shelf solution is available for this power level, but daiquiry points you in the right direction.
A transformer building company can make you two potted coils with E or cylindrical cores, one for 600V, the other one for whatever voltage you need for charging. The shore part must be enclosed in a funnel shaped housing to align the mobile part and there must be some sort of sensing mechanism controlling the power to the shore coil.

Perfect alignment is not required, once the power is switched on magnetism will do that for you. The mobile part must of course be able to swivel a few degrees.

This is one of the few moments I regret being retired.....

 

Portacruise, my point was to avoid changing or charging several times a day. Electric forklifts etc can work all day without recharging. It is just a matter of sliding in a new bank of batteries for the day.

All the equipment I have had experience with, when the batteries are being recharged they emit Hydrogen. Not a gas to be around boats and passengers especially when you are connecting and reconnecting electric connections.

If designing from scratch the battery housing can form the stern of the hull. Unhitch the stern and plug another in. And depending on budget include the motor and prop.

I've never designed a boat that doesn't work.
Err well, I've never designed a boat.
Think I'll go now.

 

Look at car batteries.
Immediately after starting the alternator replenishes the amount of energy used by charging with 50 amps or more (up to 1C), dropping to half that within the 1th minute and to 1/10 within 5 minutes. The battery survives such a treatment for several years, just like it survives delivering 100's of amps for a few seconds.

There is a lake area in this country with many waterfalls, attracting several 1000's of tourists each day.
For environmental reasons they use electric boats to carry up to 80 people from one side of a lake to the other; you could call them ferries.
The trip takes approximately 20 minutes, loading and unloading passengers takes half that time, during which they charge the battery bank. In the tourist season the boats are in commission from sunrise to sunset.

The key factor is that they have enough storage capacity to make a number of trips without charging, so they use maybe 10% for one trip and can easily replace most of that within 10 minutes. At the end of the day the battery charge condition will not be 100% anymore, but then they have the whole night to correct that.

 

CDK, good explanation on the quick charging. What type of charging contacts do the electric ferries use that you describe on your beautiful lake? A reference might help track down something less costly than a magnetic induction charger.

Sorry Poida if I came on too strong, I hope you continue posting. An electric ferry would be like an electric forklift that has only enough power for 20 minutes, impractical to change batteries. It just costs too much and weighs too much to have a ferry with batteries lasting all day. Hydrogen is very flammable, but there are special ventilation systems. Maybe your experience is with flooded lead acid deep discharge? If you use sealed lead systems (AGM) and stay within the 80% limits, essentially no hydrogen is generated, and AGMs are built to take very quick recharges.

P.

 

I don't exactly remember what the guy held in his hands. They had a rope and a cable tied together; when the boat approached the jetty a guy took it, threw the rope around a bollard and put the plug in a socket.
With wages of $800 a month in this country you don't need fancy equipment.

 

Portacruise. No offence taken from your reply. I'm only 64 and as a youngster I have a lot to learn.

In Perth Western Australia we have a ferry that goes across the Swan River and takes about 10 minutes we use diesel.

Makes you wonder about the diesel engine versus the batteries.

Diesel directly to the prop. via a power station (coal?) to the charger - to the batteries to the prop.

Sure charge the batteries real fast, dock plug 'em in use induction charge stuff the wastage, and get them going.

Or, slow trickle charge, change batteries every 24 hours.

The question is, why are we using batteries?

Are we somehow believing we are using less power, greening the planet by less efficiency.

Or have I just drank 1 x bottle of red and 6 beers and talking ****.

 

Most power stations convert fuel to electricity with a pretty high efficiency; 50% is pretty normal, with the best combined cycle plants achieving around 60%.

The best diesel engine will struggle to average more than about 35% efficiency, maybe 40% peak, a petrol (gasoline) engine will struggle to get better than about 30% efficiency.

Even accounting for distribution losses and charging losses an electric propulsion system charged from the grid can be "greener" than using fuel directly for propulsion, both in terms of fuel energy usage and emissions.

 

You plan to cycle this system every 6 minutes 7 days a week?