Re: Redox batteries

You are right about the concern with the leaks. However, I still do not know how toxic vanadium is for the environment. Of course, containment measures should be taken in the design so as to avoid any spillage.

I want to answer your question about not using lead acid batteries. I hope this will raise an interesting debate.

First, let me recall that my purpose is to build a hybrid propulsion house boat. That is, a boat that will sometimes ride at top speed (15 km/h), sometimes at half speed (most canals are limited to 6 km/h) and sometimes it will stay at a mooring for days.

The objective is to be energy-efficient. The energy source will be one or more of the following:
-a diesel generator: 20 kW;
-photovoltaic cells: at most 1 kW peak;
-wind turbine: at most 500 W peak.

To achieve optimum fuel efficiency, the generator must be used near full power exclusively. Then, the role of the battery is to buffer this pulsed power source to deliver just as much power as needed when needed.

To save energy, using the generator should, as much as possible, be avoided and power should come preferably from the sun and/or the wind.

This is where the lead-acid battery has two major drawbacks:

1) A lead-acid battery should always be fully charged, i.e. it should be partially discharged for the shortest period of time possible, to avoid the degradation process to come to play. This is not compatible with waiting until sun or wind are available.

2) A lead acid battery must be charged using precise current rates according to the state of charge. This is incompatible with the idea of accumulating all and as much energy is available at a time, i.e. always using the generator at nominal power.

3) Everyone knows that event with the utmost care, a lead acid battery shall not withstand more than say 1,500 equivalent full-discharge cycles.

I think that vanadium batteries completely address these three points, which make me hope they become available - and affordable - within a few years.

Sorry to be lengthy but I would be very pleased to discuss these arguments with as many people as possible.

Jean-Marc

Evgenij Barsukov wrote:
Jean-Marc Delaplace wrote:

I am currently trying to define what the appropriate battery would be for a hybrid boat. I found information on Vanadium batteries, that apparently are close to commercialization. Their biggest drawback is apparently the low specific energy, but this is not very critical on a boat. I also read about Cerium that could provide a higher energy density.
Does someone know about these? What is their future? Are the claimed advantages of Vanadium batteries true?
In short, I would like to discuss the topic in all its aspects, including hazard and ecologic risk.
For those who have no documentation but are chemists - which i am not - I can supply them with information I got by writing to a company that is currently developing a vanadium battery.
Jean-Marc


From the technical point of view using vanadium battery on the boat
appear to be a good idea as specific energy is basically irrelevant.
But than why not use deep-cycle lead acid cells, as same argument
applies there.

Main issue with using vanadium flow battery in a boat is the possibility of a leak. Soluble vanadium salts are toxic and the chance of damping a ton of this solution into a picturesque bay killing all forms of life for years to come appears scary.

Regards,
Evgenij
.

Relevant Pages

  • Re: Redox batteries
    ... the role of the battery is to buffer this pulsed power source to deliver just as much power as needed when needed. ... Lead Acid battery is one of the least sensitive to charging rates (probably only cylindrical NiCd beats it in this respect, ... In fact I can turn the table here - vanadium flow battery is bound to have low power capability/capacity ratio, because its electrode surface is much smaller than any conventional battery. ...
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  • Re: Redox batteries
    ... the role of the battery is to buffer this pulsed power source to deliver just as much power as needed when needed. ... Lead Acid battery is one of the least sensitive to charging rates (probably only cylindrical NiCd beats it in this respect, ... In fact I can turn the table here - vanadium flow battery is bound to have low power capability/capacity ratio, because its electrode surface is much smaller than any conventional battery. ...
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