# Would it be possible to construct an electric generator using only ionic conductors like salt water?

In a world where people are not allowed to (or choose not to) make use of electron flow current, would it be possible to construct an electric generator using ionic conductors such as tubes with salt water? If so would that work efficient enough to be practical?

Edit: Or, if I were to take a permanent magnet dynamo/magneto and replace the electric wires with salt water tubes (and make the magneto proportionally larger to accommodate the tubes, which would have a larger diameter than copper wire), would that be able to generate any kind of measurable/usable current? Or would the higher electrical resistance or something else prevent that.

• A natural occuring example for how to generate electricity without the use of conventional conductors would be lightnings. You basically create a capacitor through friction and two non-conducting materials and then attach a salt water tube. I would go with an acid though instead for better conductivity. Aug 2 '17 at 10:42
• Isn't that known as a battery? Aug 2 '17 at 11:11
• As a technicality, if you can't have electrons flowing to create current, an electric generator cannot exist because the definition of an electric generator includes causing electrons to flow in a current. Aug 2 '17 at 17:42
• Electrons are not the only particles with electric charge. Ionised atoms that move also form an electric current. That is what happens when salt water conducts electricity. Aug 2 '17 at 21:47

Well, look at it this way...

You get a flow of charge, whether ions or electrons, when there is a charge imbalance, i.e., there is an excess or shortage of charge of one type or another at one part of the circuit compared to another. The current flows to neutralize this imbalance. This, we call potential difference or voltage.

Electrolytes are electrically neutral. There is exactly the same amount of net positive charge as there is net negative charge though the actual number of ions may vary. As a result, there cannot be a potential difference within a free flowing electrolyte solution. We can have a potential difference, if the solution isn't free flowing.

As in the above picture, from https://www.revolvy.com/main/index.php?s=Polymer%20electrolyte%20membrane%20electrolysis you can put in a semi-permeable membrane between the electrodes of your cell. Now, if you pump in electrolyte solution on one side, the smaller ions can migrate through to the other side, the larger ions can't. So you've got a difference in potential, a tiny one to be sure, but you do have it. In fact, you have what could be called an electrolytic diode, and given an appropriate stimulus, you could get a tiny current across the electrodes.

Except that you don't want electrical current; you want ionic flows. In order to do that, we pull the net charged liquid out with a pump and send it towards an oppositely charged electrode, which will, hopefully give you a miniscule current, assuming that the ions don't discharge in air or within the pipeline. In other words, you can do it, but the cost would be a net negative energy transfer, i.e., you would be putting in maybe a thousand times the energy you will recover.

Now, if you replace the liquid with plasma, you can form a plasma channel, which has far less resistance to transmit charges from a static generator. Here you have the costs of generating the plasma in the first place, in addition to the fact that convection is several orders of magnitude worse at transmitting energy than conduction. On the other hand, there will be less electrical resistance.

In short, you can do it if you really want to, but it isn't very practical.

• This is not "only ionic conductors" as the OP asked. That little solar panel on top act as generator...
– L.Dutch
Aug 2 '17 at 13:02
• @L.Dutch: I know. I couldn't find a better image :( Aug 2 '17 at 13:54

What you are describing is essentially part of an MHD generator. In most MHD generators, ionized gas is passed through a magnetic field, much like a traditional generator passes a wire through a magnetic field.

MHD generator and traditional generator

Of course, much of the efficiency of an MHD generator comes from the high temperature and high speeds of the gas or plasma flowing through the magnetic fields. In theory, the flow of lower temperature gas or a mass of hot, ionized liquid could produce electrical energy as well, but the MHD device would be much larger and require a much more powerful magnet or magnets to operate. A low temperature ionic conductor probably would not work well in an MHD generator unless it was forced through at improbable speeds or improbably powerful magnetic fields were used.

The simplest possible design would be the Kelvin dropper - use conductors from wet strips of cloth and you have it!

The traditional rotating generator would be very ineffective without some ferromagnetic for amplifying magnetic field and I guess you would forbid using the most common ferromagnetic - iron. Same goes for MHD generator.

I guess chemical batteries would be the best solution.

NO

A conductor, ionic or whatever, is only capable of supporting moving charges. It cannot generate current alone.

Rephrasing your question, it is like you are asking if it is possible to transport goods only having roads but no moving carriers.

• Both traditional metal conductors and salt water can conduct because they contain mobile charge carriers. In the case of metal that are free electrons, in the case of salt water the dissolved ions. Current is induced when a changing magnetic field makes the charge carriers move. Aug 3 '17 at 8:12
• @JanKanis, the changing magnetic field or the potential difference is not the conductor. You don't generate current just having a conductor.
– L.Dutch
Aug 3 '17 at 8:24