Ecfriendly seawater powered battery

[Just_another_Dave]

This morning, I read a piece of news about a new “ecofriendly” battery that can produce energy by just adding seawater. According to that piece of news (https://www.20minutos.es/noticia/4825131/0/lampara-esperanza-zonas-electricidad-luz-agua-salada/), Waterlight, which is the name of the product, is able to generate electricity from it through electrolysis . As that sounded quite dodgy (electrolysis requires energy to happen), I searched their website (https://www.waterlight.com.co/), just in case it was a misunderstanding of the reporter, yet it does not provide almost any information about how it works. Nevertheless, they say in their website that it is rechargeable and that it uses a magnesium electrolyte to produce energy.

Adding magnesium to water produces an exothermic reaction, as well as hydrogen, so it seems that the battery might be using that reaction to produce electricity. However, if that’s the case, the battery would stop working after all the magnesium has been consumed. Consequently, it would require adding more magnesium or regenerating it from it oxide (I suppose the second option as they specify that it can be recharged).

All in all, it seems pretty dodgy to me as it is advertised as a solution for off-grid regions to produce electricity, but in the best case it would still require another energy source to recharge it. Additionally, they also say in the piece of news that I read that they want to use the hydrogen gas that it produces to obtain drinking water, which sounds great but would require huge amounts of magnesium and water to generate enough drinkable water for a single person

[Haenk]

It's not nonsense per se - Mg-based primary cells are thing. It seems like there are versions that could be kept "dry" and stored for a long time.
The nonsense part ist the lamp itself. Designer stuff with costly manufacturing and obscure technology - for a buyer who can't afford electricity. Sure, sounds like a proper business plan.
In fact, while there might be no grid, most people in poor countries do have electricity. A car battery works pretty well for that. Certainly a faint lamp will not change those peoples' lives.

[Just_another_Dave]

That’s mainly why I feel it dodgy. I’m quite sure that the lamp will work, but the expectations that they are trying to create and the obscurity of the information that provide makes me think that it has some inconveniences (cost, how it will be recharged after the first use, etc).

However, they try to avoid saying that manganese is used when they get interviewed (they basically said that just by adding water electrolysis happens inside it and energy is obtained, being posible to recharge it by changing that water when the battery is completely discharged)

[Haenk]

Changing the electrolyte is not "charging" - as the electrodes "wear down" (so to say). Those could be exchanged, but are most likely more expensive than using standard alkaline batteries.
I'm sure the "inventor" did know about this little detail, so marketing comes very close to fraud.

If you really want a cheap source of light, the traditional "one buck" garden lights (junk solar cell, junk NiMh cell, LED) are as cheap as it could get.

[Just_another_Dave]

Dynamo powered lights are usually quite cheap as well and they normally can be used even without a battery (in case it reaches its end of life). Both options seem a better solution for that application

Additionally, as it is used just for providing light, an oil or alcohol lamp might also be a simpler solution. They’re easy to manufacture and both, the lamp and the combustible, are relatively cheap