Energy storage: the membrane barrier

A development by researchers from the Technion and Primus Power is expected to accelerate the integration of renewable and green energies in the electricity supply

Researchers from the Technion and their colleagues at Primus Power have developed membrane-free flow batteries that are expected to accelerate the integration of renewable and green energies into the electricity supply. the research, which was published in the journal ChemSusChem, led at the Technion by Lehi Amit and Prof. Mati Sass from the Faculty of Mechanical Engineering and the Faculty of Chemical Engineering by Wolfson.

Renewable energy is the following: without pollution, without limitless exploitation of the earth's resources and without environmental damage that harms humans. The sun and the wind are not mutually exclusive and we have the technologies to harvest their energy to create cheap and clean electricity. 

so whats the problem? The problem lies in the fickle nature of renewable energy sources: the sun, which disappears for many hours a day, the wind comes and goes, and so on. In contrast to the instability of these sources, the electricity suppliers are required to provide a relatively stable stream of electricity to the grids that lead it to the various consumers. If it weren't for this limit, the world would probably already be based on sustainable energies at much higher rates.

And what is the solution? storage. If the electricity produced from the wind, the sun and other renewable sources is stored in large batteries, the electricity suppliers will be able to flow it at a uniform rate throughout the day.

Seemingly a simple solution, after all we all use batteries; But in fact, when it comes to storing a neighborhood, city, district or national amount of energy, the technologies required for this - flow batteries – are still in their infancy. If they are available at all, it is at a very expensive price.

Flow batteries are large batteries that store the energy, during the charging phase, in an electrochemical format - the electrons are collected into one of the twoElectrolytes in the battery made of bromine and zinc. During the discharge phase, when they are required to provide electricity, the electrons move to the second electrolyte and thus the current is created. 

The most expensive component in a flow battery is the membrane which separates the two electrolytes. In fact, the cost of the membrane can be up to 40% of the cost of the entire battery stack. And if that's not enough, while the electrolytes that produce the electricity can function well for decades, the membrane needs maintenance and must be replaced from time to time.

Now, thanks to the creative thinking of Technion researchers, it seems that in the near future we will be able to say goodbye to the membrane. In the aforementioned research, Lehi Amit and Prof. Mati Sass developed a solution in which most of the bromine is trapped in a kind of particles with a shell that serves as a membrane for them. In this way, the two types of electrolytes (zinc and bromine) move in a uniform current, and when necessary, bromine can be released from the particles into the solution according to the reaction requirement on the electrode - and this is how the electric current is created. 

The Technion researchers demonstrated the feasibility of the technology in an experimental system and they estimate that the technology will operate successfully on a commercial scale as well. According to Amit, "Without the need for a membrane, zinc-bromine based flow batteries will be relatively cheap and will operate for an extended period of time without the need for the expensive maintenance of the membrane. Our intention is that a storage unit will be attached to each renewable energy power plant that will collect some of the energy for future use, thus enabling a stable current to be provided to the power grids."

For an article in ChemSusChem