Renewable FlowStorage

Flow battery

ready for home use

Researchers have developed a redox flow battery that can store solar energy cheaply and safely – and this is good news for people with solar cells on the roof. The battery will be launched on the market in less than a year.

A scalable flow battery for home use will make solar cells a much better business for private individuals than they have been to date.

The recently developed flow battery is based on a known technology – vanadium electrolytes – where one of the advantages is that the effect and energy capacity of the flow battery can be scaled independently of each other, enabling batteries to be used in private homes.

The research group is now in full swing developing new generations of cleaner and even cheaper flow batteries based on in-depth knowledge of organic chemistry – as well as a completely new type of solar cell that can recharge the flow battery directly instead of producing electricity.

Patent on fireproof and rechargeable batteries
The organic flow batteries and photoelectrochemical solar cells are not ready for market – they still require a certain amount of research and development, even though the ideas they are based on have already been patented.

The researchers behind the ‘package’ consist of Associate Professor Anders Bentien, who is an expert on flow batteries, and Professor Adelio Mendes, who is an expert on photoelectrochemical solar cells.

“While we’re working on developing the next generations, much has already been gained in vanadium redox flow batteries. They’re not flammable like lithium-ion batteries, and they’re considerably more economical. They can also be recharged far more times than lithium-ion batteries – about 10,000 times – without losing their capacity, and the investment price is falling. We’re now on the way down towards EUR 200 per kilowatt hour – and that’s just with vanadium. With organic electrolytes we can probably get down to less than EUR 75,” says Associate Professor Bentien.

Storing solar energy pays off
It would generally be an advantage for solar cell owners to store surplus electricity at home instead of selling it to the grid. This is because solar cell owners in Denmark and many other European countries do not get nearly as much for electricity as they have to pay when they need to use it again.

The size of the advantage naturally depends on how much it costs to store the electricity at home. And this is where the new redox flow batteries prove to be quite competitive.

According to Associate Professor Bentien, the battery’s return on investment is less than 10 years for the individual owner.

“Ordinary consumers with a solar cell panel only use approximately 25 per cent of the solar energy, and they sell the rest. With our vanadium system, this would typically boost it to up to 50 per cent, making solar energy a much better business. And this would be with a moderately large battery. You could in principle get up to 100 per cent with a sufficiently large battery, but it wouldn’t be worth it,” says Associate Professor Bentien.

Development of the new redox flow battery – and particularly the coming innovations – is now located at Visblue, a spin-out company whose owners include the researchers and Borean Innovation, which has also invested in the company.

PHOTO TOP: A new type of flow battery can store electricity cheaply, safely and efficiently. Visblue is a spin-out company that expects to have a commercial product available for consumers within a year. Pictured here is Anders Bentien, one of the researchers behind the new invention. (Photo: Anders Trærup)