Organic electrolytes are intended to advance the energy transition

Organic electrolytes are intended to advance the energy transition

Organic instead of inorganic electrolytes could make the temporary storage of electricity more environmentally friendly. Lignin is a suitable raw material, electrically active plastics and salt as well.

The town of Alzenau in the far northwest of Bavaria is preparing to make a significant contribution to the success of the energy transition. A 200 kilowatt battery will start operating there in mid-2019. It is intended to store excess electricity so that it can be released without delay in times of lull.

If the powerful turbo-generators of nuclear and coal-fired power plants gradually cease to exist in the coming years, there will be no ready-to-use compensations for supply gaps in the power grid. The generators simply balance them out with their inertia - they run a tiny bit slower for a short time. However, when they are no longer available, other energy storage systems have to step in at lightning speed and supply energy. Batteries have the best cards so far to take this place.

200 KW battery with liquid electrolytes from lignin:

The size of the new electricity storage facility in Alzenau is by no means impressive. The power plant operator Steag in Essen, for example, operates six lithium-ion battery blocks with an output of 15 megawatts each. The fact that a redox flow battery is installed in Alzenau is also not a premiere. But this power storage works with liquid electrolytes that are made from lignin - a natural product that is in the order of millions of tons that is left over every year in paper production. To a certain extent, lignin is the glue that binds the cellulose fibers in the wood together so that massive logs are created. The lignin must be removed before the fibers can be finished into paper. It is usually burned.

Goal: Detach vanadium in electrolytes:

The company CMBlu in Alzenau has developed batteries and electrolytes. The latter are modified quinones, an important group of organic compounds made from lignin sulfonates. They are generated as waste in the manufacture of pulp.

Redox flow batteries typically use electrolytes that contain the relatively rare metal vanadium. A more environmentally friendly solution, where there are also no limitations due to a lack of raw materials, is the use of organic materials such as quinones or conductive plastics in a salt solution, such as Kemiwatt from Rennes in France or JenaBatteries, a spin-off from the University of Jena. While these companies are already selling energy storage, CMBlu is still at the beginning.

Premiere for lignin solution with 50 kilowatt hours:

Redox flow batteries consist of the central reaction chamber, two tanks for the electrolytes and two pumps that carry the liquids. When charging, electrons are transported from one electrolyte to the other. This happens in the reaction chamber, the heart of this battery. When discharging, the process is reversed so that electricity flows - in this case into the grid. The storage capacity of such a system, i.e. the amount of electricity that is buffered, largely depends on the size of the external tanks. CMBlu starts with small containers, so the arrangement can only deliver 50 kilowatt hours. The company claims that it is enough to optimize the system.

The automotive supplier Schaeffler, to which Continental also belongs, has been a partner of CMBlu since the end of 2018. His boss Peter Geigle sees three areas of application for his redox flow battery, also known as a river battery. First of all, there is the intermediate storage of wind and solar power, which is produced more and more frequently and in larger quantities at times when there are no customers. Large batteries can jump in at lightning speed if needed.

With Redox-Flow, e-cars are quickly charged:

This type of battery is also interesting for industry. It can cover peak loads, i.e. the short-term consumption of a particularly large amount of electricity. Obtained from the network, it is extremely expensive. And electric mobility will also benefit from this. The batteries should not be installed in cars, although electric cars with redox flow batteries can drive. Instead, they are used in quick-charging stations that easily deliver 350 kilowatts and charge vehicles quickly. The public power grid rarely offers such high performance. A redox flow battery collects electricity at times when no customer is docked, so that it can start at full power when needed. It is even possible to replace the used electrolyte liquid by tank truck - it can be charged externally.

Search for producing partners

“We don't want to produce anything ourselves. We are a research company that develops the technology to such an extent that it can be passed on to industrial companies, ”says Geigle. He has already signed contracts with customers who want to implement pilot projects over the next two years - including Schaeffler.