Long duration
energy storage

Thanks to VoltStorage's Long Duration Batteries based on iron salt technology, operators of solar and wind farms can not only ensure overall security of supply, but also make their business model fit for the future.

Pioneering solutions for wind and solar farms

Wind and solar farms throughout the country are fundamental contributors to the supply of power from renewable energies, both today and in the future, and represent a key driving force for the success of the energy transition. In order to bridge gaps in supply during periods of low wind and low sun to ensure the provision of grid scale base load, and to meet the growing demand and need for climate-friendly solutions, efficient, cost-effective and sustainable forms of energy storage are an essential cornerstone.

The energy industry in change

The need of solar and wind farm operators for long duration energy storage will increase significantly in the coming years. Currently, there is a high negative correlation between wind and solar energy generated on a monthly basis – but in order to ensure the provision of the base load on a daily and weekly basis, long duration storage is required. Otherwise, a supply from wind and solar energy is limited to a share of 60-70% in a power grid like in Germany.

The necessity for the use of storage solutions in wind and solar parks will rise due to legal regulations and specifications. The combination of solar and/or wind power plants with an efficient storage solution will increasingly be defined as the standard. On the other hand, ensuring the profitability of new solar parks or wind farms is becoming more and more important. Long duration batteries will thus become a key technology in the energy industry in the coming years.

Long duration storage as a key technology

Long duration batteries generally refer to energy storage systems that charge or discharge over a period of more than eight hours. This is in contrast to batteries such as those used in electric vehicles. The focus these battery technologies is on short charge cycles and the provision of high power in a very short period of time (often less than one hour).

Advantages of long duration storage

For certain applications, especially renewable energy storage from solar and wind farms, the focus is less on shortening charge cycles and more on longer discharge times to close the supply gap and cover the base load during periods of low wind and low sun. In addition, low costs and a long service life of the storage solution are decisive parameters in the field of renewable energies.

Groundbreaking: The long duration battery from VoltStorage

The Long Duration Battery from VoltStorage is based on the revolutionary iron salt technology. This technology is based on the redox flow technology that has been proven for years and has decisive advantages over conventional storage technologies, especially with regard to long-term storage. The materials required for the production of the Long Duration Battery are not only environmentally friendly, but also cost-effective and available worldwide. For operators of solar and wind parks, the Long Duration Battery not only generates significant cost advantages, but is also impressive in terms of durability and versatility.

Conceptualized as a long-term storage solution with cascadable storage capacities, the Long Duration Battery is suitable for stationary applications with an energy demand of 10-100 hours. The storage system has a modular design so that capacity and performance can be expanded as required. Compared with other long duration storage technologies, the storage solution is also more efficient, with an efficiency of over 70%. With a service life of more than 20 years and over 10,000 charging cycles, the Long Duration Battery from VoltStorage also promises a high degree of durability and cost-effectiveness.

You can find out more about the current state of development of the Long Duration Battery in our Innovation Lab.

Member of Long Duration Energy Storage Council

VoltStorage is a member of the international Long Duration Energy Storage Council (LDES Council). The mission of the LDES Council is to meet baseload demand from renewable energy sources using carbon-free, long-term storage to eliminate the use of fossil fuels. To this end, the LDES Council provides guidance and advice on the implementation of long-term energy storage for government and electricity grid operators, while also acting as a point of contact for industry representatives in the energy sector.

Learn more

White paper Iron Salt Technology

You want to know how on-shore wind and solarparks can provide base load power with long duration batteries based on iron salt technolgy? Find out more in our latest white paper!

Advantages of the long duration battery based on iron salt technology

The Long Duration Battery is a particularly cost-effective, sustainable and universally applicable application for solar and wind farms to bridge supply gaps during periods of low wind and low sun, to ensure the provision of base load and to meet the growing demand for climate-friendly solutions in today’s world.


In storage systems based on redox flow technology, performance can be decoupled from capacity and scaled independently according to demand. In a configuration optimized for long duration storage, this leads to a significant reduction in costs per kWh compared to other storage systems. The cost advantages of this ecological storage technology increase significantly in correlation with the storage duration, which makes this storage technology particularly interesting for use as a long duration battery from an economic point of view. Through the iron-salt technology, VoltStorage aims speed society’s transition to renewable energies.

Universally applicable

Compared to storage systems based on hydrogen or pumped-hydro power plants, the use of a long-duration battery from VoltStorage does not require any massive investments in the provision of a suitable infrastructure or any special geological conditions. For example, iron salt technology is a particularly temperature-resistant battery technology that can be used worldwide, even in climatically challenging regions. The storage system can be connected to existing infrastructures in a space-saving and decentralized manner, which additionally ensures the self-sufficient functionality of the storage solution and increases reliability.


With iron-salt battery technology, VoltStorage employs an iron-based storage medium – one of the most abundant materials in the world. The use of ecological materials allows the storage technology to be scaled according to the given necessities, thus enabling economies of scale to be gained.

100% non flammable

Operational safety plays a key role in energy storage. The iron salt technology offers a decisive advantage in this respect: The iron-based electrolyte consists exclusively of non-flammable components, and is mostly pure water.


With redox flow technology, we are relying on a proven CO2-saving battery technology. Thanks to the ecological redox flow storage technology, power from renewable energies such as solar and wind plants can be used around the clock in a sustainable way, contributing to the fight against climate change.

Iron salt technology

Thanks to the unrivaled low cost and high availability of the iron-based storage medium, iron salt technology has the great potential to shape the future of lithium free stationary battery storage.