Dr. Schichtel, thermal energy storage systems have been around for a long time. What is special about Kraftblock storage systems?
Our storage system is ideally suited to the present time: decarbonization and energy efficiency at the highest level. To achieve this, we have created a modular storage system that can be used for mobile or stationary applications. It is scaleable without permanent engineering and is based on highly efficient, cyclically stable and sustainable storage materials.
How did you get the idea of looking for a more effective alternative to the existing concrete and gravel storage materials?
Classical storage materials can serve certain niche applications or particular temperatures, but are usually dependent on an application temperature below 600 °C, and even lower in the case of concrete storage facilities.
However, it was important to us to cover as wide a temperature range as possible, to offer a significantly improved capacity and at the same time to keep an eye on sustainable and ecological parameters. For us, sustainable means that we use up to 85 percent recycled materials for the storage medium itself, but also that a good 90 percent of the total storage system can be used in some form after the end of its service life. “Ecological parameters” include in particular water consumption, but also the carbon footprint for the construction of the storage facility, which is pleasingly low at 180 kilograms of CO2 per megawatt hour of capacity.
Kraftblock storage units can not only absorb and release heat and cold, but also generate electricity from them. How does that work?
We designed our storage system on a modular basis. The storage unit is modular in that it is scalable by adding several modules. And the storage system, which consists of a charging and discharging unit and the high-performance storage unit itself, is also modular. In the simplest case, the discharge unit is an Organic Rankine Cycle (ORC) for reconversion to electricity, and then increases in size and efficiency up to a combined cycle turbine.
“It was important to us to cover as wide a temperature range as possible, to offer a significantly improved capacity and at the same time to keep an eye on sustainable and ecological parameters.”
What storage capacities do Kraftblock storage systems have?
The capacity of the storage unit naturally depends on the temperature. In the best case, the system has a gross capacity of 1.2 MWh/m³.
Conventional power storage units are limited in their service life because the lithium-ion batteries used in them are exhausted. How many charging cycles can a Kraftblock storage unit tolerate?
Ultimately, as storage material we have created a kind of synthetic stone that can last up to 15,000 cycles. At that point, the end of the service life is still not necessarily reached. This value applies to a very wide temperature range (charging at 1,200 °C, discharging at ambient air temperature, i.e. a temperature difference of approx. 1,180 °C).
What potential applications do you see for the Kraftblock storage units in the future?
Thanks to its versatility, the system can run in many applications. On the source side, electricity and various types of waste heat are suitable (ideally from 350 °C upwards). We mainly see applications in the metal-producing industry, the glass and ceramics industry as well as in the petrochemical industry and cement production. The heat sink can be located within the plant (replacement of primary energy) or outside the direct range of the waste heat source. In this case, Kraftblock can be used as a mobile high-temperature system, or we support the local and district heating lines directly.
Where can you envisage firm opportunities for cooperation with STEAG and its district heating networks?
STEAG has a fantastic customer base, many of whom are suitable both as sources and sinks. Using our system, ‘lost energy’ can be absorbed and buffered, and made available to the heating networks as CO2-free heat, whether temporarily, for example in winter, or permanently as part of mobile heating networks. This allows us to expand grid-bound heating networks to regions where “stationary” systems would be too expensive.
You are also pursuing an interesting approach to the future use of coal-fired power plants in conjunction with Kraftblock storage systems – how will that work?
These activities are summarized under the keyword ‘storage power plant’. The basic idea is to use the existing power plant infrastructure for future energy supply (electricity and heat) without burning coal. The furnace will be replaced by a thermal storage unit, which will be fed with ‘surplus electricity’ and/or industrial waste heat and then, instead of burning coal, will provide the heat for the generation of electricity.
Are you also counting on a transfer of know-how from STEAG, from which you could benefit at Kraftblock?
The transfer of know-how is certainly an exciting point for us. Among other things, STEAG is very well positioned in terms of engineering and has heat as its core business. Especially in the design and integration of our storage facilities in industrial plants, this is a valuable asset that will certainly help both parties to achieve their goals more quickly.
Dr. Schichtel, thank you for talking to us.