Vacuum insulated concrete containers for high temperature energy storage

PREFA ALFA a.s. is the only company in Slovak Republic performing research of construction of heat accumulator with intermediate-heat potential. During the last five years, the company PREFA ALFA a.s., in cooperation with Slovak Technical University in Bratislava (STU), has initiated research of possible construction of double-cup vacuum-insulated concrete containers. Several Slovak producers and partners have actively participated on the research. During the research, the company has examined also the mouldability of various concrete mixtures.

In the terminal stage of the research, the company has moulded samples of the container with composite construction, where the steel foil integrated in the walls ensured gas-tightness of the future container. However, this technical solution was financially demanding and further research should concentrate on simplifying the container construction by choosing other materials. In addition, gaining practical and theoretical information, the hitherto performed research has also resulted in establishing cooperation workplace in Kysucké Nové Mesto.

Figure1, Heat exchanger outside of inner cylinder

Figure2, Heat exchanger inside inner cylinder

Figure3, Heat exchanger pre casted inside the inner cylinder structure

The workplace is used by company PREFA ALFA a.s. and STU in Bratislava and contains technical equipment necessary for performing of applied research in the area of heat accumulators in the future. Scientific and research staff participating in the research will also participate in the research under the submitted project. The staff includes: Ing. František Zvrškovec (construction solutions), Ing. Dalibor Buc, PhD. (vacuum technology), Prof. Ing. Ludovít Filo (containers statics), Prof. Ing. Jana Frankovská (impact on geological subbase) and others. The primary supplier of technical solutions was company VUNAR a.s., (former tool research institute).

The company has exclusive right to use the portable system evolved in Slovakia that enables measuring the vacuum level during the vacuum-insulated heat accumulator production. The system, designed by Slovak Technical University in Bratislava, is installed in R&D center of company Prefa Alfa a.s. in Kysucké Nové Mesto.
Fundamental premise of effective utilisation of renewable energy is the possibility of its temporary accumulation while generating the power, and release of the energy when needed. The company has started to carry out research of energy accumulation gained from renewables.

Firstly, the company aims to examine the construction of local accumulation container made of concrete, primarily designed for thermal energy storage powered by solar concentrators. Worldwide application and interconnection of such accumulator with the district heating system would markedly decrease the fossil fuel consumption used for generation of domestic hot water. In case of successful and desired outcome, Slovakia would become an initiator in the new technology production and would predominate on the world market with such system.

Electrochemical storage

Sodium-nickel chloride batteries

The second field of study is accumulation of electric energy. The company has an ambition to utilise planar sodium-nickel chloride batteries. These high-effective electric accumulators with density 350 Wh/kg have no commercial application because their operating temperature varies between 190°C and 280°C. The research is focused on operation of such accumulator with emphasis placed on working environment. Application of this type of batteries within accumulation container is crucial for surplus electric energy storage generated by renewables and moreover for future grid stabilisation.

Further implementation of the vacuum-insulated concrete accumulators, developed by the company PREFA ALFA a.s. in cooperation with several academic partners from Slovakia and abroad, might lead to new perspective of effective utilisation of renewables. Moreover, mass application of the electric-heat accumulators to the existing energy grid, could enable consumers to become self-sufficient and gain independence from unstable energy supply in future.

Figure4, Explanation of structure from “High power Planar sodium nickel chloride battery”, Xiaochuan Lu, Pacific Northwest National Laboratory, Read more

Joint Research

Advanced Technology and Science Applications Centre

The company PREFA ALFA a.s. is also a member of Interest Association of the Legal Persons called ATASAC – Advanced Technology and Science Applications Centre, which interests are based on support of applied research in the energy and innovative materials sectors. Furthermore, the association ATASAC provides cooperation between universities and industry in Slovakia and worldwide. Additional ATASAC´s ambition is representation of members´ interests in EU structures and other multinational corporations.