The company Mall GmbH in Donaueschingen has specialised specifically in underground storage systems that are located outside the building. This means independence from the building situation with regards to space requirements, while construction and any retrofitting can be implemented at any time. The double wall buffers, made of reinforced concrete, are buried in the ground outside the building and connected to the building engineering installation via heat-insulated pipes. The heat loss is extremely low thanks to the compact buffer geometry (favourable ratio of surface to content) and the perfect insulating material.
Particular requirements are placed on the heat insulation so that the buffers can store the obtained heat energy over the longterm without any significant loss of energy. The knowledge gained about insulating materials used in the previous buffer generations has been fully included in the construction of modern buffers. The product managers at Mall took the decision to use Poraver expanded glass granulate after extensive insulating material tests and now use this lightweight material made of recycled glass to insulate the top cavity and the hollow side walls between the inner and outer containers.
The basic properties required by Mall for such insulating materials to be met over the longterm are 100% fulfilled by Poraver:
– Temperature resistant to at least 100 °C
– Aging resistant and durable
– Pressure resistant even if in a soaked condition
– Resistant against water and steam
– Good drying properties
– Insensitive to microorganisms and rodents
– Simple installation
The requirements were tested in in-house test series with the result that the stored heat volume at 60° Celsius is only reduced by just 1.5 Kelvin per day.
Mall has two buffer types in their product range, unpressurised and pressurised. Buffers with volumes containing between 2,000 and 10,700 litres are available.
The subterranean buffers can also be installed under vehicle-access routes as they are designed and con-structed to be pressure-stable. The buffers are suitable for traversing with heavy truck traffic (SLW 60).