Progress in cold buffering

02.09.2025

Source: E &M powernews

Zortea has received a European patent for a new stratification technology. It is designed to significantly improve the energy efficiency of cold buffering in buildings.

Zortea Gebäudetechnik GmbH has patented a newly developed "optimized stratification technology" for storage tanks. The patented technology addresses a central weak point of renewable energy supply: the low-loss storage and distribution of low temperatures in complex thermal systems or storage tanks. According to Zortea, the new process represents a technological advance, particularly in the field of cooling, which will become increasingly important as a result of climate change.

The stability of the temperature layers is linked to physical laws such as the temperature-dependent density of the water and the flow behavior. These parameters must be taken into account in the design of a storage tank and in the process control," explains Christian Zortea, Managing Director and Technical Director of Zortea. In stratified storage tanks in particular, the precision of the temperature stratification and its maintenance during loading and unloading is a decisive efficiency criterion.

Improved temperature stratification in buffer storage tanks is therefore at the heart of the innovation. The aim is to create and permanently maintain stable thermal layers despite small differences in density in the cold temperature range. The company refers to stratification dynamics that react around 14.5 times more slowly at 6 degrees Celsius than at 70 degrees Celsius. The new storage technology addresses this problem with an adapted stratification process.

Hydraulics as a key factor for system efficiency

Zortea has been working with hydraulic distribution and storage systems for more than three decades. The Austrian company's central technology is the so-called "Zortström central unit", which covers the performance spectrum of a complete energy system and assumes the functions of a buffer storage tank, a hydraulic separator and a control instrument. In addition to the complete hydraulic decoupling of all heating and cooling circuits, a central process of Zortström operation is the precise, multi-layered and constant temperature separation.

The complete hydraulic decoupling of the individual supply circuits - i.e. all incoming and outgoing volume flows - creates optimum system conditions for maximum efficiency in the use of high-performance technologies," says the Managing Director with conviction. This principle enables precise temperature control in each supply circuit. The "build-up effect" that often occurs with conventional distribution solutions - caused by reciprocal interference in pump operation - is avoided. As a result, energy savings of between 60 and 90 percent can be achieved during pump operation.

According to the Austrian company, the new patented layering technology extends the Zortström functionality, particularly in the low temperature range. Thanks to improved storage stability and precise temperature stratification, waste heat can be absorbed more efficiently and used via district heating or district cooling networks.

Storage can also layer cold over hot

Geothermal sources can also be integrated more easily thanks to the optimized stratification - both for heating in winter and cooling in summer. Zortea refers to the ability of the storage tanks to even enable thermodynamically complex reverse stratification, i.e. to store cold water layers on top of warm ones. According to the company, this new development is a response to the increasing importance of cooling in the building sector. According to Managing Director Christian Zortea, more energy will be needed for cooling than for heating in the future. The patented technology is a direct result of internal research into this demand.

According to Zortea, it currently holds 18 patents for the new process. Zortea wants to position the patented solution as a key component for mono-, bi- and multivalent supply systems. The technology can be used in single-family homes as well as in large-scale infrastructures - including hospitals, industrial plants, airports or district heating solutions.
The company is paying particular attention to the interaction between storage technology and heat pump systems. The latter are becoming increasingly important in rural areas, often in combination with photovoltaics. In urban areas, on the other hand, Zortea sees more potential in local and district heating networks, which would be well suited to feeding in waste heat from cooling generation.

Zortea Gebäudetechnik, based in Hohenems in Vorarlberg, Austria, specializes in hydraulic system solutions for heating and cooling supply in buildings.

Author: Heidi Roider