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Energy Storage Systems


Heat pumps for heating or cooling buildings usually draw their energy from geothermal probes or earth collectors. The building technology company leitec® took a different path: an ice energy store provides the necessary energy. WAGO technology controls the interplay between the system and the entire building automation.

Energy is created when water freezes to ice. An identical amount of energy is required to heat water from 0 to 80 degrees Celsius. Viessmann, a heating technology company, used this crystallization principle for their innovation, and developed a system based on an ice energy store and heat pumps to provide energy for heating and cooling.

Users of the technology include leitec® Gebäudetechnik GmbH, a complete service provider in energy and building technology, headquartered in Heilbad Heiligenstadt in Thuringia. Their ice energy store, consisting of an underground cement tank that is ten meters in diameter and six meters in height, holds up to 400,000 liters of water. “The system functions quite well,” states Bernd Apitz, CEO and owner of leitec®. “We were among the first to build an ice energy store of this magnitude.”

When the company installed the technology in their new building in 2011, they were mapping uncharted territory. Software, which can now easily calculate the complex systems and dimension them, did not exist then. The challenges in designing the ice energy store included consideration of several aspects: the building technical systems, specific climatological concerns for the site, and demands for subsequent use of the building.

Many Complex Individual Systems

The expense paid off for leitec®. Today, the company covers all of their heating and cooling needs with the ice energy store. “We no longer use fossil fuel,” says Apitz. The heat pump-storage combination is controlled by the WAGO-I/O-SYSTEM 750. “We’ve worked with it for a long time,” comments Project Leader Benedikt Künzel. Benefits of the system include the variety of interfaces, among others. “We have to coordinate complex individual systems in our building control systems,” according to Künzel.

In the leitec® building, these include wall installations with EIB/KNX communication, intelligent lighting management with DALI, and building security. “The WAGO-I/O-SYSTEM 750 offers a high degree of freedom during connections, so that, for example, door and window contacts for the alarm systems can be easily connected. If I had to work with standard actuators, our switching cabinet space would not have been enough. This one is very compact, and our servers are included as well,” explains Apitz. He considers the WAGO technology to be a ‘convincing industrial system’.

In addition to the wide-ranging availability of different interfaces and connection cards, the experts at leitec® also value the free programmability of the WAGO-I/O-SYSTEM. Künzel says that “WAGO is very multifunctional in programming.” The programming potentials in the standardized languages of IEC 61131-3 make it very easy for leitec® to use their software to implement tasks that emerge during projects. These include adapting interfaces to subsystems that leitec® needs to merge in their building projects. According to Künzel, “Every planner has their own preferences for their systems – and this makes it easier to link them together.”

Automated Quickly and Safely

Even in the case of the ice energy store, leitec® succeeded in combining different functional areas quickly and safely into the automation aggregate. “We developed five general scenarios with the WAGO controller,” explains the leitec® CEO. These included the operating modes of: heating using the ice energy store, heating using the solar thermal collectors installed on the roof next to the photovoltaic modules, cooling the ice energy store, regeneration using the solar collectors, and cooling using the heat pump.

Finding the optimal settings required data, which were directly evaluated by the WAGO-I/O-SYSTEM, and provided the basis for a self-optimizing system. This system is able to decide, for example, if heat for a heating period should be withdrawn from the ice energy store, or whether the solar thermal collectors can contribute more power. leitec® also uses the data to calculate efficacy metrics, which can be utilized later for documentation in customer projects.

The heat pump-ice energy store combination functions most efficiently when it is used to generate both heating and cooling. In the winter, the heat pump withdraws energy to ensure that the ice energy store freezes from the inside out. In hot months, the resulting ice mass is used to supply the collectors in the offices with cold water to lower room temperatures. Because the ice thaws slowly, and reaches a higher energy level during melting, heat is stored again for the winter.

Focus on eMobility

Apitz is convinced that the ice energy store has a good future, particularly in multi-family housing, hotels, offices, and companies in the food industry. “It makes sense, anywhere I want to heat or cool something.” Viessmann has already picked up the first ice energy store as a series solution in their catalog. leitec® is working with WAGO to further simplify and standardize the control technology, including visualization.

There are other projects that leitec® is developing in parallel: the company building has reached an electrical excess of 50% over the year, according to the balance sheet. “We’re presented with the question of how to sensibly store the excess electricity. Using it ourselves is more interesting, particularly in combination with eMobility,” states Apitz.

Text: Heiko Tautor, WAGO
Photo: Viewssmann, LEITEC®