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Mar 1, 2013 - Building

Energy Stored On Ice

There are a lot of concepts for energy-efficient industrial and commercial buildings. However, the combination of modern automation, energy, and building technology found in the company headquarters for leitec® Gebäudetechnik GmbH is something quite different. It is not only aesthetic, but with its 400 m³ ice bank, it is also especially efficient.

The building, located in between Göttingen and Erfurt in Heiligenstadt, is visually attractive and simultaneously a model for the use of energy and resource saving technologies. Three primary elements are interconnected: an extraordinary energy design (including ice bank, photovoltaics, and heat pump), an efficient heating and ventilation design, and exemplary controls using an innovative, building automation that crosses disciplines. “Our building was constructed in 2011 as a center for modern energy and building technology and has served as a reference project ever since. Whenever we show this building to customers, we can usually count on interesting projects as a result,” reports Bernd Apitz, CEO of leitec® Gebäudetechnik GmbH.

Innovative Engineering Technology

The building is completely supplied with heat and electricity without the use of any fossil fuels. On the 1200 square meter roof, more than 900 photovoltaic modules annually generate around 100,000 kWh of electricity – enough for use in the building, as well as generating an excess to feed into the grid.

The large roof surface also serves as a collection point for the thermal energy needed in the building. A thermal absorption collection system was installed between the photovoltaic elements to capture thermal energy. This energy is then fed to a 400 m³ ice bank. The capacity of this robust and relatively inexpensive storage is sufficient for a period of 60 days without solar energy. The functionality of the ice bank is based on the fact that as much energy is used to phase transition water from a cold liquid to solid ice at zero degrees Celsius as is needed to cool hot water from 80 degrees Celsius to zero. The thermal energy stored is sufficient to heat the entire building in winter and to cool it in the summer.

Efficient Heating and Ventilation Design

The building is equipped with underfloor heating. For the offices, however, leitec® had something different in mind. “By using individual room control for lighting, heat, and ventilation, we can save a lot of energy while still increasing the comfort of our employees,” explains Bernd Apitz. To accomplish this, we installed a new type of low-temperature radiators in the offices, which output two to three times as much heat and are approximately five times as effective as conventional radiators of the same style. Controlled by CO2 and presence detectors, the rooms are heated very quickly when an employee enters the office to their individually adjusted comfort level. In addition, a ventilation system supports the effective regulation of room air conditioning and ensures the offices remain cool in the summer. Bernd Apitz calculates the energy savings associated with heating to be 40 to 50 percent.

Building Automation Across Disciplines

The lighting, heating, ventilation, electrical, and security systems are comprehensively controlled using the WAGO-I/O-SYSTEM 750. The WAGO-I/O-SYSTEM serves as the global connection piece between the various disciplines and their bus protocols, such as BACnet, LON®, and KNX, and can thus simultaneously ensure heating and ventilation, an on demand illumination control, blind regulation that is sensitive to weather, and the connection of the safety system with the heating functions.

Numerous automated functions in the building regulation ensure high energy efficiency for the entire leitec® building. An important element is the automated room control. If, for example, an employee opens a window, then the radiator is automatically shut off and the ventilation is regulated using a motorized ventilation damper. Corridor lighting is controlled using movement sensors.

No consideration of the final fieldbus was required for the field-side wiring of the I/O modules. Due to the modularity of the WAGO-I/O-SYSTEM 750, any combination of digital/analog inputs and outputs is possible. ETHERNET serves as the automation medium. The KNX/EIB world is connected to the ETHERNET using the KNX IP controller. Thus, conventional sensors and actuators as well as complex connections to DALI (Digital Addressable Lighting Interface), for the control of the lighting, or to SMI (Standard Motor Interface), for control of the blinds, can be inexpensively integrated.

Using DALI modules, individual lights and entire lighting groups can be centrally controlled, and configuration data can be regulated and stored. In addition, sensors for brightness measurement and presence detection, for example, can be integrated into a DALI network. All electrical data from the supply network, from the actual consumers to the values of the heat pumps, is continuously detected using 3-phase power measurement modules for on-going energy monitoring and management.

Flexibility for Individual Solutions

This type of building automation is distinguished by high flexibility and for unusual and innovative solutions, according to the point of view of the CEO of leitec®. Of particular relevance is the open programmability according to the IEC 61131-3/CODESYS Automation Alliance. Bernd Apitz has had good experiences with WAGO’s open I/O system. The independence from specific fieldbus types and the large number of available interfaces has vastly simplified the integration of the various disciplines. The modularity of the technology was very convincing for him. Since the electronics are incorporated into the module, it is easier to exchange a module than to switch out an entire actuator. Finally, the availability of several modules from industrial automation technology and also the cost-benefit ratio were very attractive. The CEO of leitec® also mentions the constant availability of his WAGO contact person.

leitec® plans to use its positive experiences with automation, energy, and building technology for additional expansions of the design in the future, for example by integrating eMobility or wind energy. Bernd Apitz considers his company to be well positioned for supplying the growing demand for intelligent controls in private residences.


  • The heating and ventilation design savers 40 to 50 percent of the heating energy
  • The cross-discipline building automation includes heating, ventilation, lighting, and shading
  • Flexible due to fieldbus independence and large variety of interfaces

Text: Karl-Heinz Sanders, WAGO
Photo: fotografie-grimm-leinefelde, leitec, WAGO

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