Energy efficiency

Starting in September 2022, federal regulations mandated energy-saving measures in public buildings. Furthermore, the state of Hesse issued a catalog of measures with targets of reducing heating energy consumption by 15% and electricity consumption by 5% compared to the previous year. By limiting the indoor air temperature to 19°C, minimally heating stairwells and hallways, lowering the heating circuit temperature on weekends, and reducing outdoor lighting on campus, THM Technical University of Central Hesse) largely achieved its targets. The 1,330 MWh of heat saved could heat approximately 60 single-family homes. Compared to December of the previous year, energy consumption was reduced by 4.5%.

To increase energy efficiency and user comfort, hydraulic balancing was carried out on campuses A and B in 2022, and individual room control was also installed. This involved replacing the valves on nearly 1,000 radiators and hydraulically balancing the system. As part of this process, approximately 800 en:key valve controllers and a total of 345 wall-mounted control units were installed in the rooms, replacing the standard thermostatic radiator valves. The independent room sensor detects the presence of users and creates an individual usage profile. Based on this profile, an actuator on the valve raises the room temperature during periods of occupancy and lowers it again at other times. In addition to improved user comfort, this significantly reduces heating energy costs. 

Based on experience from previously implemented projects, savings of at least 10% are expected.

In building A12, IT-S operates a server room. This room is cooled by recirculating air coolers. The waste heat is transferred to a chilled water network. Previously, cooling was provided by two compact chillers. Since the commissioning of these two units, there have been recurring problems with the system hydraulics and cooling capacity, particularly during periods of high outside temperatures. As an optimization measure, the two old units were replaced with a new chiller system. The new chiller system is characterized by higher efficiency. At high outside temperatures, the system can operate in "free cooling mode." In this mode, no energy is required to operate the refrigerant compressors. The heat is dissipated exclusively via the two enlarged cooling towers on the roof. The new system has significantly increased operational reliability. The system is designed with 100% redundancy in cooling generation.

In 2022, the air volume flows in buildings D13, D14, and D15 were adjusted, resulting in significant, measurable reductions in energy consumption and noise. Preliminary evaluations show energy savings of up to 40%, particularly in heating, compared to the same month of the previous yearnat. Electricity consumption by the ventilation system was also noticeably reduced.

The conversion and renovation of a district heating distribution network was planned on the C-Campus in Giessen and successfully implemented in 2020 and 2021.

In building A21, the lighting was replaced with modern LED lighting. This wasn't always as straightforward as one might think. Simply replacing the bulb, i.e., just swapping the existing tube for, say, an LED tube, would invalidate the certification for the entire fixture. LED bulbs are significantly heavier than traditional tubes. Therefore, the only solution was to replace the entire fixture. This was partially achieved using retrofit bulbs, which kept the plastering and painting work to a minimum. However, for aesthetic reasons, some ceiling tiles still had to be replaced if the new bulbs were smaller than the old ones. We think the effort was worthwhile! This project was also funded by the IKSP (Institute for Spatial Planning and Building Technology).

In 2021, the control technology in building D16 was further optimized. Previously, the rooms were heated to 20°C and cooled from 20.5°C. As part of the optimization measures, the so-called "dead band" was increased from 0.5 to 2 Kelvin.

By changing the sequences, an energy saving of 14% was achieved in the D16 during the last heating season compared to the previous year.

Building A5 on the Friedberg campus primarily houses laboratories for the Departments of Mechanical Engineering, Mathematics, Natural Sciences and Computer Science, and Economics. Due to its age, the building suffers from significant heat loss through the facade.

The steel beams and Reglit glazing offered inadequate thermal insulation, necessitating extensive renovations in 2019. Instead of the previous glazing, insulated aluminum sandwich panels now adorn the facade, resulting in significant energy savings and improved user comfort. The windows and sectional doors were also upgraded for energy efficiency, with the latter being enlarged as part of the process.

The facade of building A7 on the Friedberg campus was renovated in 2020. This involved replacing the semi-transparent building components and windows. The insulated aluminum sandwich panels of the new facade reduce heat loss from the building and simultaneously improve user comfort.

Building D11, with a main usable area of ​​1,085 m², was completed in 2007. Due in part to its use as biochemistry laboratories, its energy consumption was unusually high in 2016, reaching 485 kWh/m² of electricity and 593 kWh/m² of heat. Following an intensive analysis, deficiencies in the existing building services were addressed.

To ensure smooth operation, the instrumentation and control technology, including the system software, was replaced. This not only improved operational transparency and enabled the implementation of new control functions, but also simultaneously increased operational reliability.

Further measures to improve existing technology included:

• Adjustment of laboratory operating times through the use of room control devices (laboratory and maintenance operation)
• Adjustment of the air volume flows of the fume hoods (laboratory and maintenance operation)

The implementation of the measures resulted in savings of 330,000 kWh of heat and 150,000 kWh of electricity per year with a payback period of approximately 1.6 years.

The implementation of energy-saving measures in existing buildings is on the one hand multifaceted and complex, but on the other hand also characterized by a high degree of effectiveness and efficiency with - under certain conditions - a relatively low financial investment.

To determine where energy-saving measures can be implemented most effectively, the energy consumption of selected buildings was systematically analyzed and compared to their area-specific consumption. For the Giessen campus, it was found that building A10 exhibits both the highest overall energy consumption and a very high area-specific energy consumption. The precise energy flows and building usage were then analyzed for this building. It is characterized by a highly heterogeneous use (physics and chemistry laboratories, lecture halls, cafeteria, pastry shop, offices, etc.) and the resulting diverse requirements for its technical systems.

To significantly increase energy efficiency, measures were identified that are characterized by low time and investment costs as well as the shortest possible payback period. The following individual measures were implemented:

• Installation of individual room control based on enOcean technology
• Insulation of the heating pipes in the building
• Retrofitting energy meters
• Adjusting the operating times of the ventilation system in the cafeteria
• Adjust the heating curve of the control loops
• Conversion of the lighting to LED technology
• Installation of CO2_trafficlights and user training
• Building automation upgrade

The pilot project was funded by the state of Hesse ("Integrated Climate Protection Plan 2025 - Innovation and Structural Development Budget") with €83,000.

As part of the project “Development of an energy concept for a CO2_-neutral university” - in short: ECO2 - an operational analysis and optimization of the ventilation system in the rented Roxy cinema in Giessen carried out.

The aim was to verify the functionality of the digital building automation system, newly installed in autumn 2016, and to identify suitable, optimized operating parameters. This was intended to enable increased user comfort with reduced energy consumption. The new parameters were based on measurements of room temperature and CO₂_{concentration}during lectures. These measurements were also carried out and analyzed by students of the "Building Systems Engineering" program as part of a project.

The system parameters have already been adjusted based on the new findings. Particularly positive is the positive response from users to the changes in the indoor climate.
The new control system and the modified operating parameters result in primary energy savings of approximately 25%. This corresponds to a reduction in CO₂_emissionsof about 9 tons annually.