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The new Willibald Gluck Secondary School: Facade-mounted coloured glass panes provide weather protection for the opening casement windows for the classrooms.
© Berschneider + Berschneider GmbH Architekten BDA + Innenarchitekten BDIA. Foto: Petra Kellner
Energy-plus concept
31.08.2017

Site plan showing the school and gymnasium
© Berschneider + Berschneider GmbH Architekten BDA + Innenarchitekten BDIA

New energy-efficient school building in the spotlight

The new, energy-optimised building for the Willibald Gluck Secondary School in Neumarkt (Upper Palatinate, Germany) utilises solar energy and near-surface geothermal energy. The first year in regular operation has provided good values: the heat pumps are contributing their planned share to the heat generation and the photovoltaic systems cover 35 per cent of the electricity consumed for the building operation and use. Storing the PV electricity in a vanadium redox flow battery has not, however, increased the proportion of self-consumed electricity during the first year of operation. The operation of the ventilation systems also provides potential for optimisation.

Pupils moved into the new building for the Willibald Gluck Secondary School at the start of the 2015/16 school year. The ensemble comprises a four-storey school building with a net floor area of 11,500 square metres, a triple-field gymnasium and a sports field. The classrooms are arranged around two covered atria, which ensure a high degree of natural light autonomy within the central internal spaces. The building has a calculated annual energy demand of 25 kWh/(m2 p.a.) and an annual cooling energy demand of 10 kWh/(m2 p.a.). The final energy requirement for electricity is 40 kWh/(m2 p.a.), which includes the requirements of the user-specific equipment. Two roof-integrated photovoltaic systems on the school and the gymnasium as well as the use of near-surface geothermal energy (agrothermal energy) significantly reduce the CO2 balance of the building complex. Scientists from the Institute of Building Services and Energy Design (IGS), headed by Prof. Dr.-Ing. M. Norbert Fisch from the Technical University of Braunschweig, have now presented the results of the monitoring for the first year in regular operation.

Energy-plus possible

The annual electricity consumption has remained significantly below the calculations at 28.5 kWh/(m2 p.a.). This is mainly due to the fact that the user-specific power consumption is lower than assumed. With an output of around 290 kWp, the PV systems account for 35 per cent of the annual balance. The system components are designed so that they can be expanded to 600 kWp. This would enable the school to achieve the energy-plus level. However, the client is currently not planning any expansion for cost reasons.

The PV yield is in line with expectations. At times it can completely cover the electricity consumption of both the school and gymnasium. On average, 44 per cent is used directly. A vanadium redox flow battery has been installed to increase the self-consumption rate. After initial regulation problems, it has been running according to plan since August last year, but only reaches an efficiency of 50 instead of the hoped for 70 per cent. Since the battery consumes more power for stand-by operation with a low PV yield than it stores, it is now being debated whether to turn it off during the winter half-year.

As planned, two heat pumps supply 70 per cent of the heat for the school and gymnasium (underfloor heating, concrete core temperature control and ventilation systems). Thermally activated foundation piles and a surface collector underneath the sports field (near-surface geothermal/agrothermal energy) and the waste heat from the servers are used as the heat source. A gas condensing boiler covers the peak loads and heats the hot water for the showers in the gymnasium.

Optimisation of the indoor environment and air quality

All classrooms are mechanically ventilated via central ventilation units with heat recovery, which are demand-driven in accordance with the CO2 concentration. The rooms are cooled passively using concrete core temperature control. In addition, the supply air is cooled using adiabatic exhaust air humidification. The concept is supported with night-time ventilation via the ventilation systems. The overall indoor comfort achieved so far has been good to acceptable. The adiabatic cooling release, supply air temperatures, switching between summer and winter operation as well as the regulation of the night-time ventilation have now been adapted to improve this. It was also discovered that the deviation between the measured and actual room temperatures was due to the incorrect positioning of the temperature sensors in the classrooms.

A high-to-medium air quality has been achieved with respect to the CO2 content. Moderate room air quality occurs mainly in rooms that are used differently in operation than was originally planned. However, initial adjustments of the airflow rate in individual rooms have already now been made in this regard. Since the mechanical ventilation automatically switches off when the windows are opened, the air quality in the classrooms can deteriorate due to windows that are tilted open or ajar. This is something that the users are still getting used to.

Monitoring successes

Several sources of faults and deficiencies have been successfully identified and corrected as part of the monitoring. For example, the settings for the building management system differed between the planning and execution, and several flow rate controllers were incorrectly connected. In addition it was noticeable that there was information missing in the function descriptions and plans, which meant that the optimal mode of operation was not clear. The support provided by the research team from the IGS and TU Braunschweig provides an expert contact partner for the committed caretaker during the ongoing operations.

The intensive scientific monitoring with operational optimisation will last until summer 2018 at the earliest.

(dg)

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Addresses

Scientific monitoring
TU Braunschweig, IGS

Links

Willibald Gluck Secondary School Neumarkt
School website

TU Braunschweig
Description of the project from the Institute for Building Services and Energy Design

Support research
Support research on energy-efficient schools organised by the German Federal Ministry for Economic Affairs and Energy

New school building with low-exergy heating concept and electricity load management
Business card for the Willibald Gluck Secondary School research project at ENERGIEWENDEBAUEN

Event note
The “A future concept for educational buildings” workshop will be held at the school on 12 October 2017.

Info tips

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Long-term monitoring of school building
BINE-Projektinfo 09/2015