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Seasonal heat management at the EnergieForum Berlin
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View of the building from the River Spree
© IGS, TU Braunschweig
The EnergieForum Berlin project was realised back in 2002 in an urban development area opposite Berlin’s Ostbahnhof railway station. The building complex comprises several historical buildings that have been refurbished and supplemented with a prominent new building. Service companies in the environmental technology and renewable energy fields are housed within the complex across 20,000 square metres. A glazed atrium also offers space for large-scale events. The building and energy concept are ambitious, whereby the intention is to achieve a “minimum energy” building standard. The integrated ventilation and energy supply concept is based on using renewable energy sources and makes it possible to dispense with traditional air-conditioning. A central element of this concept is provided by the so-called energy piles that are used for seasonal heating and cooling storage, and which form part of the building’s foundations.
Building summary
| Project status |  Optimized |
|---|---|
| Location | Stralauer Platz 34, 10243 Berlin-Friedrichshain, Berlin |
| Year of construction | 2003 |
| Refurbished | 2003 |
| Building owner | und Betreiber: HANSEATICA Sechzehnte Grundbesitz Investitionsgesellschaft mbH & Co. KG |
| Investor | R+V Versicherung, Wiesbaden |
| Gross floor area | 25,820 m2 |
| Heated net floor area | 20,693 m2 |
| Gross volume | 119,005 m3 |
| Work places | 800 |
| A/V ratio | 0.15 m2/m3 |
| Key aspects |
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Project description
The EnergieForum is situated directly on the banks of the River Spree, opposite Berlin’s Ostbahnhof railway station. The building complex formed part of an urban development project and was completed in 2003. The site once housed the central warehouse belonging to Berlin’s Municipal Gas Works, which was constructed in 1908. Together with the gatehouse and administration building, the five-storey warehouse was carefully restored as a listed building and modernised for office use. A new building was also constructed towards the banks of the River Spree that integrates the existing warehouse building. It consists of two, eight-storey, L-shaped wings and a glazed atrium.
The EnergieForum Berlin offers commercial and office space under one roof. The EnergieForum is used in particular by production and service companies, associations, institutes and scientific facilities concerned with energy and environmental technology.
Building concept
The main circulation space for the building is provided by the atrium, which can be accessed either from Stralauer Platz via an entrance tube that cuts through the warehouse building or directly from the rear on the riverside. The conference spaces are situated on the ground floor of the new building, alongside the atrium. The upper floors of the new building were designed as multifunctional spaces and are currently used as offices. Both the old and new buildings largely enable flexible room layouts. The atrium, which forms the focus of the building complex, is sometimes used as an exhibition and event space, as a communicative meeting point or as a marketplace for concepts and products. Overall, this results in a very compact structure with good thermal insulation. The facades are furnished with different combinations of glazing, solar shading and glare protection in accordance with the orientation.
Energy concept
The central component of the energy provision is provided by the seasonal thermal and cooling storage system in the ground. This consists of 196 foundation piles, each with a length of 8.5 metres and a diameter of 0.5 metres, which have been thermally activated. In winter, a heat pump connected to the foundation piles supplies heat to the concrete core activation system in the wings of the new building. The EnergieForum’s heat supply is also supplemented with a district heating connection and an exhaust air heat pump in the warehouse building. These are connected to convectors in the new building, panel radiators in the warehouse building, the underfloor heating in the atrium and reheaters for the two air supply and exhaust systems in the new building wings.
The air supply and exhaust systems are only operated in winter. In order to prevent energy being wasted as a result of windows being opened for ventilation purposes when there are low external temperatures, a display indicates to users that the heat recovery system is in operation. In summer, the concrete core activation cools the office spaces. In natural cooling mode, the cooling is provided by the energy piles. Depending on the external and office temperatures, automatic night ventilation helps to cool the thermal mass. During the day, the offices are naturally ventilated using the windows.
Automatically controlled ventilation flaps in the atrium ensure a continuous supply of fresh air, enabling the office spaces adjacent to the atrium to also be naturally ventilated. The warehouse building is ventilated by means of the exhaust air system and passive air inlets in the window parapets.
All windows facing south, east and west are equipped with manually operable internal solar shading and daylight control combined with colour-neutral solar protection glass. This ensures glare-free working with simultaneous views out and protection against overheating. It enables good use of the daylight.
A solar power system with a total output of 55 kWp was installed on the southwest facade and on the roof.
Building management
All central systems are controlled via the building control system, whereby the operators can define the time profiles and change the target values. Both the supply line temperature control for the heating and cooling systems as well as the operational releases are made centrally in accordance with the mean external temperature. This means that in accordance with the exterior temperature, the concrete core activation is also supplied via a two-pipe system in changeover operation with heating or cooling energy.
The users themselves cannot influence the control system; they can merely provide auxiliary heating with the fixed heating by individually adjusting the thermostatic valves and, by opening the windows, influence the air quality and – to a limited extent – the indoor temperature. In winter, a small display indicates that the ventilation system is in operation; the windows should not be opened during this period.
The scientific monitoring and facility management work hand in hand. On the one hand, the data derived from the building control system form the basis for the operational analyses. In return, the detailed operational analyses and optimisation proposals determined by the scientific monitoring are passed on to the facility management service provider, which is also tasked with providing the energy management in the building.
Evaluation of the building performance
During the first years of operation, the energy-related design values were still being exceeded by a considerable amount. After carrying out diverse optimisation measures that largely required no additional investment, the energy characteristic values were able to be undercut. For 2009, a primary energy consumption of 93.2 kWh/m² p.a. was recorded (design value 100 kWh/m² p.a.). The characteristic effective energy values for the heating energy and electricity were also undercut by almost 20%.
In 2009, the heat pump achieved a system coefficient of performance of 4.6 (including the circulation pump for the energy piles). A system coefficient of performance of 53 was achieved during natural cooling operation. Even during a period of warm, sunny weather without artificial ventilation and solar shading, a pleasant climate prevailed in the atrium with temperatures no more than 5 kelvin above the outdoor air temperature.
Optimisation: Potential, implementation and instruments
As part of the scientific monitoring and optimisation measures that were carried out during ongoing operation, numerous faults were rectified during the first few years and the building services equipment were made fully functional. The following is a list of the faults relevant for the energy efficiency and comfort, as well as the corresponding measures:
- Faulty control: The night ventilation and fixed heating were in operation at the same time
- An incorrectly installed bypass in the exhaust air heat pump system dramatically reduced the energy efficiency
- Heat recovery and evaporator systems failed in the geothermal system
- The operating times for the ventilation systems in winter were reduced from continual operation to the core periods.
- During the first few years of operation, the ground temperatures increased in the bedrock. By increasing the heat removed during the heating periods it has been possible to achieve a drop in temperatures since 2007. An improved, control-based coordination of the concrete core activation and the fixed heating at night (higher night setback) enabled more geothermal heat to be used for the room heating, i.e. more heat is extracted from the ground. Without accordingly adjusting the heating input and output, the natural cooling would have been placed at risk as a result of the considerably increased ground temperatures.
- An unsatisfactory comfort situation prevailed in the offices within the so-called front buildings with room temperatures greater than 26 °C during the summer months. This problem was solved relatively quickly and easily, whereby the concrete core temperature control system extended the cooling to include the rented areas in the front buildings. The hours of overheating that still nevertheless occur are caused by considerably higher internal loads than were assumed during the planning as well as by the excessively high temperature level in the ground during summer.
- When the outdoor air temperatures were between 10 and 20 °C, the air temperatures in the atrium were up to 30 °C. This was caused by the ventilation louvres for the air supply and exhaust openings in the atrium, which were closed when wind speeds exceeded 4 m/s as a result of a safety function provided by the building control system. Here the limit value was increased to 6 m/s.
Cost-effectiveness and durability
Since the measures taken to date have been changes and optimisations conducted during ongoing operation, there have been no investment costs for implementing the measures. In comparison with conventional heating and cooling systems such as district heating or vapour-compression chillers, the energy concept realised here was able to make annual energy savings for the electricity and heating amounting to 12,000 euros.
Key energy data
| Energy indices according to German regulation EnEV (in kWh/m2a) | before | after | |
| Total source energy before: Data 2004 - after: Data 2006 | 128.00 | 70.00 | |
|---|---|---|---|
| Measured energy consumption data (in kWh/m2a) | before | potential | after |
| Site energy for heating and domestic hot water (dhw) | 45.00 | 39.40 | |
| Source energy for heating and domestic hot water (dhw) | 32.00 | 27.60 | |
| Total source energy | 97.20 | 93.20 | |
| Power without usage of leasers | 23.00 | ||
| Ventilation | 4.00 | ||
| Heat pump exhaust air and energy piles | 2.00 | ||
| Other technique | 8.00 | ||
| Elevators | 2.00 |
before: before optimisation, potential: according to optimisation potential, after: after optimisation
afterwards: data 2009
