Heat pump for an apartment building
Heat pump for the Maingold apartment building
BremenEfficient and climate-neutral heating with the Ecodan air-to-water heat pump system
The Maingold construction project, a multi-family house with 13 residential units in Bremen's Neustadt district, is unique in many ways. The building was constructed between the foundation walls of a former air-raid shelter. Unlike in purely new buildings, the foundation and foundation walls of the old air-raid shelter were incorporated into the technical planning by Klaus Schierenbeck Gebäudeplanung. The result is a modern residential culture that impresses with its harmonious façade structure, floor-to-ceiling windows, balconies, and roof terraces. In addition, the building was completed in 2020 as a KfW Efficiency House 55 in accordance with EnEV. Thanks to the overall energy concept, the requirements of the GEG of July 2021 for an Efficiency House EH 55 EE were already met at that time. The heat supply had to be planned to be correspondingly modern, efficient, and forward-looking.
requirements
The building services challenge for the construction project in the Flüsseviertel district of Bremen's Neustadt neighborhood was to develop a sustainable heat supply for the well-insulated apartment building. In addition, climate protection, i.e., alow-CO2 heat supply for the building, was a priority for this project. At the same time, the heat energy required for heating and hot water was to be generated in a climate-neutral manner. And last but not least, all residential units were to have their own fresh water station and underfloor heating with individual room control.
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- Low-carbon heating solution
- Climate-neutral provision of heat and hot water
- Separate fresh water station for each apartment
- Underfloor heating with individual room control
Which solution was chosen for the "Maingold" apartment building?
Heat pump cascadeEcodan air-to-water heat pumps with Zubadan inverter technology as a triple cascade
The building was designed by architects Freudenberg/Mielke from Bremen, who have already completed several bunker conversions. The construction project was implemented by M-Projekt, led by architect Gunnar Neimke. The overall energy concept and building services engineering in this climate-neutral apartment building were designed by Klaus Schierenbeck, a specialist in building services engineering and energy efficiency expert for residential and non-residential buildings (DENA).
Since a geothermal system was not possible, Schierenbeck recommended that the builders install an Ecodan air-to-water heat pump system with Zubadan inverter technology from Mitsubishi Electric. The heat pumps are installed outdoors in a cascade of three and supplemented by a 4-pipe network with fresh water stations in each apartment.
Not only was the technology, which has been used in more than 20 apartment buildings since 2016, convincing, but so were the energy costs from a comparable property. Each of the three Ecodan outdoor units has a heat output of 11.2 kW, which means that the heat pump cascade can easily cover the heating load for the building and at the same time provide sufficient heat for domestic hot water preparation. The heat pumps extract the free heat contained in the ambient air as their energy source. The energy source, outside air, is also considered 100% environmental heat.
Advantages of the air/water heat pump solution
benefitsMore powerful. More efficient. More secure.
Cascading heat pumps offers numerous advantages over a single heat pump with a correspondingly high output. Operating within the very large modulation range of a cascade is much more efficient than running a single module at full load. This is because the units can operate simultaneously in partial load mode. A cascade control system with an auto-adapt function optimizes operating behavior and automatically searches for the best operating point for the system. In addition, a cascade offers a redundancy function for the maintenance of individual devices in the system, thus increasing operational reliability. Furthermore, the total running times of the individual modules are reduced, thereby increasing their service life.
KfW Efficiency House 55 level and class EH 55 EE according to GEG 2020
Heat pump technology was an important component in meeting the requirements for KfW Efficiency House 55 in accordance with EnEV and GEG for an Efficiency House EH 55 EE. In addition, a composite thermal insulation system with 20 cm external insulation was chosen for the building envelope. In combination with the mandatory triple-glazed windows and a ventilation system, which was necessary due to the interior bathrooms, among other things, the building achieves a final energy demand for heating and hot water of 12.9 kWh/(m²a) and a primary energy demand of 23.2 kWh/(m²a).
Operating range down to minus 28 °C outside temperature
A special feature of the heating technology used here is that the heat pumps are equipped with patented Zubadan compressor technology. The injection process used optimizes the available heating output. This means that the heat pumps can still deliver 100 percent of their heating output even at very low outdoor temperatures of down to minus 15 °C. At the same time, the lower operating range is extended to an outside temperature of minus 28 °C. This makes it possible to supply the building with heat and, even at low outside temperatures, to dispense with the support of an electric heating element or an additional heat generator.
Low flow temperature for heating and hot water
To store the heat until it is needed and to bridge any periods when the electricity supplier is not available, a buffer storage tank was also incorporated into the system design, which provides sufficient heat at all times. At the same time, the buffer storage tank provides energy for defrosting the outdoor modules in winter. The even and extremely pleasant heat distribution in the apartment building is achieved by underfloor heating in each residential unit, which can be preset via a dynamic valve for automatic hydraulic balancing and controlled individually via individual room controllers. As a low-temperature heating system, underfloor heating is ideal for combination with air/water heat pumps, as the low flow temperature has a positive effect on the efficiency of the system.
An 800-liter stratified buffer tank is located in the utility room to provide hot water for the 13 apartments. Here, sufficient heat is stored at a domestic water temperature of 53 °C for hot water preparation. Each residential unit has its own fresh water station, which distributes hot water in parallel with the heating distribution system. The outlet temperature in each residential unit is 50 °C. The indirect transfer of heat to the freshly tapped drinking water (continuous flow principle) eliminates the risk of Legionella and the requirements of the Drinking Water Ordinance according to worksheet B501 can be met in an energy-saving manner without high temperatures.
The operating principle of heat pumps is very simple: in order to utilize the energy contained in the outside air, the environmental heat absorbed by the heat pumps is transferred to a refrigerant circulating in a closed circuit. The pressure is increased in the refrigerant compressor, the temperature level rises, and the energy is transferred from the refrigerant to the heating water via a heat exchanger. A hydromodule is available in the utility room for each outdoor unit. This is a straightforward way of hydraulically decoupling the heating and heat pump circuits while ensuring a constant refrigerant volume flow.
The most important points
Summary- The apartment building in Bremen's Neustadt district meets current standards for comfort, amenities, and energy sustainability.
- The overall energy concept complies with the KfW Efficiency House 55 standard and meets the high requirements of the GEG for residential buildings.
- The heat demand for heating and hot water is covered by air-to-water heat pumps in a triple cascade configuration.
- Ecodan outdoor units are a particularly economical alternative thanks to their comparatively low investment costs and minimal installation requirements.
- The low flow temperature of the underfloor heating and the provision of hot drinking water enable particularly economical and energy-efficient operation in the low-temperature range.
- Thanks to Zubadan compressor technology, there is no longer any need for an electric heating element or additional heat generator, even when outdoor temperatures are particularly low.
- This makes the entire system extremely cost-effective for end users, with particularly low heating and hot water costs.
