Main office of Sparkasse Donaueschingen
Air-conditioning of the main office of Sparkasse Donaueschingen is provided primarily by means of 56 vertical ground heat exchangers (double U system) having a depth between 90 and 99 meters. The heat transfer medium is purely water. In the summertime the water circulates directly through the ground heat exchangers and “thermoactive” ceilings. During winter a ground-source heat pump with a heating capacity of 110 kW is used to support the heating of the building.
| Country | Germany |
| City | Donaueschingen |
| Client name | Sparkasse Donaueschingen |
| Application area | Building sector |
| Building type | Office building |
| Year of construction | 2003 |
| Heat source/sink | Brine/Water |
| Heat pump type | Electric heat pump |
| Year of installation | 2003 |
| Purpose | Heating only |
| Heat source system | Borehole heat exchanger (vertical) |
| Operation mode | Bivalent |
| Contact E-mail | service@spk-donaueschingen.de |
| Contact website | www.sparkasse-donaueschingen.de |
Project description
Building, overall energy concept
Photo 1: Ground heat exchanger system of Sparkasse Donaueschingen (systherma)
Heating and cooling of the new building of the main office of Sparkasse Donaueschingen is to a large extent provided by means of 56 vertical ground heat exchangers having a depth between 90 and 99 meters. The heat transfer medium is purely water. In the summertime the water circulates directly through the ground heat exchangers and "thermoactive" ceilings having a surface of 3.500 m2. During winter a ground-source heat pump is used to support the heating of the buildi
ng.
Photo 2: Double U heat exchanger (systherma)
To achive high planning reliability as required for such a big installation calculations using a building simulation program had been carried out. In addition the behaviour of the ground was simulated over a period of 40 years (Diagram 1). Due to optimisation of these both simulation calculations the originally planned number of borehole heat exchangers could be reduced from 75 to 56.
In the summertime the water circulating through the ground heat exchangers provides direct cooling for the ceiling heat exchangers in the offices. It is warmed up from 15°C to 18°C. The fresh air provided by five air-conditioners (22°C inlet temperature at an ambient temperature of 32°C) is cooled by the water from the ground heat exchangers too. The total cooling capacity is 275 kW, the annual cooling energy 150 MWh/a.
Heat pump system
In the wintertime the borehole heat exchangers are used as heat source for a ground-source (water-to water) heat pump with a heating capacity of 110 kW to support the heating system. The borehole heat exchangers are double U plastic pipes (HDPE) with a diameter of 32 mm. To optimise the behaviour of the borehole heat exchanger field during the summer respectively winter season, 30 heat exchangers in the middle have a depth of 99 meters and the surrounding heat exchangers a depht of 90 meters.
Photo 3: Drilling the boreholes (systherma)
The pure water circulating through the borehole heat exchangers has an inlet temperature of 6°C and an outlet temperature of 10-12°C. The supply temperature of the ceiling heating system is 45°C. The design values of COP and annual heat delivery are 4,5 and 300 MWh/a respectively. Aimed at achieving the highest possible heating capacity the supply and return temperatures of the complete heat pump system are controlled steadily.
Operation experiences
No information available.
Costs, economic efficiency, incentives
Reference year 2003:
A cost analysis according to VDI 2067 came to the result that compared to a conventional system (chillers and boilers) this ground-coupled heating/cooling system with heat pump can provide a cost efficient solution (Diagram 2)
Regulations, guidelines, benchmarking
The building is located in a zone III A water protection area. The springs of this area provide potable water for the city of Donaueschingen. Therefore the success of the project significantly depends on a highly professional drilling of the boreholes through several ground water horizons.
References
- Fachinformationszentrum Karlsruhe GmbH
BINE Informationsdienst, Innovative Energie-Projekte (in German only) - www.ilvt.de (in German only)
| Design value | Measured data | |
|---|---|---|
| Year | 2003 | |
| Heating capacity (kW) | 110 | |
| Cooling capacity (kW) | 275 | |
| COP (Heating, appliance) | 4,5 | |
| EER (Cooling, appliance)1 | ||
| SEER (Cooling)2 | ||
| Annual heat delivery (kWh/year)3 | 300.000 | |
| Annual cooling delivery (kWh/year)4 | 150.000 | |
| PER (Heating /Cooling)5,6 | ||
| Annual CO2 emissions (kg CO2/year)7 |
1 Direct cooling
2 Direct cooling
3 incl. heat recovery from ceiling cooling
4 Direct cooling and air-conditioners
5 Primary Energy Ratio: Useful heating (and cooling) energy delivered / primary energy input (kWhUE / kWhPE)
6 PEER=annual heat delivery/primery energy demand=SPF/fPE, fPE=Average European primary energy factor: 2,35 kWhPE/kWhel
7 Average European CO2 factor for electricity: 0,45 kg CO2/kWhel
| Institution/Company | ILVT Ingenieurbüro Liebert Versorgungstechnik |
| Responsibility/Function | Planning and site management for building services engineering |
| Street/PoBox | Hinterstadt 45 |
| ZIP | 78183 |
| City | Hüfingen |
| Country | Germany |
| Contact Person | Thomas Liebert |
| Phone/Fax | +49-771-61457 / +49-771-61089 |
| info@ilvt.de | |
| Website (URL) | www.ilvt.de |
| Institution/Company | Sparkasse Donaueschingen |
| Responsibility/Function | Building owner |
| Street/PoBox | Mühlenstraßße 1 |
| ZIP | 78166 |
| City | Donaueschingen |
| Country | Germany |
| Phone/Fax | +49-771 802-0 / +49-771 802 279 |
| service@spk-donaueschingen.de | |
| Website (URL) | www.sparkasse-donaueschingen.de |
| Institution/Company | systherma - Planungsbüro für Erdwärmesysteme |
| Responsibility/Function | Planning geothermal system |
| Street/PoBox | Finkenstraße 1 |
| ZIP | 72181 |
| City | Starzach |
| Country | Germany |
| Contact Person | Dr. Simone Walker-Hertkorn |
| Phone/Fax | +49-9122-87 / +49-9122-86 |
| systherma@gmx.de | |
| Website (URL) | www.systherma.de |
