Use of District Cooling from Groundwater Passage Lines for ... · sche Lösung sichert eine hohe Energieeinsparung und vermindert den Ausstoß von Treibhausgasen in ... of the refrigerant

Use of District Cooling fromGroundwater Passage Lines

for a Computer Center in Munich

June 2006

Final Report

Use of District Cooling from Groundwater Passage Lines for a Computer Center in Munich

Final Report

Michael Arnold

Stadtwerke München GmbH

Netzstrategie Emmy-Noether-Straße 2

80287 Munich

Funded by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety and the Bavarian State Ministry for Economy,

Infrastructure, Transport and Technology

Bayerisches Staatsministerium für

Wirtschaft, Infrastruktur, Verkehr und Technologie

June 2006 Version 3.0 Project Organization: Michael Arnold Date: 30.06.2006

Abschlussbericht Fernkälte 2/43

Stadtwerke München GmbH, Michael Arnold

Table of Contents

1 Introduction .................................................................................................................... 5 1.1 Brief Description of the Project ..................................................................................... 5 1.2 Extracts from Press Releases....................................................................................... 7 1.3 Bavarian Energy Award 2006 ....................................................................................... 8

2 Project and Results Achieved ....................................................................................... 9 2.1 Idea and Requirements for the Implementation of the Project ...................................... 9 2.2 The Task..................................................................................................................... 11 2.3 Description of Planning and Course of Construction .................................................. 12 2.4 Description of Geology................................................................................................ 16 2.5 Initial Operating Experience........................................................................................ 20 2.6 Project History ............................................................................................................ 23 2.7 Costs / Economic Efficiency........................................................................................ 25 2.8 Environmental Protection Effect.................................................................................. 27 2.9 Problems, Difficulties and Solutions............................................................................ 29

3 Prospects ...................................................................................................................... 31 3.1 Follow-up Projects ...................................................................................................... 31 3.2 Applicability to Other Projects ..................................................................................... 36

4 Summary ....................................................................................................................... 37 4.1 Summary .................................................................................................................... 37 4.2 Recommendation........................................................................................................ 39 4.3 Contact Persons / Project Participants........................................................................ 40

5 Digital Video and Literature Reference....................................................................... 41

6 List of Abbreviations.................................................................................................... 43



Berichts-Kennblatt

1. Berichtsnummer UBA-

2. Demonstrationsvorhaben 3. CO2 - Minderung

4. Titel des Berichts Einsatz von Fernkälte aus Grundwasserüberleitungen für ein Rechenzentrum in München Abschlussbericht 5. Autor(en) 8. Abschlussdatum Dipl.-Ing. Michael Arnold

6. Durchführende Institution (Name, Anschrift) 9. Veröffentlichungsdatum Stadtwerke München GmbH Netzstrategie Emmy-Noether-Straße 2 10. Vorhaben-Nr. 80287 München 20065

7. Fördernde Institution (Name, Anschrift) 11. Seitenzahl Bundesministerium für Umwelt, Naturschutz und 43 Reaktorsicherheit (BMU) 12. Literaturangaben Alexanderplatz 6 13 10178 Berlin 13. Tabellen und Diagramme 9 15. Zusätzliche Angaben 14. Abbildungen 16 16. Zusammenfassung Gemeinsam mit der BMW AG haben die Stadtwerke München (SWM) eine ressourcenschonende, umwelt-verträgliche und wirtschaftliche Kälteversorgung für die Rechnerräume des Forschungs- und Innovations-zentrums der BMW AG in München entwickelt und gebaut. Eine einfache, aber sehr wirkungsvolle techni-sche Lösung sichert eine hohe Energieeinsparung und vermindert den Ausstoß von Treibhausgasen in großem Umfang. Die innovative Leistung besteht darin, dass der erneuerbare Energieträger, Grundwasser aus den Dükern der Münchner U-Bahn zur Kälteerzeugung verwendet wird. Damit wird eine aus dem Na-turverbund entnommene Primärenergie ohne Umwandlung zur Endenergie. Elektrischer Strom wird ledig-lich zur Förderung und für den Transport des Kältemittels Grundwasser benötigt. Die Erwärmung des Grundwassers wird dabei auf ein umweltverträgliches Maß begrenzt und der Grundwasserspiegel an der U-Bahn-Röhre stabilisiert. Im Gegensatz zur konventionellen Kälteerzeugung mittels Kompressionskältemaschinen können mit der Kälte aus dem Grundwasser jährlich rund 10 Millionen Kilowattstunden Strom eingespart werden. Das entspricht dem Jahresstromverbrauch von rund 3.000 Münchner Haushalten. Durch diese Fernkälteanlage werden bei einer Auslastung von 90 % bis zu 6.300 Tonnen CO2 jährlich vermieden. Die im Münchner Projekt angewandte technische Lösung ist prinzipiell auf alle Bauwerke anwendbar, die Wasser vorhalten. Das betrift zum Beispiel das Fannel und Gate Projekt der Stadtwerke München Ein Folgeprojekt auf dem Gelände der Stadtwerke München befindet sich in der Durchführungsphase. 17. Schlagwörter Fernkälte, CO2-Minderung, Regenerative Energie, U-Bahn-Düker, Klimaschutz, Fernkühlung, Fernkälte-versorgung, Fernkälteleitung, Fernkältenetz, Kälteversorgung, Kühlung eines Rechenzentrums, Einspa-rung von Rückkühlwerken, Einsparung von Kompressionskältemaschinen, Alternative zu Kältemaschinen, Dezentrale Wassergewinnung, Wassergewinnung durch vorhandene Bauwerke, Wassergewinnung zur Kühlung, CO2-Einsparung, CO2-Vermeidung, 5 MW Kälteleistung, Einsparung Strom durch Fernkälte, Grundwasserkühlung. 18. Preis 19. 20.

Berichts-Kennblatt 06/2000



Report Cover Sheet

1. Report No. UBA-

2. Demonstration project 3. CO2 reduction

4. Report Title Use of District Cooling from Groundwater Passage Lines for a Computer Center in Munich Final Report 5. Author(s) 8. Report Date Dipl.-Ing. Michael Arnold

6. Performing Organization (Name, Address) 9. Publication Date Stadtwerke München GmbH Netzstrategie Emmy-Noether-Straße 2 10. Project-No. 80287 München 20065

7. Funding Agency (Name, Address) 11. No. of Pages Bundesministerium für Umwelt, Naturschutz und 43 Reaktorsicherheit (BMU) 12. No. of References Alexanderplatz 6 13 10178 Berlin 13. No. of Tables, Diagrams 9 15. Supplementary Notes 14. No. of Figures 16 16. Abstract Together with BMW AG, the Municipal Works of Munich (Stadtwerke München - SWM) have developed and built a resource-conserving, environmentally compatible and economical supply of cold for the com-puter premises of the Research and Innovation Center of BMW AG in Munich. A simple, but highly effective technical solution allows for high energy saving and reduces the emission of greenhouse gases to a large extent. It is the innovative merit that the renewable energy carrier groundwater from the culverts of the Mu-nich underground is used for cold generation. That way, a primary energy taken from the natural environ-ment becomes a final energy without conversion. Electric energy is only used for the tapping and transport of the refrigerant groundwater. In that connection, the warming-up of the groundwater is limited to an envi-ronmentally compatible extent and the groundwater level at the underground tube is stabilized. In contrast to conventional cold generation by means of compression-type refrigerating machines, cold from the groundwater allows to save about 10 million kilowatt hours of electric energy per year. This corre-sponds to the annual consumption of about 3,000 households in Munich. With a utilization of 90 %, that district cooling system avoids up to 6,300 tons of CO2 per year. In principle, the technical solution used in the Munich project can be applied to all buildings that retain wa-ter. This regards for example the Funnel-and-Gate project of Stadtwerke München. A follow-up project on the area of Stadtwerke München is in its execution phase. 17. Keywords district cold, CO2 reduction, regenerative energy, underground culvert, climatic protection, district cooling, district cooling supply, district cooling line, district cooling network, cooling supply, cooling of a computer center, saving of recooling plants, saving of compression-type refrigerating machines, alternative to refrig-erating machines, decentralized water tapping, water tapping by existing buildings, CO2 saving, CO2 pre-vention, 5 MW cooling capacity, current saving by district cooling, groundwater cooling 18. Price 19. 20.

Report Cover Sheet 06/2000


1 Introduction 1.1 Brief Description of the Project Also in our latitudes, trade and office buildings are more and more frequently cooled due to the increasing equipment with electronic data processing systems and the large shares of window areas that are usual today. For example, with a modern glass façade subject to respective solar radiation, cooling is already required from outside temperatures of 6°C on. In large administra-tive buildings, computer centers often consume especially much cooling capacity. For that pur-pose, there are normally used electric compression-type refrigerating machines that have a high electrical consumption and high operating costs. An alternative to such systems is the resource-conserving and economical cooling by groundwater. It is an advantage that the water normally has a lower temperature in comparison to the ambient temperature, is available almost without limitation and can be returned to the same or another place. That way, an energy-intensive cool-ing of the conventional refrigerant is not required at all. The project presented here deals with the "Use of District Cooling from Groundwater Passage Lines for a Computer Center in Munich (District Cooling)". The tapping of groundwater from culverts along an underground line over a length of about two kilometres and the installation of a related network having a length of about 4.6 km is an innova-tion in the area of cooling engineering. Compared with cooling by means of compression-type refrigerating machines, the cooling by groundwater in the project presented here allows to save about 6,300 tons of CO2 per year. (see also Chapter 2.8) The project of Stadtwerke München (SWM) described in more detail below is subdivided into two construction stages. Construction Stage 1 comprises a system to which all of the 8 culvert systems along the Dülferstrasse route of the Munich underground line U2 were connected. That construction stage was promoted with funds from the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) and the Bavarian State Ministry for Economy, Infrastructure, Transport and Technology (BayWiMe).

Construction Stage 2 comprises an additional extension of the system by 1 MW so that the district cooling system achieves a total capacity of 5. The extension of the system was realized by the construction of 2 additional supply wells and 2 injection wells. That was necessary because no further culvert systems were available in the closer vicinity. That construction stage was promoted with funds from the Bavarian State Ministry for Economy, Infrastructure, Transport and Technology (BayWiMe), too. Fig. 1-1: View of an underground culvert showing a horizontal drain



The use of up to 35 l per second of groundwater as service water is another cost-effective and environment-friendly effect. That way, there is saved high-quality drinking water from the urban water network required for part of the sanitary installations and air humidification of the office rooms. Costs of € 1.29 per cubic meter of drinking water are currently saved. For that purpose, however, the groundwater needs to be chemically treated for hygienic reasons so as to exclude any health risk for the staff of BMW AG. Fig. 1-2: Schematic diagram of the water tapping in the culvert, transport to the computer center and return of the water to the culvert building.

Year Construction stage

Cooling capacity

2004 3,5 MW 600 m³/h 167 l/s2005 4,0 MW 686 m³/h 195 l/s

from 2006 2 5,0 MW 857 m³/h 238 l/s

Water volume

1

Table 1-1: Development of cooling capacity according to capacity specifications by BMW AG The water volume of about 195 l/s corresponds to the drinking water consumption of a munici-pality with about 20,000 inhabitants. It is warmed up by about 5 degree centigrade and is re-turned, except for the service water.



1.2 Extracts from Press Releases


BILD-Zeitung 01/06/2004

Münchner Merkur 18/07/2003

Süddeutsche Zeitung 29/07/2003 / 22/05/2004

Abendzeitung 18/07/2003


1.3 Bavarian Energy Award 2006 Based on the outstanding innovative merits in the area of efficient utilization of energy, renew-able energies and new energy technologies, the project received the Bavarian Energy Award 2006 from Mr. Erwin Huber, Bavarian State Minister for Economy, Infrastructure, Transport and Technology, in Nuremberg on 01 June 2006.



2 Project and Results Achieved 2.1 Idea and Requirements for the Implementation of the Project In cooperation between the firms BMW AG and Stadtwerke München, there was developed an integrated energy concept for the use of groundwater as cooling energy, taking into account the planned Research and Innovation Center (Forschungs- und Innovationszentrums - FIZ). The basic decision was taken at an innovation workshop between BMW AG and Stadtwerke München in April 2002.

It was required for the project to obtain a permission under water law for the use of groundwater for cooling purposes from the Department of Health and Environment (Referat für Gesundheit und Umwelt - RGU) and the Water Resources Board of Munich (Wasserwirtschaftsamt München - WWA). A permission for the utilization of the existing culvert systems of the Munich under-ground from the Government of Upper Bavaria (RegOBB), the Munich Transport Company (Münchner Verkehrsgesellschaft - MVG) and the Building Authority of the State Capital of Mu-nich, Department for Underground Construction, were required, too, just like further local permits regarding the pipeline. • New Construction of the BMW FIZ The construction of the Research and Innovation Center of BMW AG requires large quantities of cooling capacity. The plans provided for a gradual increase of the cooling capacity from 4 MW (as from 01/05/2004) to 5.0 MW (as from 01/01/2006). In addition, it was necessary to ensure a secure supply of cooling for the operation of the highly sensitive area of the computer center of BMW AG. • Geological Conditions in Munich The geological conditions involving thick water-permeable and strongly flowing groundwater lay-ers form another requirement for the project. See Fig. 2-1. For the system capacity of 4.0 MW, there is required a water volume of about 195 l/s that is available at the existing culverts. The groundwater temperatures are ca. 11°C to 13°C. The maximum temperature difference, measured between flow and return, is 6 Kelvin with a ground-water temperature of less than 12°C and 5 Kelvin with a groundwater temperature of more than 12°C. Fig. 2-1: Groundwater Conditions in Munich



The construction of the underground lines that cross the groundwater flow from south to north and extend into the groundwater strata required the installation of culvert systems. See Fig. 2-2. They ensure that, in spite of the blocking building, the groundwater flow is not interrupted. Thus, the natural groundwater flow continues to be guaranteed.

Water flow in the culvert building

Fig. 2-2: Influence of the underground lines on the natural groundwater flow

Fig. 2-3: Culvert well under construction Fig. 2-4: Culvert in operation



2.2 The Task For making progress with the extension of the extraction of renewable energy, SWM developed jointly with BMW AG a concept for a resource-conserving, environmentally compatible and eco-nomical energy supply. The result was the utilization of cold groundwater from underground-line culverts as coolant for the new Research and Innovation Center (FIZ) of BMW AG. With the promotion and funding by the Federal Ministry for the Environment, Nature Conservation and Nuclear Safety and the Ba-varian State Ministry for Economy, Infrastructure, Transport and Technology, it was possible to achieve economic efficiency of the project in a period of 12 years and to take account of the eco-logical requirements.

• Avoidance of CO2 Emission The project was to examine to what an extent CO2 emission can be avoided with the district cooling system (pump energy only) presented here in comparison with a cooling plant using con-ventional compression-type refrigerating machines (very energy-intensive). • Geological Outline Conditions For clarifying the outline conditions with regard to hydrogeology and water resources as well as the effects of the planned utilization, the following examinations were to be made: - Determination of the usable groundwater volumes; - Examination of the groundwater quality regarding its suitability as cooling water (groundwater temperatures, chemical parameters); - Determination of the changes in the local groundwater conditions to be expected; - Optimization of the tapping and percolation volumes, such as:

• positive influencing of the groundwater levels, • security from "hydraulic short-circuits".

• Water Tapping and Transport The existing culvert systems were to be used as sources or wells. There were only required the tapping systems, including supply network and control engineering. See Fig. 2-5. It was to be determined which underground lines and/or culvert buildings are located in the vicinity of the BMW FIZ and whether the required technical and legal outline conditions for a utilization of the culverts exist. A short line with a high water tapping volume was the objective. The path realized is shown in Fig. 2-6. As a result of the examination, a feasibility study with a realization concept was drawn up. It proved that the system will be cost-effective. Fig. 2-5: Existing culvert building with installations for the district cooling line



2.3 Description of Planning and Course of Construction As soon as the feasibility study and a realization concept were available, contract negotiations were conducted with BMW AG. There had to be found a cost-effective workable solution for both parties, weighing the risks. The execution planning was already started in parallel with the con-tract negotiations so as to be able to guarantee that the deadline for the supply of cooling as from 01 April 2004 on can be met. The construction work on the line network had to be started two weeks after signing the contract with BMW AG. That was only possible on the basis of an early execution planning and invitation to tender for the supply/services. A new "district cooling" project had to be realized in a very short time in a cost-effective manner observing high quality standards. In order to guarantee that, open com-munication, fair cooperation and inter-company project responsibility were regulated with the contract partner BMW AG and the building firms under an agreement concluded before the work commenced. Project management, project control as well as planning and construction supervision were pro-vided by Stadtwerke München itself. External services, such as the hydrogeological examina-tions, the structural calculations, the construction of the system and other services were subcon-tracted by SWM to other partners. • Planning: The planning and realization of the district cooling line is based on the know-how of Stadtwerke München in the fields of district heating as well as water tapping and distribution.

Culvert BMW FIZ

Piping

Supply well

Injection well

43 l/s35 l/s

32 l/s

57 l/s

8 l/s

21 l/s11 l/s18 l/s

13 l/s

BMW FIZ 2004: 3,5 MW 167 l/s 2005 4,0 MW 195 l/s 2006: 5,0 MW 238 l/s

Culvert 195 l/s Culvert + Well 238 l/s

Fig. 2-6: Water tapping from culvert, piping network, well and consumer BMW FIZ

The water volume of about 195 l/s needed in the year of 2005 is tapped from the 8 culverts of the underground line 2/8 from west of the underground station Dülferstraße to west of the un-derground station Feldmoching. The tapped groundwater is pumped through a plastic piping (PE), mainly having an external diameter (da) of 500 and a length of ca. 4.6 km, to the point of supply, see Fig. 2-8, at the central energy station of BMW AG. The position of the culverts in-cluding route of the line can be gathered from Fig. 2-6.



The tapped groundwater has a supply temperature of 11°C to 13°C. At the central energy station of BMW AG, the groundwater delivers its energy to the cooling water network of BMW AG in a heat exchanger and then is returned through a second pipeline. That is done with a temperature of 16°C to 18°C on the groundwater flow-off side of the culverts. The tapping and injection points are distributed over a distance of about 2.0 km (see Fig. 2-6). About half of the groundwater in-flow is collected and led through by the culvert buildings. The remaining water volume crosses the underground line naturally, i.e. the underground line runs above or below the groundwater-carrying stratum. Less than 50% of the inflowing water volume is warmed up by the user for dis-trict cooling. Accordingly, the warming-up of the groundwater in the closer vicinity is relativized very quickly. During the past two decades, the groundwater temperatures did not show any significant changes in the tapping area. Long-term temperature changes due to global warming cannot be excluded, but should not exceed 1 Kelvin per century. An increase of the groundwater temperature in the inflow area of the tapping culverts by future concurrent utilization of groundwater can be excluded since respective systems are subject to a permission under water law and the influence on existing systems is checked by the water man-agement authorities. Per culvert and tapped water volume, the same yet warmed-up water volume is fed back to the culvert and thus to the groundwater strata. This guarantees that the groundwater conditions will only be influenced to a very low degree. The only exception is the groundwater used as service water (max. 35 l/s). It is used as feeding water for the cooling towers, for room air humidification and in part for the sanitary installations of BMW AG. The primary circulation (supply and return line) is owned by Stadtwerke München. Fig. 2-8 shows the point of delivery. There, the plastic pipeline of SWM is connected to the stainless-steel pipe network of BMW AG. The train of pipes from the point of delivery to the heat ex-changer and back, including heat exchanger, is owned by BMW AG.

Fig. 2-7: PE line da 500 mm Fig. 2-8: Point of delivery SWM to BMW AG



The provision of the required cooling capacity is centrally controlled by software. The host com-puter is located at the central energy station of BMW AG. All values per supply well and return are received there. That includes e.g. the water tapping (l/s), the temperature (°C), the pressure (bar), the power (kW) and other measuring values. See Fig. 2-9. All pumps are speed-controlled and only deliver groundwater for the cooling power needed. When less than 5 MW of cooling power is required, there is delivered less water, which in addi-tion saves electric energy (pump current) and CO2 emission for its generation. All information and measuring values are transmitted to the control room of Stadtwerke München and are monitored by members of the staff during 24 hours on 365 days per year. A pipe break would be immediately detected as a pressure drop and missing water volume between the point of supply at BMW FIZ and the culverts. In such case, the emergency concept drawn up in cooperation with BMW AG will enter into ef-fect. The control room informs the SWM security service that will go to the place of leakage and initiate the repair. Fig. 2-9: Monitoring The monitoring information is required for the settlement of accounts with BMW AG, as proof for the water management authority of Munich and for leak monitoring. • Course of Construction: Already before the tendering stage, Stadtwerke München developed a comprehensive traffic concept for the execution of the construction works in the public road traffic and coordinated it with the responsible authorities and parties involved (including among others public transports / Münchner Nahverkehrsgesellschaft).




The sequence of construction was planned by the building contractor on the basis of the con-struction stages that had already been agreed upon in detail. Priority was given to the construction of the pipeline along the main line (transport lines da 500 mm PE-HD) and the subsequent connection of the supply and injection wells to the main lines. After completion of the work on the main lines, including shaping of the surfaces and release of the roadways in December 2003, the measuring wells and the supply and injection wells were connected until February 2004. Then, the system could enter into trial service. In the course of building construction, in part considerable changes in the building design be-came necessary for SWM. They were not without consequences for the sequence of construc-tion work. The plastic pipes (da 500 mm PE-HD) were laid in braced pipe trenches in a bed of sand 0/2 in installation depths of up to 3.50 m. Altogether ca. 25,000 m³ of pipe trenches were excavated and refilled in the inner-city area. Due to the traffic situation, the crossings along Schleissheimer Strasse were passed using a closed type of construction. Protecting tubes were installed over a length of 35.00 m each by means of microtunnelling into which the media pipes were pulled. The required start and end pits having a depth of up to 7.00 m were installed with braced sheet-pile walls. The 12.00 m pipes were connected by means of resistance welding using sockets or by means of butt-welding (butt-welding with heat reflectors). In order to avoid time-consuming trench seams, runs of piping were pre-welded outside the pipe trench and laid into the lined pipe trench. The 8 measuring wells for installing the system, measuring, control and regulating equipment were pre-fabricated, delivered to the construction site and placed there. They were installed and connected to the submersible pumps as well as the pneumatic culvert valves (for decoupling the groundwater upstream and downstream sides) in the underground culverts. After completing the entire line network, including all connections, the pressure test was sched-uled for the beginning of February 2004. The test was performed using the contraction method according to DVGW W400 usual for PE-HD lines (viscoelastic behaviour). The TÜV Bavaria (technical control association) confirmed leak tightness of the line, whereupon test operation was started on 02 February 2004.



2.4 Description of Geology

2.4.1 Hydrogeological and Water Management-Related Conditions The project area is located in the northern part of the gravel plain of Munich. There, glacial gravel having a thickness of about 10 m is located above argillaceous and fine-sand rock from the Tertiary. The gravel shows a very high water permeability, while the tertiary layers are only little permeable. The groundwater thickness in the gravel is about 4 to 7 m. The distance groundwater-surface is about 4 m in the west and increases to ca. 7 m in eastward direction. The groundwater flows with an incline of ca. 0.3 % from southwest to northeast. The groundwater is only little thermally pre-loaded (average temperature ca. 12°C) and is neither corrosive nor strongly calcium precipitating. Due to the low depth and the high yield of the gravel aquifer as well as the chemical/physical water parameters, there exist favourable conditions for a thermal utilization of the groundwater. Neither in the inflow area nor in the flow-off area, there exist any groundwater utilizations that might be negatively affected by the use to the groundwater from the culvert systems. 2.4.2 Type and Dimensioning of the Culvert Systems The underground line 8-Nord runs between Panzerwiese in the east and Feldmoching in the west on a distance of about 2.2 km more or less vertically to the flow-off direction of the ground-water. Since the foundation bases of the underground buildings are situated in the little perme-able tertiary layers and the upper edges of the buildings are higher than the groundwater level almost everywhere, the groundwater flow-off in the gravel is blocked. Only in an about 600 m long section between Feldmoching and Hasenbergl, the groundwater flow-off is not impeded since the underground tube runs completely in the tertiary layer. Cf. also Figs. 4 + 8. Altogether 10 culvert systems serve to reduce the groundwater build-up. Each of these culverts comprises an inflow well directly south and a flow-off well directly north of the underground line. These are square wells with a side length of 2.6 m and a depth of about 15 m (see Fig. 3-5). For collecting and draining the groundwater, each of the wells is equipped with two or three horizon-tal filter tubes with a length of 8 - 12 m. These drains are located about 1 m above the base of the gravel aquifer. Even in case of a very low groundwater level, they are still covered by 2 to 5 m of groundwater; therefore, a falling-dry can be excluded. The inflow and flow-off wells are connected to culvert tubes close to their base through which the groundwater is led through beneath the underground tube. As to their design, the culvert wells are similar to horizontal-filter wells that are mostly used for groundwater tapping where a high cubic capacity shall be realized with a low groundwater thick-ness. The structural dimensioning of the culverts is based on hydrotechnical calculations; the overall length of the horizontal filter tubes per well was adapted to the groundwater inflow expected. Since these calculations were made under the general assumption of a coefficient of permeabil-ity of the aquifer of kf = 0.005 m/s, the flow values actually measured at the individual culverts in part deviate substantially from the rated values (cf. Tab. 2). According to the hydrotechnical calculations of the Department for Underground Construction, the culverts are designed for flow capacities of 15 to 34 l/s. That dimensioning was made under the assumption of a critical flow rate through the filter tube wall (SW 0.5 mm) of only 0.15 cm/s. Thus there result, in terms of calculation, relatively low cubic capacities that are substantially exceeded in practice in areas with a higher groundwater inflow (culvert 1, 2 and 3 Feldmoching).



When using the customary calculation methods for the dimensioning of horizontal filter wells, there result significantly higher cubic capacities for the culvert systems that correspond better to the actually measured flow values in areas with a higher groundwater inflow. The free groundwater flows measured in the culverts are 7 to 57 l/s per culvert in case of mean water levels. The three systems in Feldmoching showed the highest flow values. The ten culvert systems altogether transfer about 210 l of groundwater per second. In spite of the culvert sys-tems, a complete compensation of the groundwater build-up caused by the underground is not achieved. In the areas between the individual culverts, the groundwater level differences be-tween inflow side and flow-off side are at about 1 m. 2.4.3 Results of the Hydrogeological Examinations

Flow Measurements and Pumping Tests For determining the culvert flows, there were first performed impeller measurements at the cul-vert tubes or at the individual drains of the culvert wells. That work was done by divers. The val-ues measured in March and May 2002 with medium groundwater levels are summarized in Tab.2-1, line 2.

Tapping: culvert/well 1 2 3 5 6 7 8 9 10 11 Total 1 Rated value 20 15 34 20 17 15 19 21 kA. kA. 2 Free flow, measured value 35 32 57 15 7 9 11 18 26 16 226 3 Pumping test, Qmax. 74 16.5 15 16.7 21 36 22 4 Tapping applied for 35 32 57 18 8 11 13 21 195

Tab. 2-1: Culvert data, flow and tapping volume in l/s The pumping tests performed served first of all to check the response of the aquifer to increased tapping rates at the culverts and to obtain representative water samples for determining the physical and chemical water parameters. Since the preparatory work for the pumping tests re-quired a blocking of the culverts over several days, there resulted in addition valuable informa-tion on the resulting groundwater build-up. In the course of the tests, there were monitored se-lected groundwater measuring points in the inflow and flow-off areas of the culverts. The data collected were used for a validation and recalibration of the numerical groundwater model [G]. In July 2002, culverts 1 and 8 to 11 were examined in a first group pumping test. A second pumping test was performed at culverts 6 and 7 in March 2003. In the course of the pumping tests, the tapping was increased to about 120 % of the determined free flows or up to the re-spective rated value. The maximum tapping and percolation rates led to relatively low groundwa-ter level decreases or increases in the culvert wells (-0.77 and +0.38 m, respectively). The groundwater level changes at the measuring points monitored during the pumping test were rather small, too. At maximum delivery rates, a maximum lowering of 0.07 m in a distance of 30 m and of 0.03 m in a distance of 200 m from the points of tapping was measured in the inflow area. Slightly higher groundwater level changes occurred in the flow-off area north of the under-ground line. There was registered a maximum groundwater rise of 0.23 m in a distance of 60 m and of 0.04 m in a distance of 280 m.



During the pumping tests, temperature, pH-value, conductivity, and sand content in the delivered water were continuously monitored by means of sampling. Based on the temperature measurements available, there can be assumed an average tempera-ture of the delivered water of almost 12°C. During the pumping tests, turbidity and a slight sand content occurred only for a short time after starting the pumps. In the further course, the water was clear and free from sand. Also with re-gard to the chemical parameters of the groundwater, there are no objections to a use as cooling water. Numerical Groundwater Model In the area of examination, there exist about 80 groundwater levels read by the Building De-partment for Underground Construction of Munich on a weekly basis. These measurements serve to document the interference with the natural groundwater flow-off conditions caused by the underground line. The good exploration situation offered favourable conditions for setting up a numerical groundwater model. There was developed a three-dimensional groundwater flow and balance model using MOD-FLOW [E], [F]. The model area covers an area of about 2.0 x 2.7 km. The individual cells of the finite-difference model have side lengths of 12.5 m in the area of the underground line and of up to 50 m in the marginal areas. The data of about 60 drillings in the area under examination were used for preparing the hydro-geological rock model. Further information on the marginal hydrogeological conditions were gathered from the examinations made by BLASY [A], FRIED and ZIPFEL [B], PAUS and KOSLOWSKY [C] and SALAMEH [D]. The model was calibrated according to stationary conditions for low and high groundwater levels and taking into account the findings regarding the permeability coefficients of the aquifers ob-tained from the pumping tests. Within the scope of calibration, the distribution of the permeability coefficients was varied in such a manner that an optimum correspondence of measured and calculated groundwater levels was achieved. Using the calibrated groundwater model, the meas-ured groundwater levels were re-enacted with a maximum deviation of ± 5% related to the groundwater level difference of 3 m in the model area. Fig. 2-10 shows a plan of groundwater levels with flow lines of the western area calculated with the model (Feldmoching, culverts 1 to 3). As outline conditions, there were used low groundwa-ter levels according to NW 1998. The tapping/percolation volumes are 35, 15 and 57 l/s in the culverts 1, 2 and 3, respectively. The lowering cones in the area of the intake wells 1 and 3 are clearly visible. The underground line ends about 60 m west of culvert 1. From about 150 m east of culvert 3 on, the underground line runs beneath the gravel aquifer. In those areas, the groundwater can flow off without impediment. The impediment of the flow-off by the underground building, however, leads to a strong increase of the groundwater inclination there. Using the groundwater model, the maximum groundwater volumes that can be tapped and per-colated are determined for different hydrological outline conditions. Apart from the groundwater resources available, the cubic capacity of the culvert systems as well as the protection against hydraulic short-circuits between tapping and percolation wells were also taken into account in the calculation of the different variants. According to the model calculations, the mean groundwater inflow into the examination area is about 640 l/s. Further 40 l/s result from a new formation of groundwater from precipitation in the model area [G]. Theoretically, tapping and percolation volumes of up to 390 l/s would be possi-ble in the culvert systems, so that the resulting groundwater level heights would be at a natural level, i.e. a level not influenced by the banking-up effect of the underground building.


Since, in case of respectively high tapping volumes, the rated values of the culvert systems in part would be exceeded to a considerable extent, a respective permission was not obtainable from the competent water management authority. The permission under water law was based on a maximum tapping / percolation of 120 % of the free flow measured. For the three culverts in Feldmoching (1, 2, 3), there were only permitted tapping volumes to the amount of the free flow volumes since the latter are already higher than the rated values. Since a utilization of the culverts 10 and 11 was not possible for technical reasons, there was finally applied for and approved a total tapping of 195 l/s from the 8 remaining systems 1 to 3 and 5 to 9 (see Tab. 1, line 4). It turned out during the test operation that the tapping volume of 32 l/s measured and approved for culvert 2 can only be achieved with a very high groundwater lowering. The tapping / percolation was set to 15 l/s there. Thus, the total capacity of the system now is 178 l/s. In case of lowest groundwater levels, a decrease of the groundwater resources from 640 to 480 l/s is to be expected [I]. Based on the model calculations made for respective outline conditions, it can be assumed that the tapping volumes can be maintained in such a case, too. In the intake wells, a clear decrease of the water levels (up to about 1.25 m) is to be expected. The remaining groundwater covering above the horizontal drains is still clearly higher than 2 m in all culverts. Therefore a falling-dry is not to be expected. With a total tapping of only about 40 % of the low-est water offer, an overload of the aquifer can be excluded.

Dükerschacht, Versickerung

Dükerschacht, Entnahme

U-Bahn, sperrt Grundwasserstrom

Grundwasserhöhengleiche

Grundwasserströmungsbahn

100 m

N

12 3

Fig. 2-10: Groundwater level plan with flow lines




2.5 Initial Operating Experience The largest possible automation of the operation formed a decisive criterion in the planning of the overall system. That way, low operating and maintenance costs as well as an optimization of the energy consumption of the pumps (CO2 reduction) were achieved. In the following, the operating tasks are briefly described. System Monitoring By integrating the monitoring system (see section 2.3, Fig. 2-9) of the district cooling system into the existing control system of the district heating and water supply, the required monitoring staff expenditure was reduced to a minimum. For the permanently collected and transmitted measur-ing values, certain limit values were defined and programmed into the automation system so as to indicate a deviation of the system operation from the defined operating mode any time and without delay. Maintenance/Repair Maintenance/repair mainly include the maintenance of the system and the repair of any defec-tive or deficient components. For a scheduled maintenance of the system components, the safety- and operation-relevant parts and components of the system have been registered and entered into the EDP system SAP. The respective intervals and scopes of maintenance have also been recorded there for every part. That programming will ensure a regular ordering process and also a respective exe-cution monitoring. In the maintenance work carried out in the years of 2004 and 2005, there were not detected any defects or functional impairments, except the problems described in chapter 2.9. Operating Characteristics The continuous increase of IT technology at the computer center of BMW AG will continue in the next few years. It is to be expected that the full load of 5 MW of cooling capacity will be reached from 2008 on. The period from May 2004 to April 2005 was the test year used as a basis for this report. Since, during that test period, there was needed a capacity that was lower than the capacity that could have been provided, that test year does not provide a representative statement yet. Diverging from the volume needed on part of the customer, the groundwater delivery volumes were gradually increased to about 87 % of the maximum delivery capacity of 195 l/s so as to be able to submit well-founded statements on the groundwater levels and conditions to the Water Management Office of Munich.


The following diagrams show the groundwater temperatures in the supply and return line, a "TARGET-ACTUAL" comparison regarding the cooling capacity available and actually used as well as the flow rates in l/s.

0

2

4

6

8

10

12

14

16

18

Mai

04

Jun

04

Jul 0

4

Aug

04

Sep

04

Okt

04

Nov

04

Dez

04

Jan

05

Feb

05

Mrz

05

Apr

05

Mai

05

Kalendermonat

Gru

ndw

asse

rtem

pera

tur [

°C ] Rücklauftemperatur

Vorlauftemperatur

Diagram 2-1: Groundwater Temperatures in the Supply and Return Lines Diagram 2-1 shows the groundwater temperatures upstream and downstream of the heat ex-changer of the customer's system. The flow temperature curve shows a slight increase due to weather conditions during the summer months. The return temperature is regulated by the ca-pacity used by the heat exchanger.


0

500

1000

1500

Mai

04

Jun

04

Jul 0

4

Aug

04

Sep

04

Okt

04

Nov

04

Dez

04

Jan

05

Feb

05

Mrz

05

Apr

05

Mai

05

Kalendermonat

Käl

tele

is 2000

2500

3000

3500

4000

4500

tung

[ K

W ]

Anlagenleistung

Leistungsabnahme

Diagram 2-2: System Capacity TARGET and Capacity Used ACTUAL Diagram 2-2 shows the cooling capacity actually used compared with the technically possible delivery capacity. With the increasing development on part of the customer, the cooling capacity used has increased since April 2005.


0

20

40

60

80

100

120

140M

ai 0

4

Jun

04

Jul 0

4

Aug

04

Sep

04

Okt

04

Nov

04

Dez

04

Jan

05

Feb

05

Mrz

05

Apr

05

Mai

05

Kalendermonat

Dur

chflu

ssm

enge

[ l/s

]

Diagram 2-3: Groundwater Tapping Volumes in l/s Diagram 2-3 shows the flow rate upstream of the heat exchanger. Of that volume, a maximum share of 35 l/s can be used as service water for various sanitary installations as well as for the room air humidification system, etc.




2.6 Project History Below, some stations in the course of the project: When Month/Year Who What

12/01 – 04/02 SWM Feasibility study for the installation of piping in the underground tunnel of the line U2/U8; total tapping volume max. Q=100 l/s

04/02 RegOBB Negative oral comment of the Government of Upper Bavaria on the installation of the district cooling line in the underground tun-nel

04/02 BMW / SWM

1st workshop of BMW AG and SWM

03/02-09/02 SWM Examination of variants for the installation of the district cooling line in the public road area up to BMW FIZ with connection to 5 underground-line culverts in the area of the station Hasenbergl, station Dülferstr. and Panzerwiese.

05/02 all Coordination meeting for pumping test I at underground-line cul-verts with Münchner Verkehrsgesellschaft, Mater Management Office and geologists

06/02 PST Pumping test I with simulation at 5 underground-line culverts 06/02 – 07/02 Dr. Seidl Drawing-up and editing of a groundwater model for hydro-

geological assessment / feasibility of the project 07/02 BMW /

SWM 2nd workshop of BMW AG and SWM. Presentation and explanation of the project

08/02 SWM First price negotiation with BMW AG completed with success 09/02 SWM Application for promotion "More Efficient Generation and Use of

Energy" submitted to the Bavarian State Ministry for Economy, Infrastructure, Transport and Technology

10/02 SWM Realization permission granted by the management of SWM 10/02 SWM Application for promotion "Use of District Cooling from Ground-

water Passage Lines for a Computer Center in Munich" submit-ted to Deutsche Ausgleichsbank

11/02 – 01/03 SWM Preliminary planning of district cooling system 12/02 BMW /

SWM Number of the underground-line culverts increased from 5 to 8, so that a higher capacity of the system is achieved

12/02 Dr. Seidl Examination on the realization of an additional vertical well 12/02 DtA Decision of Deutsche Ausgleichsbank (DtA) to support the pro-

ject and approval of the early start of the measure by the Bavar-ian Ministry of Economic Affairs

12/02 SWM Definition of the final contractual volumes and dates of delivery (3.5 MW in 2004, 4.0 MW in 2005 and 5 MW in 2006) for the dis-trict cooling plant

01/03 BMW / SWM

Preparation of the agreement between BMW AG / SWM

03/03 SWM Order for thermal calculation of the district cooling line awarded to Stuttgart University

03/03 ABS Pumping test II with simulation and impeller measurement at fur-ther 5 underground-line culverts

03/03 – 07/03 SWM Execution planning and contract awarding for plant and line con-struction; measuring and control engineering; electrical engineer-ing

03/03 SWM / BMW

Presentation of the functional description and planning for plant and pipeline construction



03/03 SWM Publication of the project in the Official Gazette of Bavaria.

Public invitation to tender with restricted participation 04/03 WWA Alteration of the maximum tapping volumes at the underground-

line culverts 04/03 SWM Order for the preparation of the pipeline statistics awarded to the

Institute for District Heating of Hanover 05/03 Dr. Seidl Preparation of risk assessment with comment 05/03 RGU Grant of the limited permission under water law 06/03 all Submission of plant and pipeline construction 07/03 SWM Alteration of and approval to the realization decision by the man-

agement of SWM 07/03 BMW /

SWM Final negotiation and signing of the contract on cooling supply between BMW AG and SWM

07/03 SWM Contract for pipeline and plant construction awarded to the firm Kassecker

08/03 Kassecker Cutting of the first sod and start of the construction of pipeline and shafts. Connection to 8 well systems and construction of ca. 10 km of pipeline with da 500 mm

08/03 – 12/03 Kassecker Civil engineering and pipe-laying of the main line and installation of the measuring wells

12/03 – 01/04 Kassecker Connection to the culvert systems 02/04 Kassecker Pressure testing followed by commissioning of the 8 well sys-

tems 10/03 – 03/04 Nelhiebel Measuring and control engineering 11/03 – 03/04 SWM Electrical engineering and telecommunications 01/04 – 03/04 all System tests 01 April 2004 all Commissioning of the district cooling systems 04/04 – 10/05 BMW /

SWM Optimization of the system, such as adjustment of the mode of operation, fine tuning of the operating concepts and initial experi-ence from the analysis of the measuring values

12/05 SWM Release of the Final Report From 01/06 on BMW /

SWM Further optimization of the system by adding the new wells as per 01 January 2006 and successive increase of the cooling de-mand of BMW AG


2.7 Costs / Economic Efficiency The total costs amount to about € 5.6 million for the promoted 4 MW system and to almost € 6.51 for the 5 MW system. The amortization period will be 12 years, see diagram 2-4. The investment costs have been kept within the limits and are 3 % below the estimated costs. The Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) promoted the pilot project of the 4 MW system (corresponding to construction stage 1) within the framework of a demonstration project with a reduced-interest loan to an amount of about € 2.99 million. The Bavarian State Ministry for Economy, Infrastructure, Transport and Technology promoted the 5 MW system realized in the final construction (as from 01 January 2006) (corresponding to construction stages 1+2) with an investment grant to an amount of € 300,000. Amounts of € 2.31 million for the 4 MW system and of € 3.22 million for the 5 MW system were made available by Stadtwerke München. Assuming a water tapping and delivery of about 195 l/s, there result investment costs of about € 1,200 per running meter of district cooling line, including all costs. Thus, there result, merely in terms of calculation, single investment costs, excluding mainte-nance, of € 1,300 to 1,400 for the provision of 1 kW of cooling capacity. Below, the period of amortization according to the model of Stadtwerke München. Diagram 2-4: Calculated period of amortization An economic comparison between the district cooling system and the use of conventional com-pression-type refrigerating machines is hardly possible since it is not known what price for the delivery of energy and what investment costs for compression-type refrigerating machines can be assumed.



On the income side of Stadtwerke München, the original calculation was used as a basis. Cur-rently, the price of work is lower since BMW AG accepts a cooling volume of currently about 2.5 MW. The cooling capacity needed will increase in the next few months so that the 5 MW and thus the underlying estimate for the price of work will be reached in 2 to 3 years. In order to obtain a comparison nevertheless, the following assumptions are made and pre-sented in diagram 2-5: Assumptions for compression-type refrigerating machines with cooling tower: Annual capital costs: € 116,000 p.a. Investment € 1.10 million Term 20 years Interest 6 %

Operating costs: € 25,000 p.a.

Annual costs of consumption: € 502,000 p.a. Current at € 60 per MWh Water at € 1.29 per m³ Waste water costs of € 1.56 per m³

Total annual costs € 643,000 p.a. Assumptions for district cooling system: Expected annual proceeds: variable, see diagram 2-5 Basic rate plus price of work for 8,000 h p.a.

2.680

6.844

9.620

11.008

3.216

7.076

10.935


-435 -333 -232 -29 -130 -536 -529 -240 -1.000 €

403

8.232

1.401

4.068

5.456

12.396

13.784

9.649

1.930

643

4.503

5.789

8.362

12.222

13.509

27517473

0 €

1.000 €

2.000 €

3.000 €

4.000 €

5.000 €

6.000 €

7.000 €

8.000 €

9.000 €

10.000 €

11.000 €

12.000 €

13.000 €

14.000 €

15.000 €

2004 2006 2008 2010 2012 2014 2016 2018 2020 2022 2024

Betrachtungsdauer: 20 Jahre

Kos

ten

kum

ulie

rt in

T-€

FernkälteKompressionskältedelta =FK-KK

Diagram 2-5: Comparison of district-cooling proceeds and costs of compression-type cooling


2.8 Environmental Protection Effect The figures described below are based on the 4 MW system (building stage 1); the values in brackets refer to the 5 MW system (building stage 1+2) that will be available as from 01 January 2006. The environment-related benefit of this innovative cooling system is considerable. In contrast to a conventional cold generation by means of compression-type refrigerating machines, district cooling allows to save about 8 (10) million kilowatt hours of electric current per year. This corre-sponds to the annual current consumption of more than 3,000 households in Munich. The ratio of current consumption between district cooling system and compression-type refrigerating ma-chines is about 1/10. See also diagram 2-6. The saving of electric current and of the respective generation allows to avoid pollutants in the order of up to 5,000 (6,300) tons of carbon dioxide per year. Not only for economic reasons, but also for reasons of environmental protection, it is the aim to achieve a use of the capacity of the district cooling system of almost 100 %. The cooling required beyond that (peak load) will then be made available by means of compres-sion-type refrigerating machines. Whether or not that cooling is needed will depend, among other things, on the heat generation in the computer centers and on the seasonal weather condi-tions. Assuming about 90 % of full-load hours per year, there results a possible CO2 saving of about 5,000 (6,300) metric tons per year. According to the current state of knowledge, almost 8,000 full-load hours of the district cooling system will be achieved in 2 to 3 years. The pump energy consumption of about 1,300 (1,800) MWhel was deducted in the calculation of the CO2 saving. For making the environmental effect transparent, three variants of cold generation have been compared with one another and graphically represented in diagram 2-6.

1. Cold generation from groundwater, the BMW-FIZ district cooling system presented 2. Cold from district heating by means of absorption systems 3. Cold generation by means of compression-type refrigerating machines To make the variants of cold generation comparable, they were considered on the basis of the primary energy consumption. The result can be gathered from diagram 2-6. It shows that the provision of the same cooling capacity by groundwater cold generation requires altogether less than 10 % of the electric current or primary energy to be provided for the otherwise usual com-pression-type cold generation technology.

0,06

0,17

0,75

0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

kWh

Prim

ären

ergi

eein

satz

Grundwasserkälte Kälte aus Fernwärme Kompressionskälte

Diagram 2-6: Comparison of cooling variants by primary energy consumption



The determination of the avoidance of the pollutant carbon dioxide was based on an emission value of 626 g/kWh1. The district heating network of Stadtwerke München has been certified to have a primary-energy factor2 according to DIN V 4701-10 of ƒPE,WV = 0.122 for the year of 2005. Normally, that value is higher in the Federal Republic of Germany. Therefore, a value higher than 0.17 would result for cold from district heating according to diagram 2-6. It is to be mentioned here that the energy-related quality and efficiency of the district heat generation and distribution of Stadtwerke München contribute to that good primary-energy factor. Costs of CO2 and primary-energy avoidance result as follows: With average costs of € -202,000 € per year, see diagram 2-5, and a CO2 saving of 5,000 t per year, there result € -40 per t of CO2. This means the national economy does not incur any costs for the CO2 saving, but even has benefits! According to the European Energy Exchange, Ger-many’s Energy exchange that is located in Leipzig, the costs of a single CO2 avoidance certifi-cate amounted to € 28.95 per ton of CO2. on 21st April 2006.3

Comparing the district cooling project with other types of generation and/or other energy-saving measures, there result costs of primary energy avoidance of about -0.01 to -0.02 EUR/kWhPE. In comparison, district cooling is in the lower third, see diagram 2-7.

Diagram 2-7: Comparison of costs of primary energy avoidance In order to illustrate the enormous saving of ecologically harmful CO2, some examples are given below. The CO2 avoidance of 5,000 (6,300) t per year by the district cooling system corresponds to a CO2 emission of about 630 (780) households per year. The CO2 saving of the district cooling system corresponds to a mileage of passenger cars of about 31 million (38 million) km per year for spark ignition engines. To put it another way, assuming an annual mileage of 20,000 km per passenger car, this corresponds to a saving of fuel of 1,500 (1,900) driving passenger cars per year.

1 This value refers to the year of 2003 and is from the "Report on the Avoidance of Carbon Dioxide by the Use of Combined Heat and Power Generation" of Forschungsstelle für Energiewirtschaft e.V., Am Blütenanger 71, 80995 München. This value corresponds also to the GEMIS value for the year of 2003 2 From the expert opinion of Electrowatt-Ekono GmbH, Borsteler Chaussee 51, 22453 Hamburg, of 08 March 2006


3 EEX Leipzig, 21.04.2006, see www.eex.de



2.9 Problems, Difficulties and Solutions Line Installation For the 4.6 km long pipeline, there occurred unexpected disturbances in the construction proc-ess. They were caused, among other things, by sheeting units from the underground construc-tion that had not been completely removed after completing the underground line and that were not known due to a lack of documentation. Therefore, the line route had to be changed in part. Delays were made up for by additional gangs. Culvert 2, Tapping Volume See also section 3.4.3, last paragraph but one. Unlike the other culverts or tapping systems, culvert 2 had a delivery volume that was reduced by 17 l/s. The planning provided for an tapping volume of 32 l/s. That value had been confirmed by an impeller measurement performed in advance. After the commissioning of the system as per 01 April 2004, a strong groundwater lowering occurred at culvert 2. The pump of culvert 2 was taken out of the system matrix. Manual pumping tests followed. It turned out that the planned tapping volume of 32 l/s was only possible with a lowering of the groundwater level by more than 1.5 m. Of course, that was not acceptable, which is why a maximum tapping volume of 15.0 l/s was determined by iteration and programmed into the matrix. At that value, the groundwater level lowering reaches the same value as in the other tapping systems. The reason why reduced tapping volumes have resulted there cannot be explained to this day. According to our state of knowledge, a building site located in the area of influence and the re-lated site dewatering and groundwater level lowering can be excluded as the cause. It is a fact that the other culvert systems show the operating behaviour predicted by the hydrogeological calculations. Damage Caused by Corrosion on Part of the Customer (BMW AG) A short time after the official commissioning as per 01 May 2004, there occurred corrosion-related damage in the heat exchangers and in individual welded joints in the piping even though the material used was stainless steel. In detail, there occurred holes in the plates of the heat exchangers as well as leakage of pipes in the area of the weld seams. Such leakage occurred both in the supply of the primary side of the heat exchangers and in the area of the service-water supply. With the consent of the contractors for the construction of technical building equipment, BMW AG instructed a joint expert, the Federal Institute for Materials Research and Testing (BAM) in Berlin, Dr. rer. nat. J.W. Erning, to clarify the cause. The laboratory of the Federal Institute for Materials Research and Testing performed optical, chemical and metallographic examinations. The corrosion damage detected in the examined parts of the installation has various reasons.



The corrosion on the plate heat exchangers is attributable to crevice corrosion. That type of cor-rosion is caused by the formation of concentration gradients at constructional crevices, such as sealing and by a stagnation of flow over an extended period. The problem was remedied in the district cooling system by means of a minimum supply volume leading to a uniform flow rate in the plate heat exchangers. Damaged plates were replaced. The corrosion in the feeding lines of the plate heat exchangers and in the service-water distribu-tion lines was due to defective spots in the area of weld seams. Non-corroding steel loses its rustproof property when oxide layers (tempering colours) are caused on its surface by heat. The damage in part was repaired or defective connections were replaced.



3 Prospects 3.1 Follow-up Projects Along the Munich underground lines alone, about 158 culverts have been installed. Further cul-verts can be found at tunnels, sewage systems and other buildings deeply penetrating the groundwater. The cost situation and the large number of existing culverts may give new a fresh impetus to the subject of groundwater cooling and that way make a contribution to the reduction of CO2 emission. Experience from this project may show a perspective for future projects of this kind in Munich or elsewhere in the world. Based on the initial completely positive experience, further projects of that kind have been con-sidered by Stadtwerke München and one project will be realized starting in 2006. Further District Cooling Project BMW AG (still open) A further district cooling project with BMW AG has already been discussed. A first concept is already available. The project has been suspended because exact cooling requirements have not been defined yet and economic efficiency is not given at this time. The next step will be the solicitation of additional consumers in order to improve the economic efficiency. Prospects of success for the realization of that project are hard to foresee at this time. District Cooling Network (still open) Stadtwerke München has examined a district cooling network. Analogously to the BMW FIZ pro-ject, several culverts shall be combined, while in contrast to the BMW AG project, the output shall be delivered to several consumers. The planning provides for a cold output of 5 to 7 MW and investments of about € 5 million. The project has been suspended currently since the required number of prospective customers or the required volume of cold output is missing. As soon as a demand for district cooling arises, the project will be further pursued. Cooling Network (being realized) In the course of planning of the air conditioning of the building of the new Central Office of the Municipal Works (Stadtwerkszentrale - SWZ) as well as the air-conditioning and service cooling for the planned Munich Technology Center (MTZ) and further trade/office building complexes (M-Campus), considerable heat requirements resulted on the area of the former gasworks in Munich Moosach. It is the objective to meet the largest possible part of the need for cooling not by "technical cold", but rather by means of renewable energy, which is in particular possible by using groundwater. In the following, it is explained how groundwater that needs to be cleaned from an existing contamination in order to secure the groundwater flow-off shall be used for the cold generation. On the area of the former gasworks in Munich Moosach, town gas was extracted from hard coal from 1907 to 1967. During the entire operating period of the gasworks, about 15 million tons of hard coal were processed. As a by-product, about 500,000 tons of tar and tar oil were produced in that connection. Not inconsiderable parts thereof percolated - also caused by effects of the war - into the soil and caused considerable contaminations of the soil and the groundwater (see also [K, L]). The southern part was developed ready for building in the nineties and meanwhile the central office of Stadtwerke München has been built on it. In view of the planned utilization of the north-ern area (start of construction of the Munich Technology Center in the middle of 2006), that part of the former area of the gasworks now is being rehabilitated and prepared for reuse, too.


At the same time, the pump-and-treat plant (delivery of contaminated groundwater by pumping through a well system and purification by a conventional groundwater purification plant) that had been in operation on the area for containing the groundwater flow-off since 1992 was to be re-placed by a funnel-and-gate system that is more cost-effective in the long term. With that sys-tem, the contaminated groundwater is led, through a so-called "funnel" composed of guide walls blocking the aquifer (built as retention or sheet-pile walls, etc.), to a purification unit installed un-derground, the so called "gate". The groundwater flows through the gate by the natural potential difference and is purified. The figure below shows the basic principle. By a combination of reten-tion walls and passage buildings, purification and cost efficiency can be optimized.

Kontaminations-fahne

Kontaminations-herd

Trichter(funnel)

gereinigtesGrundwasser

Reaktoren(gates)

Grundwasser-fließrichtung

Funnel-and-Gate-System

Fig. 3-1: Funnel-and-Gate System During the period from December 2003 to the summer of 2005, the largest funnel-and-gate sys-tem worldwide for the rehabilitation of the former gasworks of Munich Moosach was completed and put into service. The accruing volume of purified groundwater (90 I/s or 324 m³/h) can be used for generating 1.9 MW of cooling capacity. In a cooling network, the cold will be used for cooling both the already existing central office of the municipal works and the planned Munich Technology Center (MTZ). The planning of the rehabilitation system was based on comprehensive knowledge of the groundwater situation in the area of the contamination to be contained. By means of conven-tional methods of geoscience, however, only the actual situation can be described - a prediction on changes in the groundwater regime caused by the construction of the funnel-and-gate system is not possible. For that purpose, a numeric groundwater model was developed on the basis of a finite element method [M,N]. Apart from the general analysis of the practicability of a funnel-and-gate system at the site, there was first examined the interaction between the two upper aquifers with the help of that model. Then, positioning and dimensioning of the gates were optimized and the effects on the flow conditions during the building phase as well as alternatives for handling incidents were examined. The groundwater model is moreover available for further examina-tions. Within the framework of the planning for the follow-up use of the northern part of the area, there were for example simulated the interactions between the rehabilitation system and the planned building structures and respective requirements were defined for the planning engineers on that basis. Another essential component of the model was the inclusion of the groundwater utilization for the planned cooling network up to the percolation of the warmed-up groundwater through trenches.



The technical planning of construction and equipment of the funnel-and-gate system was made on the basis of the hydraulic modelling. By means of a funnel-shaped retention wall extending up to the tight layer of the second aquifer in a depth of about 25 m and having a length of about 1.2 km, the contaminated groundwater flow is collected and led to four underground flow-through buildings. The picture below gives an overall view of the funnel-and-gate system.

Fig. 3-2: Overall view of the funnel-and-gate system

The diagonal view shows a view of the area of the former gasworks from the north, indicating the position of funnel (blue) and gates (red) as well as the flow direction of the groundwater (arrow); in the background, the new central office of the municipal works and, in the foreground, the northern part that is under rehabilitation. Fig. 3-3 shows a longitudinal section of a gate. These are shaft buildings with a length of up to 35 m, a width of about 7 m and a depth of about 14 m. The bearing structure of the gates is formed by braced steel sheet pilings, the base plate is made of reinforced concrete. The ceiling is made of removable concrete elements. In its current final condition, the entire system is cov-ered by about 2 m of soil and is located under a public green space. The gates can be accessed through shafts any time.



Fig. 3-3: Longitudinal section of a gate As can be seen in the cross section of a gate, the groundwater is collected by 16 m long hori-zontal filter wells drilled from the gates, is led through activated-charcoal canisters and purified and, under normal operation, then is released to the aquifer through horizontal filter wells. Alto-gether, 14 horizontal filter wells, 26 filter cases of glass-fibre reinforced plastics and about 350 m³ of activated charcoal were installed.


Fig. 3-4: Cross section of a gate



The piping system having a length of several kilometres is made of high-density polyethylene, all fittings are made of stainless steel. The system is completed by extensive measuring equipment that is connected to a control room and is subject to remote monitoring. The design life of the individual components is between 50 and 80 years. The special civil engineering work was completed in the summer of 2004 and the installation of plant and equipment in the summer of 2005. The commissioning was made step by step, start-ing in the summer of 2005. In April 2006, the system will pass into normal operation so that puri-fied water will be available for the cooling network then. Up to the end of 2005, the primary circulation system was completed. In the spring of 2006, heat exchangers and secondary cooling lines were installed so that the cooling network in the area of the former gasworks will be ready for operation at the end of 2006. Theoretically, i.e. assuming an average groundwater tapping of 90 l/s and a warming-up of the groundwater by 5 K, cooling capacities of about 1.9 MW can be realized. That corresponds to an avoidance of CO2 of 2,400 tons per year with 8,000 full-load hours.



3.2 Applicability to Other Projects The district cooling system presented here is not only applicable to other projects for under-ground-line culvert buildings, but also for all available buildings that retain water, such as for ex-ample the "pump-and-treat system" or the "funnel-and-gate system" for the rehabilitation of pieces of land as described in detail in section 3.1 Cooling Network above. Especially in case of area recycling or revitalization of pieces of land, it is possible, apart from obtaining ground ready for building, to achieve a further increase in value by integrating a district cooling system. For town-planning considerations and for avoiding a use of new areas "in the open countryside", the revitalization of urban industrial fallow land is given high political priority. However, industrial fallow land, first of all due to the use of substances harmful to water or the effects of war, often has become a so-called "Altlast" (abandoned contaminated site). According to current statistics of the Federal Environment Agency, about 230,000 areas suspicious of being contaminated sites exist in Germany. Only a small part of them has been examined or rehabilitated up to now. The major part of contaminated sites results from pollutions of or hazards to the groundwater. Since the Federal Soil Protection Act entered into effect in 1999, decontamination and contain-ment have been established as equivalent methods in the rehabilitation of contaminated sites. In particular groundwater damage is being rehabilitated to a large extent by means of hydraulic measures (pump-and-treat or reactive walls) throughout Germany. Thus, there results a large potential of collected groundwater purified after the treatment that can be used for thermal appli-cations. As the "funnel-and-gate system" project on the area of the former gasworks of Munich Moosach has shown, the purified groundwater can be used for cooling purposes without further additional expenditure. Basically, this can also be applied to other locations with groundwater rehabilitation. Hydraulic modelling as a planning instrument, however, is much more important at abandoned contami-nated sites than in case of a use of groundwater at an uncontaminated location, because the tapping, percolation and the temperature change of the groundwater must not cause a mobiliza-tion of harmful substances. Subject to knowledge and observance of hydrogeology, kinetics as well as hydrodynamics and thermodynamics, the combination of hydraulic containment and thermal utilization of the ground-water offers a highly efficient possibility for combining the containment of contaminated sites and the generation of cooling capacity.



4 Summary 4.1 Summary Together with BMW AG, Stadtwerke München (SWM) has developed and realized a concept for a resource-conserving, environmentally compatible and economical cooling supply. The Munich-based "District Cooling" pilot project distinguishes itself by high saving of energy and avoidance of pollutants. Due to the underground-line culvert buildings that act like existing wells, it was possible to save considerable investment costs and reduce the time of construction by 6 months. It was only nec-essary to build the groundwater supply system, including piping network and related well build-ings for the measuring and control equipment. The time of construction was 7 months. Apart from the large need for cooling for the computer premises of the Research and Innovation Center of BMW AG in Munich, the especially favourable geological conditions offered important preconditions for the "District Cooling" project. The realization of the project was facilitated by an uncomplicated grant of the permission under water law and by the possibility to make use of an interest subsidy from the promotion programme of the Federal Ministry for the Environment, Na-ture Conservation and Nuclear Safety for the Promotion of Investments of a Demonstration Character for the Reduction of Environmental Impacts - National Pilot Projects. The Bavarian State Ministry for Economy, Infrastructure, Transport and Technology contributed with an in-vestment grant. That allowed to achieve economic efficiency more quickly, to realize the project and gather experience for future projects. The geological situation was characterized by favourable conditions for a thermal groundwater use in the area of the underground line examined. The gravel aquifer close to the surface is rich and carries water with only a low thermal preload and favourable chemical parameters. For checking the capacity of the culvert systems, pumping tests were performed. The maximum groundwater volumes tappable and percolable under different hydrological outline conditions were determined with the help of a numerical groundwater model. The examinations showed that the groundwater volumes tappable and percolable under pump operation are clearly higher than the flow volumes under normal culvert operation. There was no risk of hydraulic short-circuits between intake and percolation wells. The tapping volumes, however, were limited by the technical design of the culverts. Therefore, a maximum use of the entire groundwater available was not possible. Now, a volume of up to 238 l/s is tapped and returned in the 6 culvert systems and 2 supply wells. Apart from the already existing culvert systems with the existing groundwater offer, it was nec-essary to build watertight entrance openings to the culverts. Through these openings, the pumps and lines were installed in the culverts. Quite close to each culvert, it was necessary to build a man-accessible shaft for housing the measuring and control equipment as well as the connec-tion to the flow and return of the district cooling line. With regard to the civil engineering work, the construction of the 4.6 km long district cooling line was similar to that of district heating systems. The requirements on the material of the district cooling lines (PE-HD) are lower that the requirements on district heating lines since there do not occur such high thermal loads.



The operation of the district cooling system is fully automatic; it adapts to the cooling demand by means of its speed-controlled pumps. The speed-controlled pumps in addition save pump en-ergy. SWM monitors the operation 24 hours a day, 365 days a year. Since the summer of 2004, the district cooling system has worked without any trouble. For such a complex system, it is important to keep the current costs for the operation of the sys-tem low. The new technology reduces the maintenance costs enormously compared with classi-cal compression-type refrigerating machines. A groundwater temperature that is as low as possible, an efficient operation of the system and a secure sale of cooling capacity to BMW AG are the three mainstays of an economically efficient and ecological operation. The investment costs remain about 3 % below the estimated total project costs of about € 6.51 million. The use of cooling capacity has not yet been achieved to the full extent up to now. But nevertheless, economic efficiency will be achieved as planned. Innovative Merits: Cold is traditionally generated with the help of electric compression-type refrigerating machines. The electric current required (a precious energy) is mainly generated with the use of non-renewable energy sources with a high emission of greenhouse gases. It is the innovative merit of this project that a renewable energy source, namely groundwater, is used for the generation of cold. The primary energy 'groundwater cold' extracted from the natural environment can be used without any conversion as final energy. Exclusively for the transport of the groundwater, a low quantity of outside energy is required. This simple solution provides large relief effects in terms of climate and environmental policy. The technical solution applied con-sumes only 1/10 of the electric current required by compression-type refrigerating machines. The groundwater is tapped from an already existing system for avoiding a groundwater build-up at the underground tube and subsequently is percolated there. There are only consumed low quantities of finite resources (precious energy - electric current) avoiding that way large quantities of greenhouse gases, in particular carbon dioxide. The warm-ing-up of the groundwater is limited to an environmentally compatible degree and the groundwa-ter level at the underground tube is stabilized. The environmental effect achieved is considerable: In contrast to conventional generation of cold by means of compression-type refrigerating ma-chines, district cooling allows to save about 10 million kilowatt hours of electric energy per year. This corresponds to the annual electric energy consumption of about 3,000 households in Mu-nich. With an annual use of 90 % of the capacity, this district cooling system allows to avoid up to 6,300 tons of CO2. In comparison, this corresponds to the CO2 emission of about 780 house-holds for their energy consumption of electricity, gas and a car in the town of Munich. This project has shown that an enterprise like the Research and Innovation Center of BMW AG in Munich can be supplied with cooling by means of a simple, yet innovative solution. The technical solution of this project is already being subsequently used in a follow-up project for the generation of cold on the area of Stadtwerke München. Michael Arnold of Stadtwerke München says: When walking through nature with open eyes, we can - as already in the past - continue to get and copy ideas from nature and use the existing resources in an environmentally compatible and economically efficient manner. Aside from explaining the project, this Report shall also help to find "imitators". Stadtwerke München is ready to help with its know-how.



4.2 Recommendation A duplication of the district cooling system is possible; a standardization as a product for under-ground-line culvert systems is not to be expected. Provided the geological conditions are given, well buildings exist and the pipe-tracks are not too long, projects of this kind are very sensible under ecological and economic aspects. District cooling systems will mainly have a future in large towns since large office spaces or in-dustrial and trade units exist there that need much cooling capacity for the air conditioning of office rooms and computer centers. Applicability of the district cooling system presented here to other projects is not only possible for underground-line culvert buildings, but for all existing buildings that retain water, such as for ex-ample the "pump-and-treat system" or the "funnel-and-gate system" for the rehabilitation of pieces of land as described in detail in section 3.1 Cooling Network above. Especially in case of a revitalization of pieces of land, it is possible, apart from obtaining ground ready for building, to achieve a further increase in value by integrating a district cooling system. Due to the large number of groundwater rehabilitation projects in Germany, the potential for an tapping of cold from groundwater in the rehabilitation of contaminated sites does generally exist at other loca-tions, too. There should not be any limits to imagination with regard to the use of "district cooling from groundwater". Decisive factors involve the type of water tapping, the water volume, the transport distance and the groundwater temperature.



4.3 Contact Persons / Project Participants

Stadtwerke München GmbH: Stadtwerke München GmbH Project Responsibility

Emmy-Noether-Straße 2 80287 Munich E-mail: [email protected]://www.swm.de

Michael Arnold Network Strategy Tel.: 0 89 / 23 61-22 71 Fax: 0 89 / 23 61-28 15 E-mail: [email protected]

Sales Concept Project Management Klaus Stix Business Customers Tel.: 0 89 / 23 61-49 09 Fax: 0 89 / 23 61-70 49 09 E-mail: [email protected]

Ludwig Langer Special Projects and Contracting Tel.: 0 89 / 23 61-44 61 Fax: 0 89 / 23 61-70 44 61 E-mail: [email protected]

Thomas Kühlmann Project Design Supply systems Tel.: 0 89 / 23 61-32 32 Fax: 0 89 / 23 61-33 23 E-mail: [email protected]

Bayerische Motoren Werke Aktiengesellschaft: Production-Related Envi-

ronmental Protection Project Management BMW AG Mr. Hubert Lehnert 80788 Munich Tel.: 0 89 / 3 82-4 80 07 E-mail.: [email protected]

BMW AG Mr. Alfred Hubner 80788 Munich Tel.: 0 89 / 3 82-4 78 98 E-Mail.: [email protected]

Expert Opinions for BMW AG Federal Institute for Materials Re-search and Testing (BAM) Dr. rer.nat. J.W. Erning 12200 Berlin Tel.: 0 30 / 81 04-17 33

External Parties Involved in the Planning: (Extract) Hydrogeologial calculations /groundwater model: Graduate Geologist Dr. Georg Seidl, Grillparzerstr. 47 D-81675 Munich

Traffic routing concept: VTG GmbH Engineering Office Kopernikusstraße 4 85609 Aschheim

Thermal calculations: Stuttgart University Institute for Thermodynamics and Heat Engineering (ITW) Pfaffenwaldring 6 D-70550 Stuttgart (Vaihingen)

Building Contractors: (Extract) 1st pumping test at underground-line culverts (June 2002) PST Spezialtiefbau GmbH Platanenallee 55 D-64673 Zwingenberg

2nd pumping test at underground-line culverts (March 2003) ABS GmbH Radspielerstr. 6 D-81927 München

Realization of electric measuring and control systems Nelhiebel Elektroanlagen GmbH Industriestraße 10a 82110 Germering

Plant and pipeline construction Franz Kassecker GmbH Egerer Str. 6 D-95652 Waldsassen

Chapter 3.1 Follow-up Project: Support for Chapter 3.1 Cooling Network bfm Umwelt Beratung Forschung Management GmbH Dr. rer.nat. M. Koch Emmy-Noether-Str. 2E 80992 Munich Tel.: 0 89 / 54 80 34-0 E-mail.: [email protected]

mailto:[email protected]

http://www.swm.de/

mailto:[email protected]



5 Digital Video and Literature Reference Digital video about the project: BMW AG has issued a digital video film about the district cooling project. If you are interested, please contact: BMW AG, Mr. Alfred Hubner, 80788 Munich, Tel.: 0 89 / 3 82-4 78 98, E-mail.: [email protected].

List of References: Author Content published [A] BLASY (1974): Die Grundwasserverhältnisse in der Münchner Schot-

terebene westlich der Isar- Doctoral Thesis Munich University, 109 pages

yes

[B] FRIED & ZIPFEL (1994):

Grundwasserreservoir Münchner Schotterebene – Mo-delluntersuchungen als Grundlage einer ökologisch-hydrologisch fundierten Nutzungsplanung.- Hydraulik und Gewässerkunde Mitt. Nr. 57, Special Issue Ma-thematische Grundwassermodelle in Bayern, p. C1-C14

yes

[C] PAUS & KOS-LOWSKY (2001)

Erstellung eines Grundwassermodells für das Gelände des Forschungs- und Ingenieurzentrums der BMW AG - Examination Report Gerling Consulting Gruppe, 09.05.2001

Nein

[D] SALAMEH (1974):

Hydrogeologie und Hydrochemie des nordwestlichen Bereiches der Münchner Schotterebene....- Doctoral Thesis Munich University, 168 pages.

yes

[E] McDONALD,M.& HAR-BAUGH,A.(1988):

A modular three-dimensional finite-difference ground-water flow model- U.S.Geological Survey, Open File Report 83-875, Chapter A1, Washington DC yes

[F] POL-LOCK,D.W.(1989):

Documentation of computer programs to compute and display pathlines using results from the U.S. Geological Survey modular threedimensional finite-difference ground-water flow model- U.S. Geological Survey, Open File Report 89-381, Denver

yes

[G] Seidl, G. (2002): Grundwasser aus U-Bahn-Dükern. Hydrogeologische Untersuchungen. Examination Report of 03/08/2002 for Stadtwerke München GmbH

no

[H] Seidl, G. (2002): Grundwasser aus U-Bahn-Dükern. Erschließung zu-sätzlicher Grundwasserreserven. Examination Report of 29/11/2002 for Stadtwerke München GmbH

no

[I] Seidl, G. (2003): Grundwasser aus U-Bahn-Dükern. Ergänzende Grundwassermodellrechnungen NW/NNW. Examinati-on Report of 09/04/2003 for Stadtwerke München GmbH

no

[K] Weindl, J., Dr. Koch, M., Nief-necker, F. (2004)

Grundwassersanierung im natürlichen Fluss, DVGW energie wasser-praxis, Ausgabe 10, wvgw Wirtschafts- und Verlagsgesellschaft Gas und Wasser mbH, Octo-ber 2004

yes



[L] Weindl, J., Dr.

Koch, M. , Tid-den, F. (2005)

Funnel-and-Gate-Technik zur Sanierung eines Gas-werkstandortes, Wasser, Luft und Boden, Zeitschrift für Umwelttechnik TerraTech, Supplement für Altlasten und Bodenschutz, Vereinigte Fachverlage GmbH, 7/8/2005

yes

[M] BFM GmbH (2003)

Funnel-and-Gate-System ehemaliges Gaswerk Mün-chen – Numerische Modellierung – Final Report of 04/06/2003 2004 for Stadtwerke München GmbH

no

[N] BFM GmbH (2004)

Grundwasserkältenutzung Stadtwerkszentrale Mün-chen – Numerische Modellierung der Grundwasser-entnahme und -versickerung – Result Report of 16/06/2004 2004 for München GmbH

no



6 List of Abbreviations Explanation of abbreviations, measures and symbols: Abbreviation Meaning BayWiMe Bayerisches Staatsministerium für Wirtschaft, Infrastruktur, Verkehr und

Technologie - Bavarian State Ministry for Economy, Infrastructure, Transport and Technology

BMU Bundesministerium für Umwelt, Naturschutz und Reaktorsicherheit - Federal Ministry for the Environment, Nature Conservation and Nuclear Safety

BMW AG Bayerische Motorenwerke Aktiengesellschaft da Outside diameter of pipes DtA Deutsche Ausgleichsbank Culvert Groundwater passage lines, see Fig. 2-5

FIZ Forschungs- und Innovationszentrum (Rechenzentrum) - Research and Inno-vation Center (Computer Center) of BMW AG

GW Groundwater KMR Plastic sheathed pipe l/s litres per second MTZ Münchner Technologiezentrum - Munich Technology Center MVG Münchner Verkehrsgesellschaft mbH - Public Transports Company of Munich MW megawatt PE-HD Polyethylene high density RegOBB Regierung von Oberbayern - Government of Upper bavaria

RGU Referat für Gesundheit und Umwelt - Department of Health and Environment of Munich

SWM Stadtwerke München GmbH - Municipal Works of Munich t metric tons UBA Umweltbundesamt - Federal Environmental Office WWA Wasserwirtschaftsamt München - Water Resources Board of Munich

Documents

Use of District Cooling from Groundwater Passage Lines for ... · sche Lösung sichert eine hohe Energieeinsparung und vermindert den Ausstoß von Treibhausgasen in ... of the refrigerant