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District Heating/Cooling System Optimization - The PERTAN Group

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<strong>District</strong> <strong>Heating</strong>/<strong>Cooling</strong><br />

<strong>System</strong> <strong>Optimization</strong>:<br />

Principles and Examples<br />

from US Army Studies<br />

Szenarienvorschläge für die<br />

„sanfte Energiewende“ –<br />

„Strukturoptimierung in<br />

Flächengebieten“, SWM<br />

September 20, 2009<br />

Dr. Stephan Richter<br />

GEF Ingenieur AG<br />

Ferdinand-Porsche-Str. 4a<br />

69181 Leimen<br />

Germany<br />

www.gef-ingenieur-ag.de<br />

1


Agenda<br />

1. Overview and Technical Description of a Central Energy <strong>System</strong><br />

2. Operation Modes with Variable Temperature-Variable Flow <strong>System</strong>s<br />

3. Contributions and Outcomes from Energy Assessments<br />

I. Conceptual Ideas<br />

II. Searching for ECMs<br />

I. Examples from the Fort Bragg <strong>Heating</strong> and <strong>Cooling</strong> Master Plan Study<br />

II. Experiences from about 25 On-Site Assessments<br />

2


Overview on Central Energy <strong>System</strong>s<br />

• Purpose of Central Energy <strong>System</strong>s<br />

- Provide heating and/or cooling to a group of buildings generated in a<br />

Central Energy Plant (CEP)<br />

- Heat can be used for space heating, Domestic Hot Water (DHW)<br />

preparation and for technical purposes (e.g. pressing units,<br />

dehumidification, sterilization, technical shaping etc.)<br />

- <strong>Cooling</strong> can be used for air conditioning, dehumidification and heat removal<br />

from processes<br />

• Basic Principles<br />

- <strong>The</strong> CEP generates thermal energy at a certain temperature. <strong>The</strong> thermal<br />

energy is then transported in pipelines from the CEP to the location of use.<br />

Mostly the transport medium is water or steam. At the location of use a part<br />

of the energy content is taken from the water and the temperature is<br />

reduced (= heating) or raised (cooling). <strong>The</strong> water is then transported back<br />

to the CEP and used again.<br />

- <strong>The</strong> temperature of the transported water depends on the requirements of<br />

the users: Requirements are the temperatures itself and the energy<br />

capacity.<br />

3


Central Energy <strong>System</strong>s at a Glance<br />

Combined Heat and Power Generation for <strong>District</strong> <strong>Heating</strong><br />

Turbine and Generator<br />

Boiler<br />

Transformer<br />

Power Line<br />

Heat Users and Substations<br />

Central Heat<br />

Exchanger<br />

Return Pipe<br />

Supply Pipe<br />

4


Central Energy <strong>System</strong>s at a Glance<br />

Distribution Pumps<br />

Supply Pipe<br />

Bypass<br />

Building<br />

Substation<br />

Δp<br />

DHW<br />

Space<br />

<strong>Heating</strong><br />

Boiler<br />

Return Pipe<br />

Water Treatment<br />

5


Central Energy <strong>System</strong>s at a Glance<br />

Distribution Pumps<br />

Supply Pipe<br />

Bypass<br />

Building<br />

Substation<br />

Δp<br />

DHW<br />

Boiler<br />

Space<br />

<strong>Heating</strong><br />

Return Pipe<br />

Water Treatment<br />

6


Pressure Diagram<br />

Pressure Drop<br />

Pump<br />

CEP<br />

Heat Users<br />

Problem:<br />

horizontal distance between CEP and User<br />

As distance to heat users increases the result is a greater pressure drop. A increase of sea<br />

level high results into a greater pressure drop, too.<br />

Differential pressure at the critical building needs to be higher than 10 to 14 psi<br />

7


Agenda<br />

1. Overview and Technical Description of a Central Energy <strong>System</strong><br />

2. Operation Modes with Variable Temperature-Variable Flow <strong>System</strong>s<br />

3. Contributions and Outcomes from Energy Assessments<br />

I. Conceptual Ideas<br />

II. Searching for ECMs<br />

I. Examples from the Fort Bragg <strong>Heating</strong> and <strong>Cooling</strong> Master Plan Study<br />

II. Experiences from about 25 On-Site Assessments<br />

8


Heat Demand Depends on the Ambient Temperature<br />

105 MW<br />

20°F 40°F 60°F 80°F 100°F<br />

3.5x10 8 BTU<br />

90 MW<br />

correlation factor ~ 0.75 to 0.9<br />

3.0x10 8 BTU<br />

Total Sum of Heat Demand<br />

75 MW<br />

60 MW<br />

45 MW<br />

30 MW<br />

15 MW<br />

2.5x10 8 BTU<br />

2.0x10 8 BTU<br />

1.5x10 8 BTU<br />

1.0x10 8 BTU<br />

5.0x10 7 BTU<br />

0 MW<br />

0.0 BTU<br />

-15°C 0°C 15°C 30°C 45°C<br />

Outdoor Temperature<br />

9


Satisfying the Heat Demand by Adapting the Flow and the<br />

Supply Temperature<br />

Power<br />

P<br />

Central<br />

Energy<br />

<strong>System</strong><br />

= Flow × Heat Capacity<br />

= Q&<br />

= m&<br />

× c × ΔT<br />

p<br />

of<br />

Water<br />

× Temperaturedifference<br />

Variable Parameter:<br />

‣ Supply and Return Temperature<br />

‣ Water Flow (= Water Velocity)<br />

Approach<br />

Keep the flow dm / dt and the return temperature T R constant and vary the<br />

supply temperature T S<br />

10


Central <strong>Heating</strong> <strong>System</strong> Supply Temperature Curve<br />

150°C<br />

0°F 20°F 40°F 60°F 80°F 100°F 120°F<br />

300°F<br />

135°C<br />

280°F<br />

Supply Temperature<br />

120°C<br />

105°C<br />

90°C<br />

75°C<br />

260°F<br />

240°F<br />

220°F<br />

200°F<br />

180°F<br />

160°F<br />

60°C<br />

140°F<br />

-20°C -10°C 0°C 10°C 20°C 30°C 40°C 50°C<br />

Outdoor Temperature<br />

11


Why Shall the Supply Temperatures be as Low as Possible?<br />

Efficiency of Plant Type<br />

Geothermal<br />

@ 100°C = 215°F<br />

Efficiency<br />

1990 Design Hard Cole CHP @ 530°C = 990°F<br />

Waste Incineration Plant<br />

@ 390°C = 735°F<br />

Biomass Plant @ 450°C = 840°F<br />

=<br />

T Warm<br />

T<br />

T Cold<br />

Warm<br />

T<br />

Combined Cycle Plant<br />

@ 1100°C = 2010°F<br />

2035 Design Hard Cole CHP<br />

@ 700°C = 1290°F<br />

Energy can<br />

be used<br />

not be used<br />

30 120 210 300 390<br />

T cold in°C = Return Temp from Distribution <strong>System</strong><br />

−T<br />

Warm<br />

Cold<br />

‣ In an existing system a reduction of<br />

the return temperature (= a better<br />

use of provided temperature) can<br />

increase the distribution system’s<br />

capacity.<br />

‣ More users can be supplied by the<br />

same diameters and installation<br />

costs.<br />

‣ In case of new network constructions<br />

one can use smaller<br />

diameters and, thus, save costs.<br />

‣ Flow, pressure drop and electricity<br />

for pumps can be reduced.<br />

‣ <strong>The</strong> ratio of power to heat<br />

generation increases if less<br />

heat/steam is taken from the<br />

turbine (e.g. in Munich a additional<br />

power generation of 100 GWh el per<br />

year can be achieved).<br />

12


Agenda<br />

1. Overview and Technical Description of a Central Energy <strong>System</strong><br />

2. Operation Modes with Variable Temperature-Variable Flow <strong>System</strong>s<br />

3. Contributions and Outcomes from Energy Assessments<br />

I. Conceptual Ideas: Examples from the Fort Bragg <strong>Heating</strong> and <strong>Cooling</strong><br />

Master Plan Study<br />

II. Experiences from about 25 On-Site Assessments<br />

13


Current Conditions: Overview on the Central Plants and<br />

Distribution <strong>System</strong> – <strong>Heating</strong><br />

14


Overview <strong>Heating</strong> <strong>System</strong>s<br />

82 nd <strong>Heating</strong><br />

96x10 6 BTU/h<br />

icl. DUCT Burner:<br />

140x10 6 BTU/h<br />

C-Area<br />

Faith Barracks<br />

Peak load<br />

12x10 6 BTU/h<br />

COSCOM<br />

50x10 6 BTU/h<br />

C-Area<br />

Peak load<br />

40x10 6 BTU/h<br />

Steam and<br />

Hot Water<br />

M-Area<br />

Peak load<br />

5x10 6 BTU/h<br />

D-Area<br />

Zone 1<br />

Peak load<br />

4x10 6 BTU/h<br />

E-Area<br />

Zone 1<br />

Peak load<br />

4x10 6 BTU/h<br />

CMA<br />

109.5x10 6 BTU/h<br />

D-Area<br />

Zone 2+3<br />

Peak load<br />

8x10 6 BTU/h<br />

4x10 6 BTU/h<br />

H-Area<br />

Peak load<br />

12x10 6 BTU/h<br />

E-Area<br />

Zone 2<br />

Peak load<br />

5x10 6 BTU/h<br />

SOCOM<br />

40x10 6 BTU/h<br />

15


SOCOM (<strong>Heating</strong> Zone 1) – Log Data<br />

175°C<br />

SOCOM Hot Water Zone 1<br />

HW Zone 1 Supply<br />

HW Zone 1 Return<br />

120m³/h<br />

500gpm<br />

300°F<br />

150°C<br />

100m³/h<br />

250°F<br />

125°C<br />

80m³/h<br />

400gpm<br />

200°F<br />

100°C<br />

60m³/h<br />

300gpm<br />

150°F<br />

75°C<br />

50°C<br />

40m³/h<br />

200gpm<br />

100°F<br />

25°C<br />

20m³/h<br />

100gpm<br />

50°F<br />

0°C<br />

0m³/h<br />

0 2000 4000 6000 8000 10000 12000 14000<br />

0gpm<br />

Hours since October 05<br />

16


SOCOM (<strong>Heating</strong> Zone 1) – Model Parameter<br />

Total building heat load (from PNNL FEDS<br />

model):<br />

4.46×10 6 Btu/h = 1,306 kW<br />

Peak load taken from log data 4.10 ×10 6 Btu/h = 1,200 kW<br />

Load factor ( peak load / total load<br />

) 84%<br />

Peak temperatures T supply<br />

/T return<br />

340°F/250°F = 170°C/120°C<br />

Water mass flow calculated by flow model 84.5 gpm = 19.2 m³/h<br />

Δp @ CEP calculated by flow model 33.4 psi = 2.3 atm<br />

17


SOCOM (<strong>Heating</strong> Zone 1) – Results of Flow Model<br />

Line colors<br />

critical building<br />

Rectangle colors<br />

CEP<br />

18


Operating a Modern Variable Flow Hot Water <strong>System</strong> –<br />

Hydraulic Flow Analysis in Peak Load Case<br />

supply<br />

return<br />

Pump<br />

CEP<br />

19


Current Conditions: Overview on the Central Plants and<br />

Distribution <strong>System</strong> – <strong>Cooling</strong><br />

20


Overview <strong>Cooling</strong> <strong>System</strong>s<br />

82 nd <strong>Heating</strong><br />

1820 tons<br />

C-Area<br />

Faith Barracks<br />

Peak load<br />

800 tons<br />

COSCOM<br />

1344 tons<br />

C-Area<br />

Peak load<br />

2600 tons<br />

82 nd <strong>Cooling</strong><br />

4400 tons<br />

M-Area<br />

Peak load<br />

1000 tons<br />

D-Area<br />

Zone 1<br />

Peak load<br />

600 tons<br />

H-Platons<br />

H-Plant<br />

2000 tons<br />

2000 tons<br />

E-Area<br />

Zone 1<br />

Peak load<br />

1000 tons<br />

CMA<br />

D-Area<br />

Zone 2<br />

H-Area<br />

E-Area<br />

Zone 2<br />

SOCOM<br />

3413 tons<br />

Peak load<br />

480 tons<br />

Peak load<br />

1100 tons<br />

Peak load<br />

740 tons<br />

2100 tons<br />

21


H-Plant (<strong>Cooling</strong>) – Log Data<br />

100°F<br />

40°C<br />

H-Plant Chilled Water<br />

CW Supply<br />

CW Return<br />

1200m³/h<br />

5000gpm<br />

80°F<br />

30°C<br />

1000m³/h<br />

800m³/h<br />

4000gpm<br />

20°C<br />

600m³/h<br />

3000gpm<br />

60°F<br />

400m³/h<br />

2000gpm<br />

10°C<br />

40°F<br />

200m³/h<br />

1000gpm<br />

0°C<br />

0m³/h<br />

0 2000 4000 6000 8000 10000 12000 14000<br />

Hours since October Oktober 05<br />

0gpm<br />

22


H-Plant (<strong>Cooling</strong>) – Model Parameters<br />

Total building cooling load (from<br />

PNNL FEDS model):<br />

1581 tons = 5,554 kW<br />

Peak load taken from log data 1110 tons = 3,900 kW<br />

Load factor ( peak load / total load<br />

) 70%<br />

Peak temperatures T supply<br />

/T return<br />

43°F/52°F = 6°C/11°C<br />

Water mass flow calculated by<br />

flow model<br />

Δp @ CEP calculated by flow<br />

model<br />

2947 gpm = 669.4 m³/h<br />

124.7 psi = 8.6 atm<br />

23


H-Plant (<strong>Cooling</strong>) – Results of Flow Model<br />

CEP<br />

critical building<br />

Line colors<br />

Rectangle colors<br />

24


Interconnection of the Central Plant and Distribution<br />

<strong>System</strong> – <strong>Cooling</strong><br />

25


Connected <strong>Cooling</strong> Net in the Central <strong>Cooling</strong><br />

<strong>System</strong><br />

critical buildings<br />

CEP<br />

CEP<br />

CEP<br />

CEP<br />

critical buildings<br />

26


New <strong>Cooling</strong> Pipes Required to add Bldg. to the Central <strong>Cooling</strong><br />

<strong>System</strong> and Locations where larger Pipe Diameters are Needed<br />

‣ To interconnect the heating<br />

systems, the green pipes are<br />

additionally required<br />

‣ <strong>The</strong> pipes in blue must have<br />

larger diameters to interconnect<br />

the systems<br />

‣ Pipes that need to have larger<br />

sizes are required due to the<br />

growth of the system in red<br />

27


New <strong>Cooling</strong> Pipes Required to add Bldg. to the Central <strong>Cooling</strong><br />

<strong>System</strong> and Locations where larger Pipe Diameters are Needed<br />

28


Heat Generation incl. Heat for Absorption Chillers<br />

<strong>Heating</strong> Load<br />

60 MW<br />

50 MW<br />

40 MW<br />

30 MW<br />

20 MW<br />

10 MW<br />

0 MW<br />

Boiler:<br />

peak: 118.2x10 6 BTU/Hr<br />

annual: 1.5x10 9 BTU p.a.<br />

Duct-Bruner:<br />

peak: 44x10 6 BTU/Hr<br />

annual: 15.3x10 9 BTU p.a.<br />

Gas Turbine<br />

Heat from 82nd <strong>Heating</strong> GT for 82nd <strong>Heating</strong> Absorption Chiller<br />

Heat from CMA New GT<br />

Heat from New CMA GT for NEW CMA 1-Stage-Absorption Chiller<br />

Duct Burner<br />

Boiler<br />

Demand<br />

New CMA Gas Turbine:<br />

peak: 34x10 6 BTU/Hr<br />

annual: 79.9x10 9 BTU p.a.<br />

Gas Turbine:<br />

peak: 36x10 6 BTU/Hr<br />

annual: 263.9x10 9 BTU p.a.<br />

Potential of additional heat for<br />

absorption chiller for 365 days per<br />

year chilled water supply<br />

New CMA Gas Turbine:<br />

peak: 34x10 6 BTU/Hr<br />

annual: 154.7x10 9 BTU p.a.<br />

82nd <strong>Heating</strong> Gas Turbine:<br />

peak: 10x10 6 BTU/Hr<br />

annual: 32.0x10 9 BTU p.a.<br />

1000 2000 3000 4000 5000 6000 7000 8000<br />

200x10 6 BTU/Hr<br />

180x10 6 BTU/Hr<br />

160x10 6 BTU/Hr<br />

140x10 6 BTU/Hr<br />

120x10 6 BTU/Hr<br />

100x10 6 BTU/Hr<br />

80x10 6 BTU/Hr<br />

60x10 6 BTU/Hr<br />

40x10 6 BTU/Hr<br />

20x10 6 BTU/Hr<br />

0x10 6 BTU/Hr<br />

Hours<br />

29


Suggestion: Using Pre-Insulated Bonded Pipe<br />

Components of pre-insulated bounded pipe<br />

system:<br />

Water carrying pipe made from steel.<br />

Bonding insulation made from PUR foam having<br />

a leak detection system.<br />

Jacket pipe made from polyethylene (PE).<br />

It is recommended to engage a quality control<br />

and management system during the<br />

installation of the pipes to ensure the proper<br />

installation. Sensible issues are the bevel<br />

seams, the bushings and the adding of<br />

insulating foam at field welded connections, the<br />

sand bed, the proper connection of the leak 30<br />

detection system and the expansion cushions.


Comparison between Reality and Drawings<br />

31


Schematic of Pre-Insulated Bonded Pipes<br />

Buried Valve<br />

Anchor<br />

T-Junktion<br />

Elbow<br />

Expansion<br />

Cushion<br />

Bushing<br />

32<br />

32


Cost Savings by Using European Type Standard Pre-<br />

Insulated Bonded Pipes Compared to Steel-Jacket Pipes<br />

75.0 Mil. EURO<br />

Total 5-Years Costs for replacing Steel-Jacket Steam Pipes by Kind<br />

Total 5-Years Costs for replacing Steel-Jacket Steam Pipes by Pre-Ins. Bounded Pipes<br />

Total 5-Years Savings<br />

62.5 Mil. EURO<br />

50.0 Mil. EURO<br />

37.5 Mil. EURO<br />

25.0 Mil. EURO<br />

12.5 Mil. EURO<br />

0.0 Mil. EURO<br />

-12.5 Mil. EURO<br />

-25.0 Mil. EURO<br />

2005 2010 2015 2020 2025 2030 2035<br />

5-Years Phase<br />

33


Agenda<br />

1. Overview and Technical Description of a Central Energy <strong>System</strong><br />

2. Operation Modes with Variable Temperature-Variable Flow <strong>System</strong>s<br />

3. Contributions and Outcomes from Energy Assessments<br />

I. Conceptual Ideas: Examples from the Fort Bragg <strong>Heating</strong> and <strong>Cooling</strong><br />

Master Plan Study<br />

II. Experiences from about 25 On-Site Assessments<br />

34


Central Energy <strong>System</strong>s at a Glance<br />

Combined Heat and Power Generation for <strong>District</strong> <strong>Heating</strong><br />

Turbine and Generator<br />

Boiler<br />

Transformer<br />

Power Line<br />

Heat Users and Substations<br />

Central Heat<br />

Exchanger<br />

Return Pipe<br />

Supply Pipe<br />

35


Potentials for ECMs in Distribution Piping <strong>System</strong><br />

1. Central Plant<br />

2. Piping and related Construction<br />

3. Man Holes<br />

4. Operation Modes<br />

36


1. Central Plants<br />

• Oversized or undersized pumps<br />

• Wrong/missing controls for VF-pumps<br />

• High return temperatures from field (e.g. cavitation of pumps)<br />

• Poor water treatment<br />

• Missing deaerator<br />

• Wrong sized expansion tank<br />

• Poor piping insulation<br />

• Leakages on fittings, valves, pipes, …<br />

• Oversized or undersized boilers<br />

• All problems with boilers/chillers (Presentation Al Woody/Scot Duncan)<br />

37


2. Piping <strong>System</strong><br />

• Oversized or undersized pumps (pressure drops)<br />

• Poor insulation<br />

• Improper junctions (welding, bushings, …)<br />

• Wrong connection of leak detection system wires or missing leak detection<br />

system<br />

• Missing corrosion protection if steel pipes<br />

• Missing/undersized stress/expansion compensation<br />

• Temperature too high regarding the demand (e.g. steam for space heating and<br />

DHW)<br />

• Too high differential pressure at critical bldg.<br />

• Leakages<br />

• Missing/unadjusted expansion compensation and anchors<br />

• If concrete ducts: missing down-grade in ducts<br />

• If steam: condensate losses and problems with steam traps (steam flashes)<br />

• Missing venting at high points<br />

38


3. Man Holes (if needed or existing)<br />

• Flooded man holes by groundwater, rain, …)<br />

• Uninsulated valves, fittings, …<br />

• Leaky or missing covers<br />

• Missing pump/drainage in man holes<br />

• Oversized man holes<br />

39


4. Operation Modes<br />

• Too high supply water temperatures regarding usage and demand<br />

• Constant supply temperatures<br />

• Constant flow<br />

• Steam distribution for space heating and DHW<br />

• Unadjusted codensate pumps in Bldg.<br />

• Too high return temperatures while flow is constant<br />

• …<br />

40


Variable Speed Pumps do not Work Proper<br />

Solution<br />

<strong>The</strong> variable speed pumps, frequency drivers, isolation valves and valve actuators must be<br />

replaced with new variable flow equipment. This enables the adaptation of the mass flow in<br />

the central system to meet the cooling load of the building served by central chilled water.<br />

41


Flooded Trenches and Man Holes<br />

Savings<br />

Normally pipes found in flooded pits require replacement<br />

after 15 years rather than after 30 years at a total cost<br />

estimated to be $ 360,000. This investment can be<br />

postponed by 15 years. Averaging this cost over 15 years<br />

results in an annual saving of about $ 24,000.<br />

Payback<br />

<strong>The</strong> resulting payback period is 0.125 years or one<br />

month.<br />

42


Stop Leaks – Fix Broken Release Valve<br />

Savings<br />

A 465 gal/hr leak equals about 4,000<br />

kgal/yr while the costs for 1 kgal of city<br />

water are $ 4. Thus, the annual<br />

savings are about $ 16,000.<br />

Investment<br />

<strong>The</strong> cost for a 1” valve including a full<br />

day of labor is about $ 500.<br />

Payback<br />

<strong>The</strong> resulting payback period is 0.03<br />

years or 11 days.<br />

43


Problems with Pipe Installation Requires Quality<br />

Management and Control of this type of Construction<br />

44


2 <strong>System</strong>s within a few Feet Distence<br />

#3700<br />

2 Boilers<br />

4,580 MMBH<br />

total<br />

HW 180°F<br />

60…70 psi<br />

seasonal<br />

4 Bldg.<br />

peak: 1,371 MMBH<br />

annual: 1,921 mmBTU<br />

#3700<br />

4 Bldg.<br />

1 Chiller<br />

240 tons total<br />

peak: 94 tons<br />

annual: 1,128 mmBTU<br />

#3709<br />

2 Boilers<br />

4,580 MMBH<br />

total<br />

HW 180°F<br />

60…70 psi<br />

seasonal<br />

4 Bldg.<br />

peak: 1,371 MMBH<br />

annual: 1,921 mmBTU<br />

#3709<br />

4 Bldg.<br />

2 Chillers<br />

250 tons total<br />

peak: 94 tons<br />

annual: 1,128 mmBTU<br />

45


Poor Piping Insulation in CEP<br />

46


Uninsulated Fittings<br />

47


Brocken Insulation in Overgound Piping<br />

48


Fibre Glas Condensate Pipe after Steam<br />

Flusehes<br />

49


Man Holes Without Cover and Pumps<br />

50


Man Holes Without Cover and Pumps<br />

51


Leakages in Pipes without Leakges Control<br />

and Detection <strong>System</strong><br />

52


Unsealed Foam Opening<br />

53


Poorly Installed Bushing<br />

54


Highly Corroted Equipment<br />

55


Steam Leakages<br />

56


Uninsulated Flange<br />

57


Flooded Man Hole<br />

58


Leaky Valve in Man Hole<br />

59


Swimming Pool in Man Hole<br />

60


Who is GEF Ingenieur AG ?<br />

GEF is a engineering and energy economic<br />

consulting and design company for energy<br />

supply, focused on district heating. We are<br />

developing economic solutions in the field of<br />

energy supply, media transport and environment<br />

related technologies for our customers since<br />

almost 25 years.<br />

GEF Office in Leimen, Germany<br />

www.gef-ingenieur-ag.de<br />

GEF Office in Chemnitz, Germany<br />

Our neighborship in Leimen<br />

62

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