Monitoring results and operational experiences for a ... · Monitoring results and operational experiences for a central solar district heating system with Borehole Thermal Energy

University of StuttgartInstitute for Thermodynamics and Thermal EngineeringSolar Assisted District HeatingJanet Nussbicker

Solarthermie2000plus

Monitoring results and operational experiences for a central solar districtheating system with Borehole Thermal Energy Store in Neckarsulm (Germany)

J. Nussbicker



Monitoring results and operational experiences for a central solar district heating system with Borehole Thermal Energy Store in Neckarsulm (Germany)

Outline

Introduction

Borehole Thermal Energy Store (BTES)

District heating system

Simulation results

Summary




Heating plant

1. Phase of construction2. Phase of constructionComplete construction area

BTES

Solar collectors

Introduction




-Introduction-

Heating plantwith auxiliary burner

Solar collectors5263 m²

Borehole thermal energy store63360 m3

Two buffer tanks each 100 m3

Heat distribution net

300 accomodation units & public buildings



Borehole Thermal Energy Store




M17

1. extension

2. extension

experimental store

M18

M14

M01

M02 M03

M16


-BTES-

M17

1. extension

2. extension

experimental store

M18

M14

M01

M02 M03

M161997: experimental store 1998: 1st extension2001: 2nd extension




-BTES-

Borehole wall

Grouting material( entonite-

sand-cement)Suspension of b

25 mm

115 / 150 mmPolybutene-Double-U-pipe25 x 2.3 mm

Insulation(200 mm)

Top of ground

Cov

erin

g la

yer

(app

r. 2

- 3 m

)Th

erm

al a

ctiv

e de

pth

(30

m)

Borehole-grouting

Borehole

Double-U-Pipe

Connection pipe insand layer

Scheme of a borehole heat exchanger



0.030

0.035

0.040

0.045

0.050

0.055

0.060

0.065

0.070

0 5 10 15 20 25 30 35 40 45 50 55

temperature ϑ [°C]

ther

mal

con

duct

ivity

[W/m

⋅K]

Styrodur moist with foil

Styrodur dry with foil


-BTES-

Insulation of the BTES

Measurements by M. Benner, ITW

soil (2-3 m)sealing (foil)drainagefoil, diffusibleinsulation (0.2 m)drainage

sealing layersand

soil

boreholeu-pipe

liner, non-vapor retarder

liner

liner




-BTES-

-150

-100

-50

0

50

100

150

200

250

300

350

Jan99

Jul99

Jan00

Jul00

Jan01

Jul01

Jan02

Jul02

Jan03

Jul03

Jan04

Jul04

Jan05

Jul05

heat

in M

Wh

per m

onth

-30

-20

-10

0

10

20

30

40

50

60

70Jan 99 Jul 99 Jan 00 Jul 00 Jan 01 Jul 01 Jan 02 Jul 02 Jan 03 Jul 03 Jan 04 Jul 04 Jan 05 Jul 05

tem

pera

ture

in °C

temperature first extension in 10 m depthtemperature second extension in 10 m depth

construction work for 2nd extension

charging

discharging

Charging & discharging heat amouts and temperatures in the BTES




District heating system




-District heating system-

Heating plant

1. Phase of construction2. Phase of constructionComplete construction area

BTES

Solar collectors





0

10

20

30

40

50

60

70

80

90

Jan-02

Apr-02

Jul-02

Oct-02

Jan-03

Apr-03

Jul-03

Oct-03

Jan-04

Apr-04

Jul-04

Oct-04

Jan-05

Apr-05

Jul-05

Oct-05

tem

pera

ture

in °C

0

10

20

30

40

50

60

70

80

90

volu

me

flow

in m

³/h

net supply temperaturenet return temperaturenet volume flow

supply of adjacent district heating net

connection and supplyof new buildings

supply of adjacent district heating net

connection and supplyof new buildings

Temperatures and volume flows in the heat distribution net





Q Gasboiler 3311 MWh/a

Q Heat losses 1032,5 MWh/a

(heat distribution net, calc.)

Q Buildings 3534,5 MWh/a

Q Heat losses 258 MWh/a

(solar net, calc.)

QSolar,direct 934,5 MWh/a

Q Store,discharge 321,5 MWh/a

QStorage 155,5 MWh/a

Heat balance for the district heating system (2005)




Simulations




-Simulations-

Superposition Borehole Model (for TRNSYS)

528 Borehole Heat Exchangers (BHE)

non-uniformly placement of BHE‘s

hydraulic coupling of BHE‘s (seriell, parallel)

ground layers

implementation in TRNSYS for system simulations




-Simulations-

0

10

20

30

40

50

60

70

80

01.12.97 01.12.98 01.12.99 01.12.00 01.12.01 01.12.02 01.12.03 01.12.04

tem

pera

ture

in °C

M17 (10 m)

M17 (32 m)

calc.meas.

calc.meas.thermal conductivity 1997-1998: 2.0 W/(m⋅K) 1997-2002: 2.2 W/(m⋅K) 2003-2005: 2.4 W/(m⋅K)volumetric heat capacity 2.85 MJ/(m³⋅K)




Summary & conclusions




-Summary & conclusion-

Solar fraction

2002-2005: 30-40% (measured)

design: 50%

Future: increasing heat demand?

installation of a heat pump?

further extension of the BTES?




more information:www.itw.uni-stuttgart.de/sunwww.solarthermie2000plus.de

Thank you for your attention!




-BTES-

Construction of the BTES

experimental store & 1st extension 2nd extension




-BTES-

Construction of the BTES

experimental store 2nd extension




-BTES-

-40

-35

-30

-25

-20

-15

-10

-5

025 30 35 40 45 50 55 60 65

temperature in °C

dept

h in

m

Aug. 04 Sep. 04 Oct. 04 Nov. 04 Dec. 04 Jan. 05

Feb. 05 March 05 April 05 May 05 June 05 July 05

BTES

Temperatures in the BTES




-BTES-

Connection ducts

experimental store & 1st extension 2nd extension (pipes before insulation)




-BTES-

10

20

30

40

50

60

70

Jan 99 Jul 99 Jan 00 Jul 00 Jan 01 Jul 01 Jan 02 Jul 02 Jan 03 Jul 03 Jan 04 Jul 04 Jan 05

tem

pera

ture

in °C

1. extension (0 m)

1. extension (20 m)2. extension (0 m)

2. extension (20 m)

1. extension (32 m) 2. extension (32 m)

Temperatures in the BTES





Solar gross heat gain of the solar collectors (5263 m³)

0

50

100

150

200

250

300

350

400

450

500

550

600

650

700

750

School seniorresidence

shoppingcentre

terracedhouses

carport wall senior careresidence

Eglob,coll

sola

r gro

ss h

eat g

ain

in k

Wh/

(m²·a

)

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

sola

r irr

adia

tion

(col

lect

or p

lane

, 15

°) in

kW

h/(m

²·a)

1999 2000

2001 2002

2003 2004

2005




-Simulations-

0

10

20

30

40

50

60

70

01.12.97 01.12.98 01.12.99 01.12.00 01.12.01 01.12.02 01.12.03 01.12.04

tem

pera

ture

in °C

M14 (5 m)

M14 (10 m)

M14 (32 m)

calc.meas.

calc.meas.

calc.meas.

thermal conductivity 1997-1998: 2.0 W/(m⋅K) 1997-2002: 2.2 W/(m⋅K) 2003-2005: 2.4 W/(m⋅K)volumetric heat capacity 2.85 MJ/(m³⋅K)

Documents

Monitoring results and operational experiences for a ... · Monitoring results and operational experiences for a central solar district heating system with Borehole Thermal Energy