Solar District Heating - an Innovative Approach of an ... · 24.08.2016 Solar District Heating –Mikkeli, Finland 27 LOCAL DISTRICT HEATING Low return temperature improves the solar

24.08.2016 Solar District Heating – Mikkeli, Finland© ZAE Bayern

Bavarian Center for

Applied Energy Research

Solar District Heating - an Innovative

Approach of an Established Technology

Dipl.-Phys. Manfred Reuß

ZAE Bayern, Walther-Meißner-Str.6, 85748 Garching

[email protected]; www.zae-bayern.de

24.08.2016 Solar District Heating – Mikkeli, Finland 2

Description of the solar district heating concept Ackermannbogen

in Munich

Innovative design of the district heating to achieve low return

temperature

Seasonal storage for high solar fraction

Experiences from design, construction and monitoring of operation

of the system

Outlook towards even more innovation

OUTLINE

24.08.2016 Solar District Heating – Mikkeli, Finland

LOCATION

Solar District Heating Munich Ackermannbogen

Solare Nahwärme “Am Ackermannbogen” (SNAB), München


RESIDENTIAL AREA

13 residential buildings

319 apartments

30 400 m² floor area

29 100 m² heated area

91 000 m³ heated volume


High building energy standard

Concept: heating demand ~ 30% less than building standard 2002

Planning: ~ 40% less than building standard 2004 (optimized thermal

insulation)

Space heating demand for contracts: 1070 MWh/a

Heating demand

Specific heating demand: ~ 50 kWh/m²a

Hot water demand: ~ 740 kWh/a

Specific hot water demand: ~ 20 kWh/m²a

Heating power: 1200 - 1800 kW?

BUILDINGS



in Munich


temperature



of the system


OUTLINE


Space heating without system separation

System separation only with floor heating (oxygen diffusion)

Serial connection of radiators and diffusion resistant floor heating

Temperatures:

Supply max. 60 °C, Return max. 30 °C

LOW TEMPERATURE SPACE HEATING


Space Heating: 55 °C / 30 °C

Hot Water: 55 °C / 20 °C

15 °C / 50 °C

Hot water supply on demand

Hygienic advantages (pipe vol. < 3 l)

Optimal return temperatures (27 °C)

1 heat meter only for space heating and DHW

Minimized heat losses

High system performance

HEAT TRANSFER STATIONS


District heating network

High insulation standard

Variable flow rate

Tsupply 56 °C – 60 °C, Treturn 20 °C – 45 °C (27 °C)

Heat loss ~ 60 MWh/a (< 3%)

Additional distribution losses

Design heating demand at energy plant

(Space heating, hot water und distribution losses)

Reference scenario 1: 1 996 MWh/a

Reference scenario 2: 2 295 MWh/a

TOTAL HEATING DEMAND


Temperatures:

Heat Storage: 95 °C - 10 °C

Heat Distribution: 55 °C, TReturn< 30 °C

District Heating: 130 °C - 80 °C, TReturn< 50 °C

HYDRAULIC SYSTEM CONCEPT


Collector design:

3 collector fields

Low-flow-system

Variable flow rate

Aperture area: 2 762 m²

Slope: 18,5° (14° to the east)

Fluid: glycol-water mixture

SOLAR COLLECTOR FIELD


Driven by district heating

Regenerator: Hot water (125 °C – 90 °C)

Heating: 550 kW (design point)

Evaporator: 240 kW at 10 °C

COP: 1.7

ABSORPTION HEAT PUMP



in Munich


temperature



of the system


OUTLINE


Stratified underground storage tank

Volume: 6 000 m³,

Water: 5 700 m³ (10 °C)

Storage capacity: 480 MWh (15/90 °C)

Heat losses: 80 MWh/a

Made of precast segments

Inside: Stainless steal lining

Outside: thermal insulation

LONG-TERM HEAT STORAGE TANK

Stratified

Charging

Variable

Charge

Bottom

Charge

Top charge


INTERNALS


INTERNALS


SNOW

17Nov 2007

80 °C


Spring (March till July)

Loading of heat storage tank at the upper storage layers

Summer (July till November)

Direct solar supply

Winter (November till March)

Heat pump and district heating backup-system ensure heat supply

Heat pump is discharging the storage tank step-by-step at two

successive temperature levels (25 °C und 10 °C)

Solar district heating operation

Storage tank is discharged

Heat pump is turned off, because of too low performance requirement

CONTROL CONCEPT


SIMULATED STORAGE TEMPERATURES

19

480 MWh --------------

0 MWh ---------------



in Munich


temperature



of the system


OUTLINE


MONITORING

System monitoring for analysis of

performance of components

Performance of the total system

Errors and mistakes in construction and control

Derivation of optimization measures


OPERATION MODE

storage / direct

solar operation

storage operation with

district heat supplem.

storage operation with AHP

And district heat supplem.

district heat

(Backup)

1

2

3

4

storage Heat

pump

collectorDistrict heating

network

user

City district heat

heat

exch.

Collector

network

heat

exch.heat

exch.


1

2

3

4

OPERATION MODE

storage Heat

pump

collectorDistrict heating

network

user

City district heat

heat

exch.

Collector

network

heat

exch.heat

exch.

storage / direct

solar operation


district heat supplem.


and district heat supplem.

district heat

(Backup)


OPERATION MODE

1

2

3

4

storage

Heat

pump

collector District heating

network

user

City district heat

heat

exch.

Collector

network

heat

exch.heat

exch.

storage / direct

solar operation


district heat supplementary


and district heat supplem.

district heat

(Backup)


ENERGY FLOW CHART 2008/2009

Solar radiation

Solar collectors

City district heat

storage

user

AHP


OPERATING EXPERIENCES LIBR-AHP

07/08 no operation due to problems with

the system control

AHP was used first in the heating period

08/09

Heat demand is lower than expected and

the winter was very mild – only part-load

operation was necessary

AHP shows very good part load operation

part load operation measured: COP =

1,52 above 30 % load (180 kW):

COP = 1,6 design full load:

COP = 1,76


LOCAL DISTRICT HEATING

Low return temperature improves the solar gain and the useful storage capacity

significantly

Funding requirement: 30 °C return temperature

Heating concept: direct operation & serial connection of radiator and floor heating

was a full success

DHW: decentralized fresh water preparation in each apartment

Result: 30,5 °C flow weighted mean return temperature

0

10

20

30

40

50

60

70

Okt

. 08

Nov.

08

Dez

. 08

Jan. 0

9

Feb. 0

9

Mrz

. 09

Apr.

09

Mai

. 09

Jun. 0

9

Jul.

09

Aug. 0

9

Sep

. 09

Zeit

Te

mp

era

tur

in °

C

0

300

600

900

1200

1500

1800

2100

Le

istu

ng

in

kW

Netzvorlauftemperatur Netzrücklauftemperatur Leistung Nahwärmenetz



in Munich


temperature



of the system


OUTLINE


FURTHER INNOVATIONS

Large and high efficient solar collector elements with integrated piping

Different types of seasonal storage

Borehole storage system

Combined underground water storage and borehole storage

Concrete water storage with inside VSI-element

Heat pump to increase operational temperature difference in the storage

Optimization of the hydraulic system

Retrofit of solar district heating to existing building stock

Feed in of solar heat in regular district heating


FURTHER INNOVATIONS

Different types of seasonal storage

Borehole storage system

Combined underground water storage and borehole storage


SEASONAL STORAGE CONCEPTS Different types of seasonal storage

Underground water storage Munich Ackermannbogen

Concrete water storage with inside

vacuum insulation element


CONCLUSIONS

SDH is a feasible option for space heating and DHW with a high solar fraction

Large collector field, seasonal storage and district heating network is required

High insulation standard and a high efficient heating concept incl. DHW was realized

Monitoring phase shows almost the performance of the design phase despite some

construction mistakes

Collector area and performance was lower than design requirements

Thermal stratification – could not be realized due to malfunction of the stratification

unit

Problems with the control program reduce the system performance and solar fraction

AHP shows excellent results and performance

Concept of direct coupling of district heating and heating system in the buildings

together with the decentralized DHW preparation was a great story of success

Return temperature in the district heating network was 30 °C from the early

beginning

We are ready to give technical consultancy and support if you plan such a project!

24.08.2016 Solar District Heating – Mikkeli, Finland 33© ZAE Bayern

Thank you for your attention

33

The project was funded by the Federal Ministry of Environment, Nature Conservation

and Nuclear Safety based on a decision of the Federal Parliament within the framework

Solarthermie 2000 (FKZ: 0329607G) and the City of Munich

The authors thank for this support


Some supplementary information and

details of the monitoring program


1995 Urban development measure Waldmann-Stetten barracks

1996 City council resolution for solar district heating

1999 Feasibility study for locations in Munich (ZAE Bayern)

2000 Preliminary design of system components for the location

„Ackermannbogen“

2004 Architectural competition for solar housing estate

2005 New concept, planning phase and start of construction works

2006 District heating supply

2007 Completion and commissioning of solar supply

2010 Final report and accompanying research

2011 Final workshop

PROJECT DEVELOPMENT

35


ENERGY FLOW CHART 2007/2008

Solar radiation

Solar collectors

City district heat

storage

user

AHP


SYSTEM LAYOUT AND SENSOR POSITIONS

AHP

Local district heating

Seasonal hot

water tank

Temperature sensors

Flow meter

Collector secondary circuit

Collector

primary circuit

AHP generator circuit

AHP heating circuit

AHP cold water circuit

AHP-DH-Supply


ENERGY BALANCE 07/08 AND 08/09

Evaluation:

Daily, monthly and annual energy balances

Comparison to design data

test reference

year

weather data

2007/2008

weather data

2008/2009

solar radiation at the

collector slope:1185 kWh/(m²a) 1330 kWh/(m²a) 1291 kWh/(m²a)

degree days:

(Troom = 20 °C;

heating temp. limit = 15 °C)4230 Kd/a 3506 Kd/a 3584 Kd/a

Assessment:

The weather shows in both years higher radiation and

higher temperatures than the TRY



Assessment:

Collector area is smaller and the performance is significantly lower

In the night convection occurs in the solar network – valves for stopping

were not realized

Index Design Operation year Unit

(2007/08) (2008/09)

Solar system:

Installed collector aperture 2880 2761 2761 m²

Inclination 18,5° 18,5° 18,5°

Solar radiation in the collector

slopeA 3413 3672 3563 MWh/a

Heat loss collector B 2190 2703 2546 MWh/a

Solar heat delivered to the

collection networkC 1223 969 1017 MWh/a

Heat loss collection network D 42 95 48 MWh/a

Solar heat delivered to the storage E 1181 873 969 MWh/a



Assessment:

AHP was not operated in the 1st year due to defects in the control program

In the 2nd year operation the AWP shows a SPF of 1,52

Control: in case of any disturbance city district heating mode is selected, also in case of

disturbance in the city district heating!

Long reaction time in case of any disturbance results in an increase of city district heat

consumption


(2007/08) (2008/09)

District heat:

Consumption (measurement SWM) G 892 1129 1007 MWh/a

Absorption heat pump (AHP):

Used solar energy K -- 0 200 MWh/a

Used district heat I -- 0 386 MWh/a

Heat delivered to the local network L -- 0 586 MWh/a



Assessment:

Heat consumption is small due to mild weather

Heat losses of the network are smaller


(2007/08) (2008/09)

Local district heating network:

Heat delivered to the network J+L+H 1996 1822 1815 MWh/a

Heat losses of the network N 60 43 43 MWh/a

Heat consumption of the buildings M 1936 1778 1772 MWh/a

Storage:

Change in heat content of the store O 0 -40 -35 MWh/a

Heat losses of the storage F 80 221 195 MWh/a


CHARACTERISTIC FACTORS 07/08 AND 08/09

Assessment:

Within the research project significant improvement could be achieved by manual

intervention (increase of collector yield by 5.1 %, increase of useful solar yield by

16.8 %)

The requirements of Solarthermie 2000+ were not fully achieved, but are feasible in

case of realization of the optimization measures

Index Design Operating year Unit

(2007/08) (2008/09)

Characteristic factors:

Useful solar energy J+K 1104 693 809 MWh/a

Solar fraction 55 % 38 % 45 %

specific collector yield 425 351 369 kWh/(m²a)

spec. useful solar yield 383 251 293 kWh/(m²a)

Documents

Solar District Heating - an Innovative Approach of an ... · 24.08.2016 Solar District Heating –Mikkeli, Finland 27 LOCAL DISTRICT HEATING Low return temperature improves the solar