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
24.08.2016 Solar District Heating – Mikkeli, Finland
RESIDENTIAL AREA
13 residential buildings
319 apartments
30 400 m² floor area
29 100 m² heated area
91 000 m³ heated volume
24.08.2016 Solar District Heating – Mikkeli, Finland 5
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
24.08.2016 Solar District Heating – Mikkeli, Finland 6
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 7
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
24.08.2016 Solar District Heating – Mikkeli, Finland 8
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
24.08.2016 Solar District Heating – Mikkeli, Finland 9
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
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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
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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
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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
24.08.2016 Solar District Heating – Mikkeli, Finland 13
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 14
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
24.08.2016 Solar District Heating – Mikkeli, Finland
INTERNALS
24.08.2016 Solar District Heating – Mikkeli, Finland
INTERNALS
24.08.2016 Solar District Heating – Mikkeli, Finland
SNOW
17Nov 2007
80 °C
24.08.2016 Solar District Heating – Mikkeli, Finland 18
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
24.08.2016 Solar District Heating – Mikkeli, Finland
SIMULATED STORAGE TEMPERATURES
19
480 MWh --------------
0 MWh ---------------
24.08.2016 Solar District Heating – Mikkeli, Finland 20
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 21
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
24.08.2016 Solar District Heating – Mikkeli, Finland 22
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.
24.08.2016 Solar District Heating – Mikkeli, Finland 23
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
storage operation with
district heat supplem.
storage operation with AHP
and district heat supplem.
district heat
(Backup)
24.08.2016 Solar District Heating – Mikkeli, Finland 24
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
storage operation with
district heat supplementary
storage operation with AHP
and district heat supplem.
district heat
(Backup)
24.08.2016 Solar District Heating – Mikkeli, Finland 25
ENERGY FLOW CHART 2008/2009
Solar radiation
Solar collectors
City district heat
storage
user
AHP
24.08.2016 Solar District Heating – Mikkeli, Finland 26
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
24.08.2016 Solar District Heating – Mikkeli, Finland 27
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
24.08.2016 Solar District Heating – Mikkeli, Finland 28
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 29
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
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FURTHER INNOVATIONS
Different types of seasonal storage
Borehole storage system
Combined underground water storage and borehole storage
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SEASONAL STORAGE CONCEPTS Different types of seasonal storage
Underground water storage Munich Ackermannbogen
Concrete water storage with inside
vacuum insulation element
24.08.2016 Solar District Heating – Mikkeli, Finland 32
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
24.08.2016 Solar District Heating – Mikkeli, Finland 34
Some supplementary information and
details of the monitoring program
24.08.2016 Solar District Heating – Mikkeli, Finland 35
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
24.08.2016 Solar District Heating – Mikkeli, Finland 36
ENERGY FLOW CHART 2007/2008
Solar radiation
Solar collectors
City district heat
storage
user
AHP
24.08.2016 Solar District Heating – Mikkeli, Finland 37
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
24.08.2016 Solar District Heating – Mikkeli, Finland 38
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
24.08.2016 Solar District Heating – Mikkeli, Finland 39
ENERGY BALANCE 07/08 AND 08/09
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
24.08.2016 Solar District Heating – Mikkeli, Finland 40
ENERGY BALANCE 07/08 AND 08/09
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
Index Design Operation year Unit
(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
24.08.2016 Solar District Heating – Mikkeli, Finland 41
ENERGY BALANCE 07/08 AND 08/09
Assessment:
Heat consumption is small due to mild weather
Heat losses of the network are smaller
Index Design Operation year Unit
(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
24.08.2016 Solar District Heating – Mikkeli, Finland 42
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)