district heating & heat networks - e-sieben.at · minimise maintenance using one central plant...
TRANSCRIPT
LEARNING OBJECTIVESAGENDA
- What is district heating? - Understand basic principles
and advantages of DH
- Potential heat sources – What options are available and
the benefits of CHP
- Pipe materials and properties – Selecting appropriate
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- Pipe materials and properties – Selecting appropriate
pipe materials for each individual project
- Installation and design – What key data is needed to size
a pre-insulated pipe network
- Biogas / Anaerobic digestion – How it works and what
feedstocks can be used
REHAU WORLDWIDETHINK GLOBALLY – ACT LOCALLY
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6 CONTINENTS 174 LOCATIONS OVER 15,000 EMPLOYEES
REHAU DIVISIONS
FURNITURE, HOUSEHOLD APPLIANCES,
HOSES AND INDUSTRIAL DEVELOPEMENTS
UNLIMITED POLYMER SOLUTIONS
Industry
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EXTERIOR, WATER MANAGEMENT, AIR
MANAGEMENT & SEALING
WINDOW AND CURTAIN WALLING
TECHNOLOGY, BUILDING TECHNOLOGY,
CIVIL ENGINEERINGBuilding
Solutions
Automotive
Hot water or steam is centrally produced
- Transported via insulated pipe network
- Connected to individual properties via a heat interface unit
WHAT IS DISTRICT HEATING?DEFINITION
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- Connected to individual properties via a heat interface unit
- Heat metered
- Heat delivered via conventional heating systems
More efficient to produce energy locally - minimise losses
Community based heat sources (e.g. central biomass plant)
maximise benefits of renewables
Future proof – easy to change fuel source
WHAT IS DISTRICT HEATING?BENEFITS
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Minimise maintenance using one central plant – no individual
gas checks required
USE OF DISTRICT HEATINGAUSTRIA COMPARED TO EUROPE
Percentage of Houses Supplied by District Heating
40%50%60%70%80%90%
100%
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0%10%20%30%40%
Icela
nd
Denmar
k
Estoni
a
Poland
Sweden
Slovak
ia
Finlan
d
Hunga
ry
Austri
a
Germ
any
Nethe
rland
s
UK
Austria: District Heating now nearly 11%
Lack of district heating (DH) experience in Austria -> Higher
cost to install as perceived as ‘higher risk’
Lack of awareness of DH and historically poorly conceived
schemes
WHAT IS DISTRICT HEATING?POTENTIAL BARRIERS
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Community acceptance required – once installed, closed
network, no possibility to switch provider
Control of tariffs for varying usage from end users
HEAT SOURCE OPTIONSOFF-SITE & ON-SITE HEAT GENERATION
Waste heat from power stations
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Waste heat from power stations
Energy from Waste (EfW) plants
On-site CHP (fossil fuel or renewable)
Central boiler (fossil fuel or renewable)
COMBINED HEAT AND POWERBASIC PRINCIPLE
Energy in 100%
Heat losses 70%
Useful electricity 30%
Traditional power plant
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Useful heat 55%
Useful electricity 30%
Heat losses 15%
Energy in 100% +
Combined heat & power plant (CHP)
CHP offers the following benefits:
- Produces both heat and electricity on site
- More efficient use of energy - 80-90% efficient
- Cost savings of 15-40% compared to traditional
COMBINED HEAT AND POWERHOW IT WORKS
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- Cost savings of 15-40% compared to traditional
methods (gas boilers and national grid)
- Responsive heat supply – heat can be stored
Not fuel source dependent - powered either using fossil fuels or renewable sources (such as biomass or biogas).
Biomass district heating schemes work well because:
• Biomass boilers are often bulkier than traditional boilers, hence
typically located in external plant room, not individual houses
BIOMASS CHPINTRODUCTION
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• Require regular wood chip or pellet deliveries to only one
central plant
• Can be located discreetly on site extremes
PRE-INSULATED PIPEWORKOPTIONS FOR PIPE MATERIALS
Steel pipe with PU
foam
Polymer pipe with
PU foam
Polymer pipe with PEX
foam
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(closed cell - bonded)(closed cell - bonded) (closed cell – non-bonded)
PRE-INSULATED PIPEWORKSTEEL PIPES
Advantages:
- Strong material – resistant to impact damage
- Larger diameter sizes available
- Capable of withstanding higher flow temperatures / pressure
Disadvantages:
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Disadvantages:
- Only straight lengths possible
- Joints required every 6-12m
- High installation costs
- Corrosion problems (therefore warning systems are required)
- Specialist welding required
λ ≈ 0.024 W/mK
Closed cell insulation:
Advantages:
- Excellent thermal insulation
- No water ingress if outer jacket punctured
- No thermal expansion (self-compensating)
- More flexible compared to steel
PRE-INSULATED PIPEWORKTWO TYPES OF PIPE INSULATION – CLOSED CELL
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- More flexible compared to steel
- Long coil lengths possible (less joints)
Disadvantages:
- Less flexible compared to open cell
λ = 0.022 W/mK
PRE-INSULATED PIPEWORKTWO TYPES OF PIPE INSULATION – OPEN CELL
Open cell insulation:
Advantages:
- Greater flexibility
- Simpler jointing / installation (foam easily removed)
- Ideal for confined spaces
- Long coil lengths possible (less joints)
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- Long coil lengths possible (less joints)
Disadvantages:
- PU closed cell pipes have improved thermal insulation
λ = 0.043 W/mK
PRE-INSULATED PIPEWORKHYBRID SYSTEM
Possible to combine steel & polymer for large DH
schemes.
Benefits are:
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- High temperature / volume steel mains
- Cost-effective to install flexible polymer house
connections
- Can use polymer for smaller mains off ‘spines’
Most flow temperatures are ca. 80°C:
- Reduced heat losses
- Extends pipe lifespan
- Makes a safer network (no steam)
DELTA T OF DISTRICT HEATING NETWORKSIMPORTANCE OF OPTIMISING THE FLOW / RETURN TEMPERATURES
Flow / return
temperatures (C)
Heat load
(kW)
Pipe size
required
82-71 350 110mm
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Ensure return temperature is as low as possible (high ∆T):
- Reduces pipe size - > reduce capital costs
- Ensures low-grade heat can be used (e.g. Waste heat from
CHP)
82-71 350 110mm
80-60 350 75mm
80-50 350 63mm
With an operating pressure of 6 bar, the service life of the pipes is min.
30 years under the following conditions:
- Continuous operating temperature of 85°C
- Continuous operating temperature of 80°C,
- with 90°C for one month per year and 95°C for 100 hours per year
LIFESPAN OF DISTRICT HEATING NETWORKSTEMPERATURE AND PRESSURE
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Cross-linked polyethylene (PE-Xa) has the following benefits:
• Temperature resistant to +95ºC
• High chemical resistance
• Oxygen barrier
• Simple jointing process
PRE-INSULATED PIPEWORKSIMPLIFIED STEPS TO DESIGN A HEAT NETWORK
5 kW 8 kW11 kW7 kW
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1. Calculate heat
loads for each
dwelling
2. Identify heat
source & required
capacity
3. Pipe sizing (based
on flow rates &
pressure losses
4. Create bill of
materials
Biomass boiler
31kW
Zoning the area:
- Based on proximity to buildings
- Add the heat loads to form a cumulative for each
zone
- Size the pipe based on flow rates and pressure
losses
Example DH network:
PRE-INSULATED PIPEWORKZONING DIFFERENT PARTS OF THE NETWORK
Zone 1 Zone 4
Zone 2 Zone 3 Zone 5
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Example DH network:
Zone use Total Heat load
Zone 1 10 houses – each 5kW 50kW
Zone 2 15 houses – each 5kW 75kW
Zone 3 Primary school 75kW
Zone 4 Office 150kW
Zone 5 15 houses – each 10kW 100kW
Total heat load is
450kW
∆T = 10K
Plant Room
Zone 4
150 kWZone 1
50 kW
250 kW
A
B
C
D
E
PRE-INSULATED PIPEWORKEXAMPLE OF ZONING
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Zone 5
100 kW
Zone 3
75 kW
Zone 2
75 kW
450 kW 400 kW 100 kW
B D
F
∆T = 10K
Plant Room
Zone 4
150 kWZone 1
50 kW
250 kW
90 mm
A
B
C
D
E
PRE-INSULATED PIPEWORKEXAMPLE OF ZONING
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Supply pipe feeding into buildings
(32mm)
Zone 5
100 kW
Zone 3
75 kW
Zone 2
75 kW
450 kW
110 mm
400 kW
110 mm
100 kW
63mm
B D
F
Total costs
Co
sts
OPTIMAL NETWORK DESIGNBALANCE OF INVESTMENT & OPERATIONAL COSTS
The goal should be, optimal network design in order to minimize the total annual costs - sum of investment
costs and operating costs, based on a certain period of use!
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Heat loss costs
Investment costs
Pumping costs
Co
sts
Pipe diameter
New building
Fac
tor
DIVERSITY OF HEAT NETWORKSIMPACT OF DIVERSITY FACTOR
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Old building
Renovated old building
Numbers of connections
Div
ersi
tyF
acto
r
Standard network Ring network
HEAT NETWORK GEOMETRYSTANDARD VS RING MAIN
Heat
source
Heat
source
Heat
source
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Typically a branch network (with a main distribution pipe) is used. However, a ring main offers some benefits
for certain projects:
- Allows multiple heat sources (future connections)
- Flexibility of design
- Reliability
- Redundancy
PRE-INSULATED PIPEWORKINSTALLATION
- Cover 600mm minimum 800mm with traffic loads
- 100mm of 0.8mm grade sand around the pipe
- Pipe positions:
- Besides each other
- On top of each other
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- On top of each other
Warning tape must be used!
PRE-INSULATED PIPEWORKINDIRECT CONNECTIONS
Indirect connections:
• Each house needs a heat interface unit (HIU) off the DH network
• Individual house metering monitors & control and then bills based on
the amount of heat used
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the amount of heat used
• ‘Smart metering’ – no site readings
• Typically operated by Energy Supply Companies
Direct connections can also be used (no HIUs required) but each property
is not isolated, therefore not normally preferred.
SPECIAL APPLICATIONS – ANAEROBIC DIGESTIONINTRODUCTION
District heating
Solid waste for
fertilizer
1. Cow manure is heated to
produce methane
2. Methane generated sent to CHP
unit for electrical generation.
3. Excess heat from CHP fed back
into fermenter and used for
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CHP supplies
electricity to grid
Fermenter Biogas powered
CHP
Liquid animal
waste
into fermenter and used for
district heating
4. Solid waste reused as fertiliser
BIOGAS / ANAEROBIC DIGESTIONPOSSIBLE FEEDSTOCKS
Organic substances which can be used in anaerobic
digestion systems:
- Animal waste (e.g. cow / pig manure)
- Unused crops (leaves, stalks) & grass cuttings
- Slaughterhouse waste
- Food waste
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- Food waste
SPECIAL APPLICATIONS - UTESUNDERGROUND THERMAL ENERGY STORAGE
In district heating networks with renewable
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energy sources (e.g. solar thermal), excess
heat is wasted in the summer.
COMBINING DISTRICT HEATING WITH UTESUNDERGROUND THERMAL ENERGY STORAGE
Using underground thermal energy storage with intelligent controls, optimum use of all energy sources can be
achieved.
The excess heat in summer can then be efficiently stored and then utilised in winter with an increased efficiency.
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0
100
200
300
400
500
600
700
800
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Hea
t re
qu
irem
ent
MW
h/m
on
th
Heat requirement Available solar energy
Summer
storage
Use heat
in winter
COMBINING DISTRICT HEATING WITH UTESTYPICAL SCHEMATIC
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Source: Drake Solar Landing Community
Live operation data can be found here: www.dlsc.ca
Bioenergy village, Effelter, Germany
- 160 kW Biogas plant
- Uses DH CHP system to deliver heat to 36 houses, fire
station and restaurant
DISTRICT HEATING & HEAT NETWORKS CASE STUDIES
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- Additional wood chip biomass boiler for peak demands
- System produces 1.1 million kWh/a
- CO2 saving of 370,000 kg/a
Much Fawley Farm AD plant, Herefordshire
- AD plant fed by slurry, maize & silage
- RAUVITHERM pipework connects hot water from CHP to
chicken sheds
ANAEROBIC DIGESTION CASE STUDY
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- 2,500m of pipework in total (75 UNO & 32 DUO)
Braedstrup District Heating & Solar Park, Denmark
CASE STUDY
DISTRICT HEATING & UNDERGROUND ENERGY STORAGE
System description
-1,400 homes
- DH network owned by community
- 6MW system (3,800 MWh/a)
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Heat sources:
- 16,000m² solar collectors
- Heat pump
- Peak heating through district heating network
Heat storage:
- 2,500m³ buffer tank(hot water)
- 50 PE-Xa probes at 50m deep
Solar Storage & District Heating, Crailsheim, Germany
CASE STUDY
DISTRICT HEATING & UNDERGROUND ENERGY STORAGE
System description
- 260 dwellings, school, sports hall
- 4100 MWh/a with network temperatures flow/return
65/35°C
Heat sources:
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Heat sources:
- 7,300m² solar collectors with 5,1MW peak output
- 750 kW heat pump
- Supplementary heating through district heating
network
Heat storage:
- 100m³ high temperature peak load storage (hot water)
- 480m³ buffer storage (hot water)
- 43,200m³ ground-source probe underground storage
(80 PE-Xa probes)
SUMMARY
- Understand the pros and cons of DH networks and they can be best utilised.
- Use the benefits of on-site generation with CHPs to reduce demand on fossil fuels and increase
system efficiencies
- Selecting appropriate pipe materials for each individual project, based on pros and cons of steel and
polymer
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polymer
- Designing a well-sized DH system is vital for ensuring highest possible energy efficiencies and low
pressure losses.
- Understand how anaerobic digestion works and the potential of producing energy from waste (and
reducing landfill)