implication of low temperature district heating on network ...€¦ · investment costs for local...
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Implication of low temperature district heating on network investment costs, primary energy savings and
cost benefits
Ambrose Dodoo, Leif Gustavsson and Nguyen Le Truong
Linnaeus University, Sweden
This presentation is based on an on-going project on:
Low temperature district heating and new energy efficient building blocks
Project partners include Växjöbostäder, Växjö Energi AB and Växjö Municipality
The presented results are preliminary
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Implication of low temperature district heating on network investment costs, primary energy savings and cost benefits
We consider three types of exploitation of a development area in Växjö, in southern Sweden Low exploitation Medium exploitation High exploitation
We consider two different energy performance of buildings Swedish building code (BBR 2015) Passive house criteria
We consider three temperature levels for district heating network 80/40oC 65/30oC 50/20oC
Project site in southwest of Växjö
Växjö
Växjö is a city of about 65 000 inhabitants
District heating system (DHS)
o ~ 185 MWpeak and ~ 630 GWhheat/year
o ~ 98% of production based on biomass
o 2 CHP plants and several boilers
Measured temperature in DH-network in 2013
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Project site
A new developed area in Torparängen, Växjö
Planning of ≈ 250 apartments/houses,
– 125 apartments
– 125 row houses and small houses
4, 6, 8 or 10 story-buildings
Different building frames – Concrete
– Wood
• Different heat supply options– District heating
– Electric heat pumps in each building
3D models of different exploitation alternatives
Low exploitation of townhouses and villas,9010 m2 heated floor area
Medium-exploitation of apartment buildings and townhouses, 23 540 m2 heated floor area
High-exploitation of apartment buildings, 29 350 m2 heated floor area
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Buildings heat demand
Simulated based on current Swedish building code (BBR) and passive house criteria (Passive)
Used for the design and calculation of district heat options
• For apartment buildings:
Building typeSpace heating load (kW / building)
BBR Passive
o 6 storeys, 24 apartments 54.5 27.8
• For row houses:
House typeSpace heating load (kW / house)
BBR Passive
o 2 stories, 6-13 houses/row, 140 m2/house
4.34-6.20 1.80-2.42
0
100
200
300
400
500
600
700
800
900
1000
0 1000 2000 3000 4000 5000 6000 7000 8000
Hea
t d
em
an
d (
kW)
Hour
High
Medium
Low
0
100
200
300
400
500
600
700
800
900
1000
0 1000 2000 3000 4000 5000 6000 7000 8000
Hea
t d
em
an
d (
kW)
Hour
High
Medium
Low
Profiles of total space and hot water demand for the different exploitation areas – hour by hour simulations
BBR Passive
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0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
Hea
t d
eman
d (
MW
h)
Space heating
Hot water
Scenario of building exploitation
mediumlow high
0
500
1000
1500
2000
2500
3000
Hea
t d
eman
d (
MW
h)
Space heating
Hot water
Scenario of building exploitation
mediumlow high
Annual space and hot water demands for the different exploitation areas
BBR Passive
Layout of district heat distribution network: Low exploitation of townhouses and villas
BBR Passive
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Layout of district heat distribution network: Medium‐exploitation of apartment buildings and townhouses
PassiveBBR
Layout of district heat distribution network: High‐exploitation of apartment buildings
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0
50
100
150
200
250
Dis
trib
uti
on
lo
sses
(M
Wh)
Scenario of building exploitation
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
mediumlow high
0
50
100
150
200
250
Dis
trib
uti
on
lo
sses
(M
Wh)
Scenario of building exploitation
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
mediumlow high
Local network heat losses for different alternatives and options
BBR Passive
0
500
1000
1500
2000
2500
3000
Dis
tric
t h
eat
use
(M
Wh)
Distribution losses
Hot water heating
Space heating
Scenario of building exploitation
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
mediumlow high
0
500
1000
1500
2000
2500
3000
Dis
tric
t h
eat
use
(M
Wh)
Distribution losses
Hot water heating
Space heating
Scenario of building exploitation
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0o C
50/2
0oC
mediumlow high
Local network heat losses, space and hot water heating demands for different exploitations
Local network losses: 3.9-20.1% in alternatives with BBR standard
7.4-31.8% in alternatives with passive criteria
BBR Passive
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Primary energy use for local network losses
A biomass-based DHS using the heat load duration curve of Växjö is used for calculation
0
20
40
60
80
100
120
140
160
180
200
0 50 100 150 200 250 300 350
Dis
tric
t h
eat
load
(M
W)
Day
53 MW Wood powder boiler
92 MW Wood chips boiler
40 MW CHP-BST
System:
o ~ 185 MWpeak
o ~ 630 GWhheat/year
The changed primary energy use is considered as marginal
0
50
100
150
200
250
Pri
mar
y en
erg
y u
se (
MW
h)
Scenario of building exploitation
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
mediumlow high
0
50
100
150
200
250
Pri
mar
y en
erg
y u
se (
MW
h)
Scenario of building exploitation
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
mediumlow high
Primary energy use for local network losses
BBR Passive
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0
100000
200000
300000
400000
500000
600000
Inve
stm
ent
cost
s (€
)
Substations
Network
Scenario of building exploitation
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
mediumlow high
0
100000
200000
300000
400000
500000
600000
Inve
stm
ent
cost
s (€
)
Substations
Network
Scenario of building exploitation
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
mediumlow high
Investment costs for local network and substations
BBR Passive
District heat production costs of annual local network losses
• Using biomass-based district heating system for all the scenarios
• Including capacity cost, fixed and variable O&M costs of each district heat production unit
0
20
40
60
80
100
120
140
160
180
200
0 50 100 150 200 250 300 350
Dis
tric
t h
eat
load
(M
W)
Day
53 MW Wood powder boiler
92 MW Wood chips boiler
40 MW CHP-BST
• Based on marginal cost calculation
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10
0
1000
2000
3000
4000
5000
6000
7000
Dis
tric
t h
eat
pro
du
ctio
n c
ost
s (€
)
Scenario of building exploitation
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
mediumlow high
0
1000
2000
3000
4000
5000
6000
7000
Dis
tric
t h
eat
pro
du
ctio
n c
ost
s (€
)
Scenario of building exploitation
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
65/3
0oC
80/4
0oC
50/2
0oC
mediumlow high
District heat production costs of annual local network losses
BBR Passive
Cost implication of reduced supply/return temperatures in local network with 80/40oC as baseline
The difference in annual district heat production cost relative to the baseline is calculated.
The net present value of the cost difference is calculated assuming different real discount rates and lifetimes
6% and 30 years
3% and 40 years
The net present value of the cost difference is compared to difference in investment costs
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-10000
-5000
0
Yea
rly
cost
s (€
)
Scenario of building exploitation
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
mediumlow high
0
20000
40000
60000
80000
100000
120000
Inve
stm
ents
(€)
-10000
-5000
0
Yea
rly
cost
s (€
)
Scenario of building exploitation
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
mediumlow high
0
20000
40000
60000
80000
100000
120000
Inve
stm
ents
(€)
Changes of initial investment costs (read) and yearly district heat production costs (green) with 80/40oC as baseline
BBR Passive
-90000
-80000
-70000
-60000
-50000
-40000
-30000
-20000
-10000
0
10000
NP
V (
€)
Scenario of building exploitation
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
mediumlow high
-90000
-80000
-70000
-60000
-50000
-40000
-30000
-20000
-10000
0
10000
NP
V (
€)
Scenario of building exploitation
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
mediumlow high
Increased investment cost minus net present value of reduced local network heat losses with 80/40oC as baseline
Discount rate of 6%
Lifetime 30 years
BBR Passive
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-60000
-50000
-40000
-30000
-20000
-10000
0
10000
20000
30000
40000
NP
V (
€)
Scenario of building exploitation
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
mediumlow high
-60000
-50000
-40000
-30000
-20000
-10000
0
10000
20000
30000
40000
NP
V (
€)
Scenario of building exploitation
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
65/3
0oC
50/2
0oC
mediumlow high
Increased investment cost minus net present value of reduced local network heat losses with 80/40oC as baseline
BBR Passive
Discount rate of 3%
Lifetime 40 years
Not so far considered in the analysis
District heat production benefits of operating CHP-plants at lower district heating temperatures
Reduced distribution heat losses in the whole distribution system due to reduced supply/return temperatures
Implications of investment cost for internal distribution of heat in buildings due to different supply/return temperatures