1 concrete in construction and the impact of climate change keith tovey ( ) ma, phd, ceng, mice,...
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Concrete in Construction and the Impact of Climate Change
Keith Tovey (杜伟贤 ) MA, PhD, CEng, MICE, CEnv
Energy Science Director HSBC Director of Low Carbon Innovation
CRedCarbon Reduction
Concrete Society MeetingNorwich
30th October 2007
CRed
Recipient of James Watt Medal5th October 2007
2
ZICER Building
Heating Energy consumption as new in 2003 was reduced by further 57% by careful record keeping, management techniques and an adaptive approach to control.
Incorporates 34 kW of Solar Panels on top floor
Low Energy Building of the Year Award 2005 awarded by the Carbon Trust.
3
Concentration of C02 in Atmosphere
300
310
320
330
340
350
360
370
380
1960 1965 1970 1975 1980 1985 1990 1995 2000
(ppm
)
Changes in Temperature
4
19792003
Climate ChangeArctic meltdown 1979 - 2003
• Summer ice coverage of Arctic Polar Region– Nasa satellite
imagery
Source: Nasa http://www.nasa.gov/centers/goddard/news/topstory/2003/1023esuice.html
•20% reduction in 24 years
5
"Clean Coal"
Traditional Coal ~40%- coal could
supply 40 - 50% by 2020
Available now: Not viable without Carbon Capture & Sequestration
2.5 - 3.5p - but will EU - ETS carbon trading will affect
this
Options for Electricity Generation in 2020 - Non-Renewable Methods
nuclear fission (long term)
0 - 30% (France 80%) - (currently 20% and falling)
new inherently safe designs - some practical development needed
2.5 - 3.5p
nuclear fusion unavailablenot available until 2040 at earliest
potential contribution to Supply in 2020
costs in 2020
Wholesale Price of Electricity since NETA
0
10
20
30
40
50
60
70
2001 2002 2003 2004 2005 2006 2007
Bas
eloa
d P
rice
s (£
/MW
h)
first 5 years
last 12 months
0
2000
4000
6000
8000
10000
12000
14000
1955 1965 1975 1985 1995 2005 2015 2025 2035
Inst
all
ed C
ap
aci
ty (
MW
)
New Build ?
ProjectedActual
Nuclear New Build assumes one new station is completed each year after 2018.
Gas CCGT0 - 80% (currently
35% )
available now, but UK gas will run out within current decade
~ 2p + but recent trends put figure
much higher
6
On Shore Wind ~25% available now for commercialexploitation
~ 2p
Hydro 5% technically mature, but limitedpotential
2.5 - 3p
Resource Potential contribution to electricity supply in2020 and drivers/barriers
Cost in2020
Options for Electricity Generation in 2020 - Renewable
7
Photovoltaic 50% available, but much research neededto bring down costs significantly
10+ p
On Shore Wind ~25% available now for commercialexploitation
~ 2p
Hydro 5% technically mature, but limitedpotential
2.5 - 3p
Resource Potential contribution to electricity supply in2020 and drivers/barriers
Cost in2020
Options for Electricity Generation in 2020 - Renewable
Area required to supply 5% of UK electricity needs ~ 300 sq km
But energy needed to make PV takes up to 8 years to pay back in UK.
8
Photovoltaic 50% available, but much research neededto bring down costs significantly
10+ p
Energy Crops/ Biomass/Biogas
50% + available, but research needed in some areas
2.5 - 4
On Shore Wind ~25% available now for commercialexploitation
~ 2p
Hydro 5% technically mature, but limitedpotential
2.5 - 3p
Resource Potential contribution to electricity supply in2020 and drivers/barriers
Cost in2020
Options for Electricity Generation in 2020 - Renewable
But Land Area required is very large - the area of Norfolk and Suffolk would be needed to generated just over 5% of UK electricity needs.
Transport Fuels:
• Biodiesel?
• Bioethanol?
• Compressed gas from methane from waste.
9
Photovoltaic 50% available, but much research neededto bring down costs significantly
10+ p
Energy Crops 100% + available, but research needed insome areas
2.5 - 4
Wave/Tidal Stream
100% + ultimately
techology limited - major development unlikely before 2020 ~ 3–4%
4 - 8p
On Shore Wind ~25% available now for commercialexploitation
~ 2p
Hydro 5% technically mature, but limitedpotential
2.5 - 3p
Resource Potential contribution to electricity supply in2020 and drivers/barriers
Cost in2020
Options for Electricity Generation in 2020 - Renewable
10
Photovoltaic 50% available, but much research neededto bring down costs significantly
10+ p
Energy Crops 100% + available, but research needed insome areas
2.5 - 4
On Shore Wind ~25% available now for commercialexploitation
~ 2p
Hydro 5% technically mature, but limitedpotential
2.5 - 3p
Resource Potential contribution to electricity supply in2020 and drivers/barriers
Cost in2020
Options for Electricity Generation in 2020 - Renewable
Wave/Tidal Stream
100% + ultimately
techology limited - major development unlikely before 2020 ~ 3–4%
4 - 8p
11
Wave/Tidal Stream
100% + ultimately
techology limited - major development unlikely before 2020 ~ 3–4%
4 - 8p
Photovoltaic 50% available, but much research neededto bring down costs significantly
10+ p
Energy Crops 100% + available, but research needed insome areas
2.5 - 4
Tidal Barrages 10 - 20% technology available but unlikelywithout Government intervention
notcosted
On Shore Wind ~25% available now for commercialexploitation
~ 2p
Hydro 5% technically mature, but limitedpotential
2.5 - 3p
Resource Potential contribution to electricity supply in2020 and drivers/barriers
Cost in2020
Options for Electricity Generation in 2020 - Renewable
Output (MWh)
0
100
200
300
400
500
600
700
01/0
1/20
02
15/0
1/20
02
29/0
1/20
02
12/0
2/20
02
26/0
2/20
02
12/0
3/20
02
26/0
3/20
02
09/0
4/20
02
23/0
4/20
02
07/0
5/20
02
21/0
5/20
02
04/0
6/20
02
18/0
6/20
02
02/0
7/20
02
16/0
7/20
02
30/0
7/20
02
13/0
8/20
02
27/0
8/20
02
10/0
9/20
02
24/0
9/20
02
08/1
0/20
02
22/1
0/20
02
05/1
1/2
002
19/1
1/2
002
03/1
2/20
02
17/1
2/20
02
31/1
2/20
02
Out
put
(MW
h pe
r da
y)
Output 78 000 GWh per annum
Sufficient for 13500 house in Orkney
Save 40000 tonnes of CO2
12
Photovoltaic 50% available, but much research neededto bring down costs significantly
10+ p
Energy Crops 100% + available, but research needed insome areas
2.5 - 4
Wave/TidalStream
100% + techology limited - extensivedevelopment unlikely before 2020
4 - 8p
Tidal Barrages 10 - 20% technology available but unlikelywithout Government intervention
notcosted
Geothermal unlikely for electricity generationbefore 2050 if then
On Shore Wind ~25% available now for commercialexploitation
~ 2p
Hydro 5% technically mature, but limitedpotential
2.5 - 3p
Resource Potential contribution to electricity supply in2020 and drivers/barriers
Cost in2020
Options for Electricity Generation in 2020 - Renewable
13
Solar Energy - The BroadSol Project
Annual Solar Gain 910 kWh
Solar Collectors installed 27th January 2004
14
Performance of a Solar Thermal System
Solar Gain (kWh/day)
0
1
2
3
4
5
6
7
8
9
10 20 30 9 19 29 8 18 28 10 20 30 9 19 29 9 19 29 8 18 28 8 18 28 7 17 27 6 16 26 6 16 26
Day of Month
Sola
r G
ain
(kW
h)
December January February
March April May
June July August
September October
Data collect 9th December 2006 – 30th October 2007
15
House in Lerwick, Shetland Isles with Solar Panels
- less than 15,000 people live north of this in UK!
It is all very well for South East, but what about the North?
House on Westray, Orkney exploiting passive solar energy from end of February
16
Actual Nuclear
Projected Nuclear
Actual Coal with FGD
Opted Out Coal
Renewables
New Nuclear?
New Coal ???
0
10000
20000
30000
40000
50000
60000
2000 2005 2010 2015 2020 2025 2030
MW
• Opted Out Coal: Stations can only run for 20 000 hours more and must close by 2015• New Nuclear assumes completing 1 new nuclear station each year beyond 2018• New Coal assumes completing 1 new coal station each year beyond 2018
Our Choices: They are difficult: Energy SecurityThere is a
looming capacity shortfall
Even with a full deployment of
renewables.
A 10% reduction in demand per
house will see a rise of 7% in total demand
- Increased population decreased
household size
17
Our Choices: They are difficult
If our answer is NO
Do we want to return to using coal? • then carbon dioxide emissions will rise significantly
• unless we can develop carbon sequestration and apply it to ALL our COAL fired power stations within 10 years - unlikely.
If our answer to coal is NO
Do we want to leave things are they are and see continued exploitation of gas for both heating and electricity generation? >>>>>>
Do we want to exploit available renewables i.e onshore/offshore wind and biomass. Photovoltaics, tidal, wave are not options for next 20 years.
If our answer is NO
Do we want to see a renewal of nuclear power
• Are we happy with this and the other attendant risks?
18
Our Choices: They are difficult
If our answer is YES
By 2020
• we will be dependent on around 70% of our heating and electricity from GAS
• imported from countries like Russia, Iran, Iraq, Libya, AlgeriaAre we happy with this prospect? >>>>>>
If not:
We need even more substantial cuts in energy use.
Or are we prepared to sacrifice our future to effects of Global Warming by using coal? - the North Norfolk Coal Field? –
Aylsham Colliery, North Walsham Pit?
Do we wish to reconsider our stance on renewables?
Inaction or delays in decision making will lead us down the GAS option route
and all the attendant Security issues that raises.
19
The Climate Dimension
Heating requirements are ~10+% less than in 1960
Cooling requirements are 75% higher than in 1960.
Changing norm for clothing from a business suite to shirt and tie will reduce “clo” value from 1.0 to ~ 0.6.
To a safari suite ~ 0.5.Equivalent thermal comfort can be achieved with around 0.15 to 0.2 change in “clo” for each 1 oC change in internal environment.
Care in design is needed to avoid overheating in summer and to minimise active cooling requirements
Thermal Comfort is important: Even in ideal environment 2.5% of people will be too cold and 2.5% will be too hot.
Estimate heating and cooling requirements from Degree Days
60
80
100
120
140
160
180
1960-1964
1965-1969
1970-1974
1975-1979
1980-1984
1985-1989
1990-1994
1995-1999
2000-2004
Heating
Cooling
Index 1960 = 100
Heavy Weight Buildings can help to reduce energy requirements in a warming climate.
20
The Elizabeth Fry Building 1994
Cost ~6% more but has heating requirement ~25% of average building at time.
Building Regulations have been updated: 1994, 2002, 2006, but building outperforms all of these.
Runs on a single domestic sized central heating boiler.
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0
50
100
150
200
250
Elizabeth Fry Low Average
kWh/
m2/
yr
gas
electricity
User Satisfaction
lighting +25%
air quality +36%
A Low Energy Building is also a better place to work in
Careful Monitoring and Analysis can reduce energy consumption.
Conservation: management improvements –
thermal comfort +28%
noise +26%
22
The ZICER Building - Description
• Four storeys high and a basement• Total floor area of 2860 sq.m• Two construction types
Main part of the building
• High in thermal mass • Air tight• High insulation standards • Triple glazing with low emissivity
23
The ground floor open plan office
The first floor open plan office
The first floor cellular offices
24Air enters the internal
occupied space
Return stale air is extracted from each floor
Incoming air into
the AHU
Regenerative heat exchanger
FilterHeater
Air passes through hollow
cores in the ceiling slabs
The return air passes through the heat
exchanger
Out of the building
Operation of the Main Building• Mechanically ventilated using hollow core ceiling slabs as supply air ducts to the space Recovers 87% of
Ventilation Heat Requirement.
25
Importance of the Hollow Core Ceiling Slabs
The concrete hollow core ceiling slabs are used to store heat and coolness at different times of the year to provide comfortable and stable temperatures
Winter Day
The concrete slabs absorb and
store heat
Heat is transferred to the air before entering
the room
Winter day
26
Importance of the Hollow Core Ceiling Slabs
The concrete hollow core ceiling slabs are used to store heat and coolness at different times of the year to provide comfortable and stable temperatures
Winter NightWhen the internal air temperature drops, heat stored in the
concrete is emitted back into the room
Winter night
27
Importance of the Hollow Core Ceiling Slabs
The concrete hollow core ceiling slabs are used to store heat and coolness at different times of the year to provide comfortable and stable temperatures
Cold air
Cold air
Draws out the heat accumulated during
the dayCools the slabs to act as a cool store the following day
Summer night
Summer Night – night ventilation/free cooling
28
Importance of the Hollow Core Ceiling Slabs
The concrete hollow core ceiling slabs are used to store heat and coolness at different times of the year to provide comfortable and stable temperatures
Warm air
Warm air
Summer DayPre-cools the air before entering the
occupied spaceThe concrete absorbs and stores
the heat – like a radiator in reverse
Summer day
29
• Heating energy requirement is strongly dependant on External Temperature.
• Thermal Lag in Heavy Weight Buildings means consumption requirements lags external temperature.
• Correlation with temperature suggests a thermal lag of ~ 8 hours.
• Potential for predictive controls based on weather forecasts
0
20
40
60
80
100
120
140
160
180
-2 0 2 4 6 8 10 12 14 16 18 20
Mean External Temperature (oC)
Gas
Con
sum
ptio
n (k
Wh/
day)
0.840.850.860.870.880.890.9
0.910.920.93
0 2 4 6 8 10 12 14 16 18 20 22 24
Time Lag (hours)
Coe
ffic
ient
of
Cor
rela
tion
Thermal Properties of Buildings
Data collected 10th December 2006 – April 29th 2007
30
The Energy Signature from the Old and the New Heating Strategies
0
200
400
600
800
1000
-4 -2 0 2 4 6 8 10 12 14 16 18
Mean external temperature over a 24 hour period (degrees C)
Hea
tin
g an
d h
ot-w
ater
co
nsu
mp
tion
(k
Wh
/day
)
New Heating Strategy Original Heating Strategy
The space heating consumption has reduced by 57%
Good Management has reduced Energy Requirements
800
350
Acknowledgement: Charlotte Turner
But this has only been possible because of realtively heavy weight construction
31
As Built 209441GJ
Air Conditioned 384967GJ
Naturally Ventilated 221508GJ
Life Cycle Energy Requirements of ZICER as built compared to other heating/cooling strategies
Materials Production
Materials Transport
On site construction energy
Workforce Transport
Intrinsic Heating / Cooling energy
Functional Energy
Refurbishment Energy
Demolition Energy
28%54%
34%51%
61%
29%
32
0
50000
100000
150000
200000
250000
300000
0 5 10 15 20 25 30 35 40 45 50 55 60
Years
GJ
ZICER
Naturally Ventilated
Air Conditrioned
Comparison of Life Cycle Energy Requirements of ZICER
Compared to the Air-conditioned office, ZICER recovers extra energy required in construction in under 1 year. 0
20000
40000
60000
80000
0 1 2 3 4 5 6 7 8 9 10
Years
GJ
ZICER
Naturally Ventilated
Air Conditrioned
Comparisons assume identical size, shape and orientation
33
• Top floor is an exhibition area – also to promote PV
• Windows are semi transparent
• Mono-crystalline PV on roof ~ 27 kW in 10 arrays
• Poly- crystalline on façade ~ 6/7 kW in 3 arrays
ZICER Building
Photo shows only part of top
Floor
34
Arrangement of Cells on Facade
Individual cells are connected horizontally
As shadow covers one column all cells are inactive
If individual cells are connected vertically, only those cells actually in shadow are affected.
35
Use of PV generated energy
Sometimes electricity is exportedInverters are only 91% efficient
Most use is for computers
DC power packs are inefficient typically less than 60% efficientNeed an integrated approach
Peak output is 34 kW
36
EngineGenerator
36% Electricity
50% Heat
GAS
Engine heat Exchanger
Exhaust Heat
Exchanger
11% Flue Losses3% Radiation Losses
86%
efficient
Localised generation makes use of waste heat.
Reduces conversion losses significantly
Conversion efficiency improvements – Building Scale CHP
61% Flue Losses
36%
efficient
37
Conversion efficiency improvements
1997/98 electricity gas oil Total
MWh 19895 35148 33
Emission factor kg/kWh 0.46 0.186 0.277
Carbon dioxide Tonnes 9152 6538 9 15699
Electricity Heat
1999/2000
Total site
CHP generation
export import boilers CHP oil total
MWh 20437 15630 977 5783 14510 28263 923Emission
factorkg/kWh -0.46 0.46 0.186 0.186 0.277
CO2 Tonnes -449 2660 2699 5257 256 10422
Before installation
After installation
This represents a 33% saving in carbon dioxide
38
Conversion efficiency improvements
Load Factor of CHP Plant at UEA
Demand for Heat is low in summer: plant cannot be used effectivelyMore electricity could be generated in summer
39
Conversion efficiency improvements
Condenser
Evaporator
Throttle Valve
Heat rejected
Heat extracted for cooling
High TemperatureHigh Pressure
Low TemperatureLow Pressure
Heat from external source
Absorber
Desorber
Heat Exchanger
W ~ 0
Normal Chilling
Compressor
Adsorption Chilling
19
40
A 1 MW Adsorption chiller
• Adsorption Heat pump uses Waste Heat from CHP
• Will provide most of chilling requirements in summer
• Will reduce electricity demand in summer
• Will increase electricity generated locally
• Save 500 – 700 tonnes Carbon Dioxide annually
41
Target Day
Results of the “Big Switch-Off”
With a concerted effort savings of 25% or more are possibleHow can these be translated into long term savings?
42
The Behavioural Dimension
Electricity Consumption
0
200
400
600
800
1000
1200
0 1 2 3 4 5 6 7No. people
Ave
rage
kW
h/m
onth
• Household size has little impact on electricity consumption.
• Consumption varies by up to a factor of 9 for any given household size.
• Allowing for Income still shows a range of 6 or more.
• Education/Awareness is important
43
Conclusions• Hard Choices face us in the next 20 years
• Effective adaptive energy management can reduce heating energy requirements in a low energy building by 50% or more.
• Heavy weight buildings can be used to effectively control energy consumption
• Photovoltaic cells need to take account of intended use of electricity use in building to get the optimum value.
• Building scale CHP can reduce carbon emissions significantly
• Adsorption chilling should be included to ensure optimum utilisation of CHP plant, to reduce electricity demand, and allow increased generation of electricity locally.
• Promoting Awareness can result in up to 25% savings
• The Future for UEA: Biomass CHP? Wind Turbines?
Lao Tzu (604-531 BC) Chinese Artist and Taoist philosopher
"If you do not change direction, you may end up where you are heading."