Thermal Envelopes
and
Heating Systems
UCL, 29 November 2011
David Olivier
What I Shall Talk About
•Greater Energy Efficiency in Heating
•Concern over Current Policy
•Case Studies/Proposed Projects, UK &
Denmark
More detail in the forthcoming report:
LESS IS MORE: Energy Security After Oil.
Greater Energy Efficiency -
Heating
Reduce the quantity of heat consumed; e.g. insulate the
walls, upgrade the windows and draughtproof a building to
reduce its heat loss. Some allowance in current policy.
Match the quality of energy supplied to the demand; e.g.,
replace a gas-fired heat-only boiler or electric resistance
heating by waste heat from gas CHP or perhaps heat pumps.
But c
urrent policy stresses “decarbonisation of electricity”.
The combination. Can reduce consumption of high-grade
energy and CO
2
emissions by 99%. But “just” 95% would be
Lower Heat
Consumption
0
50
100
150
200
250
300
350
400
450
500
Old, uninsulated
Typical 2000s
MINERGIE/Silver Low En. Class 2 Low En. Class 1
Passivhaus
Calculated for a 120
m
2
two-storey
well-heated detached
house, using PHPP
kWh/m
2
.yr
.
Space Heat Consumption of a
Dwelling, Different Heat Loss Levels
Good and best practice reduces emissions
95-97% versus “worst practice”, 70-88% vs.
“2000s average practice”.
Sources:
Old uninsulated
and 2000s
construction -
author’s estimate
MINERGIE - Swiss
government
standard, IP jointly
owned by the 26
cantons
Silver - AECB, the
Sustainable Bldgs
Assocn.
Low Energy Class
I and II - Danish
government
standards
Passivhaus -
standard - PHI,
Darmstadt,
Germany
0
0.2
0.4
0.6
0.8
1
1.2
GHG Emissions of Various Space and
Water Heating Systems
kg CO2 equiv. per
kWh of heat
CHP/DH
systems
oil and gas
boilers
elec. heat
pumps
electric
resistance
heating
NOTE: In line with recent work on the
subject, this chart includes the combustion
CO
2emissions of biomass heating systems.
wood-and
coal-fired
boilers
Lower-CO
2
Heat
Good practice reduces emissions
80-90% versus current practice.
Scope for Enhanced Thermal Comfort
0
100
200
300
400
500
600
700
800
14
15
16
17
18
19
20
21
22
23
24
25
Heat consumption
kWh/m
2
.yr.
UK heating season
mean temp.
Danish mean heating
season temp.
Mean daily temperature
o
C
Space Heat Consumption Versus
Mean Internal Temperature
120 m
2
detached house
Red - uninsulated existing stock
Orange - estd. 2000s construction
Blue - MINERGIE or Silver
0
500
1000
1500
2000
2500
3000
3500
4000
4500
14
15
16
17
18
19
20
21
22
23
24
25
120 m
2
detached house
Mean daily temperature
o
C
Red - uninsulated existing stock
Orange - estd. 2000s construction
Blue - MINERGIE or Silver
Green - Passivhaus
Space Heating Fuel Cost Versus
Mean Internal Temperature
Oil cost , ex-tax and duty £/yr.
Rural Fuel Poverty?
Fuel cost, oil condensing boiler.
Excludes servicing/maintenance, DHW
and household electricity costs.
Space Heating Load
Duration Curve
Danish 145 m
2
detached
bungalow. Low Energy
Class 1; i.e., near to
Passivhaus Standard.
All space heating load duration curves have the same basic shape. A lower
specific heat loss, or lower cooling time constant, tends to reduce the load
factor. These are close to daily mean values, not hourly values.
Concerns over UK Policy
Energy Economics - Money Meets Energy
The resource demands of different technologies vary widely. Energy
options are being pursued which are up to 30 times more capital-intensive
than today’s offshore oil supply (£ per delivered kW).
“A senior oil industry representative ... stated that 2004 was the ‘inflection point’
when global conventional oil production plateaued and oil stopped being cheap.
The speaker affirmed that the supply flow is more important than reserves and that
we know that $150[/barrel] oil ‘breaks the machine’ so that the global economy
cannot function above that price. ‘It does not matter how much oil is left if we can’t
afford it.’ ”
Account of 2010 peak oil summit.
Unless we are selective and invest promptly in high-EROEI resources, we
may risk perpetuating the economic problems.
Money Meets Energy: An Exponential Economics Primer
http://www.tullettprebon.com/announcements/strategyinsights/notes/2010/SIN2010
1116.pdf
(November 2010).
Concerns over UK Policy
Future Network Stability
• 94% of domestic space heating is from natural gas, oil,
LPG and coal - in built-up areas, mainly gas; in rural areas,
mainly oil.
•The gas network allows considerable energy storage.
• Heat networks, if used, can increase the pumping rate and
the flow temperature to meet peaks. Bulk heat storage is
cheap; some small cities have 100,000 m
3
hot water stores
on their DH network.
• With electricity networks, storage is costly and network
losses rise with load.
1970s Low-Rise Dwellings, London
C
avity-walled, solid ground-floored housing before and after proposed TSB
RFF retrofit. CO
2
emissions would fall 82% at ~£10k per dwelling in
widespread use for the thermal measures. Construction probably typical of
30-40% of existing dwelling stock.
•
CWI and roof insulation with
airtight material
•
Gas 500 kW(e) recip. engine
CHP, extend existing scheme,
add summer solar
•
Reglaze existing windows
when sealed units wear out
•
MEV not MVHR
•
Highly energy-efficient lights,
A++ appliances & pumps, including
CHP heat for clothes drying
•
Highly-insulated new DHW
tank and piping with improved heat
exchanger
MACC for Measures Analysed
Existing Typical Urban or Suburban Semi-Detached House
-400
0
400
800
1200
1600
2000
2400
2800
3200
3600
4000
4400
4800
5200
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
COST OF MEASURE (£/tonne)
NOTE: Base case emissions = 8.50 tonnes/year.
CUMULATIVE SAVING (tonnes/year)
NOTES:
1 More energy-efficient hot-fill dishwasher 2 More energy-efficient lighting
3 More energy-efficient refrigerator-freezer 4 Cavity wall insulation, 50 mm PU foam 5 More energy-efficient LED TVs
6 More energy-efficient hot-fill washing machine 7 Condensing boiler and compensation controls
8 Windows - replace failing doubled-glazed sealed units by argon-filled low-e warm-edge sealed units
9 More energy-efficient central heating pump 10 Gas-fired combined heat and power and heat mains
11 Windows - upgrade replacement sealed units to optimum low-e coating 12 Horizontal external perimeter insulation of ground floor, 50 mm XPS 13 MEV, miscell. draughtproofing and replace electric clothes drying by CHP heat 14 Roof, add 50 mm PU foam between rafters
15 Add solar to DH system 16 Insulate DHW system
17 External wall insulation, increase from 50 to 100 mm graphitised EPS 18 Roof, increase from 50 to 100 mm PU foam
19 Roof increase from 100 to 120 mm PU foam, with 20 mm covering rafters 20 Perimeter insulation, increase from 50 to 100 mm XPS
21 External wall insulation, increase from 100 to 150 mm EPS 22 Windows, replacement high-performance double glazing
23 External wall insulation, install 50 mm graphitised EPS, directly-rendered
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