Kurnitski Clima2010 plenary

Accounting CO2 emissions for electricity and district heat used in buildings – a scientific method to define energy carrier factors

Jarek Kurnitski

11.5.2010

CLIMA 2010

Senior Lead, Built EnvironmentSitra, the Finnish Innovation FundAdjunct Professor, Aalto University

© Sitra 2010

Assessment of emissions caused by energy used in buildings• Buildings use energy measured or calculated in kWh-s• The use of 1 kWh energy can cause very different emissions or

primary energy use, depending on production sources• This is usually taken into account with energy carrier factors in energy

performance regulation

Two main purposes of this assessment:• Estimate actual CO2-emissions or primary energy use caused by

energy production – can be calculated from energy statistics• Regulative purpose, derivation of energy carrier factors used in energy

performance requirements of building codes• Regulation has to take into account demand and capacity changes in

the market and direct construction according to energy policy

11.5.2010Jarek Kurnitski

© Sitra 2010


EN 15603 – General framework for the assessment of energy performance (EP) of buildings

• EP-rating sums up all delivered energy (electricity, district heat/cooling, fuels) into a single rating with relevant weighting factors (EN 15603)

• Relevant weighting factors for energy sources (energy carriers) are the key issue for accountable energy performance requirements

Delivered energy Building A Building B

Electricity, kWh/(m2 a) 100 50

District heat, kWh/(m2 a) 50 100

Total, kWh/(m2 a) 150 150

• With weighting factors based on CO2 emissions (example):

Delivered energy Building A Building B

Electricity, kWh/(m2 a) 100*2 50*2

District heat, kWh/(m2 a) 50*0.8 100*0.8

Total, kWh/(m2 a) 240 180

EP ≤ 200

© Sitra 2010

Energy ratings

• EN 15603: calculation of energy ratings in terms of primary energy, CO2 emissions or parameters defined by national energy policy

• Based on net delivered energy (by all energy carriers), weighted energy rating (primary energy or CO2 emission) is calculated (used in majority of member states)


Other services cause often

confusion as they are not included in the rating in all

countries

© Sitra 2010

Calculation of CO2 emissions and primary energy

Emissions [kgCO2] =energy flow [MWh] x specific emission factor [kgCO2/MWh]Primary energy = energy flow [MWh] x primary energy factor [-]Weighted energy rating = energy flow [MWh] x energy carrier factor [-]

• Example house with 18 MWh natural gas and 7 MWh electricity use:18 MWh * 200 kgCO2/MWh = 3600 kgCO2 = 3,6 tCO2 (natural gas)7 MWh * 300 kgCO2/MWh = 2100 kgCO2 = 2,1 tCO2 (electricity)in total 5,7 tCO2 per year

• Alternatively this calculation can be done with relative energy carrier factors defined in relation to some reference (gas), i.e. 1.0 for gas and 1.5 for electricity, to use kWh-units


© Sitra 2010

Primary energy

• Primary energy use refers to the use of natural resources1

• Primary energy factor for fossil fuels is 1.0 if extraction, refinery, transport etc. are not taken into account

• 1/0.4=2.5 for electricity generated from fossil fuel with efficiency of 40% • Usually, only non-renewable primary energy is considered (i.e. the factor is

close to zero for hydropower, wind, solar)• Nuclear energy is difficult to treat within primary energy concept:

- Primary energy factor depends on the selection, which energy (thermal or electrical) is used as the primary energy form

- Thermal efficiency of 33% leads to primary energy factor of 3.0 (IEA, Eurostat) and if electricity is used as the first energy form, primary energy factor will be 1.0 (UNSD)


1Definition (for a building): Non-renewable primary energy is the non-renewable energy used to produced the energy delivered to the building. It is calculated from delivered energy amounts of energy carriers, using conversion factors (EN 15603:2008).

© Sitra 2010


3,43,03,0

2,92,82,82,82,7

2,72,6

2,52,52,5

2,42,3

2,22,2

2,12,0

1,91,91,9

1,71,5

1,51,5

1,41,3

1,00,7

0,0

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0

MaltaCzech Republic

BulgariaLithuania

PolandEstoniaCyprus

HungaryGreeceFrance

BelgiumSlovakiaRomaniaSlovenia

GermanyEU-27

United KingdomNetherlands

FinlandIreland

SpainDenmark

ItalyLatvia

PortugalSweden

LuxemburgSwitzerland

Finland, Sweden, NorwayAustria

Norway

primary energy factor MWhprimary/MWhgross_electricity

Primary Energy Factors of Electricity Generation in Europe in 2006source: Eurostat 2009 (Eurostat primary energy conventions), non-renewable only

© Sitra 2010


1 1631 051

943941

816771

747714

601571

519502498

463456

448436

417388

352324

292283

228206

18288

8127

63

0 200 400 600 800 1000 1200 1400

EstoniaPolandGreece

MaltaCzech Republic

CyprusBulgariaRomaniaDenmarkGermany

NetherlandsIreland

United KingdomSloveniaHungary

ItalyEU-27

PortugalSpain

FinlandLatvia

LuxemburgSlovakiaBelgiumAustria

LithuaniaFinland, Sweden, Norway

FranceSweden

SwitzerlandNorway

specific CO2-emissions kg(CO2)/MWhnet

Specific CO2-emissions of Electricity Generation in Europe in 2006sources: Eurostat 2009 (IPCC default emission factors)

© Sitra 2010


CO2-emissions vs. primary energy concept

• Assessment of emissions vs. use of energy sources (primary energy)• Nuclear energy causes the major difference, as the primary energy

factor depends on the definition by factor 3• For other energy carriers, weighting factors are very similar

independently of the use of primary energy or CO2 approach (if calculated as relative to some reference, e.g. oil)

• ⇒ somewhat higher weighting factor for electricity if primary energy approach is used

• Use of CO2 emissions makes it more complicated to determine weighting factors for mix of many production sources, as shown in the following

© Sitra 2010

Variation of primary energy factors

Four possible definitions:A. total primary energy and nuclear energy with 33% efficiency (IEA &

Eurostat definition)B. non-renewable primary energy and nuclear energy with 33%

efficiency (IEA & Eurostat definition)

C. total primary energy and nuclear energy with 100% efficiency (UNSD definition)

D. non-renewable primary energy and nuclear energy with 100% efficiency (UNSD definition)


© Sitra 2010

Primary energy factors for electricity generation in Finland, definitions A to D


© Sitra 2010


Primary energy factors for district heat in Finland, definitions A to D

© Sitra 2010

Non-renewable primary energy factors (definition B) in Finland (blue electricity and red district heat)


© Sitra 2010

Why primary energy factors are almost constant in the long run?• Major changes in Finnish energy production until 2030:

- Significantly increased share of nuclear energy- CHP is used as much as today, almost constant district heat production- Increased use of renewables (wind, bio, solar), as much as technically

feasible, but still less dominating than nuclear or CHP

• With IEA and Eurostat definition, primary energy equivalent of nuclear and conventional condensing power very similar, so, the compensating of condensing power will even slightly increase primary energy factor (40% vs. 33% efficiency)

• ⇒ cutting emissions with nuclear energy has no effect on primary energy factor…


© Sitra 2010


Regulatory aspects

Energy performance regulation:• Controlling and directing the demand change• How much and which energy is used in buildings• Straightforward for new buildings, more complicated for existing

• Regulation is often not directly linked to policies for energy production, however the both are important:- Regulation generates demand change in the existing market with

consequences for developments in the production side- Obviously to be fitted together so that emissions can be reduced most

efficiently

• Buildings account for 41% of primary energy use in EU (Eurostat) being the largest single potential for energy savings

© Sitra 2010


Finnish case study to determine emission based energy carrier factors including demand-capacity coupling effects

• CO2-emissions from electricity generation and district heat production:- Hourly data of specific emissions from 2000-2007- Demand change analyses for electricity use- Demand change analyses for district heating use- Coupling with new capacity – scenarios- Derivation of energy carrier weighting factors based on energy system

scenario calculations to show how much one energy carrier is causing more emissions than another

© Sitra 2010


Electricity generation in Finland 2007 (GWh), in total 78 TWh(Statistics Finland)

Hydro power1399118 %

Wind power1880 %

Separate conventional

thermal power1437718 %

Nuclear energy2250129 %

Industrial CHP electricity

1143015 %

CHP electricity1533020 %

Electricity generation in Finland

Electricity generation, average specific emission 2000-2007: 273 kg(CO2)/MWh

894 kg(CO2)/MWh

439 kg(CO2)/MWh

0 kg(CO2)/MWh

0 kg(CO2)/MWh District heat production, average specific emission 2000-2007: 217 kg(CO2)/MWh

220 kg(CO2)/MWh

© Sitra 2010


Total emissions of electricity and district heat production 2007 (milj.t CO2),in total 34.9 milj.t CO2

(Statistics Finland)

Total generation of conventional thermal

power21.762 %

Total production of district heat

7.321 %

Total production of industrial steam

5.917 %

Total emissions of electricity generation 2007 (milj.t CO2), in total 21.7 milj.t CO2

(Statistics Finland)

Industrial CHP electricity

2.210 %

Separate conventional thermal power

12.859 %

CHP electricity6.7

31 %

Emissions of heat and power production(calculated with benefit allocation method)

• Electricity generation in Finland 2007: 78 TWh• District heat and industrial steam production 2007: 95 TWh

© Sitra 2010


Specific CO2 emissions of total electricity generation as a function of conventional thermal power 2006–2008

0

50

100

150

200

250

300

350

400

450

0 500 1000 1500 2000 2500 3000 3500 4000

Separate conventional thermal power, MWe

Spec

ific

CO2 e

mis

sion

s, k

g(CO

2)/M

Wh

Specific emissions calculated with benefit allocation method (Energy Statistics Finland 2008)

© Sitra 2010

Just use average specific emission factors?

• Average specific CO2-emissions 2000-2007:- 273 kg(CO2)/MWh) for electricity- 217 kg(CO2)/MWh) for district heat

• Or average relative energy carrier factors (previous ones divided by reference specific emission of oil 267 kg(CO2)/MWh)):- 1.0 for electricity- 0.8 for district heat- (reference: 1.0 for oil)

• These average factors would probably lead to increased use of electricity in buildings (electrical heating etc.) as 1.0 is very low compared to common primary energy factor of 2.5 for electricity

• What was not taken into account?


© Sitra 2010

Higher factor for electricity in winter?

• Hypotheses: peak loads cause higher specific emissions in the production

• Can be easily tested with hourly data


© Sitra 2010


Specific CO2 emissions of total electricity generation as a function of outdoor temperature 2006–2008

• Generation of separate conventional thermal power in Finland can be high in summer period due to shortage of hydro power and lack of CHP which is generated against heat load of district heating + service breaks of nuclear power plants

0

50

100

150

200

250

300

350

400

450

-26 -22 -18 -14 -10 -6 -2 2 6 10 14 18 22 26 30

Outdoor temperature at Helsinki, °C

Spec

ific

CO2 e

mis

sion

s, k

g(CO

2)/M

Wh

© Sitra 2010

Demand change analyses (emissions response to a step change in the demand)

• In the electricity production especially carbon-neutral capacity is limited• District heat CHP is produced against heat load without similar lack of

capacity (demand change has no effect on the specific emission)• Construction of new buildings or renovation of existing ones means

changes in the demand responded by electricity market• To account emissions of the step change we need to know a link between

a new or non-appearing energy use in a building and energy production source (i.e. which type of plant will generate or is cutting down this energy production)


+ or – step change in electricity or district heat

Change in emissions ?

© Sitra 2010


Demand change of electricity: allocation according to variable cost• The change in the demand is allocated typically to the production

source with highest variable cost as production sources have limited generation capacity and different variable cost

• Similar order of variable costs for the whole EU and Finland• Hourly calculation: if enough generation capacity with lower variable cost is

available, then the demand change will be allocated to that capacity (CHP or hydro).

© Sitra 2010


Results for current situation (2007)

• Results show that during 90% of the time of the year the demand change will be allocated to the separate conventional thermal power, 2% to CHP and the rest for carbon-neutral production (not shown in the Table).

• This means that an hourly weighted specific emissions by new or non-appearing electricity use is as high as 814 kg(CO2)/MWh that is average emission of total generation by factor 3.

Specific CO2 emissions by new or non-appearing electricity use (demand change) for current situationCurrent situation (year 2007) Total

electricity generation


thermal power

CHP electricity generation

Industrial CHP

Weighted average specific

emission

Specific emission kg(CO2)/MWh 279 893 439 190 814

Share of the demand change 90 % 2 % 0 %

Current situation (year 2007) Total electricity generation


thermal power


Industrial CHP


emission



© Sitra 2010


Scenario of 1600 MW new nuclear energy

• We calculated a simple scenario, where new 1600 MW of nuclear energy will replace only separate conventional thermal power with no changes in energy demand structure (calculated with 2007 data)

• 1600 MW new nuclear power decreased an average specific emission by almost of factor 2, but the ratio of the demand change and average specific emission values even increased to 3.4.

Specific CO2-emissions of the demand change for the scenario where 1600 MW new nuclear energy replaces only separate conventional thermal power

1600 MW new nuclear power replaces only separate conventional thermal power

Total electricity generation


thermal power


Industrial CHP


emission



1600 MW new nuclear power replaces only separate conventional thermal power

Total electricity generation


thermal power


Industrial CHP


emission



© Sitra 2010


Energy carrier factors for demand change relative to specific CO2-emission of oil

Specific CO2-emissions of district heating and electricity (weighted average) relative to light fuel oil (heating fuel oil) CO2-emission factor

Light fuel oil(heating fuel oil)

Electricity(weighted averagespecific emission)

Districtheating

Current situation (year 2007)

Specific emission kg(CO2)/MWh 267 814 219

Energy carrier factor 1 3.0 0.8

1600 MW new nuclear powerreplaces only separate

conventional thermal power



Light fuel oil(heating fuel oil)

Electricity(weighted averagespecific emission)

Districtheating

Current situation (year 2007)



1600 MW new nuclear powerreplaces only separate

conventional thermal power



• When calculated with 2006 data, the emissions are slightly higher for electricity, leading to factor of 2.1 instead of 1.7 (and 3.2 instead of 3.0)

© Sitra 2010

Energy carrier factors for selected scenarios

How to quantify the factors between average and demand change values?


0

100

200

300

400

500

600

700

800

900

2005 2010 2015 2020 2025 2030

Spec

ific e

mis

sion

, kgC

O2/

MW

h

Electricity, basic scenario Electricity, "less nuclear"

Electricity, "more nuclear" District heat estimate

Demand change of electricity

© Sitra 2010


Demand change in district heating energy use • The total CO2 emissions of Finnish electricity generation and district heating

production if electricity use is kept constant, but district heating is reduced (e.g. additional insulation of existing multi-storey buildings) or increased

• ⇒ Due to CHP, the total emissions do not depend on the amount of district heat used

0

5

10

15

20

25

30

0.5 0.6 0.7 0.8 0.9 1 1.1 1.2 1.295 1.3 1.4 1.5

Ratio of the district heat demand change (1 = current situation, 0.5 = 50% reduction, 1.5 = 50% increase)

Tota

l em

issi

ons o

f ele

ctric

ity a

nd d

istr

ict h

eat

prod

uctio

n, m

ilj. t

CO

2

Electricity generation District heat production

© Sitra 2010


District heat replacing electricity use or vice versa • The total use of electricity and district heat is kept constant:

- The ratio of 1 corresponds to the current situation, the ratio 0.5 means that half of current district heating energy used is replaced by electricity use and 2 that the current district heating use is doubled and electricity use reduced correspondingly

• ⇒ Replacing district heat by electrical heating drastically increases total emissions

© Sitra 2010

Demand change analyses with flexible capacity

• Main principle: energy system model allowing both changes in the demand and production capacities, annual balance calculation

1. Select reference electricity and district heat production (e.g. 90 TWh el. and 33 TWh DH, repeat the calculation for other relevant values)

2. Define rules for production sources/capacities allowing to introduce new capacity to cover increased demand:

- production sources with fixed capacity, hydro and nuclear (fixed capacity can be selected as input parameter)

- production sources with flexible capacity, in this case condensing power and CHP- limits for district heat produced by CHP, 70…80% in this case- wind power and solar electricity fixed in this case, but can be treated with similar

rules if considered flexible

3. Introduce a step change of heat and electricity demand (+3 TWh in this case) and solve energy production balance by minimizing emissions or production cost

4. Results: emissions and cost caused by +3 TWh electricity or heat production ≡ specific emission factors of the studied scenario


© Sitra 2010

Finnish case study

• +3 TWh step change of heat or electricity demand• 80 and 90 TWh reference electricity production and 33 TWh district heat

production• Flexible capacity of separate condensing power and CHP• Nuclear energy capacity fixed, several capacity values calculated• Hydropower and wind power fixed • Limits for district heat produced by CHP, to be between 70 and 80%Specific emission (energy method) and cost data used:


Production source Fuel costmilj. EUR/TWh

Specific emissionkgCO2/MWh

Nuclear energy 5 0

Separate condensing power 25 900

CHP electricity 15 300

CHP district heat 18 300

Separate district heat 22 225

© Sitra 2010

Emissions by + 3 TWh with flexible capacity

• + 3 TWh electricity increased emissions by factor of 4,0 relative to + 3 TWH district heat (0.68 Mt vs. 2.7 Mt)

• This factor of 4 would change to 3, if separate district heat production is not used• Results confirm that relevant selection of energy carrier factor for electricity should

be close to the demand change values, not average values of specific emissions


0

5

10

15

20

25

30

35

40

45

50

CO2-e

mis

sion

s, M

t

22,5 TWh nuclear energy 35,5 TWh nuclear energy

El. 9

0 TW

hDH

33

TWh

+3 T

Wh

DH

+3 T

Wh

El.

El. 9

0 TW

hDH

33

TWh

+3 T

Wh

DH

+3 T

Wh

El.

© Sitra 2010

Conclusions 1/2

• Energy carrier factors may be based on CO2-emissions, primary energy (usually non-renewable) or on energy policy considerations

• Primary energy factors are relevant for fuels, but for nuclear energy depend by factor 3 on the definition used

• Specific CO2-emissions factors are scientifically sound (independent on definitions), but average factors cannot be used for regulative purposes, because they may guide to increased electricity use, which will consequently increase emissions as shown in the Finnish case study

• Finnish average specific emission based factors (2000-2007):- electricity 1.0 - district heat 0.8- oil 1.0 (reference)

• Average factors for electricity and district heat are very close, but replacing district heat by electrical heating drastically increased total emissions in the Finnish case study and vice versa


© Sitra 2010

Conclusions 1/2• Hourly demand change allocation increased electricity factor from 1.0 to 3.0

and analyses both with fixed and flexible capacity showed that the factor caused by demand change is 3 to 4 times higher than the average one

• Energy system scenario calculations confirmed that relevant selection of energy carrier factor for electricity should be close to the demand change values, not average values of specific emissions

• Using the rule of 3 x average specific emission, one can easily calculate electricity factors for future scenarios, i.e. if the Finnish average factor will be reduced to 0.6 in 2020, the electricity factor will be 1.8

• Proposed Finnish factors are: electricity 2, district heat 0.7, fossil fuels 1.0

• Higher energy carrier factor for electricity means in the energy performance design that electricity is more valuable energy than fuel energy or district heat. Such building regulation will generally promote for more effective electricity use in buildings and limit wasteful use of electricity.

• Energy carrier factors are not constant, as depending on production sources, and are subject of revision with relevant interval of about 5 years


Kurnitski Clima2010 plenary

Education

Transcript of Kurnitski Clima2010 plenary