The infuriating inconsistency of network electricity carbon

intensity

Andrew Peacock

Heriot Watt University

World Resources Institute recommend that the grid electricity emission reduction factor should be calculated thus:

ERbaseline = ω.BM + (1-ω).OM

CO2 Emissions Saving Methodology

World Resources Institute recommend that the grid electricity emission reduction factor should be calculated thus:

ERbaseline = ω.BM + (1-ω).OM

CO2 Emissions Saving Methodology

BM – Build Margin emission rate

Assumes that the electricity reduction measure will reduce the need for future capacity

A proportion of the reduction is then assigned to the deferment of this added capacity

FIRST CONFUSION

What new plant is planned in the UK?

Installed Plant in the UK (2007/8)

0

5

10

15

20

25

30

35

40

45

Coal CCGT Nuclear Interconnector Wind

Ins

talle

d C

ap

ac

ity

(G

W)

Source: National Grid 7 year statement, 2007

Planned new plant (2013/14)

0

5

10

15

20

25

30

35

40

45

Coal CCGT Nuclear Interconnector Wind

Ins

talle

d C

ap

ac

ity

(G

W)

Source: National Grid 7 year statement, 2007

Planned new plant (to 2020)

However

Coal – 14.2 GW of new coal plant is in various stages of development

Build Margin emission rate for;

Coal (45% efficient plant) 0.776kgCO2/kWh

CCGT (50% efficient plant) 0.412kgCO2/kWh

Will coal be resurgent? Principal uncertainty – 3rd Revision of the EU Emission trading scheme

DEFRA Guidance 2007 – Build Margin Rate = 0.43kgCO2/kWh (Assumed for a CCGT Plant)

World Resources Institute recommend that the grid electricity emission reduction factor should be calculated thus:

ERbaseline = ω.BM + (1-ω).OM

CO2 Emissions Saving Methodology

World Resources Institute recommend that the grid electricity emission reduction factor should be calculated thus:

ERbaseline = ω.BM + (1-ω).OM

CO2 Emissions Saving Methodology

Operating Margin Emission Factor

Assumes that the electricity reduction measure will reduce demand

SECOND CONFUSION

What carbon intensity do we assign to the negawatts?

0.41

0.43

0.45

0.47

0.49

0.51

0.53

0.55

0.57

1994 1996 1998 2000 2002 2004 2006 2008Av

era

ge

an

nu

al c

arb

on

inte

ns

ity

(k

gC

O2/k

Wh

)System Average Carbon Intensity

0.41

0.43

0.45

0.47

0.49

0.51

0.53

0.55

0.57

1994 1996 1998 2000 2002 2004 2006 2008Av

era

ge

an

nu

al c

arb

on

inte

ns

ity

(k

gC

O2/k

Wh

)System Average Carbon Intensity

DEFRA Guidance – 5 Year rolling average – 0.523kgCO2/kWh

Not all plant will respond

If we exclude nuclear – approximate “load following”

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0.85

1994 1996 1998 2000 2002 2004 2006 2008

Ca

rbo

n in

ten

sit

y (

kg

CO

2/k

Wh

)

5 year rolling average = 0.671kgCO2/kWh

Different Carbon intensities that could be used

Factor Description Carbon Intensity (kgCO2/kWh)

BM Efficient Coal Plant 0.776

Efficient CCGT Plant 0.412

DEFRA (CCGT plant) 0.430

OM System average 0.523

Annual “Load following” 0.671

World Resources Institute recommend that the grid electricity emission reduction factor should be calculated thus:

ERbaseline = ω.BM + (1-ω).OM

CO2 Emissions Saving Methodology

World Resources Institute recommend that the grid electricity emission reduction factor should be calculated thus:

ERbaseline = ω.BM + (1-ω).OM

CO2 Emissions Saving Methodology

Third Confusion Weighting factor,

GuidanceWeighting Factor,

CFL Lighting Solar Panel – 1.5kW

DEFRA 0 0.5

World Resource Institute

0.92 0

Third Confusion Weighting factor,

Approx 2.9GW of maximum system peak demand is due to domestic lighting.

This will fall to approx 1.45GW with banning of incandescent bulbs in 2010

-200

0

200

400

600

800

1000

1200

0 4 8 12 16 20 24

Time of day (h)

An

nu

al e

ne

rgy

de

ma

nd

(k

Wh

)

Import Export Demand

No effect on system capacity

GuidanceWeighting Factor,

CFL Lighting Solar Panel – 1.5kW

DEFRA 0 0.5

World Resource Institute

0.92 0

Effect on savings from CFL Lighting and Solar-PV

0

100

200

300

400

500

600

700

800

900

CFL Lighting Solar PV

CO

2 s

av

ing

s p

er

ins

talla

tio

n

(kg

CO

2 p

a)

Using DEFRA Guidance

Effect on savings from CFL Lighting and Solar-PV

0

100

200

300

400

500

600

700

800

900

CFL Lighting Solar PV

CO

2 s

av

ing

s p

er

ins

talla

tio

n

(kg

CO

2 p

a)

Can be 76%

higher

Can be 53%

higher

Spread of possible BM and OM figures

Conclusions

Deriving a simple number for Carbon intensity of network electricity that suits all technologies is impractical and will mislead

The recognised international metric discussed here could be employed

One approach might be to assign factors to technologies based on this standard procedure

This has been a talk largely about the present – the future is more difficult still

Further Complication Time variant nature of carbon intensity

0

10

20

30

40

50

60

Time of day

De

ma

nd

(G

W)

nuclear coal ccgt gas turbine chp Interconnector oil pumped storage

Wednesday 26th January 2005

0.50

0.52

0.54

0.56

0.58

0.60

0.62

0 4 8 12 16 20 24

Time of day (h)

Ca

rbo

n in

ten

sit

y (

kg

CO

2/k

Wh

)

0

10

20

30

40

50

60

De

ma

nd

(G

W)

Time variant nature of carbon intensity

Wednesday 26th January 2005

Demand side response to reduce gradient change has the capacity to alter operating protocols that could yield reductions in CO2 intensity of network electricity

Time variant nature of carbon intensity