Earth Notes: A Note On Variations in UK/GB Grid Electricity CO2 Intensity with Time

What is "the" CO2 intensity (emissions) from consuming 1kWh from the national grid?

Analysing GB's Grid Intensity Track Record...

Jump to full-year analysis for: 2009 2010 2011 2012

The first thing to understand is that CO2 emissions or intensity per kWh generated for (and thus drawn from) the grid is not constant; it varies by time of day and by season because of fuel mix and transmission losses and transmission patterns/routes (which means that it also matters slightly where on the grid you draw from).

(Note also that the Northern Ireland grid is closely coupled to the Republic's, and so the numbers presented here are in fact for GB ie England/Scotland/Wales.)

Also, with significant penetration of intermittent renewables such as wind (~5% of peak winter demand 2008/2009 with a target of maybe 50% of peak) then the hour-by-hour intensity is even more volatile and hard to know.

There are several different 'average' values quoted and used too, eg: the UK government's 'aspirational' marginal cost of about 0.43kgCO2/kWh, the DEFRA 3-year rolling average figure (0.52kgCO2/kWh as of 2008/2009), 0.422kgCO2/kWh for grid-supplied electricity and 0.568kgCO2/kWh grid-displaced electricity to compute emissions for UK building regulations (2006, part L).

Incidentally, a working assumption of mine has been that grid CO2 intensity will peak when demand does because everything will be working flat out, including all the 'dirtiest' (most CO2-intense) generators. Clare Hanmer of the Carbon Trust did some work that suggests this is not necessarily so, and also that the diurnal/daily swing in intensity is larger in summer than in winter, given some educated guesses, etc. Part of my reason for this note is to test her interesting assertions! I'm borrowing some of her numbers and assumptions shamelessly.

Data Source: ELEXON

For the GB system, (ie the UK excluding Northern Ireland) ELEXON provides real-time and historical data on a number of grid parameters through the bmreports.com site, including generation by fuel type of plant connected to the high voltage transmission system. This does not by any means represent all generation, and may in particular under-represent wind and other distributed generation that connects at lower voltages and even within the distribution networks.

Total operational metered wind is shown with capacity 1288MW at 2009/03/10, whereas the BWEA lists (for the whole UK) 3301MW capacity. (Site http://www.renewableuk.com/en/renewable-energy/wind-energy/uk-wind-energy-database/ as of 2013/07.)

As at 2009/06/19 the BWEA UKWED database shows 3625MW of operational UK wind capacity and the BWEA's Jan Matthiesen kindly told me that 215MW of that is in Northern Ireland, ie not in the GB grid. At the same time the Elexon GB metered wind capacity is 1426MW, ie ~60% of the UK's operational capacity is embedded and not visible in Elexon's stats, so wind already is a significantly 'distributed' source.

ELEXON has very helpfully licensed me their data to conduct this study and related work.

Sample 1: Late March 2009

For the first 24-hour period that I examined from early March 2009, and ignoring the effects of pumped storage and interconnectors entirely, I saw ~20% variation in intensity in the 'high-voltage' connected generation, and an average for a consumer (including 9% loss in transmission/distribution) of well above the government's 'aspirational' marginal-generation figure and slightly above the 3-year DEFRA rolling-average. The intensity was fairly flat (and high) until about 8pm (after peak demand), and dropped to a low around midnight and rose again to 'high' around 8am, so showing a fairly strong first-order correlation of intensity with demand. There may have been more coal and less nuclear in the mix than typical.

Sample 2: Night of 2009/04/12

This 24-hour period during a bank-holiday weekend shows a 24% variance in kgCO2/kWh; intensity is relatively low because there is relatively little coal in the mix (<20%).

Effective grid carbon intensity for a domestic user is currently 327gCO2/kWh including transmission and distribution losses of 9%.

Latest available grid generation carbon intensity (ignoring transmission/distribution losses) is approximately 300gCO2/kWh at Mon Apr 13 00:55:00 BST 2009 over 26467MW of generation, with a rolling average over 24h of 350gCO2/kWh.

Minimum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 299gCO2/kWh at Mon Apr 13 00:45:00 BST 2009.

Maximum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 389gCO2/kWh at Sun Apr 12 22:05:00 BST 2009.

Average/mean grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 350gCO2/kWh over the sample data set, with an effective end-user intensity including transmission and distribution losses of 382gCO2/kWh.

Recent mean GMT hourly generation intensity gCO2/kWh (average=350); * = now
000102030405060708091011121314151617181920212223*
  • 335
  • 333
  • 327
  • 312
  • 306
  • 302
  • 317
  • 336
  • 357
  • 373
  • 378
  • 382
  • 374
  • 369
  • 365
  • 365
  • 367
  • 367
  • 365
  • 379
  • 383
  • 374
  • 331
  • 304

Overall generation intensity (kgCO2/kWh) computed using the following fuel intensities (other fuels/sources are ignored): CCGT=0.36 COAL=0.91 INTFR=0.09 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.61 WIND=0.0.

Sample 3: Evening of 2009/04/15

For some reason there seems to have been an enormous (~40%) variation min to max; hour-by-hour variation is ~30%. (Overnight intensity then dropped to 289gCO2/kWh making the mean 381gCO2/kWh and variability a whopping 44%!)

Effective grid carbon intensity for a domestic user is currently 425gCO2/kWh including transmission and distribution losses of 9%.

Latest available grid generation carbon intensity (ignoring transmission/distribution losses) is approximately 390gCO2/kWh at Wed Apr 15 21:40:00 BST 2009 over 37690MW of generation, with a rolling average over 24h of 393gCO2/kWh.

Minimum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 310gCO2/kWh at Wed Apr 15 00:15:00 BST 2009.

Maximum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 508gCO2/kWh at Wed Apr 15 20:45:00 BST 2009.

Average/mean grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 393gCO2/kWh over the sample data set, with an effective end-user intensity including transmission and distribution losses of 428gCO2/kWh.

Recent mean GMT hourly generation intensity gCO2/kWh (average=393); * = now
212223000102030405060708091011121314151617181920*
  • 389
  • 335
  • 311
  • 312
  • 312
  • 313
  • 315
  • 341
  • 369
  • 413
  • 440
  • 449
  • 447
  • 447
  • 442
  • 443
  • 444
  • 429
  • 426
  • 425
  • 418
  • 401
  • 410
  • 401

Current/latest fuel mix: CCGT@17709MW COAL@8889MW INTFR@1572MW INTIRL@0MW NPSHYD@269MW NUCLEAR@8581MW OCGT@0MW OIL@0MW OTHER@0MW PS@199MW WIND@471MW.

Overall generation intensity (kgCO2/kWh) computed using the following fuel intensities (other fuels/sources are ignored): CCGT=0.36 COAL=0.91 INTFR=0.09 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.61 WIND=0.0.

Sample 4: Evening of 2009/06/29

As of this sample there had been a potentional time-shifting saving in the last 24 hours of 35%.

Effective grid carbon intensity for a domestic user is currently 460gCO2/kWh including transmission and distribution losses of 9%.

Latest available grid generation carbon intensity (ignoring transmission/distribution losses) is approximately 422gCO2/kWh at Mon Jun 29 20:55:00 BST 2009 over 35535MW of generation, with a rolling average over 24h of 422gCO2/kWh.

Minimum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 324gCO2/kWh at Mon Jun 29 03:10:00 BST 2009.

Maximum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 494gCO2/kWh at Mon Jun 29 14:10:00 BST 2009.

Average/mean grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 422gCO2/kWh over the sample data set, with an effective end-user intensity including transmission and distribution losses of 460gCO2/kWh.

Recent mean GMT hourly generation intensity gCO2/kWh (average=422); *now (=422)
202122230001020304050607080910111213141516171819*
  • 375
  • 375
  • 357
  • 346
  • 344
  • 330
  • 325
  • 329
  • 339
  • 385
  • 438
  • 461
  • 474
  • 474
  • 478
  • 485
  • 491
  • 491
  • 489
  • 487
  • 480
  • 470
  • 460
  • 434
Mean GMT hourly generation GW (all, zero-carbon)
  • 32
  • 9
  • 32
  • 9
  • 29
  • 9
  • 27
  • 9
  • 26
  • 9
  • 26
  • 9
  • 25
  • 9
  • 25
  • 9
  • 25
  • 9
  • 28
  • 9
  • 35
  • 9
  • 39
  • 9
  • 41
  • 9
  • 42
  • 9
  • 42
  • 9
  • 42
  • 9
  • 42
  • 9
  • 42
  • 9
  • 42
  • 9
  • 42
  • 9
  • 42
  • 9
  • 40
  • 9
  • 38
  • 9
  • 36
  • 9

Hours that are basically green, but in which there is draw-down from grid-connected storage with its attendant energy losses and also suggesting that little or no excess non-dispatchable generation is available, ie that are marginally green, are shaded olive.

Current/latest fuel mix at Mon Jun 29 20:55:00 BST 2009: CCGT@16377MW COAL@9820MW INTFR@248MW INTIRL@0MW NPSHYD@135MW NUCLEAR@8539MW OCGT@0MW OIL@0MW OTHER@0MW PS@294MW WIND@122MW.

Current draw-down from storage is 294MW.

Overall generation intensity (kgCO2/kWh) computed using the following fuel intensities (other fuels/sources are ignored): CCGT=0.36 COAL=0.91 INTFR=0.09 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.61 WIND=0.0.

Key to fuel types/names:

CCGT
Combined-Cycle Gas Turbine
INTFR
French Interconnector
INTIRL
Irish Interconnector
NPSHYD
Non-Pumped-Storage Hydro
OCGT
Open-Cycle Gas Turbine
PS
Pumped Storage Hydro

Sample 5: Evening of 2010/01/05

The intensity curve is unusually flat with coal apparently doing load-following (only ~7% min to max, and within a couple of days was down to ~4%), probably because of the gas shortage in the cold weather (with a gas demand of 441m^3/4.9TWh or ~200GW average over the day, causing National Grid to issue a Gas Balancing Alert (GBA) at 13:10 for Gas Day 04/01/2010, and demand went higher still later in the week) and a lack of (nuclear, ie low-carbon) electricity imports from France. There is also a big change in usage given the first two working days back since Christmas.

Effective grid carbon intensity for a domestic user is currently 583gCO2/kWh including transmission and distribution losses of 9%.

Latest available grid generation carbon intensity (ignoring transmission/distribution losses) is approximately 535gCO2/kWh at Tue Jan 05 20:10:00 UTC 2010 over 54357MW of generation, with a rolling average over 24h of 533gCO2/kWh.

Minimum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 513gCO2/kWh at Tue Jan 05 05:00:00 UTC 2010.

Maximum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 549gCO2/kWh at Mon Jan 04 22:05:00 UTC 2010.

Average/mean grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 533gCO2/kWh over the sample data set, with an effective end-user intensity including transmission and distribution losses of 581gCO2/kWh.

Recent mean GMT hourly generation intensity gCO2/kWh (average=533); *now (=535)
212223000102030405060708091011121314151617181920*
  • 546
  • 543
  • 530
  • 525
  • 522
  • 519
  • 519
  • 516
  • 517
  • 528
  • 534
  • 537
  • 536
  • 538
  • 537
  • 537
  • 539
  • 540
  • 539
  • 540
  • 537
  • 540
  • 537
  • 542
Mean GMT hourly generation GW (all, zero-carbon)
  • 51
  • 8
  • 46
  • 8
  • 42
  • 8
  • 42
  • 8
  • 42
  • 8
  • 41
  • 9
  • 40
  • 9
  • 40
  • 8
  • 40
  • 8
  • 44
  • 8
  • 50
  • 8
  • 53
  • 8
  • 54
  • 8
  • 55
  • 8
  • 56
  • 8
  • 56
  • 8
  • 55
  • 8
  • 55
  • 8
  • 54
  • 8
  • 56
  • 9
  • 58
  • 9
  • 56
  • 9
  • 55
  • 9
  • 54
  • 8

Current/latest fuel mix at Tue Jan 05 20:10:00 UTC 2010: CCGT@21678MW COAL@22760MW INTFR@0MW INTIRL@0MW NPSHYD@219MW NUCLEAR@7761MW OCGT@0MW OIL@0MW OTHER@0MW PS@1076MW WIND@863MW.

Current draw-down from storage is 1076MW.

Generation by fuel category:

fossil
44438MW [CCGT, COAL, INTIRL, OCGT, OIL, OTHER]
nuclear
7761MW [INTFR, NUCLEAR]
renewable
1082MW [NPSHYD, WIND]
storage
1076MW [PS]
zero-carbon
8843MW [NPSHYD, NUCLEAR, WIND]

Overall generation intensity (kgCO2/kWh) computed using the following fuel intensities (other fuels/sources are ignored): CCGT=0.36 COAL=0.91 INTFR=0.09 INTIRL=0.7 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.61 WIND=0.0.

Key to fuel codes:

CCGT
Combined-Cycle Gas Turbine
INTFR
French Interconnector
INTIRL
Irish Interconnector
NPSHYD
Non-Pumped-Storage Hydro
OCGT
Open-Cycle Gas Turbine
PS
Pumped Storage Hydro

Sample 6: Evening of 2010/11/26

This was an unseasonably-cold day with the very unusualy circumstance of very flat (~6%) grid intensity (possibly due to exports to France) with peak demand still being in the lowest intensity quartile.

Effective grid carbon intensity for a domestic user is currently 572gCO2/kWh including transmission and distribution losses of 9%.

Latest available grid generation carbon intensity (ignoring transmission/distribution losses) is approximately 525gCO2/kWh at Fri Nov 26 17:55:00 UTC 2010 over 54644MW of generation, with a rolling average over 24h of 533gCO2/kWh.

Minimum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 520gCO2/kWh at Fri Nov 26 04:20:00 UTC 2010.

Maximum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 548gCO2/kWh at Thu Nov 25 20:35:00 UTC 2010.

Average/mean grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 533gCO2/kWh over the sample data set, with an effective end-user intensity including transmission and distribution losses of 581gCO2/kWh.

Recent mean GMT hourly generation intensity gCO2/kWh (average=533); *now (=525)
181920212223000102030405060708091011121314151617*
  • 531
  • 539
  • 545
  • 542
  • 542
  • 536
  • 528
  • 528
  • 528
  • 525
  • 521
  • 527
  • 537
  • 543
  • 544
  • 542
  • 534
  • 531
  • 531
  • 531
  • 534
  • 534
  • 529
  • 524
Mean GMT hourly generation GW (all, zero-carbon)
  • 55
  • 7
  • 53
  • 7
  • 50
  • 7
  • 47
  • 7
  • 43
  • 7
  • 39
  • 7
  • 38
  • 7
  • 37
  • 7
  • 37
  • 36
  • 7
  • 36
  • 7
  • 38
  • 7
  • 42
  • 7
  • 48
  • 7
  • 50
  • 7
  • 52
  • 7
  • 52
  • 7
  • 52
  • 7
  • 52
  • 7
  • 51
  • 7
  • 51
  • 7
  • 51
  • 7
  • 53
  • 7
  • 55
  • 7

Hours that are basically green, but in which there is draw-down from grid-connected storage with its attendant energy losses and also suggesting that little or no excess non-dispatchable generation is available, ie that are marginally green, are shaded olive.

Current/latest fuel mix at Fri Nov 26 17:55:00 UTC 2010: CCGT@23528MW COAL@21395MW INTFR@1261MW INTIRL@0MW NPSHYD@758MW NUCLEAR@6185MW OCGT@0MW OIL@0MW OTHER@0MW PS@1185MW WIND@332MW.

Current draw-down from storage is 1185MW.

Generation by fuel category:

fossil
44923MW [CCGT, COAL, INTIRL, OCGT, OIL, OTHER]
nuclear
7446MW [INTFR, NUCLEAR]
renewable
1090MW [NPSHYD, WIND]
storage
1185MW [PS]
zero-carbon
7275MW [NPSHYD, NUCLEAR, WIND]

Overall generation intensity (kgCO2/kWh) computed using the following fuel intensities (other fuels/sources are ignored): CCGT=0.36 COAL=0.91 INTFR=0.09 INTIRL=0.7 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.61 WIND=0.0.

Key to fuel codes:

CCGT
Combined-Cycle Gas Turbine
INTFR
French Interconnector
INTIRL
Irish Interconnector
NPSHYD
Non-Pumped-Storage Hydro
OCGT
Open-Cycle Gas Turbine
PS
Pumped Storage Hydro

Sample 7: Morning of 2012/02/08

For the last few days, partly because of the very cold weather across Europe, the normal pattern has been broken with highest carbon intensity seen in the wee hours even though demand is low, and the lowest intensity around peak times and with pumped storage in use.

One consequence is that the 'supergreen' flag has not been active for days, which would be the normal combination of bottom-quartile intensity and no draw-down from storage. I haven't seen this behaviour before.

Note that wind generation has varied between ~100MW and well over 2GW, so that is not the main factor: high and consistent coal-fired generation has probably had a bigger effect. Note the relatively flat (~9%) intensity. We were exporting ~3GW to France and the Netherlands around the sample time, and have probably been proping up the French and German grids with our coal.

Effective grid carbon intensity for a domestic user is currently 576gCO2/kWh including transmission and distribution losses of 7%.

Latest available grid generation carbon intensity (ignoring transmission/distribution losses) is approximately 538gCO2/kWh at Wed Feb 08 08:50:00 UTC 2012 over 53298MW of generation, with a rolling average over 24h of 557gCO2/kWh.

Minimum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 531gCO2/kWh at Tue Feb 07 17:45:00 UTC 2012.

Maximum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 582gCO2/kWh at Wed Feb 08 05:25:00 UTC 2012.

Average/mean grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 557gCO2/kWh over the sample data set, with an effective end-user intensity including transmission and distribution losses of 596gCO2/kWh.

Recent mean GMT hourly generation intensity gCO2/kWh (average=557); *now (=538)
091011121314151617181920212223000102030405060708*
  • 557
  • 557
  • 555
  • 558
  • 555
  • 554
  • 553
  • 544
  • 534
  • 536
  • 543
  • 550
  • 560
  • 561
  • 567
  • 568
  • 567
  • 575
  • 576
  • 571
  • 579
  • 564
  • 547
  • 541
Mean GMT hourly generation GW (all, zero-carbon)
  • 53
  • 9
  • 53
  • 9
  • 53
  • 9
  • 53
  • 9
  • 53
  • 9
  • 52
  • 9
  • 52
  • 9
  • 54
  • 10
  • 57
  • 10
  • 57
  • 10
  • 55
  • 10
  • 52
  • 10
  • 49
  • 10
  • 45
  • 11
  • 41
  • 11
  • 41
  • 11
  • 41
  • 11
  • 41
  • 11
  • 40
  • 11
  • 39
  • 11
  • 41
  • 11
  • 45
  • 11
  • 51
  • 11
  • 53
  • 11

Hours that are basically green, but in which there is draw-down from grid-connected storage with its attendant energy losses and also suggesting that little or no excess non-dispatchable generation is available, ie that are marginally green, are shaded olive.

Current/latest fuel mix at Wed Feb 08 08:50:00 UTC 2012: CCGT@17080MW COAL@23930MW INTFR@0MW INTIRL@0MW INTNED@0MW NPSHYD@634MW NUCLEAR@7983MW OCGT@132MW OIL@0MW OTHER@500MW PS@732MW WIND@2307MW.

Current draw-down from storage is 732MW.

Generation by fuel category (may overlap):

fossil @ 78%
41642MW [CCGT, COAL, INTIRL, INTNED, OCGT, OIL, OTHER]
import @ 0%
0MW [INTFR, INTIRL, INTNED]
nuclear @ 15%
7983MW [INTFR, NUCLEAR]
renewable @ 6%
2941MW [NPSHYD, WIND]
storage @ 1%
732MW [PS]
zero-carbon @ 20%
10924MW [NPSHYD, NUCLEAR, WIND]

Overall generation intensity (kgCO2/kWh) computed using the following fuel intensities (other fuels/sources are ignored): CCGT=0.36 COAL=0.91 INTFR=0.09 INTIRL=0.7 INTNED=0.55 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.61 WIND=0.0.

Key to fuel codes:

CCGT
Combined-Cycle Gas Turbine
INTFR
French Interconnector
INTIRL
Irish Interconnector
INTNED
Netherlands Interconnector
NPSHYD
Non-Pumped-Storage Hydro
OCGT
Open-Cycle Gas Turbine
PS
Pumped Storage Hydro

Sample 8: Morning of 2012/07/16

Very interesting lack of correlation between demand and intensity overnight.

Effective grid carbon intensity for a domestic user is currently 538gCO2/kWh including transmission and distribution losses of 7%.

Latest available grid generation carbon intensity (ignoring transmission/distribution losses) is approximately 503gCO2/kWh at Mon Jul 16 09:20:00 UTC 2012 over 39247MW of generation, with a rolling average over 24h of 446gCO2/kWh.

Minimum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 425gCO2/kWh at Sun Jul 15 12:45:00 UTC 2012.

Maximum grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 506gCO2/kWh at Mon Jul 16 07:25:00 UTC 2012.

Average/mean grid generation carbon intensity (ignoring transmission/distribution losses) was approximately 446gCO2/kWh over the sample data set, with an effective end-user intensity including transmission and distribution losses of 477gCO2/kWh.

Recent mean GMT hourly generation intensity gCO2/kWh (average=446); *now (=503)
101112131415161718192021222300010203040506070809*
  • 433
  • 434
  • 429
  • 428
  • 428
  • 430
  • 430
  • 430
  • 430
  • 434
  • 437
  • 437
  • 441
  • 439
  • 440
  • 444
  • 445
  • 443
  • 452
  • 469
  • 490
  • 505
  • 504
  • 465
Mean GMT hourly generation GW (all, zero-carbon)
  • 33
  • 9
  • 33
  • 9
  • 32
  • 9
  • 31
  • 9
  • 31
  • 9
  • 31
  • 9
  • 32
  • 9
  • 32
  • 9
  • 31
  • 9
  • 31
  • 9
  • 31
  • 8
  • 30
  • 8
  • 27
  • 8
  • 24
  • 8
  • 24
  • 8
  • 24
  • 8
  • 24
  • 8
  • 23
  • 8
  • 24
  • 8
  • 27
  • 8
  • 33
  • 8
  • 37
  • 8
  • 39
  • 8
  • 35
  • 9

Hours that are basically green, but in which there is draw-down from grid-connected storage with its attendant energy losses and also suggesting that little or no excess non-dispatchable generation is available, ie that are marginally green, are shaded olive.

Current/latest fuel mix at Mon Jul 16 09:20:00 UTC 2012: CCGT@12342MW COAL@15806MW INTEW@0MW INTFR@996MW INTIRL@0MW INTNED@992MW NPSHYD@335MW NUCLEAR@7206MW OCGT@30MW OIL@0MW OTHER@146MW PS@472MW WIND@922MW.

Current draw-down from storage is 472MW.

Generation by fuel category (may overlap):

fossil @ 72%
28178MW [CCGT, COAL, OCGT, OIL]
import @ 5%
1988MW [INTEW, INTFR, INTIRL, INTNED]
nuclear @ 21%
8202MW [INTFR, NUCLEAR]
renewable @ 3%
1257MW [NPSHYD, WIND]
storage @ 1%
472MW [PS]
zero-carbon @ 22%
8463MW [NPSHYD, NUCLEAR, WIND]

Overall generation intensity (kgCO2/kWh) computed using the following fuel intensities (other fuels/sources are ignored): CCGT=0.36 COAL=0.91 INTEW=0.45 INTFR=0.09 INTIRL=0.45 INTNED=0.55 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.3 WIND=0.0.

Key to fuel codes:

CCGT
Combined-Cycle Gas Turbine
INTEW
East-West (Irish) Interconnector
INTFR
French Interconnector
INTIRL
Irish (Moyle) Interconnector
INTNED
Netherlands Interconnector
NPSHYD
Non-Pumped-Storage Hydro
OCGT
Open-Cycle Gas Turbine
OTHER
Other (including biomass)
PS
Pumped Storage Hydro

Sample 9: Wee hours of 2012/08/17

At this point about 50% of GB demand as seen by Elexon was coming from zero-carbon sources: 80% of that nukes and most of the rest from wind. (Note that about half of wind is not metered here, and these numbers also looked better from a zero-carbon point of view a little earlier.)

Current/latest fuel mix at Fri Aug 17 03:30:00 UTC 2012: CCGT@5516MW COAL@8267MW INTEW@0MW INTFR@0MW INTIRL@0MW INTNED@0MW NPSHYD@105MW NUCLEAR@8527MW OCGT@0MW OIL@0MW OTHER@0MW PS@0MW WIND@2182MW.

Generation by fuel category (may overlap):

fossil @ 56%
13783MW [CCGT, COAL, OCGT, OIL]
import @ 0%
0MW [INTEW, INTFR, INTIRL, INTNED]
nuclear @ 35%
8527MW [INTFR, NUCLEAR]
renewable @ 9%
2287MW [NPSHYD, WIND]
storage @ 0%
0MW [PS]
zero-carbon @ 44%
10814MW [NPSHYD, NUCLEAR, WIND]

Historical Survey of Full-Year 2009 Data

The fuel-mix (FUELINST) data is only available from Nov 2008, so here is an initial analysis for the whole of 2009. (I intend to update this periodically with new data.) This is generation intensity, ie ignoring transmission/distribution losses.

Note how carbon intensity is higher during the day, during the working week, and in the colder winter months, all where demand is highest; ie there is a fairly clear correlation between demand and intensity.

Note also how the mean variability (ie the maximum available CO2 savings from load-shifting) during each day varies from a low of 8% mid-winter to more than 4 times that in summer/autumn. My assumption is that nuclear (baseload) and renewables (zero carbon) are effectively used preferentially in the grid, but demand above their generation is satisfied by increasingly carbon-intense fuels, firstly gas (eg relatively-clean CCGT) all the way up to coal. In winter the zero/low carbon fuels make only a relatively small dent, but moving towards summer at night they cover a large chunk of demand and bring carbon intensity down further than is possible in winter.

It seems to be a good idea from an intensity point of view as well as an infrastructure-sizing and cost point of view to avoid running deferrable load at times of peak demand. If you can delay major loads (such as the dishwasher or washing machine at home) until late in the evening or the small hours after midnight you will probably significantly reduce your carbon footprint.

Note, however, that if the only reduction is a virtual one because of relatively fixed non-dispatchable zero-carbon generation (nuclear), then in order to achieve real footprint/emission reductions, and not just make everyone else's consumption higher/browner, you may have to defer load until other zero-carbon sources do increase output eg because the wind is blowing stronger or the sun shining brightly, rather just when zero/low carbon sources happen passively to form a higher proportion of extant demand. Having said that, if the demand curve becomes flatter though behaviour changes, then it will be possible to have (for example) more nuclear in the mix, and reduce the inherent waste of energy in using (eg pumped) storage, which would reduce long-term carbon footprint through requiring less fossil-fuel peak-demand support. This area requires more analysis.

Input data runs from Thu Jan 01 00:00:00 GMT 2009 to Thu Dec 31 23:55:00 GMT 2009.

Data Analysed By Hour-of-Day (GMT)

QtyHour-of-Day (GMT)
Bucket000102030405060708091011121314151617181920212223
Sample Count438043704368436843684368436843764376433142694286433143574368436743644368436843684368436843684368
Max gCO2/kWh604607603603596599600601598591589589592602595595590575587590593601602600
Mean gCO2/kWh
  • 375
  • 372
  • 368
  • 366
  • 368
  • 386
  • 419
  • 444
  • 456
  • 463
  • 465
  • 466
  • 465
  • 463
  • 460
  • 460
  • 465
  • 463
  • 458
  • 454
  • 446
  • 429
  • 398
  • 377
Min gCO2/kWh229229227230234233235236250272280287247277270270277282280284285257237229
Variability63%63%63%62%61%62%61%61%59%54%53%52%59%54%55%55%54%51%53%52%52%58%61%62%

Data Analysed By Week/Weekend

QtyWeek/Weekend
BucketWeekWeekend
Sample Count7471429877
Max gCO2/kWh607584
Mean gCO2/kWh
  • 445
  • 387
Min gCO2/kWh234227
Variability62%62%
Mean variability (available CO2 savings from load-shifting) during each Day28%24%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day138g99g

Data Analysed By Month

QtyMonth
Bucket010203040506070809101112
Sample Count890180648822860489288605892089018604878385618898
Max gCO2/kWh607593540508525494503484519545547544
Mean gCO2/kWh
  • 561
  • 519
  • 450
  • 393
  • 395
  • 394
  • 374
  • 354
  • 390
  • 446
  • 417
  • 453
Min gCO2/kWh471390291276272247234231227297266309
Variability23%35%47%46%49%50%54%53%57%46%52%44%
Mean variability (available CO2 savings from load-shifting) during each Day8%12%22%29%28%31%32%34%35%31%36%25%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day46g65g105g132g127g137g139g141g161g160g179g126g

Data Analysed By Year

QtyYear
Bucket2009
Sample Count104591
Max gCO2/kWh607
Mean gCO2/kWh
  • 428
Min gCO2/kWh227
Variability63%
Mean variability (available CO2 savings from load-shifting) during each Day27%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day127g

Data Analysed By EachHour

Datum count: 8724

Range: 2009/01/01 00:00 to 2009/12/31 23:00; all times UTC.

See CSV file for full data set...

Other Analysis

Correlation of demand against grid intensity: 0.8660.

Correlation of fuel use against demand (+ve implies that this fuel use corresponds to demand): CCGT=0.5651 COAL=0.9180 INTFR=-0.1421 INTIRL=-0.3996 NPSHYD=0.6066 NUCLEAR=-0.1435 OCGT=0.1892 OIL=0.6604 PS=0.3952 WIND=0.0523.

Correlation of fuel use against grid intensity (-ve implies that this fuel reduces grid intensity for non-callable sources): CCGT=0.2461 COAL=0.9735 INTFR=-0.2110 INTIRL=-0.3704 NPSHYD=0.4422 NUCLEAR=-0.3301 OCGT=0.1661 OIL=0.4989 PS=0.2331 WIND=-0.0036.

Generation Fuel Intensities Used

CCGT=0.36 COAL=0.91 INTEW=0.45 INTFR=0.09 INTIRL=0.7 INTNED=0.55 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.61 WIND=0.0.

Report generated at Sat Jan 19 19:56:58 GMT 2013, generation time 23064ms.

Historical Survey of Full-Year 2010 Data

Here is the 2010 analysis: note that mean generation intensity for the year seems to have risen from 428gCO2/kWh in 2009 to 444gCO2/kWh in 2010, with less scope for emissions savings from load shifting.

(All intensity figures are for generation unless otherwise stated. Until 2011/09/14, ie up to and including these 2010 figures, I have been using DEFRA's suggested values of 2% transmission losses and 7% distribution losses for a total of 9% losses, though a 5% distribution loss now appears to be a better estimate. According to "Annette", thank you, distribution losses range from from 3.7% for Yorkshire area to 8% for Scottish Hydro. Also, to be clear, intensities used up to and including these figures are: CCGT=0.36 COAL=0.91 INTFR=0.09 INTIRL=0.7 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.61 WIND=0.0.)

Possible initial explanations:

The numbers may simply be slightly wrong due to a number of factors, eg:

Input data runs from Fri Jan 01 00:00:00 GMT 2010 to Fri Dec 31 23:55:00 GMT 2010.

Data Analysed By Hour-of-Day (GMT)

QtyHour-of-Day (GMT)
Bucket000102030405060708091011121314151617181920212223
Sample Count437343714368436743684382438043804376434743204330434643824380437343674368438143804380437043584367
Max gCO2/kWh568570569571567565561564565621563563564563563562560561558559563568571567
Mean gCO2/kWh
  • 396
  • 392
  • 388
  • 386
  • 391
  • 409
  • 439
  • 460
  • 469
  • 474
  • 476
  • 476
  • 476
  • 474
  • 471
  • 471
  • 472
  • 471
  • 466
  • 464
  • 459
  • 446
  • 419
  • 399
Min gCO2/kWh266265262261262268281283300316334342341334331333337336324321322313296271
Variability54%54%54%55%54%53%50%50%47%50%41%40%40%41%42%41%40%41%42%43%43%45%49%53%

Data Analysed By Week/Weekend

QtyWeek/Weekend
BucketWeekWeekend
Sample Count7488429930
Max gCO2/kWh621556
Mean gCO2/kWh
  • 458
  • 408
Min gCO2/kWh275261
Variability56%54%
Mean variability (available CO2 savings from load-shifting) during each Day25%21%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day122g93g

Data Analysed By Month

QtyMonth
Bucket010203040506070809101112
Sample Count889780648892863988098638890189028633889386408906
Max gCO2/kWh563548553520523518621508565537571571
Mean gCO2/kWh
  • 488
  • 486
  • 419
  • 412
  • 412
  • 411
  • 420
  • 391
  • 435
  • 450
  • 485
  • 515
Min gCO2/kWh352339282295275292283263287261335430
Variability38%39%50%44%48%44%55%49%50%52%42%25%
Mean variability (available CO2 savings from load-shifting) during each Day17%16%26%27%27%32%28%28%28%26%20%10%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day87g81g120g124g123g155g132g123g135g128g106g51g

Data Analysed By Year

QtyYear
Bucket2010
Sample Count104814
Max gCO2/kWh621
Mean gCO2/kWh
  • 444
Min gCO2/kWh261
Variability58%
Mean variability (available CO2 savings from load-shifting) during each Day24%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day114g

Data Analysed By EachHour

Datum count: 8741

Range: 2010/01/01 00:00 to 2010/12/31 23:00; all times UTC.

See CSV file for full data set...

Other Analysis

Correlation of demand against grid intensity: 0.8532.

Correlation of fuel use against demand (+ve implies that this fuel use corresponds to demand): CCGT=0.7412 COAL=0.9344 INTFR=-0.2906 INTIRL=-0.0665 NPSHYD=0.4151 NUCLEAR=0.5051 OCGT=0.1508 OIL=0.4116 PS=0.3717 WIND=0.0678.

Correlation of fuel use against grid intensity (-ve implies that this fuel reduces grid intensity for non-callable sources): CCGT=0.4360 COAL=0.9571 INTFR=-0.3890 INTIRL=0.0380 NPSHYD=0.3238 NUCLEAR=0.3204 OCGT=0.1121 OIL=0.0457 PS=0.1925 WIND=0.0334.

Generation Fuel Intensities Used

CCGT=0.36 COAL=0.91 INTEW=0.45 INTFR=0.09 INTIRL=0.7 INTNED=0.55 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.61 WIND=0.0.

Report generated at Sat Jan 19 19:48:25 GMT 2013, generation time 21457ms.

Historical Survey of Full-Year 2011 Data

Stefan Adamof at Edinburgh University has kindly provided an example chart using the hourly intensity data that I have started extracting 2013/01, for use in the CHARM project.

Input data runs from Sat Jan 01 00:00:00 GMT 2011 to Sat Dec 31 23:55:00 GMT 2011.

Data Analysed By Hour-of-Day (GMT)

QtyHour-of-Day (GMT)
Bucket000102030405060708091011121314151617181920212223
Sample Count437643804374436843684368436643664366433643004318435543684368436843684368436843684368436643684365
Max gCO2/kWh575575569570572588587581580578580583586590588586573565573579583589596591
Mean gCO2/kWh
  • 397
  • 392
  • 387
  • 384
  • 388
  • 406
  • 431
  • 450
  • 458
  • 463
  • 464
  • 464
  • 464
  • 462
  • 460
  • 461
  • 460
  • 458
  • 454
  • 453
  • 449
  • 439
  • 418
  • 401
Min gCO2/kWh245240233224214214232250280302307303298288288290293293290293302273249243
Variability58%59%60%61%63%64%61%57%52%48%48%49%50%52%52%51%49%49%50%50%49%54%59%59%

Data Analysed By Week/Weekend

QtyWeek/Weekend
BucketWeekWeekend
Sample Count7446930215
Max gCO2/kWh596581
Mean gCO2/kWh
  • 449
  • 404
Min gCO2/kWh240214
Variability60%64%
Mean variability (available CO2 savings from load-shifting) during each Day23%22%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day108g93g

Data Analysed By Month

QtyMonth
Bucket010203040506070809101112
Sample Count892680458926863889108615892689288630885786408643
Max gCO2/kWh546538540477469523480527505543596590
Mean gCO2/kWh
  • 476
  • 470
  • 475
  • 374
  • 371
  • 396
  • 386
  • 400
  • 414
  • 451
  • 518
  • 502
Min gCO2/kWh315327363240214249261246270305345298
Variability43%40%33%50%55%53%46%54%47%44%43%50%
Mean variability (available CO2 savings from load-shifting) during each Day14%18%16%26%28%27%26%28%27%23%17%18%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day72g90g81g108g117g118g110g126g124g112g92g95g

Data Analysed By Year

QtyYear
Bucket2011
Sample Count104684
Max gCO2/kWh596
Mean gCO2/kWh
  • 436
Min gCO2/kWh214
Variability65%
Mean variability (available CO2 savings from load-shifting) during each Day22%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day104g

Data Analysed By EachHour

Datum count: 8734

Range: 2011/01/01 00:00 to 2011/12/31 23:00; all times UTC.

See CSV file for full data set...

Other Analysis

Correlation of demand against grid intensity: 0.7809.

Correlation of fuel use against demand (+ve implies that this fuel use corresponds to demand): CCGT=0.6598 COAL=0.8823 INTFR=0.0861 INTNED=-0.1022 NPSHYD=0.4247 NUCLEAR=0.1300 OCGT=0.2477 OIL=0.1690 PS=0.3698 WIND=0.0389.

Correlation of fuel use against grid intensity (-ve implies that this fuel reduces grid intensity for non-callable sources): CCGT=0.2343 COAL=0.9526 INTFR=0.0137 INTNED=-0.1327 NPSHYD=0.4063 NUCLEAR=-0.1644 OCGT=0.3089 OIL=0.3661 PS=0.1657 WIND=0.0614.

Generation Fuel Intensities Used

CCGT=0.36 COAL=0.91 INTEW=0.45 INTFR=0.09 INTIRL=0.7 INTNED=0.55 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.61 WIND=0.0.

Report generated at Sat Jan 19 19:42:04 GMT 2013, generation time 23740ms.

Historical Survey of Full-Year 2012 Data

(I hope to re-run this with some extra goodies/stats...)

Capacity of WIND up significantly this year, but so was burning of COAL due to good "dark spread" vs "spark spread" and Large Combustion Plant Directive deadline drawing near, so mean grid intensity was significantly up from last year. (Though more embedded renewables, and possibly biomass cofiring not reflected in these numbers properly, probably means that this overstates the case.)

Note that apparent available savings from load-shifting are falling year-on-year also.

Input data runs from Sun Jan 01 00:00:00 GMT 2012 to Mon Dec 31 23:55:00 GMT 2012.

Data Analysed By Hour-of-Day (GMT)

QtyHour-of-Day (GMT)
Bucket000102030405060708091011121314151617181920212223
Sample Count439243924392439243864390438743924392435943354356438143904392439143924392439243924392439243924392
Max gCO2/kWh614617606605603629617603596589590593593588588589586582577578594596611608
Mean gCO2/kWh
  • 481
  • 477
  • 472
  • 468
  • 472
  • 487
  • 498
  • 503
  • 504
  • 504
  • 504
  • 504
  • 506
  • 507
  • 507
  • 505
  • 502
  • 501
  • 501
  • 503
  • 506
  • 505
  • 496
  • 486
Min gCO2/kWh311298300289283293297306288310357387385392394398399409411398390381343335
Variability50%52%51%53%54%54%52%50%52%48%40%35%36%34%33%33%32%30%29%32%35%37%44%45%

Data Analysed By Week/Weekend

QtyWeek/Weekend
BucketWeekWeekend
Sample Count7502330232
Max gCO2/kWh629603
Mean gCO2/kWh
  • 503
  • 477
Min gCO2/kWh308283
Variability52%54%
Mean variability (available CO2 savings from load-shifting) during each Day16%16%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day82g77g

Data Analysed By Month

QtyMonth
Bucket010203040506070809101112
Sample Count892883498903864088818616892689278614892886168927
Max gCO2/kWh587608629586542533539521551602612575
Mean gCO2/kWh
  • 496
  • 530
  • 552
  • 508
  • 475
  • 451
  • 464
  • 439
  • 467
  • 535
  • 528
  • 506
Min gCO2/kWh288414477373338312316283328397437325
Variability51%32%25%37%38%42%42%46%41%35%29%44%
Mean variability (available CO2 savings from load-shifting) during each Day20%12%10%13%14%20%15%21%25%12%13%14%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day108g64g56g65g67g93g75g98g128g69g71g73g

Data Analysed By Year

QtyYear
Bucket2012
Sample Count105255
Max gCO2/kWh629
Mean gCO2/kWh
  • 496
Min gCO2/kWh283
Variability56%
Mean variability (available CO2 savings from load-shifting) during each Day16%
Mean available CO2 savings per kWh from load-shifting, eg ~1 wash load, during each Day80g

Data Analysed By EachHour

Datum count: 8778

Range: 2012/01/01 00:00 to 2012/12/31 23:00; all times UTC.

See CSV file for full data set...

Other Analysis

Correlation of demand against grid intensity: 0.5560.

Correlation of fuel use against demand (+ve implies that this fuel use corresponds to demand): CCGT=0.8320 COAL=0.8644 INTEW=0.4262 INTFR=-0.1407 INTIRL=0.1017 INTNED=-0.1421 NPSHYD=0.6162 NUCLEAR=0.0082 OCGT=0.3345 OIL=0.1618 OTHER=0.3017 PS=0.3401 WIND=0.1111.

Correlation of fuel use against grid intensity (-ve implies that this fuel reduces grid intensity for non-callable sources): CCGT=0.2758 COAL=0.8579 INTEW=0.4858 INTFR=-0.4193 INTIRL=0.0045 INTNED=-0.1158 NPSHYD=0.2848 NUCLEAR=-0.3655 OCGT=0.2252 OIL=0.2571 OTHER=0.2185 PS=0.0475 WIND=-0.2111.

Generation Fuel Intensities Used

CCGT=0.36 COAL=0.91 INTEW=0.45 INTFR=0.09 INTIRL=0.45 INTNED=0.55 NPSHYD=0.0 NUCLEAR=0.0 OCGT=0.48 OIL=0.61 OTHER=0.3 WIND=0.0.

Report generated at Sat Jan 19 16:40:48 GMT 2013, generation time 61230ms.

Automation Test Footnote

As of 2009/05/10 I had one hosted Web server drop to reduced power mode unless it can detect that the status is 'green' over HTTP, and also our dishwasher was controlled via X10 and the HEYU software to run when grid status is 'green' with status updated hourly to ensure that a 'quick' wash (<1h) could not be interrupted, but the dishwasher control had to stop when we 'upgraded' to a replacement that could not simply be turned on at the wall and work.

What Emissions Can One Household Save?

Let us first assume that on average each household could defer 1kWh from the day/evening to overnight each day, which is about one warm/hot wash load for example. Many families will be running more than one a day, for example, so only need to defer some of their normal activity.

That would be 365kWh/household deferred from near maximum to near minimum intensity if it can be timed roughly right.

(The government (eg in DUKES) reports there to be ~25M UK households, so that would be ~9TWh of shifted load ie about 8%-ish of domestic demand, which seems within the bounds of pausibility.)

According to my partial data and analysis above it looks as though there's at least 100g/day (~20%) of CO2 to be saved per shifted kWh over the year as at 2009 (higher including summer months).

That suggests >30kg CO2 emissions per year saved by this for each load timeshifted per day.

That is the same saving as turning off our heating entirely for half a week in the middle of 2009's very severe winter.

Given a target that Europeans (well, everyone on the planet, but India and China are there more or less in 2009) should be aiming for of (say) total 2tCO2 per person per year that's maybe 2% of the total allowance so quite significant, with the remaining portion looking like 10%+ of that target 2t/y.

I take from this incidentally that we can probably keep our (efficient) dishwashers and washing machines and such mod cons and meet that target.

Code

Code used to collect and compute GB grid intensity numbers, live and historical, published under an BSD-style free/open licence.

20110124: initial snapshot of Eclipse project:

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