Carbon intensity of electricity:towards more realistic numbers    Professor Gareth Harrison   Institute for Energy Systems...
Institute for Energy Systems   Our research spans and maps to the renewable energy supply chainResources           Capture...
What are we trying to do?•   Gain an understanding of the carbon chain now and    in the future•   Estimate the carbon imp...
How do we calculate carbon          intensity?•   The carbon intensity of electricity produced by a    given generation te...
How good are these simple          estimates?•   Several areas where these values fall down    •   Consumption patterns an...
Time variability?                  60000                  50000                                                           ...
Time variability?                                    700     Carbon Intensity (gCO 2/kWh)                                 ...
Technology Considerations•   The generator technology has a very large impact on    emissions    •   Gas peaking plant (OC...
Technology Considerations•   Generator operation has a big impact on its emissions•   Traditional steam and CCGT stations ...
Technology Considerations•   Starting and stopping requires extra fuel to be used    to maintain at or return generator to...
Technology Considerations•   Starting and stopping requires    extra fuel to be used to    maintain at or return generator...
Towards better estimates?•   Highly complex problem•   Emissions are largely market-driven and increasingly    reflect non...
Towards better estimates?•   Estimating future intensity is much harder…•   Substantial uncertainty over fuel types, techn...
Upcoming SlideShare
Loading in …5
×

Carbon Intensity of Electricity: Towards More Realistic Numbers | Professor Gareth Harrison

1,284 views

Published on

Published in: Technology, Business
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
1,284
On SlideShare
0
From Embeds
0
Number of Embeds
184
Actions
Shares
0
Downloads
10
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Carbon Intensity of Electricity: Towards More Realistic Numbers | Professor Gareth Harrison

  1. 1. Carbon intensity of electricity:towards more realistic numbers Professor Gareth Harrison Institute for Energy Systems University of Edinburgh
  2. 2. Institute for Energy Systems Our research spans and maps to the renewable energy supply chainResources Capture Conversion DeliveryEnergy and Marine Machines and Power Climate Energy Electronics Systems Innovation Policy and Regulation Standards Environment
  3. 3. What are we trying to do?• Gain an understanding of the carbon chain now and in the future• Estimate the carbon impact of intervention strategies• Reward technologies that reduce carbon• All of these require credible estimates of the carbon intensity of electricity
  4. 4. How do we calculate carbon intensity?• The carbon intensity of electricity produced by a given generation technology is given by Emissions factor = fuel use / generation• The DECC emissions factors are based on total fuel use and total energy production per fuel type • simple cross-industry measure • reflect differences between fuels • widely exploited for estimating carbon footprints, impacts and payback
  5. 5. How good are these simple estimates?• Several areas where these values fall down • Consumption patterns and production are not flat profiles • Emissions vary within same fuel type • System and generator operation ultimately dictates intensity
  6. 6. Time variability? 60000 50000 windGeneration (MW) 40000 ps 30000 ocgt coal 20000 ccgt 10000 intfr 0 nuclear 1 20 39 58 77 96 115 134 153 172 191 210 229 248 267 286 305 324 -10000 Period Simple analysis: First week in Nov 2008, BMreports aggregated production.
  7. 7. Time variability? 700 Carbon Intensity (gCO 2/kWh) 600 2008: 500 Coal 903 400 Oil 730 Gas 404 300 This week: 200 Ave 551 100 0 1 20 39 58 77 96 115 134 153 172 191 210 229 248 267 286 305 324 PeriodSimple analysis: First week in Nov 2008, BMreports aggregated production and 2008DUKES emission factors; www.realtimecarbon.com, Ecotricity and GridCarbon do similar
  8. 8. Technology Considerations• The generator technology has a very large impact on emissions • Gas peaking plant (OCGT) much less efficient • Older power stations tend to be less efficient Coal 903 Gas 404 Oil 730
  9. 9. Technology Considerations• Generator operation has a big impact on its emissions• Traditional steam and CCGT stations were designed to operate at highest efficiency at full output• Operation at part-load, starting and stopping all result in additional emissions• Part-loading may raise emissions by as much as 10% Relative station efficiency
  10. 10. Technology Considerations• Starting and stopping requires extra fuel to be used to maintain at or return generator to operating temperatures
  11. 11. Technology Considerations• Starting and stopping requires extra fuel to be used to maintain at or return generator to operating temperatures• The frequency of cycle and Operation duration of downtime are both important• Intensity during warm up: • CCGT ~800gCO2/kWh • Coal ~1200-1400gCO2/kWh Emissions
  12. 12. Towards better estimates?• Highly complex problem• Emissions are largely market-driven and increasingly reflect non-dispatchable renewable generation• Simple emissions factors not sufficient to inform important choices• Estimating historic carbon intensity conceptually simpler • We can measure production and fuel burn • The small extent of changes (wind etc) means simple marginal assumptions (dCO2/dP) can be credible • We still need to reflect operational characteristics in estimates
  13. 13. Towards better estimates?• Estimating future intensity is much harder…• Substantial uncertainty over fuel types, technology and operational characteristics• Large injections of wind will see more flexible use of thermal plant: more cycling and greater reserve holding • Lower emissions due to energy substitution but more emissions per kWh of thermal generation• We need to fully understand this…

×