Wednesday, 29 October 2014

Comparing carbon emissions of wind and nuclear power

The wikipedia page is sourced from the IPCC [page 982].

Aggregated results of literature review of LCAs of GHG emissions from electricity generation technologies (g CO2 eq/kWh).

IPCC figures for Nuclear, Wind, Gas:
NuclearWindGasAv W+GAv W+2G
25th percentile88422215284
50th percentile1612469241317
75th percentile4520548284372

PS: The last 2 columns are mine. They are averages of wind and gas. Av W+G = Wind:Gas @ 50:50; Av W+2G = Wind:Gas @ 33:67

The wikipedia link only shows the 50th percentile. Estimates vary over ranges of 81 to 2 for wind, and 220 to 1 for nuclear. There's clearly vast disagreement among scientists, engineers, and economists over what the true values are. I think the IPCC should've done their own studies. At the very least, the IPCC should have excluded some of the outlier estimates. Afterall: this is one of the most important 'findings' of their report.

The carbon emission intensity figures one sees for wind always pretend it to be an independent source. It's never. Wind is totally dependent on fossil fuels. From time to time, UK wind drops to low levels throughout.

At times like that fossil fuels generate electricity or the lights go out. When calculating carbon emissions from wind I factored in the necessary fossil fuel (Av W+G, Av W+2G columns) The last 2 columns are carbon emission values for Wind and Gas combined. Carbon emissions (g CO2 eq/kWh) of 241 or 317 for wind and gas combined tell the real story.

Roll on the day when we get nuclear power using Gen IV reactors fueled on reprocessed spent nuclear fuel. This will considerably cut the nuclear power carbon footprint.

The large variation in emissions estimated from the collection of studies arises from the different methodologies used - those on the low end, says Sovacool, tended to leave parts of the lifecycle out of their analyses, while those on the high end often made unrealistic assumptions about the amount of energy used in some parts of the lifecycle. The largest source of carbon emissions, accounting for 38 per cent of the average total, is the "frontend" of the fuel cycle, which includes mining and milling uranium ore, and the relatively energy-intensive conversion and enrichment process, which boosts the level of uranium-235 in the fuel to useable levels. Construction (12 per cent), operation (17 per cent largely because of backup generators using fossil fuels during downtime), fuel processing and waste disposal (14 per cent) and decommissioning (18 per cent) make up the total mean emissions.

An alternative to the IPCC figures, considered superior by many, are those from NREL.

The economics of wind power

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