Sunday 19 August 2012

Running the numbers on wind power

An interesting view on how wind power actually produces more CO2 than gas fired generation - when you take into account the impact of wind on the rest of the power generation system.

[A]s wind rarely produces more than 25% of its faceplate capacity it needs 75% backup - which due to the necessity of fast response times needs OCGT generation (CCGT can respond quickly but the heat-exchanger systems upon which their increased efficiency relies, cannot - so CCGT behaves like OCGT under these circumstances). CCGT produces 0.4 tonnes of CO2 per MWh, OCGT produces 0.6 tonnes. Thus 0.6 tonnes x 75% = 0.45 tonnes. Conclusion: Wind + OCGT backup produces more 0.05 tonnes of CO2 per MWh than continuous CCGT.

I love this comment, although he proceeds to go over the top by invoking Godwin's Law:

the purpose of the windmills is not to save CO2. it's to provide carbon trading/offset receipts for the banks and to support the Euro by a non-national taxation. There is also the political narrative: they are like the Easter Island Statures, a symbol of the power of the ruling elite whilst the workers willingly toil at green jobs.


Rob said...

In Australia our wind farms have an average capacity factor of 33%, newer installations are surpassing 40% with turbine design improvements and improved knowledge about site selection. However the average for all NEM wind farms is 33%. This means potentially 66% OCGT back up, although we do have other rapid dispatch back ups, primarily hydro in Tas (basslink interconnected), Vic and NSW. But assuming all the spinning reserve is OCGT total CO2 intensity is 66%x0.6 = 0.396 tonnes/Mwh or just below CCGT base load generation.

Compare wind/NG of either kind to Coal as most of the Eastern Australia uses now and they're not even in the same ballpark, Hazelwood for example produces 1.58 tonnes CO2/Mwh the highest intensity of any OECD power plant.

The full potential of renewables however will be realised when grid storage technology matures, then storages can be filled when wind, sun, waves, tide etc are available and discharged when they are producing less then needed, this will abolish any issues with intermittency and abolish the need for spinning reserves, until then like most things in life they involve trade-offs.

Minicapt said...

Again, Rob makes number cry.


Rob said...

Sorry Minicapt was there a particular number or fact you're rebutting or disputing? I only ask because you provide neither.

Anonymous said...

Rob, if you're going to make a point about ‘Australian Wind Farms’ at least point to a web site that does cover all wind farms.

Cherry picking and sweeping generalisations will get you nowhere.

Rob said...

I was under the impression that covered all NEM windfarms larger then 30 Mw, so it might miss a few very small installations but it covers the overwhelming majority of Australian NEM wind capacity, have you got a better link with NEM farms, their size and capacity factor? I found this website which has a chart showing a weighted capacity factor of 34.1%, a little higher then my original claim so It seems unlikely my original 33% is cherry picked.
I hardly think its a cherry picking or generalisations to use the capacity factors of 2071.95 Mw of Australian wind farms, it certainly seems less like a generalisation then using UK data to criticise wind power in Australia as BoaB has.

Rob said...

Oops * I found this website