Thursday 21 July 2011

Wind farms - claims vs reality

The PM opened a new wind farm this week. Depending on who you believe, it will supply the equivalent of either 23,000 homes or 30,000 homes. What's the story?

There's a very useful site called Wind Farm Performance that details how much power Australia's wind farms actually produce. Let's have a look at the claims of the spruikers.

Pacific Hydro for instance have 13 wind farms in operation or development. On the Pacific Hydro website, each project has a page that shows total capacity and the number of homes that it can supply with "clean power".

For instance, Challicum Hills opened in 2003 and has a claimed capacity of 52.5MW - enough to power 23,000 homes each year. This is based on average household usage of 6MWh per year (although I have seen 8MWh quoted for NSW). On average, it is supposed to produce 141GWH per year.

According to the Wind Farm Performance website, which draws its data from AEMO, the capacity factor for Challicum Hills in 2010 was 27.1%. That is, instead of producing 52.5MW as claimed, it only put out an average of 14.2MW.

Challicum Hills performance 20 July 2011
The above graphs show how Challicum Hills has performed over the last 24 hours - it's been pretty good at around 50%.

At an average capacity factor of 27.1%, this farm would have produced about 124GWh last year - not enough to power 23,000 homes. At 6000MWh per household, they'd consume about 138GWh. If you take the NSW figure of 8000MWh per household, they'd need 184GWh per year - a large shortfall.

Clements Gap opened in 2010. Claimed capacity is 56.7MW, supplying up to 30,000 homes. This is odd, as in Victoria, 52.5MW is claimed to supply up to 23,000 homes. I guess it all depends on what figure you pick as the average usage per household - 5.3MWh, 6MWh or 8MWh.

In 2010, the Clements Gap average capacity factor was 32.1%.

It didn't produce anything from about noon to 8pm yesterday.

Clements Gap
So let's calculate how much power Clements Gap would have produced in 2010. 24 hours x 365 days x 56.7MW x 32.1% capacity factor = 159GWh. Dividing that by 30,000 homes gives an average of 5.3MWh per household per year. That's oddly less than the average of 6MWh quoted for Victoria and 8MWh quoted for NSW. Hmm.

Codrington. 18.2MW. Generates 49GWh per annum. No statement regarding how many homes it would serve. It doesn't appear on Wind Farm Performance, so who knows how it's going.

Portland (Yambuk). 30MW capacity, 100GWH per annum. The page for this site states that its numbers are based on average household usage of 5.3MWh per year, but it doesn't say how many homes it could supply.

Average capacity factor for 2010 was 34.3%.

Portland (Cape Bridgewater). 58MW, 195GWh pa, no statement on how many houses it could supply and its average capacity factor is lumped in with Yambuk to give 34.3%.

All I can say is that the numbers are all over the place like a mad woman's breakfast.


Margo's Maid said...

This is a pretty awesome find...Will be interesting to follow this up

Anonymous said...

Don't you think this is just a little pedantic? Lets address just your first example, you point out that they have produced 124 GWh in the last year but would need to have made 138GWh to supply the 23,000 homes estimated, in actually there annual production would only have supplied 20,667 homes. Do you really mean to tell me that an annual error of 10% in estimating average wind speed (something very difficult to estimate beyond a few days) is some huge revelation or possibly even evidence of underhanded propaganda for wind farms??
How about you try and estimate the average wind speed night and day for all the locations around Australia with a wind farm for the next 12 months and well see whether you can do better?