Sometimes, telling you things is OK, but if you actually do some of the work yourselves, you get the point better. So, let me give you a short exercise to do, and I’ll lead you through it, and once you’ve done this little task, I’ll then add a short explanation.
Musselroe wind plant –
image courtesy Ross Marsden, TheMercury
Go to the following link – it will open up in a new window – then you can navigate back to this page for the simple instructions.
Wind Farm Performance Monday 03 Jun 2013 (Note: automatically opens in new tab/window)
- This page has three graphs on it, and first I want you to scroll down a little until the third graph shows on the screen (Electricity Demand (MW)). This shows the total power consumption for nearly all of Australia, that black line indicating the total power, and the coloured lines below that showing the power consumed in each of those 5 States. The horizontal axis shows the hours in the day, from Midnight through the day and then back to Midnight. The Vertical axis indicates total power shown in MegaWatts. (MW) This is what is referred to as a Load Curve.
- On the graph itself, that black line at the top shows how much power is being consumed at that time. Note how there’s a dip from Midnight to around 5AM, you know, while most of the population is actually asleep, and notice the bottom of that dip, just on 18,000MW. So while nearly everyone is sound asleep, Australia is still consuming those vast amounts of power. Then, the graph rises, as everyone gets up, has their breakfast, prepares for work and school. Then it dips slightly as that morning Residential power peak subsides slightly. Power then levels off and begins to rise again around 5PM. When the second Residential Peak begins, as everyone gets home does their chores, prepares dinner etc. This Peak lasts until around 10PM, the evening Residential Peak.
- This is a typical Load Curve for the Winter Months of the year, and it looks similar for towns, cities, States, and whole Countries.
Here’s the first part of this exercise. Now, see under the graph there are some ticked boxes. These are for 5 of the States in Australia, virtually all of Australia, except for Western Australia and the Northern Territory.
- Untick the boxes for NSW, Qld, Tas, Vic, Selected, and All. So now you have just SA ticked and the graph now shows a red Load Curve, and while the time axis stays the same (hours in the day), the vertical axis has changed to indicate a smaller scale. This is the Load Curve for South Australia one of the smaller States by population, hence consumption is lower.
- Note how the Curve looks similar to the original larger black curve with those two peaks for Residential power.
- Now look specifically at that time period between 7AM and 10PM, where the curve breaks through the 1600MW mark in the AM, and then sinks below the 1600MW mark at 10PM. This is the normal period of highest consumption, and as you can see here the average power being consumed over that period comes in at around 1,750MW, for those 15 hours.
Now you can see that, then here’s the second part of the exercise I have for you.
- Scroll back up the page now until just that second graph is on the screen with the legend of ticked boxes under it. Note how those are also arranged into States.
- Now, untick all the boxes down the left side, and on the right side untick the All box. So, now, all you have ticked is all the Wind Plants for S.A. (South Australia), 15 of them in fact with around 600 of those huge towers in all.
- Note the box titled ‘Selected’. That shows the total Nameplate Capacity for all those Wind Plants. That’s 1,223MW. Keep in mind that during this day, the average for that time period was 1750MW, so effectively, Wind Power makes up a large percentage of the possible total for the State. That’s not the correct total because Wind Power total Nameplate Capacity for S.A. comes in at around 40 to 45% of that total Nameplate Capacity. However, because the Wind power is variable, what needs to be concentrated on here is not that Nameplate total, but the actual power delivered to the grid for that State, and that is shown by the black line on this graph.
- Now, using the same time period for when the most power is being consumed, 7AM until 10PM, look at the actual power delivered from all those Wind towers shown by the black line.
- See how it starts (at 7AM) at around 75MW, and then drops to literally stumble along the bottom of the page, which is zero. The average power for that 15 hour period from 7AM until 10PM is 20MW. That means that for 15 hours barely 10 of those 600 huge towers had their blades turning delivering power, and for most of the time, that was down to five with long periods when none of them were actually turning at all.
- The total power actually being consumed in the State is 1750MW. So for that 15 hour period Wind Power, from the largest wind powered State in Australia came in at 1.1% of total power actually needed, and delivering its power at a Capacity Factor of 1.6%.
Ok then, the State has to get its power from somewhere. S.A. does have one medium sized coal fired plant, The Northern Plant, with a Capacity of 520MW, a plant that actually can deliver its power on a 24/7/365 basis on demand, but it has been closed since the end of Summer, mainly because with the added cost of the CO2 Tax, the operators only use it at times of highest demand, which is always in those three Summer Months. So, instead of having ready access to that cheaply generated coal fired power, which S.A. proudly claims it does not need now that it has so much Wind Power, we find that the grid is desperately short of power, power that now has to be sourced from somewhere.
What happens now is that desperate grid controllers now have to get all the plants they can to provide power. Nearly all of these plants are specifically designed to operate for just a few hours a day, mainly during that evening Peak, so perhaps for four hours a day at the most, if needed at all. The operating costs for these smaller plants are much higher, naturally, so the power that they do provide is expensive to generate.
So then, how expensive?
Look at this chart which shows the cost for power across that same coverage of States, and this chart is from the main electrical power regulator in Australia.
AEMO Average Price Table. (Note: automatically opens in new tab/window)
Note the text just above the chart which details the Peak RRP as being the times from 7AM until 10PM, the same time period I directed you to for both graphs
Look at the cost for electricity for S.A. for that day, Monday 03 Jun 2013.
$866.41 per MWH.
That cost is 15 times higher than the next highest, and 20 times higher than the cheapest. In fact, that cost, the wholesale cost that retailers have to pay for the electricity they then onsell to consumers, that huge price is actually 4 times higher than the retail price they sell that electricity for.
Most of those States have their power provided from coal fired power sources, except for Tasmania (Tas) which sources most of its power from Hydro.
This is Wind Power’s dirty little secret. When the wind is blowing and the towers are actually delivering power, the cost of that power is really expensive. Then, when the wind is not blowing and the turbines are not turning at all, they are still expensive because replacement power is required to back them up, and that replacement power, as shown so dramatically here, is also very expensive. They require constant backup ready to come online at a moment’s notice. Expensive when running, and even more expensive when not running.
Is wind power cheap? Well you’ve just done the exercise yourself. You be the judge.
Other articles by Tony from Oz
© Tony from Oz 2013