Tassie’s “summer” demand peak comes with cold weather | RenewEconomy

Tassie’s “summer” demand peak comes with cold weather

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Looking at what happened in Tasmania over the “extended summer” period 2014-15.

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Watt Clarity

Over the past two weeks, we have walked through 4 of 7 metrics to ascertain what the extremes have been in terms of demand, and wind production.  That leaves 3 still to go.

Turning to one of our favourite destinations, we look at what happened in Tasmania over the “extended summer” period 2014-15.

1)  What actually eventuated?

Returning to NEM-Review, we produce this trend of Tasmanian region scheduled demand over the 4-month period:


Of interest to us is the fact that the demand peak occurred towards the end of what we defined as “extended summer” (on 26th March) and at 6:50 in the morning – so we’re inferring that early-morning heating might have been a contributing factor on that day (see how neighbouring days were also higher demand).

If this is true, we have an “extended summer” peak demand of 1,389MW occurring at a time when it was cold enough for heating to push demand higher.

I’ve also highlighted on the chart two obvious instances where system technical issues resulted in the trip of significant amounts of Tassie demand (including some major industrial loads).  We did find at least one other, in a quick inspection of the data (this was in the middle of the day, so is not as obvious in the above).  There may have been other occasions.

Keep this in mind when looking at the minimum demands below!

2)  How well was this expected?

This summer, in conjunction with our traditional “main prize”, we also offered to give away a “consolation prize” for the closest to the market at guesstimating what the peak demand would be for the TAS region (this was Competition #6 of a total of 7 competitions this summer).

2a)  Was it expected, by our competition entrants?

Collating all the entries and plotting a distribution, we see this pattern:


With reference to the above, keep in mind that I have used small (100MW) steps in the distribution curve and, even with these small steps, we find the actual peak demand coincided with the high point in the distribution curve.

Hence we could conclude from this that the peak demand in Tasmania is much more predictable than in any of the other competitions we’ve seen to date.

A glance at the chart above, which shows much less variation in demand from week-to-week than the other regions, illustrates why.

Hence, in terms of entries, this one came much more down to the wire.

We see a small percentage of entries trailing off to the right in the distribution, including some above 2,000MW.  However in general terms the entries were clustered tightly around what actually happened.

2b)  Was it expected, by AEMO?

On New Year’s Eve, I posted these tips about summer peak demand in Tasmania – to help entrants sharpen their pencils and put in their best entries.

Included in these tips was this image highlighting AEMO’s forecasts for peak Tassie demand – shown in conjunction with current demand data:


As noted in the image, Tasmania is (unlike the other 4 northern regions now) distinctly winter-peaking.

One of our entrants pointed out when making his entry that, because we extended our definition of summer to include March, we left open the possibility of a cooler period late in March delivering higher demand than had been experienced in the three regular months or summer.  That’s what’s seemed to happen.

3)  Looking in more detail?

As we did for other regions last week, we include this trend of the headline stats for TAS for the “5 less cold(?) months” of 2014-15 and the 6 preceding financial years:


As noted in this chart, the effect of the tripping of a significant proportion of load (500MW or so, on occasions) can be clearly seen in the suppression of minimum demand for 2014-15.  It should be noted, as well, that I did not check the prior years to see if the same thing had happened.

Compared to the same chart for South Australia or Victoria, we can see that the average demand in Tasmania is much more evenly spaced between maximum and minimum (i.e. Tasmania is much less peaky – again contributing to the ease of forecast).

To provide more detail, we generated the following distribution curve for TAS:


With respect to this curve, we can see that it is almost a natural bell curve (at least, much more the case than is the case for the other regions we have looked at).

The three areas highlighted still apply:

3a)  Minimum demand

Down at the bottom end of the curve (marked “Area 1”) we see  a shift in the demand pattern occurring between 2009-10 and 2010-11 – and, further up the curve, between 2010-11 and 2011-12.

I am not familiar enough with the Tasmanian region to hazard a guess as to what this might be – it might have resulted from a combination of a number of initiatives, such as:
1.  More efficient street lighting; and
2.  Better insulation

Right down the bottom end of the curve, it does not seem that there has been much change at all in the demand pattern (for minimum demand) over 7 years.

3b)  Afternoon demand

Up in the area of afternoon demand (marked “Area 2”) we see a more distinctive pattern of change, beginning 2009-10.

Whilst solar PV will have been one of the factors, the installed capacity in Tasmania is relatively small (and harvesting not so great, at the southern end of the country) – so I can only think that there will have been other factors at work.

Perhaps some of our readers can suggest?

3c)  Peak demand

As noted above, Tasmania is much less peaky than the other regions we’ve looked at to date.

For completeness, however, we include the same chart, focused on the higher end of the demand curve:


As noted on the graphic, we can see a significant drop in the curve from 2008-09 to 2014-15 which (if seen on its own) might give cause for some to believe that the peak demand challenge had been tamed.

However the much more similar load shape between 2008-09 and 2013-14 (5 years apart) implies that the challenge still remains, ready for weather extremes to unleash it again.


Source: Watt Clarity. Reproduced with permission.

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  1. Peter B 5 years ago

    “Hobart’s extended summer” is an oxymoron when referring to this last season. There were only about two x two day periods that could in anyway be labelled “summer”. Both times were the back end of a southern mainland high pressure system before the next front hit. So glad the author had “extended summer” in parenthesis, it shows his sense of humour!

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