In Wednesday’s post, we highlighted how two trends have been seen to emerge simultaneously:
1) Aggregate output from wind farms has climbed steadily to be approximately 3.5% of energy supplied in the 365 days to 25th July; and yet
2) There remain 6% of the trading periods in many months (approx 40 hours in a month) when aggregate wind farm output is below 145MW right across the NEM – this has been the case despite the commissioning of four wind farms in southern NSW in recent years. On the flip side peak daily output has been increasing and surpassed 50,000MWh for the first time on 4th July 2013.
There’s considerable intermittency in daily wind production patterns (or variability, if you prefer that term) – even taking into account the current degree to which wind farms are stretched from South Australia through to southern NSW including TAS. This result gives some hints that there may be issues arise as more wind farms are commissioned to meet the escalating requirements of the expanded MRET target.
1) How much wind energy could be accommodated, theoretically?
We wondered about projecting forwards in time – to see what these daily production patterns might imply by the end of the decade with respect to the possible contribution of wind towards the MRET target?
Given wind production has continued increasing steadily, we took a look at the 365 days leading up to 24th July 2013 and grew the daily wind output by 1060% – this revealed the following pattern of hypothetical output (in green) compared to the actual pattern (in blue):
In taking this approach, the simplifying assumption is that the installed capacity of wind would just be grown by this percentage, with the same relative distribution around the NEM as is currently the case, and with the same technology profile – hence the same output profile. As shown above, this assumption results in the hypothetical production from wind on 27th April 2013 equating to 100% of the operational demand in the NEM – with the percentage on other days scaled back from this.
Aggregated over the year, this hypothetical case represents a theoretical maximum contribution of wind on an annual basis being 37% of energy consumed in the NEM – subject to the assumptions below.
2) What would be the “spare” capacity required
Also of interest to us in this hypothetical daily production trend is the fact that there are a significant number of days when daily contribution would still have been below 10%. In other words, the “daily energy unsupplied by wind” (in the scenario above) would have looked as follows:
A daily energy supply requirement of 500,000MWh equates to an average daily demand of just below 21,000MW – meaning that, in the scenario above, the NEM would still need to have at least* 21,000MW of non-wind installed capacity available to supply energy demand for those days when the wind was absent.
* we say that the installed non-wind capacity would need to be at least this much in order to provide for the variability of wind and demand within each day – and to cater for (planned and forced) outages of this non-wind capacity.
3) Key assumptions in the above
Obviously there have been a number of simplifying assumptions made in the above – including the following:
Assumption #1) That demand across the NEM in 2020 is the same as it was for 2012-13.
We’ve discussed previously how demand in the NEM has been declining for a number of reasons – the outcome of which meaning that it’s a lot less certain, now, where demand will be at the end of the decade.
In the recently 2013 issue of AEMO’s “Electricity Statement of Opportunities”, the three different energy growth scenarios show a less bullish forecast than was the case even just a year ago:
Even if the volume of energy does grow to 2020, assuming that the pattern of daily demand does not significantly change, the above analysis would still be true (in terms of percentage supplied).
Assumption #2) That wind harvesting patterns do not fundamentally change:
In the analysis above we have just grown daily production from wind by the same ratio across all days – i.e. in effect assuming that each existing wind farm was grown in installed capacity by the same percentage, on the same site.
In reality it is likely that the wind harvesting patterns would change somewhat* due to:
(a) More geographically diverse sites being developed – especially if these were to be in northern NSW or Queensland (where, presumably, the wind distribution patterns show more difference from the aggregate ones above).
(b) Other technologies being deployed (such as turbines that can harvest lower or higher wind speeds, etc…)
* This is not our area of expertise and so would appreciate comments from readers below who have some facts that might inform us?
Assumption #3) That there is no large-scale energy storage technology deployed in the NEM.
Currently energy storage technology cannot be commercially deployed across the NEM, at scale.
There are organisations working on a variety of technologies that might, one day, provide for storage at scale – we would also welcome comments below from people who know more about storage technologies than us.
Should energy storage technologies be deployed in the NEM, then this would fundamentally change the above. The analysis above highlights some of the technical challenges that would be imposed on such technology (e.g. the extremely peaky nature of the demand for storage, taking into account the large variability in wind farm output).
4) With respect to the current MRET target
Currently the MRET target is not for renewable supplies anywhere near 37% of the energy consumed in the NEM.
Even with the current level of the target, however, the above analysis illustrates the degree to which there will need to be other, complementary technologies installed and available to meet demand when the wind is absent.
Some of these might be other renewable sources (solar PV being the current growth area) – however in 2020, at least, the significant contributor will still remain gas-fired or coal-fired thermal generation.