The ACT Government has a target for 100% renewable electricity by 2020. Most of that renewable energy is coming from wind farms in South Australia, Victoria and NSW, while a smaller fraction is coming from solar farms within the ACT.
The electricity from all these wind and solar farms gets fed into the national grid, and no-one really knows where the electricity goes or what fraction is consumed within the ACT.
However, the basic idea is that averaged out over a year, the amount of generation coming from the wind and solar farms will match the amount of electricity used by the ACT.
The generation from wind and solar is quite variable. Sometimes there is a lot more renewable electricity than the ACT is using, while at other times there is a lot less, as can be seen in this following chart showing a fortnight of generation (wind=green, solar=orange) and demand (black line). But averaged out over the year, they should approximately match.
There is only a comparatively small amount of electricity storage on the national electricity grid, and as a result, nearly all electricity must be used at the same time as it is generated.
Thus, as a result of the variability of the wind and solar generation, it is clear that sometimes ACT demand is being supplied by electricity that was not generated by the wind and solar farms.
It is also clear that sometimes the wind and solar generation is greater than ACT demand, and some fraction is therefore supplying users outside of the ACT.
This article aims to answer various questions about the ability of this wind and solar generation to meet the ACT demand. And, by using 7 months of data from Nov 2018 to May 2019, it is possible to assert the following:
– Wind and solar generated 98% of the ACT’s net demand over the period;
– 78% of the ACT’s electricity could theoretically have been supplied directly from the wind and solar generation (ie. without the need of any storage), the remaining 22% would need to have been sourced from other generators on the grid;
– 19% of the wind and solar generation was, at the time it was generated, in excess of the ACT’s need, and instead was used by users in other states. It had the effect of greening their electricity supply;
– 96% of the time wind and solar generation exceeded 100 MW, which corresponds to the average demand requirements of about 125,000 ACT homes;
– 48% of the time wind and solar generation exceeded 300 MW, which corresponds roughly to average ACT demand.
Explanation of the 100% renewable electricity goal
The ACT Government has a target for 100% renewable electricity by 2020. It plans to achieve this through a few different routes:
– It has signed contracts with large-scale wind and solar farms with predicted generation representing approximately 3/4 of the ACT’s demand.
– Approximately 5% of ACT electricity is expected to come from rooftop solar within the ACT.
– The remaining ~20% is to be sourced from the ACT’s share of the national renewable target with a small residual from GreenPower purchases.
The contracts with large-scale wind and solar farms work in the following way: The ACT guarantees the wind and solar farms will receive a given price for every MWh of electricity that they generate, through a contract for difference (CfD) scheme.
The guaranteed price is shown the table below. In return, the ACT gets the renewable certificates (LGCs) from the projects, which are what are used to justify the claim to being powered by renewables.
The contracted wind farms are located in South Australia, Victoria and NSW, and the solar farms are in the ACT. All electricity generated is fed into the national electricity grid. It does not go directly to ACT consumers.
The output of the wind and solar farms is also quite variable, and does not correlate with the ACT’s demand. Both of these points have led to criticisms that the ACT claim of 100% renewable is not valid.
This article aims to provide some facts regarding the second point, by investigating how the variability of the wind and solar generation relates to ACT demand.
It should be noted that the 100% renewable target is for 2020. While most contracts between the wind and solar farms and the ACT Government have commenced, the final contract does not until October 2019.
However, all the wind and solar farms have been generating at full capacity and exporting to the grid since November 2018, and the analysis in this website assumes all generation has been contracted since this date. More details about the projects are provided in the following table.
The figure above summarises the monthly results. The green and yellow columns indicate the average power delivered by wind and solar during the month respectively, while the solid black line shows average ACT demand.
The red dotted line shows the ratio of the average power delivered by the wind and solar to demand.
Thus, in most months the wind and solar farms supplied more electricity than was needed by the ACT. In January and May it supplied less.
We expect to see more months when renewable generation is less than demand during the winter months when ACT demand is considerably higher.
The blue dotted line shows the fraction of ACT demand that theoretically could have been supplied directly (without storage) by the wind and solar during the month.
In other words, when looking at the fortnightly chart at the top of this page, the blue dotted line represents the fraction of the area under the black demand line that is covered by renewable generation. It is equal to the red dotted line minus the fraction of renewable generation that was excess to ACT’s needs at the time it was generated.
Renewable generation Probability of Exceedance chart
The blue curve in the following chart indicates the fraction of the time that the wind and solar farm generation exceeded various generation levels, based on the 30 minute generation data.
From the chart, it can be seen that about 96% of the time, wind and solar generation exceeded 100 MW, which is the average demand requirements of about 125,000 ACT homes. About 48% of the time, renewable generation exceeded 300 MW, which is approximately the average demand requirements of the ACT.
Each of the following charts show the renewable generation over a fortnight at a 30 minute resolution.
The green tinged areas represent wind generation, while the orange/yellow tinged areas represent solar generation. See the explanation notes at the end of this report for more information about how all these quantities were calculated.
Detailed Explanation Notes:
– Green areas in the fortnightly charts represent generation from wind farms: Coonooer Bridge (Vic), Ararat (Vic), Crookwell (NSW), Hornsdale 1, 2 & 3 (SA) and Sapphire (NSW). Data is obtained from AEMO.
– The ACT has contracted only part of Ararat (33%) and Sapphire (37%) wind farms, so the AEMO data from these projects has been scaled by these percentages. There is also a green component indicated by LRET wind, which indicates an estimate of ACT’s share of wind generation on the NEM due to the LRET and the residual GreenPower purchases. It is obtained by scaling total NEM wind by 3.1%.
– The yellow area represents generation from utility solar: Royalla, Williamsdale, Mugga Lane and Majura, all within the ACT. AEMO data is only available for Royalla and Mugga Lane, and total utility data has been estimated by adding the Royalla and Mugga Lane data and then scaling by 143%, representing the ratio of total utility solar capacity to the capacity of Royalla and Mugga Lane.
– There is also a dark orange component indicated by LRET PV, which indicates an estimate of ACT’s share of utility solar generation on the NEM due to the LRET and residual GreenPower purchases. It is obtained by scaling NEM utility PV by 3.1%.
– The brownish area represents generation from rooftop solar within the ACT. It is estimated by scaling NSW rooftop generation as obtained from AEMO by 4.9%, which is approximately equal to the ratio of the installed capacity of rooftop PV in the ACT to that in NSW, as indicated by the Clean Energy Regulator.
– Recent ACT demand is not available, so it has been estimated by scaling NSW demand by a matrix of scale coefficients. The matrix is a function of time of day and month, has an average value of 4.1%, a maximum value of 5.3% for 8am in August and a minimum value of 3.1% for 1am in April.
– This matrix of scale coefficients relates demand in the ACT to demand from NSW, and was calculated using the ratio of ACT to NSW demand from the 2017-2018 financial year. Rooftop PV is then added, as it is excluded from both NSW and ACT demand data sets. NSW data is obtained from AEMO.
– Crookwell wind farm only reached full capacity in November 2018. That is why this analysis starts in this month. I intend to update this web-page on a semi-regular basis, hopefully monthly.
– The contract between the ACT Government and the Hornsdale 3 wind farm does not commence till October 2019. The wind farm has, however, been providing generation into the grid for a couple of years, and this analysis has assumed that it is contributing to the ACT target during the entire period. Its contribution represents ~13% of ACT demand.
– The analysis does not consider the impact of loss factors. Note that LGCs are calculated by multiplying generation by the marginal loss factor (MLF) of each generator. A more detailed analysis would be required to calculate if the ACT had obtained sufficient LGCs in order to satisfy its claim to be 100% renewable.
– The LRET + Greenpower components have been calculated by scaling NEM renewables by 3.1%, which is the fraction required to meet approximately 20% of ACT demand over 2019. The renewable power percentage is expected to be approximately 20% in 2020, and therefore the GreenPower residual is likely to be relatively small.
Quarterly data on the costs of the Contract for Difference (CfD) scheme can be obtained from the ACT Government here, though it usually has a lag of several months. The table above shows the CfD price for each project. Each project sells their electricity on the wholesale market.
If they sell it for less than the CfD price, then they get topped up to the CFD price. If the project sells their electricity for more than the CfD price, then they have to refund the difference. In return for guaranteeing the price, the ACT Government gets to keep the Renewable Energy Certificates. In simple terms the CfD scheme can be thought of as an economic way of purchasing renewable certificates directly from the renewable generator.
The following image shows the cost paid to each generator per MWh of generation over the last couple of years.
This cost represents the cost of the certificates to the ACT. It is clear that the cost of certificates from solar generation is quite high, generally around $100 per certificate, while the cost from wind is usually less than $20 per certificate. As more wind generation enters the scheme, the weighted average cost has come down substantially.
Since the inception of the scheme, the ACT has paid $24.89 per certificate. In the 2018 calendar year, it paid an average of $19.53 per certificate. As can be seen, during some months, the cost of the certificates has been negative.
This indicates that the project sold their electricity on the market for a higher price than the CfD strike price, and therefore had to refund the difference back to ACT consumers.
Disclaimer: This website has been created by David Osmond, who has worked in the renewables industry for nearly 20 years. David has worked at Windlab since 2003, and Windlab developed one of the wind farms which won a contract with the ACT Government for supply of renewable energy, Coonooer Bridge Wind Farm. The work presented here is his own, and is not endorsed by Windlab.