8 Concluding remarks

In this scoping study, we presented findings on the social and technical impacts of DER curtailment by running focus groups and interviews and analysing real operational data from sites located in South Australia. The results obtained from the focus groups and interviews indicate that energy users have limited understanding of the issue of curtailment and expect more transparency as the issue is anticipated to become more significant in the future. The research participants raised concerns around the fairness of curtailment and believe that it is mainly the responsibility of government and network operators to resolve the issue. The findings from the social science analysis suggest that all three dimensions of energy justice –distribution, recognition, and process (Jenkins et al, 2019) – are relevant in considering the impacts of DER curtailment and possible measures to manage it. Prior research and this report’s technical findings indicate that some energy users experience higher levels of curtailment than others, according to a range of factors such as the size, type, location and age of a D-PV or BESS system, and the research participants identified the uneven distribution of impacts as a matter of ‘unfairness’. Our findings show that justice as recognition is another important dimension to be considered, by ensuring different households (including those without D-PV) and their interests are represented in decision-making around the issue of curtailment. Participants expressed that recognition of the positive role of D-PV is likely to be an important part of this. Finally, the third, procedural dimension of energy justice is at issue here too, as our research indicates that people expect transparency and information about the extent to which they are being or might be affected by curtailment, in order to make informed decisions about DER investment or management.

The technical analysis focused on two types of curtailment, tripping (anti-islanding and limits for sustained operation) and V-VAr, from both energy users’ and aggregators’ perspectives. Consistent with some of the prior research results, curtailment was found to be insignificant for most households. However, some households incurred significant generation loss due to curtailment, which raised concerns regarding the fairness of curtailment. The findings however have also highlighted that inverter set points are an important area for further investigation. The analysis of VAr characteristics showed that most BESS did not show a defined V-VAr response because they have legacy settings which did not mandate V-VAr response. Similarly, most D-PV did not show any V-VAr response and either operated at fixed unity power factor or increased or reduced its power factor with increasing real power. Further research is needed to investigate potential reasons behind this type of behaviour. Overall, D-PV systems experienced higher revenue loss due to curtailment than BESS, which is attributed to the storage capability of BESS, reducing the excess generation and enabling the use of the curtailed output at a later point in time. To understand what curtailment would look like if all BESS and D-PV operated according to reference VVAr curves, scenario analysis was carried out. Four V-VAr curves were investigated from TS-129, AS/NZS4777-2015, ENA and AS/NZS 4777-2020 and it was seen that V-VAr curtailment increased for BESS when they operated according to one of these V-VAr curves with the ENA curve resulting in the highest curtailment. On the other hand, D-PV curtailment was reduced when it operated according to one of the reference V-VAr curves, as some D-PV inverters absorbed higher amount of VArs with its default power factor and VAr settings. It is important to emphasise that the study did not investigate V-Watt curtailment, which is expected to result in higher curtailment overall than the analysed tripping (antiislanding and limits for sustained operation) and V-VAr when it is enabled. Another limitation of this analysis is that the analysed operational voltage, BESS, and D-PV data may not be representative of a future scenario as both DER uptake and DNSP’s management strategies are changing very quickly.