When we first published the Exemplary Weather and Energy Index (EWEI) in “Exemplary Advances“ in 2014, it included “an SAM model of a typical 3 kWpeak solar PV system designed by GSES.” In a context where grid connection was novel and home batteries were only used in remote area (grid isolated) systems, the most cost effective size was 1.5 kWpeak – small enough for the household to consume all that it produced when it produced it. But Exemplary and GSES were both aware that grid connection was coming fast and elected for a system double that size; looking to “future proof” the PhotoVoltaic index in a wide development context. But growth has continued apace.
In the July 2021 edition of “Exemplary Advances” we referred to a “Renew Economy article” reporting an increase in rooftop solar systems to an average of 8.7 kW. At that time Exemplary, continuing its partnership with GSES, updated the system size for the EWEI simulations from a 3 kW system, to account for the past continuous increase in capacity of Australian PV deployment and energy generation trends that better reflect the market.
However, GSES recommended a 5 kW PV system for our model, citing that although the average Australian PV system size has reached the 8 kW mark, this figure is skewed by a relatively small number of high powered 3 phase systems. As most residential owners use a single phase power supply, a more accurate representation would be 6.6 kWDC array connected to a 5 kWAC inverter. Also this power capacity is the default limit for a single phase inverter to constrain the effects of power imbalance. This limit is imposed by AS/NZS 4777.1 and also by network operators, who have the authority to provide exceptions where they see fit.
Exemplary’s PV system model now has the parameters of SMA 5000TL inverter with Trina Honeyblack 330WDC panels. Upon comparison with the earlier model, the monthly energy outputs showed an increase by around 120% for all the four EWE analysis locations. We also performed comparative studies to understand how the new and the original PV system models stand when compared to the long term average climate data (Reference Meteorological Year – RMY) and projected future climate data (Ersatz Future Meteorological Year – EFMY).
The example shown above is based on a concatenated year of recent months and charts a sensitivity analysis exercise for Canberra; similar exercises were done for three other capital cities of Brisbane, Perth, and Sydney. The modest shift in the percentage differences validates the PV system model update in our EWE analysis late last year to provide meaningful continuity to our percentage comparison based on the latest weather for our readers and solar PV owners while switching to a more currently recognizable system size. This enables a fuller understanding of the performance of their installed PV systems when compared to the long term average weather and its estimated performance in future weather conditions.
Ultimately, it must be noted that while the Exemplary Weather and Energy Index analysis is focused on non-residential buildings, the residential PV installations are still dominating the market and it is thus our focus for the PV analysis of the EWEI. Additionally, efficiencies of scale for PV systems are modest, as corroborated by this sensitivity analysis. Therefore the results obtained in the analysis, expressed as percentage differences, continue to be indicative for all fixed-array residential and commercial rooftop systems of near-north orientation.