More than 20% of Australian households have rooftop solar panels, equating to around two million houses. While this number is positive, the increase in PV systems is creating challenges for the Australian electricity industry.

UniSA solar researcher Kirrilie Rowe says one key problem currently facing home PV stems from the discrepancy between the times of peak use and peak production.

“Solar panels on residential dwellings are typically installed facing the equator to maximise the energy collected, but the power generated by an equator-facing panel peaks at around midday, whereas residential loads typically have peaks in the morning and afternoon,” she says.

Currently, households are paid a ‘feed-in tariff’ for excess electricity sent to the grid. But as the number of homes producing solar power increases, the viability of exporting to the grid reduces.

“In some markets at certain times we’re already seeing over-supply during peak production times, which can cause grid instability and is leading to reductions in feed-in tariffs,” Kirrilie says.

“The real challenge now facing the solar industry is finding ways to balance production and consumption by maximising self-consumption for the solar panel owner.”

A solution that Kirrilie’s research suggests aims to rethink the orientation of solar panels, better aligning match times of production to patterns of consumption, even if it results in a slight energy generation reduction.

“Traditionally, PV panels are mounted facing the equator as this creates more energy per square metre of PV panels, but this orientation does not necessarily maximise the community self-use of the energy prior to the excess being exported to the wider grid,” she explains.

“By orienting panels in different directions rather than just facing the equator, it’s possible to minimise the shortfall between load and generation.

“This benefits the end-user by decreasing the amount of electricity required to be imported, and the stability of the grid by decreasing the amount of variability between peak and low loads.”

A study by Kirrilie and associate professor Peter Pudney calculates the optimal self-consumption panel orientations for a community of 29 individual dwellings and another with 42 apartments.

“Our analysis uses detailed load data and detailed irradiance data and shows that optimal panel placement for self-consumption is never towards the equator,” Kirrilie says.

“In both cases, if the panel area is small enough so that the household will not export, then facing the panel north is best. But as panel area increases, it becomes better to face the panels facing north-west to meet the afternoon loads, and if even more panel area is available then panels should be faced north-east and west.”

Over the next few years, as solar uptake increases, feed-in tariffs fall and the cost of solar batteries remains prohibitive, the real value of solar self-consumption will continue to rise.