Free electric vehicle charging at work? It's possible with optimum solar

Engineering researchers based at the University of South Australia (UniSA) Mawson Lakes campus say that using renewable energy to power EV day charging is the key, lowering electricity grid demand in the evening and helping to support Australia's net zero emission targets by 2050.

The campus currently has rooftop solar panels on 18 buildings, supplemented by ground-mounted solar panels. The 2019 installation was based on energy needs at the time, but prior to the rapid uptake of electric vehicles.

A new model proposed by the UniSA research team shows that by nearly doubling the existing PV system on campus, free charging could be available to more than 200 electric vehicles -- or 25% of the available parking spots on campus.

By introducing a nominal charging fee, the campus could support 100% EV penetration in the future, saving more than 20% in energy costs.

UniSA Professor Mahfuz Aziz, Dr Mohammed Haque and UniSA PhD researcher Yan Wu have published their findings in the journal Renewable Energy.

"We looked at different models to determine the most efficient way to support electric vehicle charging, while decreasing the campus's net annual energy costs," says Yan Wu.

"At 25% EV penetration, the UniSA Mawson Lakes campus could reduce its annual electricity costs by more than 9% by upgrading its existing solar PV system to optimum capacity, supporting free EV charging during the day. This would also help lower peak power demand by at least 12%.

"By optimising the PV system, more energy would be exported to the grid, which does not attract any revenue. However, providing EV charging services at a nominal fee using the excess PV generation is a sensible solution.

"By doing so, the campus can potentially support 800 EV cars, the maximum number of parking spaces at Mawson Lakes, while incurring almost the same annual energy costs as that for 25% penetration with free charging."

The researchers used data from the Victorian Integrated Survey of Travel and Activity (VISTA) to obtain average daily travel distances and campus arrival/departure times. The modelling based on this data was further validated using actual parking data from Monash University's Clayton campus.

South Australia has a very high rate of solar PV penetration, driving high solar generation during the day. This results in a substantial decrease in grid power demand around midday and a dramatic increase in grid demand during the evening when solar generation falls.

"This causes significant operational challenges," says Professor Aziz.

"Excess power generated by rooftop solar and exported to the grid creates major grid issues as dispatchable power must be ramped up suddenly to replace dwindling solar power later in the day, causing a so-called duck curve.

"Workplace charging of EVs helps address this challenge by using excess renewable generation during the day. Prioritising daytime workplace charging reduces pressure on the grid during the evening peak hours by decreasing the demand for home charging of EVs.

Dr Haque says Australia would use solar more efficiently if it established comparable EV charging infrastructure in private and public facilities.

"This initiative not only helps in achieving a more balanced grid demand profile, but also promotes a greener environment," Dr Haque says.