Optimal use of solar PV systems on commercial and public buildings may enable electric vehicle recharging to be feasibly provided to workers during the day either free of charge or through the levy of a nominal fee, new research has found.

In their latest study, researchers from the University of South Australia (UniSA) sought to develop a new model to deliver maximum benefit from provision of electric vehicle (EV) charging facilities using rooftop solar panels.

To do this, the researchers examined their own campus at Adelaide’s Mawson Lakes. The campus currently has rooftop solar panels on 18 buildings, supplemented by ground-mounted solar panels.

They found that by nearly doubling the existing solar PV system on campus, free charging could be made available to more than 200 electric vehicles.

This represents 25 percent of the available parking spots which are provided on campus.

Through these measures, the campus would be able to reduce its annual electricity costs by as much as 9 percent.

Such provision would also help to reduce peak load demand on the electricity system.

Further, the research found that the introduction of a nominal charging fee would enable the campus to support 100 percent EV penetration in the future.

This would save the campus more than 20 percent in energy costs.

The latest modelling comes amid challenges regarding the integration of electric vehicles into the energy grid throughout Australia.

As at July last year, the Electric Vehicle Council reported that EVs account for approximately 8.4 percent of new car sales in Australia.

By 2030, this number is expected to increase to 27.3 percent of all new car sales.

Greater uptake of electric vehicles is considered to be a critical part of Australia’s efforts to decarbonise its transport system and to reach its target of 43 percent reduction in carbon emissions compared with 2005 levels by 2030.

However, there are concerns that large numbers of EV owners may recharge their vehicles simultaneously during the early evening after arriving home from work.

This may place extra demand on the grid during the peak energy period.

To overcome this, one strategy is to encourage EV charging to occur during the day while people are at work.

This would be achieved through provision of EV charging facilities in commercial offices and public buildings.

When coupled with rooftop solar, EV charging can occur during periods of the day where solar power generation is at its highest.

The latest study was undertaken by UniSA Professor Mahfuz Aziz, Dr Mahammed Haque and UniSA researcher Yan Wu.

Findings were published in the journal Renewable Energy.

Yu said the project has helped to determine the most efficient way to support electric vehicle charging whilst also reducing net energy costs for the campus.

“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,” Wu said.

“At 25 percent EV penetration, the UniSA Mawson Lakes campus could reduce its annual electricity costs by more than 9 percent 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 percent.

“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 percent penetration with free charging.”

Speaking particularly from a South Australian perspective, Aziz and Haque say that potential benefits to the grid from EV charging during the day are significant.

This is particularly the case as the state has a high rate of solar PV penetration.

As a result, the state experiences a substantial reduction in grid power demand at around midday.

This is followed by a significant increase in grid demand during the evening when solar generation levels fall away.

“This causes significant operational challenges,” Aziz said.

“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.

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,” he says.