By Thara Philip, e-mobility Doctoral Researcher, The University of Queensland
Electric vehicles (EVs) are key to decarbonising road transport, but they could also play a crucial role in supporting the transition of Australia’s electricity grid to renewable sources.
As the number of EVs increase on our roads, so too will the demand for electricity to charge them. Without proper coordination, this increased demand could potentially trigger the need for additional electricity generation and extensive upgrades to infrastructure.
But by optimising charging, EVs could be critical to decarbonising both the transport and energy sectors. Let’s look at EV charging from the perspective of an EV owner and more broadly from the position of supporting a low-cost renewable energy transition for all consumers.
When is the best time to charge my EV?
Electric cars rely on charging from the local electricity network. EVs offer greater energy efficiency compared to conventional vehicles, reducing energy consumption and emissions.
But how and when EVs are charged will determine their overall effectiveness in reducing greenhouse gas emissions, grid impacts and charging costs incurred by the EV owner.
Financial considerations
A general rule of thumb is not to charge in peak hours or high-energy use times, typically 4pm-8pm. This not only means cost savings for the EV owner, but also helps to balance the grid and lower the costs of electricity for all consumers.
Many retailers offer time-of-use (ToU) tariffs that vary according to the time of day. Currently these rates are typically lowest overnight due to less demand and lower wholesale cost during those hours. EV users can capitalise on these tariffs, ensuring cheaper charging.
Home charging at reduced ToU rates is usually the cheapest method for those without rooftop solar. ToU tariffs are also applicable at some public charging stations. But EV owners who have rooftop solar and feed-in tariffs that pay them less than the retail cost of electricity will usually find charging cheapest using electricity generated from their solar that would otherwise be exported to the grid.
Environmental considerations
The environmental impacts of charging at different times of day are more nuanced. EVs produce no tailpipe emissions and, if powered by renewable energy, also have zero greenhouse gas emissions. An EV charged through renewable sources like solar and wind boasts a greener footprint compared to one relying on coal-generated power.
But are EVs in Australia powered by renewable energy? Technically, the emissions impact of electricity use depends on where the additional electricity comes from. Currently any increase in electricity demand is usually met by additional coal and gas generation, except for during the middle of the day when it’s more likely to be solar.
That’s partly because of Australia’s high rate of rooftop solar penetration – more than one third of households. Solar power generation typically peaks between 10am-4pm, depending on theregion and weather conditions.
When additional electricity use comes from live or stored solar and wind power, EV charging is emissions-free. EVs charged in the middle of the day therefore tend to support the transition to a renewable grid.
It’s important to note that as the grid increasingly relies on renewables, there will be a positive convergence of both financial and environmental considerations. Cheaper charging options are now becoming available during daytime hours thanks to an abundance of cheap solar power.
Some electricity retailers offer cheaper rates during the middle of the day. Soaking up this abundant electricity by charging during the day will therefore be cheaper, lower the stress on the grid and have positive environmental impacts.
How can I optimise charging of my EV?
Most EVs come with programmable charging settings that allow users to schedule their charging times. This means EV users can plug in their vehicles at their convenience and the EV only draws power from the grid during the scheduled time.
Using this function, EV owners can aim to maximise their benefit from lower electricity rates and reduced environmental impacts. There are also third-party smartphone apps to help EV owners schedule and automate charging, considering factors likeelectricity rates and renewable energy availability.
What is the future of EV charging?
The future of EV charging in Australia is an exciting prospect with the roll-out of technology including managed charging (V1G) and Vehicle-to-Grid (V2G). Managed charging (V1G) enables EVs to dynamically modify their charging rates and time based on grid demand and availability of renewable energy sources.
Initiatives are underway in Australia to optimise energy usage and reduce grid stress during peak periods, with EV owners able to sign up for the AGL EV smart charging trial and Endeavour Smart EV Charger plan. Vehicle-to-Grid (V2G) technology enables EVs to feed excess energy back into the grid.
This is especially significant in the context of the ‘duck curve’, a graph depicting timing imbalance in the grid’s demand and supply over the course of a day. Charging EVs during the day can help support the grid’s performance and stability by balancing this demand.
Most importantly, as V2G rolls out, capable EVs can export surplus energy stored in their batteries back into the grid during peak demand hours. It’s projected that by 2050 the National Energy Market would need 640 gigawatt-hours (GWh) of energy storage to successfully transition to renewable energy sources. By this time EV batteries are expected to have about four times more capacity.
By tapping into even a fraction of the potential of technologies like V2G, there is opportunity for substantial savings on large-scale battery infrastructure costs.
In summary, smart charging offers significant potential to develop sustainable transport and energy infrastructure in Australia through EV adoption.
This article has been republished with permission from The University of Queensland. It first appeared on UQ’s Australian Institute for Business and Economics website.
Want to be part of the solution?
The University of Queensland’s Australian Institute for Business and Economics (AIBE) is currently running a research project looking at whether EV owners can be incentivised to charge their cars when the grid has peak renewable energy. EV owners interested in taking part in future UQ research projects can register their interest here.
