This is part two of a three-part series on electric vehicle (EV) charging strategies. You can find part one here and part three here.

In conjunction with the modal shift to better public and active transport, electric vehicles (EVs) offer a massive opportunity to reduce emissions and improve urban air quality. However, crafting effective EV charging strategies requires holistic thinking at the intersection of transport, energy, the built environment, behavioural science, and economics. 

Part one of this three-part series examined the EV owner experience and introduced charging policy fundamentals. Part two reconsiders electric vehicles as “batteries on wheels” and assess the implications for charging policies, technologies and integration. 

Batteries on wheels

As electricity grids migrate from emissions-intensive coal and gas to renewables and storage¹,  electricity production (generation) switches from predictable to variable. Nevertheless, existing consumption patterns persist: higher demand in peak summer and/or winter due to higher use of air conditioning and heating (particularly as heating is electrified); plus a workday evening peak when commuters return home and turn on appliances, but factories and offices are still ramping down.

For obvious reasons, solar generation peaks in the middle of the day, and is highest in late Spring closer to the summer solstice, and when skies are clear but temperatures not too hot. Fortuitously, the wind tends to blow more consistently at night, so a good mix of solar and wind generation across a regional area is fundamental to a renewable grid.

The problem is, we’re already seeing markets where there’s too much solar generation for a few hours in the middle of the day, and not enough wind to serve the evening peak. Enter battery storage to smooth out these peaks and troughs. And what is an EV, but a battery on wheels?

EVs have a huge role to play in grid stability. To the extent that EV owners can be persuaded or incentivised to charge during the day and – especially – not during the evening peak, they can become a huge asset to the grid. Moreover, because EV’s are such a distributed battery resource, they can also alleviate local distribution network congestion (more on that later).

And with most new EVs sold from about 2025/6 expected to be “vehicle to grid” capable (assuming deployment of the updated CCS bidirectional charging protocol), their value could be much greater. If incentives can be aligned with owners’ expectations and vehicle manufacturers’ warranty constraints, a proportion of the EV fleet could act as a giant distributed battery, selling power back to the grid when there are shortfalls elsewhere.

In fact, if we get this right, an EV fleet used in this way could massively reduce the extent to which distribution networks would otherwise need to be upgraded to cater for the additional loads (of EVs and electrification of building heating); and substantially reduce the amount of renewable generation that needs to be built to make a fully renewable grid a reality. 

In Australia, for example, our fleet of around 20 million vehicles, if fully electrified, could be equivalent to over 1 million MWh of storage – about three and a half times the massive “Snowy 2.0” Pumped Hydro Storage project currently under construction. Even a relatively small proportion of that capacity would be tremendously useful. Unlike Snowy 2.0, which is in the mountains far from population centres, the vehicle fleet is broadly distributed around the country and our cities, making it more valuable in avoiding network and transmission upgrades.

How do we make it happen?

Driving patterns

By and large, vehicles are typically used in one of the following ways: 

*Holiday driving is often an infrequent use case for a vehicle that is typically used as a shopping trolley or for commuter driving

Table 2 - Typical vehicle usage patterns

Matching charging with available power

It’s clear from Table 2 there are plenty of opportunities to match charging with excess solar generation, including locally generated on people’s rooftops, and on grid. But will that match driver behaviours?

Apart from commercial vehicles, people with long commutes, and holiday road trips, there’s generally no need to charge every day (just as people don’t typically fill an ICE vehicle’s tank every day).

However, unless charging is undertaken at the vehicle owner’s home or business, then someone else needs to be able to recover the costs of providing EV charging equipment and supplying electricity. A range of charging service companies have sprung up, whose business models are predicated on:

a) charging a markup on the electricity (including significant “maximum demand” supply charges) to cover the costs of the equipment, service, and profit margin; and 

b) maximising daily utilisation of each charger (in terms of kWh delivered)

Unless governments regulate and/or directly provide or subsidise charging infrastructure (at a more sophisticated level than individual planning application determinations), these companies will have a big say in where chargers wind up and how they get used, which may wind up being sub-optimal for distribution networks. 

It may be useful for policymakers to consider charging infrastructure as a public utility, which should be provided equitably to everyone at a basic level for a reasonable cost. There’s a public health and safety angle to this: regular fast chargers along highways could prevent drivers from becoming stranded in heatwave conditions. Similarly, providing chargers in numbers and locations that all socio-economic levels can reasonably access.

For drivers with off-street parking (which often coincides with those in outer rim suburbs who rack up higher commuter mileage), charging at home will always be the cheapest option, in the absence of contrary regulatory mechanisms.

With many people on the road or at work during the day, there’s a danger that large numbers of drivers will want to charge at night, during periods of lower generation from renewables. As noted, early evening is a particularly precarious time to imagine thousands of EV owners seeking to charge given the existing consumption peak described above. It could trigger constraints within both suburban distribution networks, and overall grid capacity, given the lack of solar generation during that period.

On the other hand, a vehicle that can charge during peak day-time solar generation is an asset to the grid, because it is soaking up generation that might otherwise need to be curtailed. That’s great for “shopping trolley” cars that are often idle in the middle of the day. Even better if they are soaking up the owner’s rooftop solar, because that’s effectively free fuel.

Incentivising workday charging

Will commuters want to charge their vehicles at work or at “park and ride” facilities next to mass public transit hubs? Sure, if they don’t have off-street parking and it doesn’t complicate their journey. But would commuters with off street parking want to pay a premium to charge in a commercial car park, when they can do so at home for their normal retail electricity rate?

Maybe: if commercial day time charging could be made as cheap or cheaper than at-home evening charging, via variable tariffs that can dynamically take advantage of ultra cheap day time wholesale electricity rates.

Aligning fleet charging

Scheduled buses are an awesome use case for electrification, particularly in conjunction with urban solar installed in and near bus depots. Bus fleet utilisation is highest during the morning and afternoon school and commuter peaks. Much of the fleet is furloughed at depots in the middle of the day, providing a perfect opportunity to soak up excess solar. Buses are then back in their depots later to take advantage of low overnight electricity rates, fortuitously missing the precarious evening electricity-usage peak. School buses might even be available to discharge during that peak, providing valuable network stability services.

Delivery vehicles run different shifts depending on their use, so that’s a mixed bag, but really important to be grid-orchestrated if it is likely to involve charging many vehicles at the same time.

It’s worth pointing out that there are viable EV solutions even for dual shift vehicles. Over a typical shift a driver is generally obliged to take at least one break. Given a super charger can take a vehicle from 10 to 80% charge in as little as 10 minutes, they are the answer for light vehicles. 

Long-haul trucking has a solution too, in the form of Australian start-up Janus Electric’s battery swap system. They take existing diesel prime movers, replace the engine with an electric motor (a prime mover typically has an engine rebuild about every six years anyway), and replace the fuel tanks with standardised removable batteries on the sides of the cab. 

Here’s the best bit: Janus Electric is creating an “ecosystem” of battery swap stations at intervals along major inter-city routes that coincide with mandatory driver rest stops (and have ensured that their system delivers the appropriate range). Instead of spending up to 20 minutes pumping diesel, the batteries are swapped via forklift in just a few minutes. The empty batteries are then plugged in to charge, so they’re ready for another driver, with the company becoming an off-taker of nearby solar or wind farms. While they’re big batteries, they don’t need super-fast charging, so the swap and charge stations are less of a drain on the grid. And potentially, while they’re waiting for the next truck, they could also provide local voltage and frequency stabilisation for the grid!

Managing distribution capacity

Imagine the electricity grid as a network of ropes and strings. Some ropes are thicker than others - they can carry more power at once. Where ropes meet in the middle of the network, there are electrical substations - they have capacity constraints too. So do the transformers closer to the edges of the network. Imagine houses at the edge of the network being connected via threads of cotton. An office building, shopping mall or factory by a thin rope. 

If the building has rooftop solar, then power might be flowing towards the network during the day, but in the other direction at other times. Finally, imagine big generators and grid batteries attached to some of the fatter ropes, variably delivering power via the various substations to the buildings.

The critical thing with electricity is that you need to supply almost exactly the same amount as users demand at any given moment, otherwise you lose system stability, leading to brown or black outs. Batteries are great at responding to these fluctuations, because they can be turned off or on in an instant.

If the 100 or so homes connected to a suburban transformer (in Australia often a green box about the size of a large refrigerator that you might see by the side of the road; elsewhere found on power poles) now have EVs with standard Level 2 chargers, and a fair number of them decide to charge simultaneously, then it’s likely to trip that transformer (like blowing a big fuse). And if a bus or truck depot suddenly has dozens of buses fast charging simultaneously (each using as much as a supermarket), then there might be capacity constraints back to the zone substation or beyond.

Given these challenges of timing and variable network capacity, what’s the solution? Find out in part three of this series, where we put together the essentials of electric vehicle charging policies.

illuminem Voices is a democratic space presenting the thoughts and opinions of leading Sustainability & Energy writers, their opinions do not necessarily represent those of illuminem.

¹ If a country has nuclear power, by all means leave it in the electricity generation mix and expand it if it makes sense to do so. If it doesn’t, consider adding it to decarbonise the grid, but don’t let that slow down the deployment of highly modular, scalable, cheap renewables. Australia is blessed by abundant sunshine, wind, land and coastlines, making it perfect for a grid based on renewables and storage with no need for nuclear.