If drivers are slow to upgrade to EVs maybe owners of bus fleets will surprise us all by rolling out new clean rolling gear? They will need to have a lot of charging smarts in place to do so.

If electric vehicles have the potential to provide an enormous aggregate service to the grid, not to mention our lungs, let’s not forget electric buses.

About 20,000 public transport buses are employed across the country, shuffling Australians between stops, or about 100,000 if you include private fleets and school buses. If public transport buses in every state were all electric and connected to the grid, that would add up to about 7GWh or so of capacity.

This massive magnitude of new storage won’t appear on our roads overnight (or ever), but owners of bus fleets are thinking about the transition to electrified vehicles and the requirements for charging gear. In NSW, about 8,000 government buses will be electric by 2030; Victoria has started a zero-emission bus trial and will stop buying diesel buses by 2025; and the ACT is moving to electricity part of its bus fleet.

“Each state is moving at a different pace but all signs suggest significant conversion from diesel to electric in the next decade,” says Enel X head of Asia Pacific Jeff Renaud.

Well known as a leading aggregator of demand response services to large industrial energy users, Enel X is working with fleet owners to get the ground ready for electric buses.

The task includes assessing upgrades required to convert bus depots from low load centres to far greater ones, with charging hardware and a software offering that will orchestrate charging to optimise the cost of power and fleet timetable. Enel X will also manage long-term energy supply arrangements with options for 100% renewable power.

Not so fast

The battery in an electric bus is generally 350-400kWh and timetable scheduling will allow for cheaper alternatives than expensive rapid charging. “There should be enough downtime in the day-to-day life of a typical bus to allow them to charge at the depot on a more moderate scale,” Renaud says, “which is still fast by typical EV standards.”

Renaud suggests a 150kW charger would be able to charge a bus in a few hours, with the possibility of a depot also hosting a smattering of fast chargers – or “opportunity chargers”. The fit out would amount to one charger for every two buses, as a rule of thumb.

It’s too soon to predict how these gigawatts of new load connected to the grid will be utilised but “qualitatively the contribution can be significant,” Renaud says.

The aggregate loads of electric bus fleets aren’t a perfect complement to the cheapest energy – solar – as they do most of their work during daylight hours. There is plenty of time between the morning and after-school/after-work peaks, however, where Renaud says advantage can be made of cheap solar.

“The windows of time when the buses want to charge naturally are outside of the most stressful times on the grid,” he says. “The times power prices are highest and reserve margins are lowest because of solar’s impact are first thing in the morning and in the evening when the sun starts to set – and generally the buses don’t need to charge at those times. Naturally, buses don’t want to consume power when the grid is at its highest levels of demand.”

Many buses, then, will be able to soak up solar and the others can charge overnight when demand is at its lowest. There will also be the opportunity for fleets to support the grid during the evening peak. “They could act as a battery does to support the grid, either to help mitigate high power prices or provide frequency control to stabilise the grid,” he says. “We see a lot of opportunity to create value in terms of reducing the cost of running bus fleets and helping electric buses play a role in supporting renewable power on the grid.”

The daily duck curve

Enel X manages services such as demand response for around 6GW of total capacity at global level and 123MW of storage capacity worldwide, as well as around 186,000 electric vehicle charging points around the globe.

In Australia the company operates a virtual power plant that connects not only solar and battery storage in commercial- and industrial-sized systems but also equipment, back-up power generation, UPS systems and electric vehicles.

“We use our VPP during critical prime periods where reserves are short and power prices are high – we run it essentially as a peaking power plant to take advantage of that opportunity,” says Renaud, also pointing to its role in intraday shifting of load to take advantage of low and negative pricing.

“The duck curve is now a daily phenomenon, so there’s an opportunity to shift load or utilise distributed energy resources every day to … start to shift the shape of power demand overall, to be more in line with the renewable general profile we see more and more on the grid.”

As large-scale batteries are connected to the grid the FCAS market is predicted to become saturated and less lucrative. “Those markets aren’t huge. But there will probably be more FCAS required over time,” Renaud says, as thermal generation is removed from the grid and a two-second FCAS market is initiated. “There’ll be swings and roundabouts as to where we land exactly – it’s hard to say.”