Warning: electric cars could overload our power network

If you are an electric car driver, chances are you suffer from a touch of "range anxiety". A fear that your electric car will run out of spark at an inconvenient moment. The cure for range anxiety is to make sure you keep your battery topped up - normally by plugging it in when you get home every evening.

But now power companies are being hit by vicarious range anxiety. The fear that increasing numbers of electric vehicles being recharged at home will compete with households cooking dinner, turning on the heater, and powering up their devices. This will create additional load on existing electricity networks during already high usage times. And heaven forbid, say two new reports on the issue, it might force change to the way power is priced.

Auckland-based network company Vector warns that the sheer volume of household electricity required to recharge a load of electric cars with long-distance batteries will place a strain on existing networks and force costly upgrades. The strain is likely to be greatest in the early evening.

The other report, by Wellington firm Concept Consulting for network owners Powerco, Orion and Unison, has a similar warning. Unless electricity pricing changes to encourage EV owners to charge cars after 9pm, expensive network upgrades are unavoidable, report author Simon Coates says. He estimates the cost of such an upgrade at around $4 billion in net present value terms.

Both reports also warn that the new generation of EVs, with larger batteries and far greater driving ranges, will take more than two days to fully charge from a standard wall socket. To avoid that, they predict demand will rise swiftly for fast-charging technology, which will place many times more load on local networks than socket-charging.

"Electricity networks have traditionally been sized according to the number of houses on a street, with little spare capacity. The local network was not designed for... any significant uptake of EVs and the consequent demand for charging at home."

Concept says any such costs should be borne by EV owners rather than all electricity users, and fears the "fantastic opportunity for New Zealand, both in terms of massive gains to the environment and delivering genuinely cheaper transport services" will be frustrated by current electricity supply arrangements.

"With mass EV uptake just around the corner and greenhouse (gas) reduction targets getting ever-more urgent, there is a real-time imperative to resolving this issue", says Coates. More than 6,000 EVs are now on New Zealand roads, with registrations more than doubling in 2017. The previous government targeted 64,000 EVs by 2021 and the new administration is, if anything, more enthusiastic about encouraging EV ownership. Reducing transport emissions represents one of the country's few easy wins as it seeks to meet emissions reduction targets set for 2030.

There is some hope. Concept says "these financial and environment costs are avoidable with smarter, more cost-effective electricity prices that encourage EV-owners to charge their vehicles smoothly overnight". One answer would be to have technology already embedded in the software of the vehicles themselves; a system similar to, but more sophisticated than, hot water 'ripple control'.

The Vector 'green paper' says often there is little excess capacity at a street-by-street local level, meaning the impact of an increasing numbers of cars being charged in the evening could be significant. 

"Electricity networks have traditionally been sized according to the number of houses on a street, with little spare capacity. The local network was not designed for... any significant uptake of EVs and the consequent demand for charging at home."

That created a risk not only of higher electricity prices, but also of being unable to rely on charging an EV at home.

However, use of smart metering, dynamic charging and carefully considering where to locate charging infrastructure also held out the prospect of benefits for EV owners, including being able to sell electricity from their car batteries back into the grid when market conditions favoured that.

Given that the average light vehicle travels only 29km daily in New Zealand, EVs would theoretically only need a charge every three days or so, but 'range anxiety' and convenience were expected to make owners keen to keep their batteries topped up, the Vector paper says.


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