Electric vehicles could solve solar power storage

The powers that be

Five and a half years ago, a powerful windstorm struck South Australia, plunging nearly every South Australian home into a blackout. Although many customers near Adelaide had their power restored by late that evening, regional and rural residents waited days for power to be restored, suffering significant losses.

To prevent any similar sort of “cascading” failure – where an outage at any point in the network can cause the whole network to shut down – the state invested in what was, at the time, the largest lithium-ion battery in existence, the Hornsdale Power Reserve. Built by automaker Tesla in less than 100 days for around $90 million, the “big battery” provides 129 megawatt-hours of electric storage that can be fed into the grid through a 100 megawatt connection. The battery stabilises South Australia’s electricity grid, providing power to compensate for any outages, while also smoothing over any peaks in electricity demand. That means gas-fired electric generators designed to handle peak demand – at a price – have been used far less often since the battery came online. Hornsdale Power Reserve has saved South Australia’s grid, saved consumers money, and spares the planet a fair bit of carbon. It’s so useful – and profitable to owners Neoen –  that just two years after it went online, they set to work on adding 50% more capacity to the battery.

Hornsdale Power Reserve has saved South Australia’s grid, saved consumers money, and spares the planet a fair bit of carbon.

The success of Hornsdale Power Reserve got the attention of energy companies throughout Australia. According to the Australian Financial Review, by the end of 2022, there’ll be at least 1.1 gigawatts of battery capacity installed throughout the nation – the equivalent of six Hornsdales. All of this means that quick-to-fire-up-but-expensive-to-run gas generators may no longer be needed to smooth us through the peaks in electricity consumption. There could well be enough battery storage in place by the end of the year to make that sort of backup supply redundant. Our gas future has started to look more like a lithium future. And that’s only the opening chapter of a much more comprehensive battery-driven future.

In the middle of February, the ABC reported that after some years of delays, the first two-way chargers for electric vehicles would soon be licensed for import to Australia. These chargers come in two varieties: vehicle-to-home, or V2H, which allows an EV to charge a home battery, or be charged by it; and vehicle-to-grid, or V2G, which allows an EV to act as grid storage – a scaled-down version of Hornsdale Power Reserve. Rather than just flowing into the battery of an EV – which is pretty much how all electric vehicles operated until quite recently – these two-way charging systems make the vehicles peers on the grid.

Our gas future has started to look more like a lithium future.

An average electric vehicle holds about 70 kilowatt-hours of power – not a lot when measured against the 193.5 megawatt-hours stored at Hornsdale. But it’s all a question of scale. At most, there’s only ever going to be a few tens of these gigantic “grid scale” batteries scattered throughout Australia. On the other hand, if current predictions hold true, there will be somewhere around a million electric vehicles in daily use in Australia by the end of this decade. A million times 70 kilowatt-hours is 70 gigawatt-hours. Now we find ourselves in the range of the entire power requirements for the nation as a whole. That much power will be driving around Australia’s streets, or sitting in its garages and car parks, grid connected, sharing what electrons they have with the grid when the grid asks for it, and taking from the grid when the grid has capacity to spare.

For many years we’ve been informed that “baseload” power meant we had to keep some fossil fuels burning alongside “intermittent” renewables. Massive, distributed battery storage more than covers for any baseload requirements – and we’ll have that amount of storage in place sometime before 2030. But we’ve recently realised that we’ve already installed two other “batteries” of sorts – and they’ll come into play over the next few years, helping us to smooth the transition.

Right now there’s nowhere to put that power; we don’t yet have enough batteries to store it.

The first of these seems so obvious it’s a wonder we didn’t see it sooner. It takes advantage of one of the weaknesses of solar power generation – that the installations have been designed to deliver full output at a lower angle of the sun’s rays than they receive during the middle part of the day. In other words, these systems nearly always overproduce power between 9am and 3pm. Right now there’s nowhere to put that power; we don’t yet have enough batteries to store it. So instead of storing it in a lithium battery, why not store it in our homes – as heat energy?

Most Australian homes have water heaters that fire up on an on-demand basis to keep a steady supply of hot water pouring from our faucets. Allowing those water heaters to fire up during those peak hours of solar overproduction turns those excess electrons into litres of piping hot water, nearly for free – and saving those homes from using electricity to heat water after sunset. Every hot water tank in Australia is actually a battery – if we choose to use it as such. There may need to be some modest infrastructure changes – such as a new controller on our water heaters, so they’d know when to operate most efficiently – but that small change adds an enormous amount of nearly free energy storage, quickly paying for itself.

Even more intriguingly, a recent paper from two researchers in California pointed to an entirely unexpected – and again, completely obvious – form of energy storage. In it, Jennifer Switzer and Barath Raghavan define something that they call an “information battery”.

Every hot water tank in Australia is actually a battery – if we choose to use it as such.

The “cloud” where all of our data gets stored these days can be incredibly power hungry – probably 3% of all electricity generated globally gets consumed by massive cloud data centres. Some of this energy is needed continuously – every time you publish something on social media, for example, that data needs to be distributed far and wide. But some of it – probably, far more of it – is calculated on a scheduled basis. For example, a company’s order sheet and supply chain information might be updated daily, after the close of business. There’s a lot of processing involved in something like that, and it makes sense to do that processing “opportunistically” – that is, when it can be done the most inexpensively. If your cloud computing centre is powered by solar generation, that means doing the most intensive calculations during those hours of peak sunshine, when the electrons needed to drive those chips can be had almost for free. Time-shifting calculations to when they can be performed in sync with the overproduction of renewable power means that the calculations themselves become a form of energy storage – an information battery.

This information battery is the easiest of all to implement. It can all be done in software – just ping the power-provider to find out whether it’s overproducing energy, and use that signal to fire up the most energy-intensive programs running on the cloud computer. It’s simple, elegant and effective.

The information battery shows us that storing energy isn’t as hard as we once thought. We’re rethinking energy storage. And once we get the hang of it, we’ll surely find other clever ways to store the energy we need.

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