A better pacemaker for the grid

How behind-the-meter battery storage is set to turn domestic energy consumption from a problem into a solution.

 

A new breed of white goods has cropped up recently in the kitchens, utility rooms and garages of St Helier, South London. Being about the same size, it aligns neatly with washing machines and can be mistaken for a portable air conditioner when standing alone. However, while white goods and HVAC appliances are liabilities on your electricity bill, the new box on the block can become a major asset.

 

The families participating in Powervault’s government-backed commercial project can get first-hand experience of the benefits of lithium-ion battery (LIB) storage in the household. Those who already have solar panels installed on their roofs will be able to store excess energy generated during sunny hours and use it in the evenings when demand rises, rather than just let electricity generated off-peak go down the drain.

 

This kind of behind-the-meter storage, first installed two years ago in Barnet, can also create revenue streams for households supplied with smart meters and on smart tariffs. One way of achieving this is charging the battery with electricity from the grid when it’s cheap and consuming it during peak hours. The other – where electricity stored with a capacity of 3-20kW can become part of something much larger – is providing balancing services for the grid.

 

The frequency of the grid in most countries around the globe needs to be at a steady 50Hz. Even minor deviations from this value can cause major problems, which network operators avoid by shifting the load on and off the grid in line with the mismatch between supply and demand. Domestic batteries, no matter how low capacity they are, can contribute energy when there is shortage of electricity and help store some of the load while there is too much, thus earning money.

 

Can LIB maintain its hegemony in battery storage?

 

When three chemists developing different aspects of the lithium-ion battery independently several years apart were awarded the Nobel Prize last year, it alerted even those fumbling for their chargers and power banks to the influence the invention had exerted since it first entered the market in 1991. All the three main application areas were mentioned: consumer electronics such as mobiles and laptops which dominated the 1990s; electric vehicles (EVs) which have taken off recently; and the battery storage of intermittent renewable energy, a nascent industry with considerable potential.

 

However, many resent LIB’s expanding dominance, maintaining that it diverts money from the innovation of battery solutions which could better meet needs specific to storage, wouldn’t require expensive metals that come at a premium and would be easier to recycle. But LIBs also come in many shapes and sizes depending on the elements making up their anodes, cathodes and electrolytes, with different combinations offering different trade-offs that accommodate each specific application. Some of them, for example, have a very low cobalt content, or none at all. What most of them have in common, though, is unrivalled energy density – the amount of energy a kilo or a litre of them is able to contain and poor storage duration with average times currently ranging between four and eight hours.

 

Moreover, the boundary between EV and storage solutions is still very porous. Not only does NMC (Nickel Manganese Cobalt Oxide), arguably the most successful LIB, power Nissan’s electric model Leaf but it also stores energy in the world’s currently biggest battery in Hornsdale, South Australia. Another case in point is the emerging trend of second-life batteries, where end-of-life packs from electric cars still retaining 70 to 80 per cent of their original capacity are used for another ten years in more affordable energy storage systems.

 

He gives twice who gives quickly

 

No matter how rivals old and new keep challenging LIB on some performance metrics, experts expect it to reign supreme for another decade. Recently, blackouts in Australia and the UK provided it with new opportunities to shine. It was power cuts induced by network instability that brought Tesla’s electricity storage facility in the Hornsdale Power Reserve to life in the first place, and since its launch in 2017 it has prevented power failures becoming major blackout incidents multiple times. The fast energy dispatching capability of battery storage played a crucial role in averting bigger disruption during the UK blackout on 9 August 2019 as well. In that case, batteries of a windfarm and five large LIBs on a solar park near Luton Airport took only a couple of seconds to restore the grid’s frequency to normal. 

 

The combined electrical capacity they shifted to the grid was about 86MW, just a fraction of the 1,5 GW shortage. However, what did matter was that the batteries only took a couple of seconds to respond to the emergency. Their task was to hold the fort until other, long-duration storage (LDS) facilities had come online – such as age-old pump-hydro, which releases energy by moving water from a top to a bottom reservoir through turbines, or new ones, such as the liquid air energy storage, to be built by Highview Power in the North of England. What LIB batteries can bring to the table is the minutes of leeway that LDS systems take to stir to life.

 

Virtual power plants (VPPs) – the likes of the digital platform that was launched by Powevault as part of the St Helier pilot project – remotely network thousands of electricity producers, consumers and storage systems in real time with the help of AI to build scale. Although one family with 9KW electricity storage won’t make too much difference, if you join 10,000 of them into a distributed network, they can provide the storage capacity that saved the UK on 9 August. Electric cars seem to be likely to join the system at a later stage.

 

The ROI of these domestic battery storage systems is not easy to calculate due to how different depths of charge and top-ups affect battery cycle times and degradation during the grid balancing service. However, initial metrics are promising. Sooner rather than later it will be time to decide whether to make room for the new white box in the kitchen, the utility room or the garage.

 

As this article was going to press, Tesla was applying for a licence to build and operate utility-scale batteries in the UK. 

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