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Harnessing thousands of batteries in the grid’s hour of need

  • avatar
    Karl Bach
    Co-founder @ Axle
  • avatar
    Ben James

As December '23 arrived, the GB grid was severely strained. On the 1st of December, Axle fired up over 2000 home batteries to keep fossil fuels off the grid, and returned over £26,000 to battery owners in the process. This blog explains how we did it, and why.

Crunch time

At the start of December, the GB grid saw its highest power demand since January. On Friday 1st, power demand reached 45 GW because of the cold weather - 23% higher than average. Electricity generation was scarce, as the UK’s formidable offshore wind fleet was suffering from low wind. As the evening peak approached, domestic generation capacity wasn’t enough to meet demand. The grid was forced to import large quantities of power from abroad, for over 12% of our supply.

Luckily, the UK Electricity System Operation (ESO) had seen this coming, and made preparations. It chose to deploy the Demand Flexibility Service (DFS) - a new instrument that pays energy users to consume less energy when the grid is strained, instead of paying fossil generators to produce more.

The ESO put out a call for a huge 550 MW of power (equivalent to an average UK gas power plant) between 16:30 to 18:00 on Friday. At Axle, our systems sprung into action to help stabilise the grid. Our algorithms automatically dispatched our customers’ home batteries and EV chargers, according to their preferences and tariffs.

In Friday’s window from 16:30 to 18:00, there was low wind generation, low solar generation (it was dark), and we were already importing considerable power from Europe. This meant that any increase in demand would be supplied by turning up gas power plants. Conversely, any decrease in demand took fossil fuels off the grid.

Our algorithms dispatched a fleet of batteries and EV chargers during the 16:30 - 18:00 peak window, directly preventing dirty gas peaker plants from firing up.

Let’s dig into how we did it with one of our partners, GivEnergy.

A lot of batteries

GivEnergy’s batteries make up the largest portfolio of home batteries in the UK. Through our partnership, Axle completely automates the participation of GivEnergy batteries in the DFS. Thanks to GivEnergy’s tech infrastructure and APIs, battery owners who opt in can have their batteries optimally charged and discharged by Axle.

Here’s the aggregate performance of the battery fleet last Friday. Between 16:30 and 18:00, over 2000 batteries sprung into action, exporting their energy back to the grid.

DFS event performance

Battery owners were well compensated at £4.20 per kWh of savings. The average participant earned £13, and many users earned over £50 during the 1.5 hour event. With DFS events set to continue frequently throughout the winter, participation in the coming months looks to be lucrative.

How we do it

Axle is the only provider who fully automates the participation of batteries and EVs in the DFS.

We’re proud of the intelligence we’ve built into our algorithms to customise every battery’s response individually.

As soon as our systems learn of a new DFS event, we notify our opted-in customers, and our algorithms get to work 🤖. Our systems:

  • Calculate the optimum charge level for each battery, based on its capacity
  • Calculate the optimum charging schedule, based on the user’s electricity tariff and forecasted home energy profile. Batteries are charged cheaply overnight (where possible), and topped up during the day prior to the event.
  • Automatically dispatch the batteries according to these parameters, reading and processing over 600 datapoints per battery, per event.
  • Collect metering and operational data, crunch the numbers, and settle payments with the ESO. Customers receive their earnings the next day (as cash, not points!).

We’re pretty proud of what we’ve built - a system that lets battery owners earn money for keeping fossil fuels off the grid. GivEnergy battery owners will soon be able to participate in a wide range of flexibility markets, earning money throughout the year and balancing the grid at local and national levels.

How to learn more and get involved

You can find the nitty gritty details of the DFS here.

Axle is a software platform that connects assets like EVs and batteries to flexibility markets, including the DFS. We can help you with the soup-to-nuts of participating, from customer consent through baselining, aggregation, bidding, and delivery.

If you’re keen to learn more, drop us a note.