Energy Flexibility in a Nutshell

To operate a flexibility service, we need to know the future state of the electricity grid. We do this by combining two live data sources:

• Elexon Insights API: Tells us the day-ahead forecast for wind generation across Great Britain.
• National Grid Carbon Intensity API: Tells us exactly how "dirty" or "green" the electricity will be for every 30-minute block in the future.

The graph below shows the predicted Megawatts (MW) of wind generation, aligned to each 30-minute carbon forecast period.

For perspective: 1 Megawatt (MW) is a massive amount of power, equal to 1,000 kilowatts (kW). An average Electric Vehicle (EV) battery holds about 50 kWh of energy. If the UK generates 10,000 MW of wind power for one hour, that produces enough energy to fully charge 200,000 EVs from empty to 100%. High wind output is often a strong signal that electricity will be greener, so these are attractive times to target.

High wind generation drives down the Carbon Intensity. We measure this in grams of CO₂ emitted per kilowatt-hour of electricity used (gCO2/kWh).

If the system has to dispatch more fossil-fuel generation to meet demand, this number spikes (often 250+ gCO2/kWh). If the wind is howling and the sun is shining, the number drops dramatically (often below 50 gCO2/kWh). Let's look at the actual carbon forecast for the next 24 hours:

Let's take a real-world scenario. Normally, a person would get home from work at 6:00 PM and immediately plug in their Electric Vehicle. They don't actually need to drive the car until 7:00 AM the next morning, but the car starts charging right away, exactly when everyone else is cooking dinner and the grid is struggling (and therefore highly reliant on burning dirty fossil fuels).

The Energy Flexibility approach: Axle's software intercepts that charging session. It pauses the charger at 6:00 PM, looks at the forecast, and schedules charging for the greenest available window before the car is needed the next morning.