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Local Carbon Intensity Forecast (a 'when to charge' iOS Widget)


Nov 6, 2019

Exploring the installation of solar to make my CO2 footprint less - I've been realising I can't fit enough to justify it (my urban semi has poncy dormers etc).

So - thinking about the interesting carbon intensity forecast API VanillaAir pointed at recently - and the UK electricity market/my green tariff - I wondered if I could time my car's charging to reduce it in some meaningful way.

The result is an iOS widget based on the same the Scriptable technology underlying the Tesla Data widget from a few months back.


It makes nice graphs:



...which show your postcode's local carbon intensity forecast; the current value; the best minimum to charge at; and the fractional generation mix as it varies over time (see the GitHub notes for more on that - but note it downplays the contribution of renewables as the height of the graph is CO2 intensity, not generation. Even if renewables were suppling the entire grid at 2x its normal power - it would have zero height).

The far above was the Bank Holiday’s windy storm blowing through - and the other is this weekend's storm coming in. Pick the right time, and more than halve your CO2.

I delayed my last weekend's charge by a day and got it to a 1/3rd of the CO2 it would have been.

The instructions are on GitHub - but basically just dump this into Scriptable, edit the postcode, and make a Widget:

https://raw.githubusercontent.com/n...st/main/Carbon Intensity Scriptable Widget.js

I appreciate tolerating a lower SoC isn't something everyone can do, and Octopus Go will complicate it (when the blinking new SMETS2 meter works that is) - but this might be a bit interesting if you've an iPhone, if not of actual use to you.

Myself I intend to use it to guide topping-up from now on - might cause more charge operations - but I hope it makes a small bit of a difference.

However - that talk of 'meaningful' above...I’m not entirely sure of the economics of demand shifting like this (I have a 100% green tariff - so someone else gets a green unit when available if I consume a dirty unit now. So what's it matter?), but maybe demand shifting helps balance the grid/generate more demand for the good stuff when available + less for the bad stuff. I'd be interested in opinion/anything more informed there!.

I found it interesting to see how the local power generation mix varied with time, and was surprised at the % of French nuclear we have down here in Surrey - a Brighton interconnect I hear. So it's not just Jersey then...

If anyone wants to take this and Android-ise it, please feel free.

(*) - "When to Go Faster?": I also did an analysis of the API data for my area and nationally last year. Turns out midnight to 4am was a lower CO2 intensity period on the average diurnal composite - around 10% less than peak. I'm hopeful I'll get Go and the low-points to coincide a couple of times a week.

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