iiinova — where your digital self keeps evolving

Robert McQueen

@ramcq.net

245 followers 347 following 67 posts

Cambridge-based husband, father, free software & green energy geek, digital rights & equity advocate, open source technologist, CEO of Endless Access, Vice President of GNOME

Posts Replies Media

Robert McQueen @ramcq.net · 14/09/2025

You can't heat old buildings with heat pumps!!! *checks notes* www.cai.cam.ac.uk/decarbonisat... n/m

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Robert McQueen @ramcq.net · 01/12/2024

Just the way of things with heat pumps, solar generation and when it's cold don't really correlate meaningfully. But I use the battery with Octopus Intelligent to shift a bunch of daytime consumption to the cheaper (and lower carbon) overnight power.

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Robert McQueen @ramcq.net · 01/12/2024

All of them are next to useless in the winter! But actually the gap closes. I think that's mostly because my east/west panels have a very slight angle - 10° compared to 35° pitched roof for the north ones. This is the performance for the past month.

The same panel diagram from earlier, but showing the past month rather than year. The east/west panels range from 54 to 78Wh and the north 33 to 72Wh.

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Robert McQueen @ramcq.net · 01/12/2024

I got 10 East/West and 10 North facing panels as I have the North-facing half of the semi... The North ones still do about 1.5MWh a year which is 7-8% of our annual use, and the rest about 3MWh. (20MWh including the heat pump and the EV!)

Screenshot from the Solar Edge app showing the annual yield from each panel. Ten on the flat roof in an east/west system generate between 304 and 337kWh a year, and ten facing north are between 126 and 177kWh.

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Robert McQueen @ramcq.net · 22/11/2024

Bit jealous tbh... Still thinking I should have a 2nd... The cold weather makes light work of our one!!!

Graph showing Powerwall charging to 100% overnight and then discharging almost completely between 05:30am and 08:30am

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Robert McQueen @ramcq.net · 19/11/2024

Victorian semi with a 50/50 mix of solid walls and newer built extensions. 12kW heat loss at -3C, 12kW Vaillant Arotherm Split heat pump. Currently 5C outside and flow at 43C, house sitting comfortably at 20.5C as intended. Designed with 55C flow at -3C but was able to turn it down a little.

The graph of flow temperature vs outdoor temperature for my heat pump. Starts at 24C flow when 20C outdoors, 49C when 0C outdoors, rising to 69C when -20C.

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Robert McQueen @ramcq.net · 19/11/2024

This can't be right. Heat pumps don't work?! My internal temperature is all over the shop now the outside temp is dropping. 📉 Oh wait no it's fine... 😂 Flow is 45C now. COP was 3.9 last week, 3.1 so far this week. The system was designed to average 3.5 over the year and tends to do 3.6.

A graph from the Vaillant heating application showing a stable internal temperature of 20.5C, with external temperature dripping over the course of the month to just above freezing.

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