Energy Monitoring - New Year Thoughts
Published on 18 Jan 2010 at 5:38 pm.
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After spending all available free time rebuilding my PCs I had lost the thread of finishing the monitoring kit at least to the point where others can use it. Got a Mac to put an end to all that so I can now get back to my main project.
We had concluded that monitoring is very important but is not the end solution. Controlling the heating automatically is the way forward. Until such time as an affordable commercial solution hits the market we need to keep hacking on.
The three key challenges were external temperature, boiler control and the all-important algorithm. The first two because in my own setup I had run a lot of wiring. That would not work for most people. I’m not worried about network wiring as power-line devices are readily available for those who do not want to run Cat5. (Low-power devices like Arduino do not support WiFi.)
External temperature is easily solved by using feeds from the Weather Underground. The node near our house is driven by a nice piece of kit with more than enough accuracy. The server grabs that data as needed. It’s refreshed at least every 15 mins. Boiler control can be done with a ByeByeStandby socket and controller. I think this is reliable enough but if not I’ll package up the controller I was able to build thanks to the nice people at BBSB having documented their wire protocol. This leaves the algorithm where I have something very simple in mind.
I have enough stored measurements to extract two pieces of information: our house loses heat at the rate of about 0.7 deg C/ hour when it’s freezing outside and gains heat at just over 1 deg C/hour when the boiler is firing. The effect of the sun is hard to predict at the moment so more measurements are needed but I can guess a figure and tune it in coming months. These figures can be used by the controller to decide, based on external temperature, when to fire the boiler in the morning and, importantly, when to shut it off. Although it’s too late to shut off the boiler when the target temperature is reached, the internal thermometer can be used to make sure all is working as expected.
Next step is to test this arrangement and see how it performs. It it does the job we can expect further savings.
