TL;DR: Ilari setup a Lora sensor for humidity and Node-red based control for electrical heating and hopes to save approx. 600€ this winter. See the real time status on a map look like this:
I have a log frame cottage in eastern Finland. It’s far away from Tampere, but it’s nice to visit and a link to my family. I’ve been keeping it warm (+7 Celsius, 44 F, 244 K ) during winter times. I have never really had to think that it’s too much money, as electricity is dirt cheap in Finland. Environmental concerns? No. I mean I’m happy that I can reduce Co2 foot print, but let’s be honest, it was not the primary motivation.
As we know, Putin decided to f#¤k Ukraine and after sanctions back and forth, price of electricity sky rocketed. I used to pay 5 cents / Kwh, now I pay 25 cents. I’m ok with this, it’s better to pay with money than blood. I calculated that if I’d keep the cottage warm, I’d need to pay about 500-700€ for the winter and that is not something I’m willing to do. Time to change something.
Options, what do I have? Keep it warm – too expensive. Sell – don’t want to. Have someone live there an pick up the bill – nope for several reasons. Let is go cold – yes. But how?
I’ve read about the possibility to let cottages go cold for the winter, but never looked into it in more detail. This is not a common practice, as 1) energy has been cheap 2) old folks say it will ruin your cottage. After some studying I figured out it’s worth the try. The trick is not let the relative humidity go above ~80% so the water stays in the air, does not condensate and cause damage.
How do we make sure condensation does not happen? I have no means of drying the air. As temperature goes up, air can keep more water in it. So the straight forward way is to make it warmer when relative humidity starts to go up. How do we do that?
First thing to do is to figure out how humid i is. Is this even a problem? For this we need a measuring device. For the extra heat, well you need a heater. I have electricity in the cottage, so electric heater! For the overall solution I considered few options. There are some heaters which are designed exactly for this; they have a humidity sensor and heater combo and will heat when needed. Unfortunately other people have the same problem and those products were all was sold out. Plus a good one costs ~200€. I like to do things the hard and cheap way. DIY time!
In Profirator we have some bits and pieces in place. We have servers, Lora sensors and smart engineers. When you smash all that together, you get this:
I’ll save you from the iterations for the solution, but if you are wondering why we are not locally measuring the humidity, the answer is stupid: we ran out of time, we did not get the Arduino code + sensor integrated when I had to go to the cottage.
Some alternatives we tested and evaluated: We started with a Arduino based cool kit from Heltec, which has Lora radio and it could have sent measurements and receive commands via lora. Perfect, but we ran into a dead end, since the device did not have any DevEUI allocated for it and we did not want to cowboy with some self generated DevEUI. After that we poked around with IFTTT, but it seemed too closed, gimmicky an tightly integrated to their cloud.
Then took a “simpler” approach, use a 4G router. Transfer measurement data via Lora and commands via mobile network. Encrypted. Simple. Basically the flow goes like this: 1) we listen to the measurements. 2) store measurements to database via Scorpio. 3) based on treshold, send a command to turn on the heater via Shelly Smart plug.
Few days before I left we had the pieces all together and working:
One concern was that the lora indoors coverage (blue area) stopped just outside my cottage:
This story is part one of the series on how we saved money in heating by remote sensoring and control. Read the next part to find out what happened!