The nearest star from Earth is Sun. And it emits a massive amount of energy, which is free. No surprise, many people try to get most of it at a minimal cost. Photovoltaic solar panels still have low efficiency and yet are quite expensive. Every day we hear how their effectiveness is increased by introducing new technologies. Anyway, solar panels require direct Sun, which in some regions doesn’t appear very often. So how can we get this energy with almost no initial cost? The easiest way to do so is to build a solar thermal collector. You can find lots of high efficient commercial collectors. They look great and, at some level, works in the wintertime when Sun shines. I decided to go simpler. I need hot water only in spring, summer, and fall. In the wintertime, I burn wood to heat the house and so water. I usually boiled water using an electric boiler in the summertime, which generates excellent bills at the end of the month. No more…
So I started this project, which is still in the testing phase. But seems to work fine. Let’s go through the build process to make a simple solar collector using an old window frame. I was lucky I’ve got this old window frame, which area is about 1 square meter.
It has two glasses on both sides. I removed one glass and replaced it with an OSB sheet. Then placed about 30mm of Rockwool for thermal resistance:
Luckily the window frame opens like a book. Four screws hold it together. Depth from glass to the middle is about 30mm – enough space for insulation on one side and placing heat carrier pipe on another. OK, the next step was to put a Tin sheet which will accumulate Sun radiation energy.
Tin is reflective and reflects most of the energy like a mirror. We need to absorb as much power as possible. The best solution for this is to cover it with black paint. I covered it with non-glossy paint so it would not reflect any light. The darker is better. I found that paint coating works excellently as it is non-glossy.
After this is done, we can proceed to the pipe, which will remove heat from the black tin absorber. Here you can argue that metal pipe will work best (maybe copper or aluminum) if you have one around – use it. I had several meters of PP-R plastic aluminum 18mm diameter pipe (7 meters of it). I didn’t want to waste money on a new one, so I used it. Painted it with some black color and bent it to form a serpentine shape:
Painted non-black spots at fixture places and covered with the top part of the window with glass.
Now the fun part begins. I wanted to integrate a solar collector into an existing home water system. So I attached pipes to the same water heater that works with the home boiler. I used a three-way pipe connector with valves so I could disconnect any of them at any time. In the summertime, I want to run a solar heater only, so I unplug the boiler from the house heating system and leave just solar to circulate hot water. I used 20mm plastic pipes to connect the collector to the boiler as they are cheap and easy to assemble:
We all know that the best place to put solar collectors is the roof. Here it gets most of the sun and is in a safe place. I decided to go a different way. When you put a solar collector on the roof, it is higher than the water boiler. You will need a water pump to circulate hot water down. I wanted natural flow when water from the collector flows upwards without any pumps. So I decided to put it lower than the boiler, which is on the ground. You can see that pipes are going up from the collector. I insulated the hot water pipe to preserve hot water from cooling until it reaches the water heater tank.
I found a spot where the sun shines most of the day and is convenient to put. Still, considering flowers on the ground, but it seems that they don’t significantly affect the collector. It might be I’ll leave them for a while.
Set up is still fresh and in the testing phase. Probably one collector won’t be enough to heat 120L of water. There is another same-sized window frame lying in the garage, so perhaps I will assemble another one to put aside. I will give updates on how it works pretty soon.