This solar heater contains 50 liters of water which can be heated by the sun to temperatures higher than 50 ºC, and thick thermal insulation around the heater keeps the hot water until morning. This white pipe will be surrounded by those 50 liters of hot water, and this green hose is connected to the cold water pipe of my summer cottage. Those 50 liters of water heat the cold water when it goes through the white pipe, and then clean hot water moves through this hose to this washbasin mixer and to this shower.
The making of my system began with this box which is thermal insulation with a thickness of 10 cm. Then I put these pieces of old black films. Those 50 liters of hot water will be inside this sleeve of black polyethylene film, and usually such sleeves are sold 150 cm wide.
Now we see the black sleeve inside the box, those 50 liters of water and the white pipe. Then I put this black wall which is also thermal insulation with a thickness of 10 cm. The making of my system ends with the installation of this transparent covering which should consist of several transparent sheets. For example, I used these two glass sheets and this cellular polycarbonate with a thickness of 4 mm.
The heater is a relative of this of my old solar heater which provided hot water to my summer cottage 2 months ago, and it was described by one of my old videos. Unfortunately, this old solar heater will not work well in Europe or Canada in the autumn months due to the low height of the sun above the horizon. In addition, it will work poorly in the tropics in winter if the height of the sun above the horizon is less than 30-40 degrees.
That is why I use this black wall which makes my new solar heater able to work in autumn and winter. This is because the radiation from the low sun is absorbed by the black wall, and therefore it is heated to temperatures greater than 100 ºC. The hot black wall transfers some part of its energy to the water of the black sleeve using infrared radiation and heating the air over the black sleeve.
Here we see how high temperatures damaged black polyethylene film after one short experiment, and I remind you that the melting point of polyethylene is a little more than 100 ºC. Now we see the melting of expanded polystyrene, and we understand that this phenomenon was due to a temperature of about 100 ºC.
That is why now my black wall has these wooden battens. Then I install mineral wool which is covered with sheets of this wooden material with black paint. However, we understand that ordinary black paint is not designed for temperatures greater than 100 ºC.
Let’s look at this experiment on 15 October when those 50 liters of water had a temperature of 32 ºC in the morning. It was a sunny day with such sky, and therefore those 50 liters were heated to 52 ºC in the evening. Of course, the water will lose some of its heat at night, and now we see its temperature the next morning of 16 October. It is obvious that the evening and morning temperatures should be greater in summer due to warmer ambient air and a higher sun.
I am in Ukraine, here, at 50 degrees north latitude, and the midday height of the sun above the horizon was 32 degrees in that experiment on 15 October. Thus, those my experiments correspond to the height of the sun for the winter months here, around the Mediterranean or in the center of the United States. Unfortunately, this solar heater does not work well during non-solar periods, and therefore, I do not recommend using it in Northern Europe from November to March.
We understand that it will be better to connect the heater outlet to the inlet of a tank electric water heater or possibly to the inlet of a tankless electric heater. This connection ensures that you will have hot water always, and the electricity consumption of your tank or tankless heater will decrease several times. But it is obvious that these hoses should be replaced with reliable plastic pipes.