In this article, we’re going to explain completely how exactly the ETC solar water heater works. ETC is an evacuated tube collector.

1.   Components

The heater has a 20 litre water tank. Then we have these around 16 evacuated tube collectors over the frame on which the entire setup has been mounted. 

The tubes are two layered. One layer is the top glass layer and inside that there is a dark layer which is going to absorb the maximum heat is going to heat the water. In between that there is a space or a gap, that is completely vacuum. If you remove this pipe, both the ends are completely covered from both sides.

Over a period of time if there is some air that is collected inside this vacuum the silver coating is going to make sure that it is going to absorb all of that with the help of a chemical reaction. They're actually easy to remove and replace as well. If some damage happens to one of the tubes it can be just removed after emptying the tank. The cost of this tube is roughly around 400 to 500 rupees. If you want to replace it, you can replace it manually by yourself because it has been just connected with a simple mechanism. These tubes are just inserted inside and there is a washer that is going to run inside the tank.

2.   Working

We have an overhead tank there from which water is going to move on the other side. The cold water pipe going in that is connected to the one way wall. What this exactly does is make sure water is only going inside and never coming out of the tank .

The water in this tank gets heated and since the hot water always has a low density it tries to come up. If there’s no one-way wall it is going to push the hot water to this and the overhead tank as well. So always make sure you have this one-way wall that has been fixed to your inlet wall. If you don't do it even if there might be sunlight outside you might not get enough hot  water because it is getting mixed with the cold water in the overhead tank.

Once the water inside enters inside these tubes, it fills them and when there is sunlight it heats the water. As the water gets heated, the hot water moves up and the cold water starts coming down. As the density of the hot water will be less it tries to move inside back up. Once it goes up again it tries to move to the top of it, that's how there is going to be a complete water   circulation. So when this happens for a couple of hours in sunlight, certainly you're going to have very hot water.

There is a thick layer of insulation that is surrounding the complete tank. This insulation which runs in the complete tank is going to make sure the heat is not lost during the entire day or whenever we are going to use it. So even if you are using it the next day there might be a drop of only around two to four degree centigrade. These tubes run inside the insulation and go into the tank and that's how exactly it makes sure  the water is going to be pushed inside as well.  This is how the complete process works.

The moment water gets heated up it just moves up. Once it moves up, it comes to the top. On the other side, we have a hot water outlet. Since hot water is going to have less density it is always going to rise up so when we turn on the tap for using water, the hot water from that top layer is going to come inside from this pipe and is going to be circulated. We also have a valve here that has been fixed for when you want to turn off the supply.

There is also one more section which says connecting diagram for backup. For example in winters or where there is no proper sunlight or during the rainy season where you don't see a good amount of sunshine, in that case water is not going to be heated much in this tank because there is not much solar energy. So in that case you can also fix a heater and it can help you to make sure the water is getting heated inside the section.

Let’s see the advantages and disadvantages of having this section. For example, in winters or in the rainy season when you don't have proper sunlight you can put a coil here. Since this is a 200 capacity water tank, you might be going for 200 litres or 150 litres of water. That means   when you insert this coil it needs to hit this entire 200 litres or 150 litres whatever the tank capacity is going to be. That means it is going to consume a lot of energy. Instead of that, if you can have a separate electric water heater in your room it is going to consume less energy and certainly you are going to get really hot water from that as well. So as per a lot of research and understanding from experts it is not good advice to set this up but of course you have an option for that as well.

Now coming to the setup part, one important thing that you always need to remember is that the air vent should always be at a point which is higher than your overhead tank.

Coming to the price of the water heater, this costed around 23,000. Brands such as v guard, supreme are good.

3.   Maintenance

Coming to the maintenance, one advantage with the ETC model is if any damage happens to any of the tubes, you just have to replace the single tube. It's going to cost anywhere around 500 to 1000 to replace along with the service charge. The older solar water heaters used to come with a panel where water used to run inside the copper tubing. The insides might collect the residues of salt and it requires regular maintenance. ETC does not have so much maintenance to be done. The best time to clean these tubes is before sunrise or after 7 pm so that when we are using water or wet cloth it suddenly does not change the temperature of the tubes which might affect their proper working.