Compact solar water heaters – Are they worth it?

Consumers researching the market to choose a solar water heater will sooner or later discover so-called “compact solar water heaters” and be bombarded with arguments about their advantages. But are compact solar water heaters always a good choice? Before answering this question, we need to explain what compact solar water heaters are and how they work.

Construction structure compact solar water heater.

The following diagram illustrates the typical structure of a compact solar water heater.

 

 

 

 

 

 

 

 

 

The idea is very simple and, in simple terms, involves placing a metal container inside an insulated box. The box is lined with reflective material to diffuse radiation, and the top is covered with glass. Despite what the manufacturers of compact solar water heaters say, this idea is not new or innovative at all. The first solar water heaters manufactured in America were exactly that: metal containers placed in an insulated wooden box.

 

 

 

 

 

 

Today, with improvements in plastic technology, the box is made of plastic and the insulation is polyurethane.

How the compact solar water heater works

As with all solar applications, the function of the compact solar water heater is to harness solar energy. Solar energy penetrates the glass of the solar water heater and directly heats the tank containing the water.

 

 

 

 

 

 

 

 

 

The reflective lining of the container’s interior helps to utilize more of the solar energy for heating the water.

Advantages of compact solar water heaters.

Compact solar panels, due to the way they are manufactured, have a number of advantages, such as:

• Easy transport of packaged products
• No assembly required
• They are easy to install, even by non-specialists.
• They do not have a closed circuit that requires filling.
• The total cost of purchase + installation is lower than that of conventional solar systems.

Disadvantages of compact solar water heaters

The only but significant disadvantage of the compact solar water heater is the high heat loss due to its construction.
In order to absorb energy, the tank of the compact solar water heater that contains the water for use is uninsulated, which means that both at night and on cold winter days, the energy collected by the solar water heater is released into the environment.

 

 

 

 

 

 

 

 

 

So, despite the fact that compact solar water heaters work well during the day, they lose their energy during the night, with the result that users do not have hot water available in the morning, even in summer. For the same reason, compact solar water heaters do not work well in winter, because heat loss to the cold environment dramatically reduces their efficiency. This disadvantage is very serious and negates the advantages of compact solar water heaters.

Things you will hear about compact solar water heaters

A salesperson attempting to sell you a compact solar water heater will use a series of false arguments, such as:

1. The compact requires no maintenance.

This argument is false. Compact solar panels require descaling and anode replacement to ensure a long service life, just like all solar systems.

2. The compact works perfectly all year round thanks to its adjustable tilt.

Changing the tilt of the solar panel requires work on your part, which you probably won’t feel like doing two or more times a year, since the purpose of buying a solar panel is to make our lives easier, not to take on unnecessary obligations. However, even if you are willing to constantly change the tilt of the solar panel, the increased losses will not allow your solar panel to heat the water sufficiently, except at very specific times of the day and under conditions of intense radiation.

3. The compact works even when it’s cloudy.

This argument does not hold water for the reasons explained above. Not only do compact solar water heaters not work better on cloudy days, but their performance is clearly inferior.

Compact solar water heater applications

Despite their low efficiency, compact solar water heaters have a number of applications, mainly in holiday homes and summer accommodation (rented rooms, small hotels, etc.) that are only in use during the summer, since:

• In summer, heat loss during the day is low, so the compact solar system keeps working really well.
• Peak hours in summer are mainly in the afternoon, before the sun has a chance to cool down.
• in the morning, when the water has cooled down from overnight losses, users are satisfied even with lukewarm water

In such cases, it is advisable to choose a compact solar water heater, especially on islands and in remote areas where installing a conventional solar water heater can be difficult and expensive due to a lack of technicians. Choosing a compact solar water heater allows us to install it ourselves, saving money and mental stress.

Conclusion

From the above, it is perhaps clear that compact solar water heaters, although slightly cheaper than classic split solar water heaters, are inferior to them and should be avoided wherever possible in favor of split solar water heaters.
Nevertheless, like all devices, compact solar water heaters are ideal when an inexpensive solution for hot water is required in summer accommodations and vacation homes.