One of the components of a solar water heater is the solar collector, there are different types of solar collectors . The collector is located on the roof, absorbs the sun’s heat rays there and then releases this heat to the pipe system. 

Then you can use this heat to heat the water in your home. All about the different types of solar collectors , prices, properties, … you will discover in this article.


There are two types of solar collectors: the flat plate solar collector and the vacuum tube solar collector.  

Type of solar collector.Half price
Flat plate solar collector (2,5m²)€ 500 to € 550
Vacuum solar collector (2,5m²)€ 700 to € 750

1. Flat plate solar collectors 



A flat solar collector, also known as a flat plate collector, consists of a  rectangular tray approximately 10 cm thick with a dark absorbent plate therein  . Copper pipes that are filled with a liquid run behind this plate.

The set is covered with insulating material,  so that   temperature  losses are  limited. Of course, the upper part of the collector must remain transparent and, therefore, it is  covered with a glass plate  . When the sun shines on the flat plate, it gets very hot and the copper tubes and the collecting liquid are also heated.

What are the advantages of a flat plate solar collector?

  • High efficiency per square meter (on sunny days).
  • Cheaper than a vacuum solar collector.
  • Strong surface It is not necessary to maintain a vacuum environment as with a pipe system.

What are the disadvantages of a flat plate solar collector?

The efficiency in colder days, with diffuse light, is lower than in vacuum tube collectors. This has to do with the heat losses in the system. The flat plate cools relatively fast.

2. Vacuum tube solar collectors

A vacuum tube collector consists of a series of double-walled glass vacuum tubes that are mounted side by side  . Because the tubes are under vacuum, the heat is well retained and the collector cools less quickly.

Inside, the tubes are  provided with an absorbent material  that can efficiently absorb the sun’s heat.

The copper tubes (heat pipes) run into the tubes through which the collecting fluid circulates  . When the sun shines on the collector, the pipes and heat pipes heat up quickly and the collector fluid also gets hot.

What are the advantages of vacuum tube solar collectors?

  • High efficiency on cold days with diffused sunlight (spring, autumn, winter). This has to do with the good insulation of the pipes, so little heat is lost.
  • The collector heats up quickly and there is a fairly constant performance.
  • Low wind load due to open construction.

What are the disadvantages of vacuum tube solar collectors?

Slightly more brittle than flat plate collectors: the tubes can break and the insulation vacuum is lost.

The price is higher than flat plate collectors.



How much energy can be saved with solar collectors?

If the system is well adapted to your needs and all the components of the system have been assembled carefully, you can save on average from 50% to 65% in the annual cost of hot water.

If you also preheat the house with collectors (heating support), the savings are on average 15% to 25%. This lower performance has to do with the fact that it needs heating, especially in periods when the sun shines little. Less sun means less heat output from the collectors.


Points to consider when installing solar collectors.

The following aspects should be taken into account when installing the solar collectors:

1. How many solar collectors do you need?

The number of solar collectors you need is easy to calculate. On average, you should consider 1 to 1.5 m² of collector space per person in the home  . Therefore, a household with four people needs an average of 4 to 6 m² in collection space.

With regard to the size of the storage tank, you must assume 50 to 60 liters per square meter of collector surface. 

2. Better orientation for solar collectors

It is important that the solar collectors are placed in such a way that the heat output is maximum. That means an  orientation to the south (or southeast or southwest) at an angle of 30 to 65 degrees  . 

With deviations to the west or east, you will have to deal with the losses. With a somewhat lower roof slope (eg, 40 degrees), losses are limited to 20% to 30% less performance.

Environmental factors also play a role. Avoid the shade  through trees, buildings, dormer windows, … so that the light shines less in the collectors.

3. Liquid composition of the collector.

The liquid that flows through the vacuum and flat solar collectors usually consists of a mixture of water and glycol. 

The glycol is necessary to protect the collectors against frost (up to -28 ° C) and is also resistant to the high temperatures that can occur in a solar collector (160 – 200 ° C). Glycol is also often used as antifreeze in automobiles (coolant, windshield washer fluid).


Should I buy a vacuum tube solar collector or a flat plate solar collector?

Which of the two types of solar collectors is the best now? In Belgium and the Netherlands, where the climate is moderate, it is usually better with vacuum solar collectors  than with flat collectors.

The performance of vacuum solar collectors occurs mainly during periods when the sun shines a little less than that of flat plate collectors.

The vacuum manifolds are also well insulated and suffer less heat loss than the flat plate variant. As a result, they perform well throughout the year in our temperate climate. 

Undoubtedly, in combination with underfloor heating, it is better to opt for solar vacuum collectors.

In Spain, the south of France or other warm places, it is better to meet with flat collectors. This is because they perform better in sunny periods. They are also cheaper than vacuum collectors, which means you can recover them faster in sunny places.

Read more about Thermal solar energy by concentration

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