General requirements

The main element of the hot-water producing solar collector systems is the solar collector itself. But in order to have a proper working and highly efficient system, we need to choose well the other accessories as well.

The realization of the solar collector system is a building mechanical engineering task, the installation processes are similar to the heating and water-pipe system installations. The used constructional and installation materials are also similar. But you can meet some special considerations, which you should highly take into consideration.

These are the following ones:

·         The solar collector systems do not have a fixed, permanent performance. The energy supplied by the collector can vary from time to time, depending on the sunshine and the temperature. Therefore when designing and calculating the system, you have to calculate with the daily or a given period’s general utilizable heat amount.

·         The neutral gear temperature of the good quality collectors can be very high, can reach the 180°C. Neutral gear can always happen, one cannot fend it off (e.g. power cut) therefore when restarting the system – for a short period – this high temperature, which can be above 100°C, appears in the system, and all the accessories must endure this heat. Therefore plastic pipes, or pipes with plastic elements cannot be applied.

·         One must take into consideration the thermal expansion possibilities, above a given performance the collector must be cooled in summertime.

·         Due to the high agent temperature, the operation pressure is also high, therefore to avoid the boiling of the heat carrier agent, the operation pressure must be defined very carefully, which also effects the temperature of the boiling point. Therefore the operation pressure should be fixed under 3-4 bar, since in this case boiling point of the mixture of the antifreeze and water does not get higher than 150°C.

·         In building construction generally 1-1,5 bar operation pressure is used with a safety valve enduring 2,5 bar pressure. Therefore it must be verified that the highest allowable pressure of the applied accessories must be higher than the opening pressure of the safety valve.

·         Solar collectors used all year round must be filled up with antifreeze liquid. This process requires attention and caution, since these liquids are poisonous, propylene-glycol base, or monopropylene-glycol base liquids, and also it must be verified that these liquids do not get into the drinking water system.