Additionally to the standard procedures the validity limit of the functions has to be determined. The examples shown in the chapter “The limit is dependent on the absorber temperature and on the ambient temperature” are related to an idealized relatively sharp limiting behavior. In reality such limiting measures may not have this sharp onset in […]

This limiting behavior can be observed, for example, in the case of an adequate thermotropic layer that is mounted on the inner side of the glazing of the collector. This type of temperature limitation is only satisfying in the case of non-selective absorbers and double glazed collectors because a good thermal coupling from the thermotropic […]

These tests and computations may not reflect the requirements for polymeric (and other) collectors if they have measures to limit the temperature of the absorber. 18.6.2.1 The Limit is Dependent Mainly on the Absorber Temperature This limiting behavior will arise, for example, in the case of an adequate thermotropic layer that is mounted on the […]

Robert Hausner 18.6.1 Description of the Specific Test and Test Procedure Within EN 12975-2, the following tests and calculation procedures are concerned with discontinuous efficiency curves of polymeric collectors with temperature limiting measures, such as thermotropic layers, temperature-controlled ventilation, or other active or passive measures. In the following chapters of EN12975 second-order dependencies on the […]

The destruction limit for flat plate collectors with toughened glass is in the range of about 45 mm diameter and normative impact speed of 30.7 m s—1 Impacts at lower levels usually do not cause any problems. 18.5.2.2 Typical Normative Requirements So far the impact resistance test is not mandatory for the European certification. It […]

The impact resistance test is not only a problem for polymeric collectors but also for other collectors such as evacuated tube collectors. There are no real doubts about the suitability to assess the impact resistance using the current methods. Depending on the norm, certification scheme, or also building insurance codes the required impact energies may, […]

Andreas Bohren and Stefan Brunold 18.5.1 Description of the Specific Test and Test Procedure Two different test procedures for the assessment of impact resistance are found in the different international test and certification standards. Depending on the standard there are only some minor differences in the application. One method involves using steel balls dropping from […]

The methods for assessing the wind and snow loads can be considered as adequate and there is no reason to introduce new test methods. It is certainly advisable to take into consideration applying these tests only to collectors that have been pre-aged to include the potential weathering induced brittleness of the cover. 18.5