Fotovoltaické systémy

Oblast zaměření: Fotovoltaické systémy
Komise : IEC/TC 82 (Solar photovoltaic energy systems)
Původce: ISO\IEC\CEN\CENELEC
K připomínkám do: 4.12.2018
Zobraz více Zobraz méně
 

This part of IEC 62788 describes methods to measure the permeation properties of polymeric materials. The degradation of PV modules is known to proceed by many different corrosion processes. These degradation processes may depend upon moisture ingress into the encapsulant, edge seal, frontsheet, or backsheet materials. Typical polymeric materials used include (amongst other polymers) ethylene-vinyl acetate (EVA) and polyolefins for encapsulants, polyisobutylene (PIB) for edge seals, and polyethylene terephthalate (PET), polyvinyl fluoride (PVF), or polyvinylidine fluoride (PVDF) for backsheets. Therefore, knowing the moisture permeation characteristics of polymeric materials is relevant to module design. These properties can be determined as a function of temperature and relative humidity. With these parameters, simple scaling rules for time and distance can be used to extrapolate to the use environments.

This standard provides methods for measuring the steady state water vapor transmission rate (WVTR), water vapour permeability (P), diffusivity (D), solubility (S), and moisture breakthrough time (Ƭ10%) (defined as the time to reach 10 % of the steady state WVTR) for polymeric materials such as encapsulants, edge seals, frontsheets and backsheets. These measurements can be made at selected temperatures and humidity levels as deemed appropriate for evaluation of their performance in PV modules. Measurement is accomplished by inspection of the transient WVTR curve and by fitting it to a theoretical fickian model. This standard is best applied to monolithic films. If multilayer films are used, the D and S values are only apparent values, but the steady state values can still be measured.

This standard was written for the measurement of water permeation, but it may equally be used for other permeants such as O2. In this case the same diffusion equations, fitting procedures, and scaling arguments may be used

Oblast zaměření: Fotovoltaické systémy
Komise : IEC/TC 82 (Solar photovoltaic energy systems)
Původce: ISO\IEC\CEN\CENELEC
K připomínkám do: 4.12.2018
Zobraz více Zobraz méně
 

This part of IEC62788 provides procedures for standardized test methods for evaluating the properties of materials designed to be used as edge seals. When modules are constructed with impermeable (or extremely low permeability) front- and backsheets designed to protect moisture sensitive photovoltaic (PV) materials, there is still the possibility for moisture to get in from the sides. This moisture ingress pathway may be restricted by using a low diffusivity material around the perimeter of a module between the impermeable front- and backsheets. Alternatively, one may wish to use a low diffusivity encapsulant which may significantly reduce moisture ingress over the lifetime of the module and would want it to be evaluated similarly to an edge seal material.

 

In addition to restricting moisture ingress, edge seal materials must also provide electrical insulation. To perform these functions, edge seal materials must remain well adhered.

 

The test methods here are intended to be used to standardize the way edge seals are evaluated. Only some of these tests are actually required for IEC qualification tests for PV modules and that status depends on the application. It is not required that all of these tests be performed, but it is recommended that these properties be measured as indicated.