Hier kan je lezen wat wel en wat niet opgenomen is in het verhaal van systeem verliezen.
JRC 5 maakt dus gebruik van een meer up to date database dan JRC 4, maar de systeemverliezen worden in geen van deze databases opgenomen.
Nu zal het wel aan mij liggen, maar wat is dan de reden om van 14% naar 8% verlies te gaan?
Een knip en plak over de systeemverliezen zoals beschreven door PVGIS:
System losses and degradation with age
All the calculations described above will in the end give the PV power that can be delivered at the connectors of the module (or array). But before the power arrives at the grid it must be transformed into AC current by the inverter, which causes another loss. There are also losses in cables and because the modules are not all exactly the same power. At the moment we do not have enough information to calculate all these effects, so the loss can be input by the user.
In addition the power of PV modules tends to decrease slowly with age. A large study (Jordan and Kurtz, 2013) found that PV modules typically lose about 0.5% of power per year of operation. With an expected system lifetime of 20 years this would mean that the power at the end of the 20 year period the power would be down to 90% of the original power and on average over 20 years the power would be 95% of the original power.
Considering the system losses and the losses due to ageing we recommend a value of 14% for the "system loss" that the user gives as input to PVGIS.
Other effects not considered in PVGIS
There are a number of other effects that can influence the energy output of PV systems. These effects are not included in the PVGIS calculations. Among these are:
Snow. If the PV modules are covered (even partially) by snow the energy output is typically very low. This effect depends on how often it snows but even more importantly on how long the snow stays on the modules before melting or sliding off. This in turn depends on the temperature but also on the module inclination and how the modules are installed.
Dust and dirt. In areas with a lot of dust in the air the modules will tend to be covered in dust. How long the dust stays on the modules depends on rainfall and on the inclination of the modules. The effect will of course be different if the modules are cleaned from time to time.
Partial shadowing. If only a part of a PV module is in shadow it may reduce the energy output strongly. This effect is very local and depends on the exact way the modules are installed. At the moment we have no way of taking this into account, but it should of course be considered when installing the PV system.