TIC definition
Based on the principles for defining the respective capacity measures in section 3 above, the TIC would be based on the output capability of the solar array given uninterrupted exposure to sunlight over a sustained period at its installed location. Suitable data on which this figure can be based is produced by the European Commission’s Joint Research Centre at Ispra, which maintains a resource called the Photovoltaic Geographical Information System (PVGIS)7.
PVGIS is based on extensive solar energy data throughout Europe. It has facilities to derive for any location and solar array angle three irradiance measures: Global ‘clear sky’ irradiance Global ‘real sky’ irradiance Diffuse ‘real sky’ irradiance
We propose to use the best month’s clear sky irradiance as the basis for the TIC calculation. This is the highest of the three figures, and that which best matches the ‘without interruption’ requirement of the definition.
We will use actual tilt angle and azimuth offset figures for installations constrained by the surface on which they are mounted (e.g. roofs). In the case of stand-alone and ground-mounted PV systems we will use the optimum tilt angle (also given by the PVGIS resource), and assume the array is oriented towards true South.
The TIC will then be calculated as the power output of the solar array at the average irradiance derived in this way.
DNC definition
The net output of a PV system, after conversion of light energy in each solar module, will be affected by configuration factors, such as ‘mismatch’ losses from the series and parallel interconnection of the modules, cable losses, voltage drops in metering and protection devices and the efficiency of the inverter and any other power conditioning equipment.
As described in section 4 above, it is proposed that these factors are deducted from the TIC to derive the DNC.