Photovoltaic Performance

DRAFT

A key metric for evaluating the overall performance of a photovoltaic (PV) system is the cumulative [yellow]Energy[/yellow] produced over a time period (e.g., daily, monthly, or annual). In other words, energy production is an arbitrary aggregate of the instantaneous power estimations over a time series. In turn, the instantaneous (effective irradiance, and thereby) power values reflect the [italic]current[/italic] output of the photovoltaic (PV) system at each moment in time. How does PVGIS calculcate photovoltaic power output ?

1. We calculcate the position of the sun in the sky relative to the positioning of a solar surface. Essentially this boils down to one trigonometric paramter : the solar incidence angle. This angle depends on the solar altitude and solar azimuth angles on any given moment in time combined with the location, the orientation and the tilt of the solar surface itself.

2. We ..

Analytically, we can break down the algorith as follows: Let us go through the calculation step-by-step.

Hence, .. :

1. Define an arbitrary period of time

2. Calculate the solar altitude angle series

3. Calculate the solar azimuth angle series

4. Derive masks of the position of the sun :

i. above the horizon and not in shade ii. very low sun angles iii. below the horizon

1. Calculate the direct horizontal irradiance component for ..

2. Calculate the diffuse and reflected irradiance components for the sun above the horizon

3. Sum the individual irradiance components to derive the global inclined irradiance

4. Read time series of the ambient temperature, the wind speed and the spectral factor

5. Derive the conversion efficiency coefficients

6. Estimate the photovoltaic power as the product of the global irradiance and the efficiency coefficients.