Here is how you can calculate the annual solar energy output of a photovoltaic system

A photovoltaic system is designed to supply usable solar power by means of photovoltaics. It entails arrangement of several components including solar panels which absorb and convert sunlight into electricity, a solar inverter which changes the electric current from DC to AC and other electric accessories like cable to set up a working system. With the encouragement from Indian government every year more PV systems are installed.  Looking into the growing usage of renewable energy, it’s a good grab for those inclined toward the solar energy and have an understanding of the calculations associated with PV cells.

Globally a formula E = A x r x H x PR is followed to estimate the electricity generated in output of a photovoltaic system.

E is Energy (kWh), A is total Area of the panel (m²), r is solar panel yield (%), H is annual average solar radiation on tilted panels and PR = Performance ratio, constant for losses (range between 0.5 and 0.9, default value = 0.75).  r is the yield of the solar panel given by the ratio : electrical power (in kWp) of one solar panel divided by the area of one panel

Example : the solar panel yield of a PV module of 250 Wp with an area of 1.6 m² is 15.6% . It is worth mentioning that this nominal ratio is given for standard test conditions (STC) : radiation=1000 W/m², cell temperature=25 °C, Wind speed=1 m/s, AM=1.5 The unit of the nominal power of the photovoltaic panel in these conditions is called “Watt-peak” (Wp or kWp=1000 Wp or MWp=1000000 Wp).

Now you have to find the global annual irradiation incident on your PV panels with your specific inclination (slope, tilt) and orientation (azimuth) to calculate H.

PR: estimates the quality of a photovoltaic installation as it gives the performance of the installation independently of the orientation, inclination of the panel. It includes all losses which depend on the size of the system, technology used and the site.

The DC Current generated undergoes a series of losses before it can finally become AC Current and used by us.

Example of losses that gives the PR value

• shadow losses
• Temperature losses
• DC cables losses
• AC cables losses
• Inverter losses
• Losses due to dust