The Watt measures the rate of energy conversion and it is the main unit of power used in photovoltaics.
How much energy does one panel produces?
Electrical energy is generally measured in kilowatt-hours (kWh). If a solar panel produces 100 watts for 1 hour, it has produced 100 watt-hours or 0.1 kWh.
The amount of energy produced per day will depend on the area, shading, orientation, and watt-class of the panel.
In areas with high irradiation, a properly oriented panel that produces 100 Watts at noon on a sunny day will produce an average of about 0.5 kWh/day during the winter and 0.8 kWh/day during the summer months.
In an area with low irradiation, the same panel will still produce about 0.25 kWh/day during the winter and 0.6 kWh/day during summer months.
An effective orientation for a solar panel installation is 100 percent south, at an angle of 10-20°.
There are several standard measurements to describe a solar panel installation.
NOMINAL SYSTEM SIZE
number of panels x watt class per panel
Ex: Pig Farm in Gadendorf, Germany
434 panels x 215 REC AE-series panels = 93.31 kW system
number of sun hours for the region x system size (also called "effect") x performance ratio (80-85%)
Following the same example as in the calculation below:
1 380 sun hours x 93.31 system size x 80 % = 103 014 kWh
It is also possible to use a solar radiation map to determine the sun hours.
Furthermore it is often advisable to insert a correction factor of 1.1 (an average value representing roof-top angle, orientation, shadowing etc.).
ANNUALLY SAVED AMOUNT OF CO2
CO2- reduction in electricity- local mix (Germany 650 kg pr 1000 kWh) x annual capacity
For this example:
0.65 kg/ kWh x 78,791 kWh = 51.214 tons annual CO2 savings.
HOUSEHOLD EQUIVALENT POWER PRODUCTION PER YEAR
annual capacity / average electricity consumption
To determine how much electricity per household is produced by this farm, we need to know the average electricity consumption for a family of four, in Germany is it 4.500 kWh. So:
78 791 kWh / 4 500 kWh = 17.5
This number means that this installation produces enough electricity to satisfy the needs of 17.5 families per year.