Insolation
A Peak Sun Hour (PSH) is a standardized unit that is used to quantify the amount of solar energy that a location receives during an day, month or year. A Peak Sun Hour is defined as 1m² receiving sunlight with a irradiance (sunlight intensity) of 1000 W/m² for 1 hour. The average PSH value for a given location will largely determine the amount of energy that a PV system produces, therefore it is a very important value for PV system design.PSH for a location is based upon real world testing and observation and can be calculated for a particular day as follows:
Peak Sun Hours (PSH) = sum of average irradiance measurement for each hour ÷ 1000 W/m²
- Example 1: An irradiance testing station gives you the following data for a particular day. What is the PSH value for this day?
Time 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 Average irradiance 200 W/m² 300 W/m² 500 W/m² 800 W/m² 1000 W/m² 1000 W/m² 800 W/m² 500 W/m² 300 W/m² 200 W/m²
- Peak Sun Hours (PSH) = (200 + 300 + 500 + 800 + 1000 + 1000 + 800 + 500 + 300 + 200) W/m² ÷ 1000 W/m²
- Peak Sun Hours (PSH) = 5600 W/m² ÷ 1000 W/m² = 5.6
Estimating PV production with PSH
The power rating of PV modules is determined by testing under standard test conditions, one of which specifies that the test be performed with light of an irradiance (sunlight intensity) of 1000 W/m². A basic calculation of energy production for a PV system can be performed using the power rating of the PV source and the PSH value for the location during a given period. Note: additional PV module loss factors must be taken into account to arrive at a realistic estimate of production under real world conditions. The losses due to these factors can be substantial.
PV source production estimate = PV source power rating × Peak Sun Hours
- Example 1: You have a 100 W PV module. It will be installed in a location without shade that has an average daily Peak Sun Hour value of 4. Without accounting for loss factors, how much energy will this module generate on average per day?
- PV source production estimate = 100 W x 4 PSH
- PV source production estimate = 400 Wh
- Example 1: You have a 100 W PV module. It will be installed in a location without shade that has an average daily Peak Sun Hour value of 4. Without accounting for loss factors, how much energy will this module generate on average per day?
