How to Calculate Expected Solar Energy
The following information will prove beneficial for those who are planning a solar system for their building; whether the system is for a business or home, and whether the system will be designed for generating electricity or for heating water. Here, the terms “solar array” and “solar panel” will be used interchangeably, and the information is applicable to either type of system.
What is solar energy?
Solar energy can be defined as the combined amount of sunlight expected at the preferred site of installation, and the expected strength of the sunlight. The amount will depend on two factors: the time of year and Earth’s position in relation to the sun. The term “insolation” is used to refer to this combination, with the amount expressed in watts per square meter, and known as average irradiance. A more useful measurement is kilowatt hours per square meter with a daily spread, expressed as kWh/m 2/day. (1 square meter = 9.9 square feet)
Usefulness of measurement
In order to determine how much power can be generated from the solar panels you are researching, you can find the find an expected watts number listed on the solar electric panels. This number is based on 1,000 watts per square meter solar irradiance, which is the expected solar power at noon in mid-summer. However, it is not a definite daily figure, nor is it an average reading. It is an expectation. It is easy to compute the daily energy amount your solar array will generate when you have daily average figures for solar irradiance. Just multiply the solar irradiance by the solar panel wattage.
Solar irradiance computation
The solar irradiance figure is not constant through the whole year. For a good estimate, a monthly figure for solar irradiance is required.
NASA has determined an easy way to calculate solar irradiance. Its geostationary weather satellite network is effective in checking the amount of solar irradiance across the surface of the Earth over long periods. Solar irradiance information is available for locations in the United States, Britain and Ireland, as well as for Canada and many other European locations. These figures allow us to calculate the daily solar panel power per month by multiplying the solar panel wattage and monthly irradiance figure.
The daily energy that can potentially be generated can be computed by multiplying the sunlight hours and solar panel wattage.
Hours of Sunlight x Panel Wattage = Watt-hours per day