How Solar Radiation Sensors Work
Solar radiation sensors are also known as pyranometers. A type of actinometer, these devices are used for measuring broadband solar irradiance as well as solar radiation flux density, which means that they measure the power of the light and heat from the sun. When placed on a flat surface, pyranometers can be used for identifying solar radiation. The term pyranometer comes from the Greek word pyr, which means fire, and ano, which means sky.
Pyranometers work by measuring the number of small units of light, known as photons that impact a physical or chemical device located within the instrument. Solar radiation sensors are typically not powered due to the fact that the components located in the device either are influenced by or react to solar radiation in a direct manner.
There are two primary types of solar radiation sensors. One is a PAR sensor that is capable of measuring photosynthetically active radiation, or PAR, within the 400 to 700 nm range. Pyranometers are comprised of a thermopile sensor that typically has a black coating. The sensor is designed to absorb solar radiation and provides a flat spectrum that covers from 0 to 1500 W/M2. Pyranometers detect both direct and diffuse radiation. The radiation that is absorbed by the sensor is converted to heat. That heat then flows through the sensor to the device’s housing. In addition, the dome helps to protect the thermopile sensor from convection. The glass dome fitted over pyranometers is also important in terms of ensuring proper directional elements and limiting the response of the device to within a range of 0 to 1500 W/M2.
Solar radiation sensors are commonly used in climatology, meteorology, building physics, and solar energy studies. They are also used in weather stations and are usually installed in a horizontal manner near solar panels. The level of possible measurement of a solar radiation sensor will vary based on the position of the sun. In ideal conditions, the sun will be located directly overhead. With that said, certain measurements may be obtained via varying angles.