Solar Radiation Measurement using Pyranometer Sensor & Arduino

Overview:
In this tutorial we will interface
Pyranometer Sensor
with
Arduino
& measure
Solar Radiation
value.
A
pyranometer
is a type of sensor that measures the
solar irradiance
or the
power of sunlight
in
watts per square meter (W/m²)
. The word “pyranometer” is derived from the Greek words “
pyr
” meaning “fire” and “
ano
” meaning “sky”. They are widely used in meteorology, climatology,
solar energy studies
, and agriculture to monitor and study the available
solar radiation
There are two types of Pyranometers, i.e.
Thermopile Pyranometers
and
Silicon Pyranometers
. In this project, we will use Thermopile Pyranometer from
Renkeer
. The sensor can measure
solar irradiance
between
0-2000W/m²
with a resolution of
1W/m²
. The sensor works on
RS485 protocol (4-20mA,0-5V, 0-10V)
. Hence we will use MAX485 Module to request the output data.
Using the RS485 Module, the Pyranometer Sensor data is processed by
Arduino
in readable format. Finally the Solar Radiation value is displayed on
16×2 LCD Display
, interfaced to Arduino Board.
Bill of Materials
Following are the components that we need for reading Pyranometer Sensor data using an Arduino. The components can be purchased from given links.
S.N.
Components
Quantity
Purchase Link

Arduino UNO Board

Amazon
AliExpress
SunFounder

Pyranometer Sensor

Renkeer

16X2 I2C LCD Display

Amazon
AliExpress
SunFounder

MAX485 Module

Amazon
AliExpress
SunFounder

12V Power Supply

Amazon
AliExpress
SunFounder

Jumper Wires

Amazon
AliExpress
SunFounder

Breadboard

Amazon
AliExpress
SunFounder
Pyranometer Sensor
A pyranometer is an instrument designed to measure the solar irradiance, quantifying the sun’s energy in watts per square meter (W/m²). Solar radiation varies significantly among regions. Season and time of day are major considerations, but surrounding terrain elevation, man-made obstructions, and surrounding trees can also cause large variations in locations with a small area.
Renkeer Pyranometer Sensor
The
Renkeer Pyranometer Sensor
is currently one of the best sensor for measuring
Solar Radiation
. It measures the solar energy received from the entire
hemisphere
(180 degree field of view).
Utilizing the
thermoelectric principle
, this pyranometer accurately measures solar radiation within a
spectral range
of
0.3~3μm
. The sensing element adopts a
wire-wound electroplating thermopile
, and the
sensing surface
is a
black layer
with high absorptivity.
Using the
thermal effect of radiation
, it absorbs solar radiation and converts it into
thermoelectromotive force
. It also has a
temperature compensation
function, which can accurately measure solar radiation. The double-layer glass cover above the
sensing surface
can not only reduce the influence of air convection on the device, but also
block the radiation
of the cover itself. And add a radiation shield to measure scattered radiation.
To prevent dew accumulation inside, it incorporates a
desiccant-filled cartridge
. Additionally, with an integrated
bubble level
and adjustable screws, the sensor can be precisely leveled without the need for a separate base. The product adopts the standard
Modbus-RTU 485
communication protocol, which can directly read the current
total solar radiation
value.
Specifications of Renkeer Pyranometer Sensor
Power supply range
: 10V～30V DC
Spectral range
: 0.3~3μm
Measuring range
: 0-2000W/m²
Resolution
: 1W/m²
Accuracy
: ±3%
Working environment
: -40℃~60℃, 0~95%RH (non-condensing)
Sensitivity
: 7～14 μV·W-1·m2
Internal resistance
: about 300Ω
Response time (99%)
: ≤30s
Non-linear error
: ≤±3%
Corresponding error of directionality
: ≤±30W/m²
Temperature response error
: ≤±8% (-40℃～+40℃)
Yearly stability
: ≤±3%
Spectral selectivity
: ≤±10%
Cosine response error
: ≤±5%
Tilt response error
: ≤±2%
Output mode
: RS485, 0-5V, 0-10V, 4-20ma
Working Principle Pyranometer Sensor
The working principle of Pyranometer Sensor is explained as follows:
Thermopile Sensing Element
: At the heart of the pyranometer is its sensing element, which is typically a wire-wound, electroplated thermopile. A thermopile is a combination of multiple thermocouples (devices that generate a voltage based on the temperature difference between two junctions) connected in series or parallel. The design and arrangement of the thermopile help in amplifying the signal generated due to temperature differences.
Absorptive Black Layer
: The sensing surface of the pyranometer is coated with a black layer possessing high absorptivity. This ensures that the maximum amount of solar radiation is absorbed, which is crucial for achieving accurate measurements. As this black layer absorbs the incoming solar radiation, it heats up.
Thermal Effect of Radiation
: The fundamental concept driving the pyranometer’s operation is the thermal effect of radiation. When solar radiation is absorbed by the black layer, it generates a temperature difference across the thermopile. This temperature gradient leads the thermopile to produce a voltage difference.
Output Measurement
: The voltage produced by the thermopile is directly proportional to the absorbed solar radiation. Thus, this voltage becomes the pyranometer’s output and is used to determine the intensity of the incident solar irradiance.
Temperature Compensation
: A significant aspect of the pyranometer is its built-in temperature compensation mechanism. Changes in ambient temperature could potentially skew the readings of the instrument. However, the temperature compensation function ensures that the pyranometer provides accurate measurements of solar radiation, regardless of the surrounding temperature conditions.
Pyranometer Sensor installation
Make sure to install the bracket, and the radiation sensor is parallel to the ground (leveling can be done through the leveling knob)
Use screws to pass through the mounting holes on the sensor to fix the sensor on the mounting bracket
After installation, remove the protective cover
Please pay attention not to damage the glass cover during the installation process, so as not to affect the measurement accuracy
The installation location should be an open place all around and without any obstructions.
Pyranometer Sensor Maintenance
The glass cover should be kept smooth and clean, often wipe it with a soft cloth or fur
There must be no water in the glass cover. If it encounters heavy rain, snow, ice, and other long-term weather, it is recommended to cover it
It is recommended to check whether the desiccant in the dryer has become damp at regular intervals.
The specific manifestation is that the orange turns into a dark color. If this happens, replace the desiccant in time, or remove the desiccant to dry and put it back into use
The equipment has been used for more than two years, and the sensitivity must be re-calibrated by the manufacturer or measurement department
Applications of Pyranometer Sensor
Meteorology
: Pyranometers provide data for climate studies and weather prediction.
Solar Energy
: Engineers and researchers use pyranometers to assess and monitor the performance of photovoltaic (PV) systems.
Agriculture
: To study the effect of sunlight on crops, enabling farmers to optimize irrigation and planting strategies.
Building and Architecture
: For assessing solar irradiation for building design and energy modeling.
Research
: They’re commonly used in many scientific studies relating to the earth’s energy balance, climate change, and more.
Data Frame Format Definition & Communication Protocol
Data frame format definition
Using the Modbus-RTU communication protocol, the format is as follows:
Initial structure ≥ 4 bytes of time
Address code = 1 byte
Function code = 1 byte
Data area = N bytes
Error check = 16-bit CRC code
Time to end structure ≥ 4 bytes
Host query frame structure:
Address Code
Function Code
Register Start Address
Register Length
Check code Low Bit
Check Code Hi