Difference Between Pyranometer and Pyrheliometer

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In the field of solar radiation measurement, there are two devices that are commonly used – pyranometers and pyrheliometers. Both instruments measure different aspects of solar radiation, and understanding their differences is crucial for accurate solar resource assessment.

Background Information

To begin with, let’s understand what these devices actually measure. Pyranometers are used to measure total incoming solar radiation from the entire sky dome, while pyrheliometers only detect direct solar radiation from the sun. This means that pyranometers provide a more holistic measurement of solar irradiance, whereas pyrheliometers focus on measuring direct sunlight.

Component Differences

One of the main differences between these two instruments lies in their design. Pyranometers have a flat detection surface, which enables them to measure radiation from all angles. On the other hand, pyrheliometers have a restricted field of view and can only detect direct sunbeams.

Calibration Methods

Another important aspect to note is how these devices are calibrated. Pyranometers are calibrated using calibrated lamps, which provide a known amount of radiation for accurate calibration. Pyrheliometers, however, require regular on-site calibration due to their cosine response degradation. This means that pyranometers are easier to maintain and calibrate compared to pyrheliometers.

Applications

Both pyranometers and pyrheliometers have different applications based on their capabilities. Pyranometers are commonly used for solar resource assessment and solar plant monitoring, as they provide a more comprehensive measurement of solar irradiance. Pyrheliometers are mainly used for sunshine duration measurement and research on the solar constant.

Maintenance Requirements

In terms of maintenance, both devices require periodic cleaning to ensure accurate measurements. However, pyrheliometers have more stringent cleaning schedules due to their precise sensors. On the other hand, pyranometers are relatively easier to maintain.

Cost Comparison

Lastly, let’s talk about the cost comparison between these two instruments. Pyranometers are more affordable due to their simpler design and mass production. On the other hand, custom-built pyrheliometers for research purposes can be quite expensive due to their complex components and specialized use.

Conclusion

In conclusion, the main difference between pyranometers and pyrheliometers lies in their design and applications. While pyranometers provide a more comprehensive measurement of solar radiation, pyrheliometers are mainly used for specific research purposes. Both devices have their own advantages and limitations, and understanding these differences is crucial for accurate solar resource assessment.

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