Solar radiation measurement in process and environmental engineering: a pyranometer is an instrument used for measuring which component of solar irradiance on a horizontal surface?

Introduction / Context:
Pyranometers are ubiquitous sensors in solar energy studies, greenhouse operations, climatic testing of materials, and heat balance calculations in chemical and environmental engineering. The question checks whether you can distinguish among types of solar measurements: global (total), beam (direct normal), and diffuse components, and recognize which instrument measures which.

Given Data / Assumptions:

• Pyranometer is a thermopile-based radiometer with a hemispherical (cosine-response) dome.
• We assume the sensor is mounted horizontally unless otherwise specified.
• Standard solar radiation components: beam (direct) on a normal surface, diffuse from the sky dome, and global (beam projected onto horizontal + diffuse).

Concept / Approach:
A pyranometer measures the irradiance received from the entire hemisphere above the sensor. When installed on a horizontal plane, it captures the sum of the diffuse sky radiation and the beam component projected onto the horizontal (cosine of solar zenith angle). This total is called global horizontal irradiance. By contrast, a pyrheliometer points directly at the sun and measures only the beam (direct normal) component through a collimated tube. Bright sunshine duration is commonly logged by a sunshine recorder (e.g., Campbell–Stokes) or electronic threshold devices rather than a pyranometer alone.

Step-by-Step Solution:
Identify the instrument: pyranometer (hemispherical field, cosine response).Identify the plane: horizontal mounting implies horizontal global irradiance.Map to solar components: global = beam (projected) + diffuse.Select the option describing total/global on a horizontal plane.

Verification / Alternative check:
Standards (e.g., ISO/IEC for solar measurements) describe pyranometers as broadband instruments for global or diffuse on a plane (with shading for diffuse). Pyrheliometers are specified for direct normal irradiance using solar tracking.

Why Other Options Are Wrong:
Beam only: That is a pyrheliometer function.Bright sunshine duration only: That is a recorder/logger concept, not a radiometer reading.Diffuse only: Requires a shading device; a bare pyranometer reads global.None of these: Incorrect because global is precisely what a pyranometer measures on a horizontal plane.

Common Pitfalls:
Confusing “global” with “direct”; forgetting that a horizontal pyranometer captures both diffuse and the cosine-projected beam; overlooking the need for shading to isolate diffuse measurement.

Final Answer:
Global (total) radiation on a horizontal plane