Documentation:Solar Cell and Radiative Properties

Objectives

This protocol is meant for use with the solar cells/ photocells and multimeters in the Introduction to Biometeorology course (APBI 244/GEOB 204) at the University of British Columbia associated with lab 2: Radiative properties of natural surfaces. The goals of this lab are:

1. Measure the coefficients of reflection of several natural surfaces under fluorescent and incandescent light.
2. Compare the coefficients of reflection, transmission, and absorption of a leaf under fluorescent and incandescent light.

Equipment

Multimeter with solar cell (photocell) attached to the electrodes and measuring reflectance (since the dark side is facing down) from the desk surface (radiation in mV).

• Multimeter
• Solar cells
• Fluorescent lights
• Incandescent lights
• Lamps
• Soil samples dry (clay, organic soil, sandy soil)
• Soil samples wet (clay, organic soil, sandy soil)
• Cow hides of different colours
• Freshly collected leaves

Procedures

1. Turn the miltimeter to the 300 mV position and plug in the positive (red) and negative (black) electrodes.
2. Be gentle with the solar cells as they are quite fragile.
3. Hold the exposed piece of the black wire from the solar cell to the negative electrode and the exposed piece of the red wire to the positive electrode. Ensure you have a good connection and the solar cell is functional by registering a change to the multimeter reading.
4. The darker (sensitive) side of the sensor should be facing the radiation source that you want to measure.
5. Record your measurements, for example:
   • Turn on the fluorescent/incandescent lamp directly above your first sample (soil, leaf, mulch, hide etc.).
   • Turn off the lights in the classroom and ensure the window coverings are drawn.
   • To measure the amount of short-wave radiation striking the soil surface, place the photocell horizontally and 0.5 cm above the soil sample, facing the light source. Read the voltage from the meter.
   • Turn the photocell over and hold it with the sensitive side facing down and horizontally about 2 cm above the soil surface. If the sensor is held too close to the surface, it may register its own shadow. Read the voltage from the meter.
   • Calculate the coefficient of reflection for your sample:
     • $\alpha =(reflectedradiationreading(mV)/(incidentradiationreading(mV)$
   • Calculate the coefficient of transmission for your sample (if of interest, for example with leaves):
     • $\tau \lambda =(transmittedradiationreading(mV)/(incidentradiationreading(mV)$