Finding the Efficiency of a Solar Panel and Motor
Introduction
In this solar car investigation you will determine the percentage efficiency of the solar panel in converting energy from a heat/light source (light bulb) into electrical energy. To do this you will need to use a light sensor to measure the intensity of emitted light (power/area) and a multimeter to measure electrical power.
Preliminary Questions
Go to: http://www.solarhome.org/infohowdosolarpanelswork.html
http://micro.magnet.fsu.edu/primer/java/solarcell/
http://www.solartechnologies.com/cm/About-Solar-Power/How-Does-Solar-Power-Work.html
1. How does a solar panel work?
2. What is electric “current”?
3. In a water wheel analogy with rotating buckets of water, voltage is compared to the energy of each bucket of water (energy/water buckets) due to its height. Current is the number of buckets of water that reach the bottom of the wheel per unit of time (water buckets/time). If you multiply these two quantities together what units do you get? What is this quantity called?
Materials
Light Sensor (CH 1) Vernier LabPro Stopwatch
Lamp (200W) (2) Solar Panel
Multimeter Ruler Genecon Hand Generator/Motor
Procedure for Measuring and Determining Light Intensity and Power
4. Set up the equipment as shown in the diagram below. Position the center of the solar panel under the center of the lamp. Turn on the lamp for at least 15 mins before taking measurements.
5. Open: groupshare – Solar Panel Efficiency.cmbl
6. Select: Setup – Sensors – Light Sensor 150 000 lux – Ok
7. Position the light sensor on the edge of the desk with the photo-diode (top of probe) pointing towards the center of the light bulb. The axis of the probe should be about vertical. Keep the probe very steady. Collect data for at least 20 seconds and use the stat button to get the average intensity. Write down the illumination reading in lux.
Illumination = _____________ lux
8. Measure the dimensions of your solar panel. Only measure the blue crystalline area.
Width = _________ cm = ________ m Length = ___________ cm = ___________ m
Area = Width__________ m x Length _____________ m = _____________ m2
Photometry Background:
The lux is defined as a lumen per square meter (lumen/m2) and is a unit of illuminance.
1 lux = 1 lumen / m2
This is essentially the intensity (Power/Area) of emitted light by the bulb at a certain distance. As such, it measures the amount of visible light striking a surface. To find the power of light on the solar panel in lumens simply multiply the illuminance (lux) by the area of the panel (m2).
# lumens reaching = Illuninance ________ lux x Area ________ m2 = __________lumens
the panel
The lumen is the standard unit for luminous power of a light source. It is defined by:
Luminous Power = Radiant Power (Watts) x 683 (lumens/Watt) X luminous
(lumens) Efficacy
We are going to assume that most of the energy emitted by the bulb is not in the visible part of the spectrum and so the luminous efficacy will be 2.6%. (see http://en.wikipedia.org/wiki/Luminous_efficacy) . The Radiant Power is thus:
Radiant Power (Watts) = Luminous Power (lumens) = ___________ Watts
683 lumens / Watt x 0.026
Procedure for Measuring and Determining Electrical Power
9. Set up the equipment as shown below. You are going to use the Genecon as a motor and not as a generator of electricity. You will use the rotational rate (rev/sec) of the handle as an indicator of how much energy is going to the motor.
10. Connect the Genecon to the panel as shown with the handle positioned so that it rotates in a horizontal plane. Turn on the light and give the handle of the Genecon a little push to start it moving. It should continue to rotate as energy from the panel is delivered to the motor thus enabling the handle to turn. Time how many times the handle turns in a period of time, say 20 seconds. Determine the rotation rate of the handle
Rotation rate = # handle revolutions _________ revs = __________ rev/s
Total time ________seconds
11. Measure the potential difference (voltage) across the Genecon using the multimeter. Remember to set the multimeter in DC volts. Connect the multimeter leads in parallel with the Genecon.
Potential Difference across motor = _________V
12. Measure the current through the motor. Set the multimeter to the 500mA range. The multimeter leads should this time be connected in series with the genecon as shown.
Current through motor = __________ A
13. Determine the power input (Watts) to the motor. This is the potential difference across the motor multiplied by the current through it.
Power input = Potential _________ V x Current _________ A = ___________ W
Difference
14. Determine the percentage efficiency of the solar panel in converting solar energy into electrical energy.
% Efficiency = Power output of the panel x 100 = _________ W x 100 = ________ %
Power input to the panel W
15. Let’s now look at the effect of adding panels together and their effect on motor speed.
i) Attach two solar panels in series. Repeat step 11 with the Genecon.
Rotation rate = # handle revolutions _________ revs = __________ rev/s
(Series) Total time ________seconds
Compare this rotation rate for two panels in series with only one panel. How much more power does two panels in series provide over one panel?
ii) Attach two solar panels in parallel. Repeat step 11 with the Genecon.
Rotation rate = # handle revolutions _________ revs = __________ rev/s
(Series) Total time ________seconds
Compare this rotation rate for two panels in parallel with only one panel. How much more power does two panels in parallel provide over one panel?
Solar Panels in the Home
Go to: http://rredc.nrel.gov/solar/old_data/nsrdb/1961-1990/redbook/atlas/
16. Select: 1. Average 2. Annual 3. Flat Plate Tilted South at Latitude 4. view the map
17. From the map determine what the average annual solar radiation is per meter squared per
day for a south facing angled array, situated in Michigan.
Work:
Av. Solar radiation = _______________ kW-hr/m2/day
18. A solar panel has a efficiency of 12%. If it typically has an area of 1m2, determine how much
solar energy it converts into electrical energy each day.
Work:
Electrical Energy produced by each panel = ______________ kW-hr/day
19. The average American household uses about 11 000 kWhr of electrical energy per year.
Determine the average daily use of electrical energy.
Work:
Av. Daily consumption = ______________ kW-hr/day
20. Determine how many solar panels are needed to provide the electrical energy needs of a
typical household living in Michigan.
Work:
Number of solar panels (each 1m2) needed = _____________ panels