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Investigating the Characteristics of a Solar Panel - Practical Notes Saverio Ciccone Overnewton Anglican Community College Prior to undertaking experiments with solar panels it is useful to undertake an experiment to investigate the current, voltage and power output of a dry cell battery, as a source of limited output. This will enable students to be more insightful about the output of a solar panel Current-Voltage Characteristics of a Dry Cell Equipment and Method (per group) 1 new and 1 old 9V drycell batteries 5 leads Voltmeter (or multimeter) Ammeter (or multimeter) Potentiometer (Variable resistor - 0-25 Switch (optional) Do not take long in the conduct of the practical as the internal resistance of the battery may increase – we want this to be a controlled (constant) parameter. 1. You will need the following equipment to be set up as follows (use the new drycell) Ammeter – series connection Voltmeter – parallel connection 9V – battery nominal 0 – 25 ohm variable resistor Use the middle and an end terminal for connections 2. Turn the axle of the resistor so that the voltage changes by 0.5 V approximately each time and record the current and voltage pairs. Repeat for an old 9V battery 3. Import your data into a spreadsheet for fast manipulation. Col A Col B Col C Voltage V current A power W Col D External resistance ohms Analysis 1. Determine the power supplied by the battery (watts, W) and the external resistance (variable resistor value in ohms, by programming the spreadsheet columns C and D Note Power (W) = Voltage (V) Var. resistor value ( x Current (A) Voltage (V) Current (A) = col A x col B = col A ÷ col B 2. Plot a graph of the current vs voltage and comment on the relationship between the two. 3. Plot a graph of the Power vs voltage and comment on the relationship between the two. At what voltage is the maximum power delivered and how does this voltage compare to the open-circuit voltage (x-intercept)value ? 4. Plot a graph of the Power (W) the two. At what external resistance is the maximum power delivered? New 9V current A 0.291 0.307 0.322 0.337 0.345 0.358 0.379 0.402 0.419 0.437 0.457 0.475 0.494 0.526 0.551 0.598 0.748 0.868 0.963 1.021 1.089 1.182 1.305 1.589 New 9V Battery Current (A) vs Voltage (V) 1.8 1.6 current (A) 1.4 1.2 1 0.8 0.6 0.4 0.2 0 0 1 2 3 4 5 6 7 8 voltage (V) New 9V - Power (W) vs voltage (V) 4.50 4.00 3.50 power(W) Voltage V 7.49 7.41 7.34 7.25 7.2 7.13 7.04 6.93 6.84 6.75 6.63 6.53 6.43 6.27 6.15 5.93 5.35 4.86 4.31 4 3.51 3.03 2.27 0.71 3.00 2.50 2.00 1.50 1.00 0.50 0.00 0 1 2 3 4 5 voltage (V) Power (W) vs ext resistance (ohms) 4.50 4.00 power (W) 3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 0.00 5.00 10.00 15.00 resistance (ohms) 20.00 25.00 30.00 6 7 8 Old 9V Current A 0.033 0.028 0.025 0.023 0.021 0.019 0.017 0.015 0.014 0.013 0.013 Old 9V - Current (A) vs Voltage (V) 0.035 0.03 current(A) 0.025 0.02 0.015 0.01 0.005 0 0 0.05 0.1 0.15 0.2 0.25 0.3 voltage(V) Old 9V - Power (W) vs Voltage (V) 0.0050 0.0045 0.0040 0.0035 Power (W) Voltage V 0.01 0.05 0.08 0.1 0.13 0.21 0.24 0.27 0.31 0.33 0.34 0.0030 0.0025 0.0020 0.0015 0.0010 0.0005 0.0000 0 0.05 0.1 0.15 0.2 voltage (V) 0.25 0.3 0.35 0.4 0.35 0.4 Current-Voltage Characteristics of a Solar Panel You will need the following equipment: Sunlight or a desk/lamp on a day where it is cloudless a photovoltaic cell/solar panel a voltmeter, ammeter light meter (measuring in watts per sq. m is preferable – some schools will have a lux meter instead) potentiometer (with 10 ohm protective resistors) as follows Source of light Sun light - maximum brightness (≈ 1000 W/m2) Sun light – half sun brightness(dull) (≈ 500 W/m2) Desk lamp Variable resistor required (0 – 50 ohm) or possibly (0 – 100 ohm) (0 – 250 ohm) or possibly (0 – 500 ohm) (0 – 1k ohm) or possibly (0 – 10k ohm) Use a 10 ohm protective resistor in series with the variables so they don’t overheat and burnout under high power output. Method PART A The experiment should be done outside under constant temperature and sunlight conditions – ie no clouds The experiment should also be performed quickly to avoid overheating of the panel that may then change the characteristics during the data-collection Make sure that you don’t cast any shadows or reflections over the panel during the experiment. Set-up the circuit below (using the middle and either of the outer pins of the variable resistor) in area of maximum sun voltmeter variable resistor panel 10 ohm res ammeter Once you have fixed the panel it is NOT TO BE MOVED DURING THE EXPERIMENT. Record the sunlight intensity using the light meter (in W/m2) by holding its face parallel with the face of the panel. Turn the axle of the variable resistor so that you can record current and voltage pairs increasing at approximately 1 V intervals. Include uncertainties. Determine the short-circuit current by removing the variable resistor from the circuit and measuring the current under no load. Check that the voltage is ZERO for this measurement and add this data to your table. Determine the open-circuit voltage by measuring the panel voltage without the load - connecting only the voltmeter across the panel – ZERO current. Measure the dimensions of the panel face or a cell so as to determine its area in m 2 (include errors of course) PART B Repeat for a position where the panel faces away from the sun. Analysis Enter the data on a spreadsheet as follows: Panel/Load voltage (V) 1. 2. 3. 4. 5. 6. Current output (A) Power output (W) Load resistance (ohms) Enter your data onto a spreadsheet with the voltage column first according to the table above. For each current-voltage pair determine the power developed by the solar panel by using the spreadsheet (P=VI) For each current-voltage pair determine the load resistance developed by the solar panel by using the spreadsheet. (R=V/I) Plot the current (A) (y-axis) vs voltage (V) (x-axis) and power (W) (y-axis) vs voltage (V) for all 3 trials – by producing an XY scatterplot- including error bars. You should have separate graphs with each graph showing the current and power developed vs voltage. Locate the maximum power points produced by the panel by determining the maximum power points for each of the sets of data using the graphs that you have generated. – determine the voltage, current, power and circuit resistance at the maximum power point. Determine the maximum power supplied to the panel by the sunlight as follows: Power Supplied by Sun = Irradiance (W/m2) x panel area (m2) Questions 1. Compare the voltage (V) vs current (A) graphs for each panel position and note any differences. 2. Compare the different maximum powers, voltages, currents and external resistances for the different panel positions and comment on their comparison. 3. Comment on how power output is affected by the external resistance loaded to a solar panel. 4. Calculate the maximum output efficiency for each part as follows: Maximum efficiency (%) = Maximum power output of panel(W) x 100 Power supplied by the Sun(W) Comment on the significance of the size of the efficiency. Solarex Panel - current (A) vs voltage (V) - 843 W/sq m irradiance - 100 ohm var res 0.650 0.600 0.550 0.500 0.400 0.350 0.300 0.250 0.200 0.150 0.100 0.050 0.000 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Voltage (V) Power(W) vs Voltge (V) - Solarex Panel - 843 W/sq m - 100 ohm var res 8 7 6 Power(W) 0 5 4 3 2 1 0 0 5 10 15 20 voltage(V) Power(W) vs Ext Load (ohms) - Solarex Panel - 843W/sq m 8 7 6 power(W) current (A) 0.450 5 4 3 2 1 0 0 100 200 300 ext res (ohms) 400 500 600