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To what extent does the output potential difference across a solar cell/ solar plate depend on the angle of inclination with respect to direction of light which falls on it if intensity of the light source and its perpendicular distance from the center of the solar plate is kept constant?
Introduction - Recently our government has implemented the idea of providing subsidies on production of solar panels to use the renewable solar energy to reduce costs. In my opinion this is a great step for reducing opportunity cost and investing government revenue in other sectors for welfare of our economy. Our Government wasted no time and soon this step to save electricity was on being put into action. Hence, nowadays, one can see a lot of traffic lights installed with solar panels. As others in the city, I noticed it too. Whenever I commuted in the city, I used to see a solar panel being installed at least once. What caught my eye was that these solar panels were placed on a particular angle instead of being exactly parallel to the road. I couldn’t help but wonder why they did so. One of my few thoughts was that this was done to make it more efficient. This seemed pretty obvious as the government wishes to reduce costs with this idea, it’ll make sure that it does this in the most efficient way. However, this theory of mine only stayed true for few minutes as I soon realized that the angle wouldn’t be fully effective throughout the day because the position of the sun changes with time. As a result of this, a solar panel might turn out to be useless at later hours of the day. This gave me the idea to investigate the effect of the angle, at which a solar panel is placed, on the output potential of it. I spoke to my physics teacher at school about this lab idea. After getting his inputs, I planned an experiment to determine the extent to which the output potential difference across a solar cell depend on the the intensity of light falling on it. In this lab experiment, I had to be sure of a two particular things: perpendicular distance, of the light source from the center of the solar cell, doesn’t change and the intensity of the light source remains constant. For doing so, I made sure I used the same light source for all the readings and did not move the solar cell throughout the experiment.
Historical background – Alexandre Edmond discovered photovoltaic effect in 1839. This phenomenon explains how electricity can be generated from sunlight. He asserted that “shining light on an electrode submerged in a conductive solution would create an electric current.” However, even after a considerable amount of research and development, photovoltaic effect proved to be inefficient and hence it was mainly used for measuring light. Approximately hundred years after this discovery, Russell Shoemaker Ohl an American engineer, invented and patented a usable and efficient solar cell. Our modern day solar cells were invented after the invention of transistor.
What are solar cells? A solar cell is an electronic device that is used to convert the energy in sunlight into electricity. These are often installed in groups in order to make a solar panel that can supply enough electricity to make an electric appliance function.
How do solar cells work? A solar cell consists of n-type silicon and p-type silicon which are blue and red respectively. Electricity is generated through a phenomenon known as photovoltaic effect. When light falls on a solar cell, the surface is bombarded with photons which carry their energy through the cell. The electrons use this energy to delocalize. The electron then starts moving, and this flow of electron is known as generation of electricity.
Hypothesis – To help me deduce the effect of angle on the output potential of a solar panel, I’ll be using the help Lambert Cosine Law. As I have to determine the effect of change in intensity of light has on the output potential of the solar cell, this law will prove to be useful. It states that intensity is directly proportional to cos^2 , where is the angle made by the solar panel with respect to the virtual normal line of the surface in radian. My initial expectations were that, the solar cell will have the highest potential when its placed perpendicular to the light falling on it i.e. at the angle of 90. This is because, in this position maximum light will fall on it and the most amount of energy will be absorbed, which means the light will have the highest intensity. However, I didn’t know to what extent will the output potential change with a certain change in the angle at which the solar panel
obtain a total three readings and reducing random error. Then I changed the angle by 10 and recorded the necessary readings. I conducted the same experiment while placing the solar cell on eight more different angles (0, 10, 20, 30, 40, 50, 60, 70, 80, 90) and noted down the readings.
Raw data – Angle/ Voltage/ V^ Average voltage/ Trail 1 Trial 2 Trial 3 V 0 1.3420 1.2970 1.3870 1. 10 1.3016 1.2516 1.3516 1. 20 1.1852 1.1552 1.2152 1. 30 1.0068 0.9818 1.0318 1. 40 0.7880 0.7380 0.8380 0. 50 0.5551 0.5201 0.5901 0. 60 0.3361 0.2861 0.3861 0. 70 0.1575 0.1225 0.1925 0. 80 0.0408 0.0008 0.0808 0.
These are the readings I obtained while conducting the experiment. Now, as the correlation is between voltage and cos^2 instead of , I’ll need to calculate cosine square of all the angles
Processed data –
S. no. Angle/
cos^2 Uncertainty in cos^2 / Δcos^2
Voltage/ V Average Voltage/ Vav
Uncertainty in voltage/ ΔV
Trial 1 Trial 2 Trial 3
These seem to be fit to be used for plotting a graph as these contain the average voltage obtained through experiments.
Graph of Voltage against the squared cosine angle between the the solar cell and the surface’s normal -
angle between the normal drawn from the solar panel and the light ray falling on it, the output potential of the solar cell increases. This result can be helpful for future installation of solar panels. For instance, the government subsidized installation of solar panels on traffic lights should now make sure that the solar panels installed are at an angle of 0 as that will prove to be the most efficient, productive and useful.
