Due to soaring price and negative impact to the global environment of fossil fuel, demand for clean and renewable energy has increased quickly in recent years. Solar energy stands out as it is relatively easy to install and require little maintenance. Current applications range from power supply for calculators to satellites and space stations. Also, many people decide to mount solar panels on their properties to provide energy for water heating. In some countries, not only it is cheaper but owners also get paid for extra electricity they produce which is sent to power plants. Solar panels are a large amount of solar cells connected in series.
Solar cells are also known as photovoltaic (PV) cells. Which means it generate electricity from electromagnetic radiation. They are made of semiconductors and utilizes photoelectric effect, thus when photon hits the material it excites electrons and create current flow. There are various factors that can affect the power output of the PV cell. In this experiment we are going to exam the effect of changing irradiance, which is the density of radiation incident on the surface, and temperature on the voltage and current output of the PV cell.
In this report we will look at the theory related to factors that influence PV cell output and then two experiments designed to test the theory followed by a discussion of the results and finally a conclusion and summery. The two experiments will be discussed separately focusing on different aspects.
There are three important variables that determine the characteristics of a PV cell, all of which is shown in Figure 1, a graph of power and current versus voltage. The short-circuit current (Isc) is when the cell’s positive and negative terminals are connected directly, thus the largest possible current. The open circuit voltage (Voc) is when there is no load connected to the cell and it is the maximum voltage supplied. Another important point is the maximum power point (Pmp), this is the ideal operating point of the PV cell as it provides most energy. Other factors affecting the cell may be shown as a shift in the I-V curve.
Figure 1. Current and Power versus Voltage graph for a typical PV cell
Both irradiance and temperature can affect the behaviour of output voltages and current. Change in current is directly proportional to a change in irradiance, because greater light intensity results in more electrons being stimulated. Although voltage change is also directly proportional to a change in irradiance, it is not as significant as the case with current. This is shown in Figure 2, a graph showing the shifts of current versus voltage curve due to changes in irradiance. This indicates that voltage can operate mostly near the rated value for normal circumstances. However, the voltage changes more notably with temperature variation.
Figure 2. Graph showing how the current versus voltage curve varies with irradiance
The output voltage of a PV...