Purpose:

The purpose of this lab is to explore solar cells and what they do in different lighting situations. The measurements we make can be hoped to provide some additional insight when we discuss solar cells in class.

COVID: Here is the version of the lab that we will do in a remote or online class environment. Handling solar panels and see how they behave in different settings is preferrable to simulations but you're not likely to have solar panels lying aound in your kitchen junk drawer.

Procedure:

Solar Cells (photovoltaic cells or PV cells) are a device which shares it's technological roots with the transistors that make our phones and computers work.

Along the way I hope that you will learn a little bit about using a DMM (digital multimeter). The digital multimeter is a useful and inexpensive tool that can be very handy around the house or apartment.

Voltage and current are concepts which are initially confusing for many people. If we think of current being carried by charges which are a little bit like bowling balls the voltage is how high up the hill we carry them. Bigger voltage means more energy available for each bowling ball. Current is how fast the bowling balls move down the hill. More rocks or sagebrush on the hill and the balls move slower. More bowling balls coming down the hill means more energy being carried down the hill. We'll see if this helps your thinking (but probably it won't....). More voltage is needed to push current through a resistor. For an LED the voltage is pretty constant but more current means more energy delivered which makes the LED brighter.

The following are the steps we will take:

• I) Solar Cells:

  In this section I want you to write a paragraph describing what you observe about the various solar cells. Before you write this paragraph spend some time looking at the different types of solar cells. You will probably find some characteristics they all share and some that are different. We will discuss your observations collectively before you write your paragraph.

• IIa) Getting something to happen (no load): The purpose of the solar cell is to “make some voltage”. By doing so the solar cell can move current (electrons) from place to place which delivers energy to different objects. What we want to do is measure that voltage. We will use the DMM to measure the voltage produced by the solar cells after we spend some time discussing how to use the DMM. Once you understand how to make this measurement I want you to explore around the lab (and outside if the weather is nice) and see how much voltage is produced when you put your solar cell under different lights. For this part of the lab make sure you point the solar cell directly at the light. Record your data in a table. This table will be transfered to your written document later.

  IIb) What do you observe (no load)? As you look at the data you collected do you see any patterns in the data? Do you get more voltage with dimmer lights? Do you get more voltage from sunlight or flourescent lights?

• IIIa) Getting something to happen (load): Now we will hook up a resistor or an LED to our solar cell so that it has to provide energy. This is sort of like putting the solar cell under stress. Watch as you repeat your measurements from part II and notice whether it shows the same or different behavior. If you are using an LED when does the LED get brighter or dimmer which is an indication of more current flowing.

  IIIb) What do you observe (load)? As you look at the data you collected do you see any patterns in the data? Do you get more voltage or current with dimmer lights? Do you get more voltage or current from sunlight or flourescent lights?

• IVa) Shading your solar cell: Find a reasonably bright light that produces a reproducible (what is this?) energy supply from your solar cell. Using pieces of paper or a folder explore how much the energy produced by your cell changes as you shade the cell. When you record your data make sure you note which part of the cell you shaded and what percent of the cell was shaded.

  IVb) What do you observe? Again, consider your data and write a paragraph describing how the energy produced by the cell changes, or not, in response to shading. The following questions may be helpful.

• V) Mutiple Cells: You will have to collaborate with another group to perform this experiment. What happens to the voltage produced if you connect two cells together sequentially (this is officially called being in series). You'll need to think about what you think this means and whether there are different ways you might do this. What happens when you connect two cells together 'side by side' (this is officially called being in parallel) Record your data and observations here.

• VI) Analysis (What might it mean?): Now you've spent some time exploring a simple solar cell system. What are two things that you have learned about solar cells that you will remember in future conversations about PV systems?

 

LAB DELIVERABLES (turn in):

Turn in your descriptions, data, and observations in one document (thru Turnitin on Bb) that show your work on each of the steps given above. Draawings of your experimental setup can be inserted as images or drawn using a simple illustration tool if you have access to one. In places where you need to show your data create a table with labels for appropriate columns and rows. Be sure that your conclusions are based on the data shown in your table.