RelationshipBetweenComponentsinaSmallSolarElectricSystem ActivitySheet

Lesson 3—Solar Energy Activities Lesson 3—Solar Energy Activities Name:___________________________________________________________________Date:____________________ Per:__________ Solar Cell Power: Series or Parallel? Materials: (per group) 2 Solar panel units (2 solar cells) Desk lamp (light source) Sets of leads (black & red) Load (LED light, motor w/fan blade, holiday lights, incandescent light source, etc.) Ruler Optional: Color filters (ex: red, blue, green) Solar panel covers (tissue, white paper, clear plastic, black paper) Multimeter Calculator Safety notes: Desk lamps can get very hot, so take care when moving them. Color filters should be kept far enough away from light to not melt. Teacher may reduce lighting in classroom to maximize results collected & observed—move around room carefully. If using the motor/fan, be careful not to injure yourself since high rpms can be achieved. If you are unsure how to set up your circuit throughout the lab, ask your teacher about your arrangement so you don’t burn out a bulb or motor. Directions: Simple Circuit to Load A simple circuit includes the power source (solar panels/cells), conductors to carry electricity (wires), and a load (motor/lights). Connect wires from solar to load. Aim at the lamp and observe. Change the angle of the solar panel to the lamp. What angle seems to work best for the load? Notice which way the motor spins. Switch connections to the load and observe. What happens when you switch them (reverse polarity)? Series Circuit to Load Series wiring connects PV cells in a chain, from positive (+) to negative (-) between each panel. The electrons follow one path. Connect the black (-) wire of one solar panel to the red (+) of another cell. Connect the remaining wire from each panel to the load wires. Is the load different than it was in the simple circuit? Explain. What happens when you shade one panel? Why do you think this happens in a series circuit? Parallel Circuit to Load When PV cells are wired in parallel, the positives (+) of each panel are connected to one side of the load, and the negatives (-) of each panel are connect to the other. This gives two paths for the current to follow through the load. Parallel circuits are often used to power loads on a cloudy day. Connect the red wires from two solar panels onto one load wire. Connect the black wires from the panels onto the other load wire. Is the load different compared to the simple & series circuits? Explain. What happens when you shade one panel? Why do you think this happens in a parallel circuit? Now that you have made all the circuits, conduct additional investigations according to your teacher’s directions. You may now be using a multimeter & Ohm’s law. Explore the effects of- Moving the lamp closer & further away Partially covering and uncovering the solar panel(s) with one or multiple materials Tilting the panel(s) backwards and forwards Using different colored light filters For your new experiment, you must write a hypothesis, list you independent & dependent variables, controls, and construct a data table for results, calculations (if applicable), & observations. Also include a procedure that explains what you did. Attach your information by stapling to this sheet. Analysis & Conclusion: Summarize all of your results. Include appropriate electrical terminology. Explain any possible sources of error or any problems/issues during the experiment(s). How do your results relate to real conditions with the Sun? Explain your answer. Explain how your results could apply to someone using solar energy to generate electricity. Series and Parallel Circuits Basics Name: Directions: Log on to your computer. Go to the following website: _http://phet.colorado.edu/index.php_ Click the button “Play with sims…” Click on the Physics category on the left, then the application that says Circuit Construction Kit (DC only). Click “Run now.” You now have the raw material to create a circuit. Take a moment to look over the site and find all the different materials. To build a circuit you will need several wires, a light bulb, a voltage source, a voltmeter, and a non – contact ammeter. Play with it to see how to grab and manipulate these tools. Click the reset button. Series Circuits Build a simple series circuit that consists of 6 pieces of wire, 1 light bulb, and 1 battery (voltage source). In order to complete the circuit, the red circles at the end of each must overlap. Please note that the light bulb also has TWO circles. Your circuit is complete and working when the light comes on and the blue dots begin moving. Draw a picture of your circuit here: What do you think that the moving blue dots represent? Use the tools at the side to get a voltmeter and a Non-contact ammeter. Put the voltmeter near the battery and place the red tab at one end and the black at the other. What is the voltage? __________ Place the ammeter crosshairs over the moving blue dots. What is the reading? _______ What does this tell us about the circuit? Use the left button to play with the resistance and voltage of the battery. Make observations on how this changes the readings on the voltmeter and ammeter. Record your observations below. Be sure to record the changes you made and then the effects. Click the advanced tab and alter the resistivity of the wire. Record your observations: Parallel Circuits Click the reset button to begin working on a parallel circuit. Parallel circuits provide more than one path for electrons to move. Sketch below a parallel circuit that includes 10 wires, 2 light bulbs and 1 voltage source: Create this using the simulator tool. The blue dots will be moving and both lights will be on once the circuit is complete. Use the voltmeter and non-contact ammeter to measure electron flow and push. Voltage:_______ Ammeter:______ How does this compare with your observations in the series circuit? Is this surprising? WHY or WHY NOT? Alter resistance and voltage and record your observations below: Now right click on one of the wires connected to a light bulb. Remove the wire and record your observations: Does this affect the voltage, amperes, or visually change the appearance of the light bulb? Replace the wire. Now remove one of the wires touching the voltage source. What happened? What is the difference between removing the first wire and the second? Why is this significant? Comparisons Create a second series circuit and record your observations about the two once they are side by side. You may use the tool to play around. Create a circuit using a switch. Diagram your circuit below and record observations: Energy, Electrical Components, Circuits, and Terminology Background Information: What is Voltage? Voltage is to electricity as pressure is to water; both are forces that move things. Voltage is the force that moves electrons through a circuit; the greater the voltage the greater the force of electron movement. Voltage is generated by creating a “potential difference” between positive and negative elements of the device generating it. Like water, the higher the voltage, the more force it exerts. Water falling from a height uses gravity to create force; the higher the water falls (its potential difference), the more force or pressure it creates. Unlike water, however, voltage is not created by gravity but by chemical, optical, or magnetic forces. Batteries use chemicals to generate voltage while common fuel cells use electrons in hydrogen gas to create voltage. Solar panels use optical means to capture the sun’s photons to do the same and wind turbines use rotating magnets that are very close to coils of wire that generate voltage based on the magnetic fields created by the magnet’s rotation. Voltage is measured in units called volts What is Current? Electrical current is to electricity as the volume of water is to water flow. A fire hose can carry more water at higher pressure compared with a clogged showerhead. So too can lager wires carry more current as compared with smaller wires. Electrical current carries electrons along a path (called a circuit) like water carries water molecules through a hose. More electrons mean more current flow. Water normally flows from upstream to downstream using gravity as a force. Electrical current normally flows from positive (+) to negative (-), which is called direct current or DC for short, but gravity is not involved. Unlike water, electrical current can flow in either direction – positive to negative and negative to positive. The latter is usually called alternating current, or AC, since the current switches (alternates) between positive and negative directions. Electrical current produced by batteries are DC while electrical current coming out of the wall socket is AC. Both have their applications in electronic circuits. Current is measured in units called amperes or amps What is a Power Source? An electrical power source is a device that produces electrical voltage and current and power. Power sources can use chemical energy like a battery or fuel cell, solar energy like a solar panel or wind energy coupled with magnetic energy such as a wind turbine. Each of these power sources converts one kind of energy (chemical, light or mechanical) to electrical energy. The equation for electrical power is shown below: P = V * I where P = Power in watts V = Voltage in volts I = Current in amps What is a Circuit? A circuit is any “unbroken” or closed connection of electrical components that form a continuous conducting path for current to flow; if the circuit is “broken” (or open as in an open circuit) no current can flow and no power or energy can be delivered. The most basic electrical circuit is made up of a power source (like a battery) attached to a load (like a resistor). What is a Load? A load is a device that absorbs the power coming from a power source and uses the power to do work, like spin a motor, or simply dissipate the power into heat like the coils of wire in a toaster. In all cases, loads are used to both consume and regulate the power being produced. Generally speaking, a load is measured as resistance in units called ohms. In relative terms, a “light” load has a large resistance and a “heavy” load has a small resistance. This may be counter intuitive, but it is the case, nevertheless. For example, a 100 ohm resistor presents a “lighter” load to a circuit as compared with a 10 ohm resistor. The motor-propeller is about 2 to 4 ohms making it a very heavy load. What is a Series Circuit? In an electrical circuit several devices such as light bulbs can be placed in a line - or in series - between the positive and negative poles of the battery. This is called a series circuit. A major problem is if one light bulb burns out, then it acts like a switch and turns off the whole circuit. On the other hand a major advantage of a series circuit is that it saves wires that are needed in a parallel circuit. What is Power? Power is the combination of voltage and current. Voltage is the pressure component of power forcing electrons to move through a circuit, and current is the quantity component of power indicating the amount of electrons in the flow. Both voltage and current are required to produce the electrical force called power. Power is instantaneous and is not measured over time like energy. When you measure power, you measure voltage and current for a given instant of time. This is an important distinction – time, or lack of it, is the essential difference between power and energy. Power is instantaneous while energy is power measured over time. Electrical power is measured in units called watts. What is a Parallel Circuit? Devices can be arranged in a parallel circuit such that if any bulbs burn out the circuit still remains intact and operates. Holiday lights are wired in parallel so that if one bulb burns out the others remain lit. The circuit below shows two lights wired in parallel. If one light burns out the other one stays on. What is Energy? Energy is power over time. Energy is the power flowing through a circuit for a given time like one second, one minute or one hour. When we speak of energy we mean power times time. Energy is measured in units similar to power but with a time component as in watt-seconds (or Joules), watt-minutes or watt-hours. If a circuit generates 1 watt of power for 1 hour, it is said to generate 1 Watt-Hour of energy. If an electric meter measures power in Watt-Hours (3600 Joules), that can be converted to any other time frame by understanding how time is measured – one hour = 3600 seconds. Energy can be measured in Joules (watt-seconds). _www.solarschoolhouse.org_ NOTES & PRACTICE Helpful Facts & Figures _www.solarschoolhouse.org_ VOLTS measure the force that pushes an electrical current through a wire. AMPS (or amperes) measure the number of electrical particles in an electric current. WATTS measure electrical power: the rate at which electricity is generated or used. Volts x amps = watts. SERIES WIRING – Connected in a string: (+) to (–) between each cell or module. The voltage of all the cells is added together; the current stays the same as a single cell. PARALLEL WIRING – All the (+) are connected together, all the (-) are connected together. The amps of all the cells are added together; the voltage stays the same as a single cell. THE POWER FORMULA (Ohm’s Law): Volts x Amps = Watts The Power Triangle The Power Triangle can calculate all forms of the power formula. Just cover the value to be calculated, and the other values show how to do the calculation. Example: You have a 60 watt, 12 volt light, and you want to know how many amps it’s drawing. Cover the “I” and you’re left with “P” over “V”, or watts divided by volts:  P 60 watts 12 volts  = 5 amps V X I SOLAR CELL & BATTERY COMPARISON CHART Feature SILICON SOLAR CELL BATTERY CELL Voltage Function of its chemistry Silicon Cells =~0.5V per cell Function of its chemistry Fully charged batteries: Alkaline batteries = 1.5V per cell NiCad batteries = 1.2V per cell NiMH batteries = 1.2V per cell Li-ion batteries = 3.7V per cell Amps (Current) Function of the AREA of the cell & the available sunlight. The larger a solar cell is, the more amps it can deliver in the same amount of light. A2 can deliver more current than A1 A1 A2 Function of the SIZE of the battery. All energy is stored inside the cell. The larger the battery cell is the more amps it can deliver. D cell can deliver more current than AA cell. D DC or AC? (Direct Current or Alternating Current) DC DC Stores Energy NO (Needs sunlight) YES Name_______________________________________________________________________ Date______________________ Per__________ How to Write a Quality Scientific Lab Report (Rubric) Lab Report Guidelines: Scientists report their findings to each other by writing up lab reports and scientific essays that they publish in subject specific science magazines called journals. Considering that we are all scientists, we will write formal lab reports that detail what we do and what we discover by doing it. Below is a rubric that states what you must include, how you should format it, and how I will be grading the lab report that you write. Please refer to the provided examples if you are at a loss for where to begin. Introduction: Your introduction should begin by introducing the science behind what you are investigating (what you already know) and why it is important to investigate this science. You must justify the experiment or activity that you did in this portion so the reader has motivation to find out what happened. Answer questions like: Who is this work important to? Why is this work important? What is the value (economic, social, aesthetic, etc.) of your findings? Include the hypothesis, independent, and dependent variables in this section. Conclude this section with a short summary of what you did in your experiment. Ultimately this section should be the second longest after the discussion section. If you reference other work you must cite your source! 15pts. Materials and Methods: Tell me what you used and how you used it. Be sure to discuss how you got the data. It is appropriate to list all materials and quantities used. You should discuss how you used them and in what order you conducted the steps of the investigation. This section should not be terribly long, but it should be thorough. Use past tense language here because it is supposed to be what you actually did (e.g. “We set up our experiment” instead of “you should set up…”) 10pts. Results: This should be a written account of your data only! Summarize important pieces of data, but do not draw any conclusions from them. You will lose points if you try to explain what anything means. You should refer to tables or graphs, if appropriate, using this format: “see Table 1” or “Fig 2 shows…” or “Figs 2 and 4 details…” Tables and Figures: You should include any tables, graphs, or charts that were requested or you deem necessary in this section. All figures must be appropriately labeled. You will lose points if you lack axis labels, titles, and/or legends. All tables and figures included must be referred to in the text of the lab report. 20pts. Discussion: This section is by far the most important. Here we will discuss what our data and results say about our hypothesis. The absolute simplest and clearest way to accomplish a good discussion of our results is to use the Claim-Evidence-Reasoning format. You should start your discussion section with a small recap of the science introduced in the introduction and the purpose of the lab. You should then make a claim about what your data shows as is relates to your hypothesis (e.g. My data supports my hypothesis that said…). You should then talk about your evidence from the lab that supports the claim you just made. You should then tell your reader exactly how your evidence supports your claim by giving a logical reasoning that tells exactly what your evidence says to you. Your discussion should end with a few sentences on anything that might have gone wrong or might have been improved in your lab. You should also discuss how you might revise your hypothesis, take this lab further, and why this type of science is important for you/humanity. 20pts. Works Cited and in-text citations: When you are writing your introduction and discussion sections you will most likely need to cite sources. After you cite a source or material you used from a source you should cite that source using this format: (Author, Date published) The last section of your lab report should be a Works Cited section that includes the references to all works that you referred to in your text. Use the following formats depending on the type of source: Author(s). Year. Title. Publisher Location:Publisher. Author(s). Year. Title. Journal Title Volume: Pages Author(s). Year. Title. Website URL. Date Retrieved Examples: Kittington, Donald Von. 2004. Students prefer to write lab reports over texting their chums. Journal of Educational Truths 23: 121-133 Picard, Jean Luc. 1994. Writing without citations is plagiarism. Fisher, Illinois: McStewart Publishers Format: You must use complete sentences and you must write in paragraph form. Spelling, punctuation, and grammar will be graded as well. Include headings for each of the four sections listed above. Avoid casual language like "we think..." instead say things like "our data suggests..." 5pts. If you have questions on how to write your lab report, be sure to ask. (Total: 70pts.) ADDITIONAL TEACHER NOTES: Possible Student Informational Videos: Energy 101: Solar Power _http://www.youtube.com/watch?v=NDZzAIcCQLQ&feature=share&list=PL0b3Fb64jOxLLylT5-3cZQpyV7xdDUY9q_ Wiring panels: series vs. parallel _http://youtu.be/1MVuBkPxLtc_ Teacher Background: Electrician background (solar panel hookups)-teacher review _http://youtu.be/N86eHRGRJwQ_ See also: pHet online activity/simulation Reference Maps (pdf) Attached Background Notes (Student and/or Teacher) Lab Report Rubric (possible assessment tool) Other reference materials/sites Possible extensions: Take students outside, different times of day, different times of year, change loads. Have the students present/share results to the class. Students study solar energy maps and decide on location(s) where solar energy/cells should be further developed/utilized. Have students research: How does a photovoltaic cell work? A company that produces photovoltaic cells and find applications they market PV cells for. A scientist or career that involves solar energy/cells. Develop a timeline showing developments in PV cell technology. What research/developments is/are underway to improve cost, accessibility, or efficiency of PV cells?