Unit 3: Electrical Systems

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1 Adapted from: Envirolution, Project ReCharge 2009 Grade Level: 7-12 Time: 90 minutes Updated July, 2017 Unit 3: Electrical Systems Lesson 2: Appliances Science Standards For a full description of each standard see the Unit Overview. Next Generation Science Standards (NGSS) High School HS-E3S3-2. Evaluate competing design solutions for developing, managing, and utilizing energy and mineral resources based on cost-benefit ratios. HS-ESS3-3. Create a computational simulation to illustrate the relationships among management of natural resources, the sustainability of human populations, and biodiversity. HS-ESS3-4. Evaluate or refine a technological solution that reduces impacts of human activities on natural systems. HS-ESS3-6. Use a computational representation to illustrate the relationships among Earth systems and how those relationships are being modified due to human activity. HS-ETS1-1. Analyze a major global challenge to specify qualitative and quantitative criteria and constraints for solutions that account for societal needs and wants. HS-ETS1-2. Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering. HS-ETS1-3. Evaluate a solution to a complex real-world problem based on prioritized criteria and trade-offs that account for a range of constraints, including cost, safety, reliability, and aesthetics as well as possible social, cultural, and environmental impacts. HS-PS3-1. Create a computational model to calculate the change in the energy of one component in a system when the change in energy of the other component(s) and energy flows in and out of the system are known. HS-PS3-2. Develop and use models to illustrate that energy at the macroscopic scale can be accounted for as a combination of energy associated with the motions of particles (objects) and energy associated with the relative positions of particles (objects). HS-PS3-3. Design, build, and refine a device that works within given constraints to convert one form of energy into another form of energy. HS-PS3-5. Develop and use a model of two objects interacting through electric or magnetic fields to illustrate the forces between objects and the changes in energy of the objects due to the interaction. HS-LS2-7. Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity. Electrical Systems

2 Next Generation Science Standards (NGSS) Middle School MS-PS1-4. Develop a model that predicts and describes changes in particle motion, temperature, and state of a pure substance when thermal energy is added or removed. MS-PS3-5. Construct, use, and present arguments to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object. Common Core State Standards for Mathematics 7.EE.B.3. Solve real-life and mathematical problems using numerical and algebraic expressions and equations. Apply properties of operations to calculate with numbers in any form; convert between forms as appropriate; and assess the reasonableness of answers using mental computation and estimation strategies. 7.EE.B.4b Use variables to represent quantities in a real-world or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities. 7.SP.A.2. Use random sampling to draw inferences about a population. Generate multiple samples (or simulated samples) of the same size to gauge the variation in estimates or predictions. 21st Century Competencies C-1. Students are required to work in pairs or groups. KC-1. The activity requires some knowledge construction. Lesson Objective Students will be able to determine how much money we spend on appliances. Students will be able to determine how much energy different appliances use. Essential Questions How much energy do different appliances use? How much does appliance use cost annually? Which is a smarter investment: an appliance that uses a smaller amount of energy or one that costs less to buy? Which refrigerator will pay off your friend s investment the quickest? How do energy analysts find phantom loads in appliances? How do my choices of appliances at home add up? Concepts Power, energy, phantom load, watt, watt-hours, kilowatt-hours. simple payback, energy consumption, energy cost, energy savings. phantom loads, energy conservation measures (ECM), Reduce/Upgrade/Control/Maintain (RUCM). Adaptations for ELL, Special Ed, or G.T. Special Ed. adaptation: Have student go into an appliance store and take photos of the various options for buying a washing machine, hot water heater, or clothes drier. Ask them to find out the price and energy rating of each and report their findings to the class. Management Strategy Group students in teams of 3-4. Make sure you have enough electrical outlets for the appliances. Electrical Systems

3 Background knowledge Teacher : If you're trying to decide whether to invest in a more energy-efficient appliance or if you would like to determine your electricity loads, you may want to estimate appliance energy consumption. Use this formula to estimate an appliance's energy use: (Wattage Hours Used per Day) 1000 = Daily Kilowatt-hour (kwh) Consumption 1 kilowatt (kw) = 1,000 Watts Multiply this Daily Kilowatt-hour Consumption by the number of days you use the appliance during the year for the Annual Kilowatt-hour Consumption (in kwh per year). The updated equation would look like this: (Wattage Hours Used per Day x Days used per year) 1000 = Annual Kilowatt-hour (kwh) Consumption To estimate the annual cost to run an appliance, multiply the annual kwh consumption (that you calculated above) by your local utility's rate per kwh consumed. Note: To estimate the number of hours that a refrigerator actually operates at its maximum wattage, divide the total time the refrigerator is plugged in by three. Refrigerators, although turned "on" all the time, actually cycle on and off as needed to maintain interior temperatures. Examples : Window fan annual cost: (200 Watts 4 hours/day 120 days/year) 1000 = 96 kwh 11 cents/kwh (the utility rate per kwh) = $10.56/year Personal Computer plus Monitor annual cost: [(120 Watts Watts) 4 hours/day 365 days/year] 1000 = 394 kwh 11 cents/kwh = $43.34/year You can usually find the wattage of most appliances stamped on the bottom or back of the appliance, or on its nameplate. The wattage listed is the maximum power drawn by the appliance. Since many appliances have a range of settings (for example, the volume on a radio), the actual amount of power consumed depends on the setting used at any one time. If the wattage is not listed on the appliance, you can still estimate it by finding the current draw (in amperes) and multiplying that by the voltage used by the appliance. Most appliances in the United States use 120 volts. Larger appliances, such as clothes dryers and electric cooktops, use 240 volts. The amperes might be stamped on the unit in place of the wattage. If not, find a clamp-on ammeter -- an electrician's tool that clamps around one of the two wires on the appliance -- to measure the current flowing through it. You can obtain this type of ammeter in stores that sell electrical and electronic equipment. Take a reading while the device is running; this is the actual amount of current being used at that instant. When measuring the current drawn by a motor, the meter will show about three times more current in the first second the motor starts than when it is running smoothly. Many appliances continue to draw a small amount of stand-by power when they are switched "off." These " phantom loads " occur in most appliances that use electricity, such as VCRs, televisions, stereos, computers, and kitchen appliances. Some people refer to these phantom loads as energy vampires. Most phantom loads will increase the appliance's energy consumption a few watt-hours. These loads can be avoided by unplugging the appliance or using a power strip and using the switch on the power strip to cut all power to the appliance. Electrical Systems

4 Typical Wattages of Various Appliances Here are some examples of the range of nameplate wattages (in watts) for various household appliances: Aquarium = Furnace = 750 Microwave oven = Clock radio = 10 Whole house = Vacuum cleaner = Coffee maker = Hair dryer = Toaster = Clothes washer = Heater (portable) = Toaster oven = 1225 Clothes dryer = Clothes iron = VCR/DVD = / Dishwasher = (using the drying feature greatly increases energy consumption) Refrigerator (frost-free, 16 cubic feet) = 725 Water bed (with heater, no cover) = Dehumidifier = 785 Laptop = 50 Water heater (40 gallon) = Electric blanket Single = 60 / Double = 100 Fans Ceiling = Window = Radio (stereo) = Water pump (deep well) = Personal computer CPU - awake / asleep = 120 / 30 or less Monitor - awake / asleep = 150 / 30 or less Televisions (color) 19" = " = " = " - 61" Projection = 170 Flat screen = 120 Source: Department of Energy website Student : Life Experience Students have used appliances in their homes, schools, and public buildings throughout their lives.some may be aware that certain brands or products are more energy efficient than older models, especially if their family has upgraded any appliances in the past. Students could infer based on usage patterns or function which appliances use more energy than others. Electrical Systems

5 Materials List: Unit 3: Lesson 2: Activity 1-4 For each group : 1 Kill-A-Watt meter 1 Calculator * Supplied by the teacher (use the duplication master to make copies of handouts). For the class : At least 5 various classroom and home appliances for the students to measure (examples include: coffee maker, mini fridge, space heater, fan) * Handouts : Appliances: Watt Does It Cost? * Appliances: Simple Payback * Clean Energy Analyst: Appliances * Appliances At Home Survey * Before Class : Arrange the appliances in stations around the classroom. Before printing Watt Does it Cost? handouts for students, print one copy and fill out the appliances in all 3 tables and then make photocopies for the students from the prefilled handout. (This eliminates the need for students to input the same information 3 times). Safety procedures Be careful not to trip over the electrical cords with so many appliances plugged in. Go over the safe use of the Kill-A-Watt meters.. Lesson Body TTW = The Teacher Will (what the teacher should be doing) & TSW = The Student Will (what the student should be doing) Engagement: TTW introduce the essential question(s) to the class: How much energy do different appliances use? How much does appliance use cost annually? Which is a smarter investment: an appliance that uses a smaller amount of energy or one that costs less to buy? TTW group students in teams of 3-4. Each team should form a single-file line at the whiteboard, or at a large sheet of paper that they can write on. TTW tell students that they will be in a relay race to see how many appliances they can list in 30 seconds. Appliances are any device that plugs in and uses electricity. Each team member will write one word, pass the marker to the next student, and return to the back of the line. Using the appliances from the relay race, have students answer the following questions: Electrical Systems

6 Which of these appliances do you think uses the most energy to operate? What appliance do you think costs you the most money? Are they the same? TTW record answers on the board. Exploration: Activity 1-2: Watt Does It Cost? (45 minutes) and Simple Payback (30 minutes) TTW use the same teams as before and give each team a Kill-A-Watt meter. TTW ask students to describe the device, predict how they will use it, and help identify the function they will use to measure the appliances. For clarification, students will need to plug each appliance into a Kill-A-Watt, plug the Kill-A-Watt into an outlet, and press the Watt button. It may be helpful at this point to explain that watts measure electrical power. TTW hand out Appliances: Watt Does It Cost? sheet and Simple Payback sheet to each student. TTW show students the appliances they will be measuring and ask them to predict the appliance that will cost the most money annually. This prediction will be recorded on their Appliances: Watt Does It Cost? sheets. Teacher Note : You will need to have set up at least 5 stations with an appliance to test. About half of the class at a time will be able to rotate through these stations. The other half will have time to work on the Appliances: Simple Payback sheets. TSW begin testing appliances, rotating through each station. Students should record their data on their sheets. Formative Assessment : TSW complete a series of discussion questions in the Evaluate section. Explanation: TTW ask these questions as a way to make sure students have understood the content of the lesson so far. Use the discussion to further explain and clear up any student misconceptions. Which appliances cost the most money? What was their environmental impact? How do appliances contribute to CO 2 emissions? [Appliances use electricity that is most often generated by burning coal or natural gas. The burning of these fossil fuels releases CO 2.] Discuss question #1 under the Evaluate section of the Appliances: Watt Does It Cost? sheet: Was the appliance that used the most watts when it was on, the same appliance that used the most kwh annually? Why or why not? [Often, the appliance that uses the most watts when turned on is not the same as the appliance that uses the most kwh annually. This is because watts are a measurement of power, while kwh is a measurement of energy.] Have students try to describe the difference between power and energy. [Watts describe how much power it takes for an appliance to work, while kwh measures that power accumulated over a period of time.] Electrical Systems

7 TTW introduce the formal vocabulary definitions for: power, energy, phantom load. Power is a rate at which energy will be consumed over time. Using water as an analogy, we can compare power to how fast water is flowing out of a pipe. Energy is the total amount, or quantity, of work that is done. Again using water as an analogy, we can compare energy to the volume of water that comes out of a pipe. After defining phantom load, TTW discuss question #2 under the Evaluate section of the Appliances: Watt Does It Cost? sheet: Did any of the appliances draw power when they were turned off? Why do you think they did? [Appliances that continue to draw power when they are off or in standby mode are said to have a phantom load. Sometimes a phantom load is easy to identify, as in the case of a DVD player with a blinking time display. Other appliances require a watt meter to discover phantom loads.] Elaboration: TTW discuss the completed Appliances: Simple Payback sheet. Ask students, Which refrigerator will pay off your friend s investment the quickest? Will this refrigerator also save her the most money in the long run? Why or why not? [Although Fridge #3 will be paid off the quickest, Fridge #2 will ultimately save the most money in the long run by looking at their annual energy costs in the first calculation we see that Fridge #2 uses about $11.50 less electricity per year than Fridge #3.] TTW tell students, energy analysts most often use this calculation to let their clients know how long it will take for them to start seeing returns on their efficiency investments. Although we used refrigerators as an example, almost any efficiency upgrade can be evaluated in this manner. Evaluation: Activity 3 and 4: Clean Energy Analyst (15 minutes) and Appliances At Home Survey (30 minutes) -In class and take home handouts Formative : Qualitative Data Revisit the essential question(s) How much energy do different appliances use? How much does appliance use cost annually? Which is a smarter investment: an appliance that uses a smaller amount of energy or one that costs less to buy? Assess Progress: Use these questions to reinforce concepts emphasized in the lesson: As they work on their investigations, ask the students which they would rather have: an appliance that uses a smaller amount of energy or one that costs less to buy. Tell them to defend their answers with reasoning and facts. What is the difference between energy and power? [Power is a measurement of the rate at which energy is consumed, and energy is a measurement of the quantity of work being done.] List three appliances that you think may have a phantom load and give your reasoning. [Answers will vary.] Explain how appliance usage impacts the environment. [Appliances use electricity, which is most commonly generated by burning fossil fuels.] List three ways that homeowners can improve the energy efficiency of their appliances. [Answers will vary, but may include reducing appliance use, properly maintaining Electrical Systems

8 appliances, upgrading to more efficient appliances, or using power strips and timers to control appliance use.] See each section for additional Formative Assessment recommendations. Summative : Quantitative Data- In class or Take Home Assignment Activity 3 and 4 TSW answer a series of questions on the Clean Energy Analyst: Appliances sheet. This assessment can be completed during class or at home. TSW complete an Appliances At Home survey at home and bring the results into class the next day. Discuss classroom variations at the beginning of the next class period. Clean-up : Have a spot picked out to store the appliances and ask students bring them to that area when the investigation is finished. Closure : Revisit the essential question of how much money do we spend on our appliances. Remind the students that the cost of an appliance to an individual is just part of a bigger picture. The price of having energy wasting appliances for the world at large is that we run out of resources sooner. The investigation gave them tools to judge the technology of the appliance in a broader way than most consumers do. Vocabulary Energy: a measurable quantity of work; energy = power multiplied by time. Power: the rate at which energy is used; power = energy time. Watt: energy unit, equivalent to the power you need to lift 100g (a small apple) a distance of 1 Meter in 1 second. Watt-hours: a measure of energy usage; watts times hours of use. Kilowatt-hours: watt-hours divided by Phantom load: the electric power consumed by an appliance when it is switched off or in standby mode: sometimes called vampire load. Electrical Systems

9 Handouts for Unit 3: Electrical Systems Lesson 2: Appliances Appliances: Watt Does It Cost? - Print two pages, one-sided, taped together horizontally Appliances: Simple Payback - Print one page, one-sided Clean Energy Analyst: Appliances - Print one page, one-sided Appliances At Home Survey - Print one page, one-sided Electrical Systems

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12 Name Date Appliances: Simple Payback Introduction : Though energy efficient products are often more expensive to purchase, they act as an investment that ultimately earns you money on day-to-day energy savings. As these savings add up the product effectively pays for itself. The amount of time this will take a calculation called simple payback is one way for energy analysts to determine the best investments for their clients. For example, let s say that your friend has an old refrigerator that consumes a lot of energy 1200 kilowatt hours (kwh) a year and is ready to be replaced. She s narrowed her choices down to three refrigerators that are all the same size with the same functions, but have different purchase prices and different energy consumption ratings. Each of these choices will save her money on her utility bill, but which one will pay off her investment the quickest? Which one will save her the most money in the long run? Use the process below to find out. Fridge #1 Purchase Price : $ Energy Consumption : 683 kwh/year Fridge #2 Purchase Price : $ Energy Consumption : 383 kwh/year Fridge #3 Purchase Price : $ Energy Consumption : 749 kwh/year Step 1. Calculate the annual energy cost of each refrigerator (including the old one!): Old Fridge Fridge #1 Fridge #2 Fridge #3 Energy Consumption (kwh) x Price of electricity per kwh $0.12 $0.12 $0.12 $0.12 = Annual Energy Cost Step 2. Calculate the annual energy savings of each NEW refrigerator: Fridge #1 Fridge #2 Fridge #3 Annual Energy Cost of Old Refrigerator minus (-) Annual Energy Cost of each new fridge = Annual Energy Savings Step 3. Calculate the years it will take for the annual energy savings to pay back the purchase price: Fridge #1 Fridge #2 Fridge #3 Original purchase price Annual Energy Savings of each new fridge = Simple Payback (in years) Electrical Systems

13 Name Date Clean Energy Analyst: Appliances Directions : Read the following to discover how energy analysts evaluate appliances. The Challenge Appliances can be defined as anything in your house that plugs in and uses electricity, from computers and televisions to blenders and hair dryers. Appliance use is calculated in watt-hours, a measure of the appliance s power demand (watts) multiplied by its hours of operation. In addition to the time that an appliance is in use, some appliances continue to draw power when they are turned off or are in standby mode. This power draw is known as a phantom load. Together, appliances account for about 20% of a typical American home s total energy consumption ( The biggest household energy consumers are clothes washers & dryers, dishwashers, and refrigerators. Often times, this energy consumption can be reduced by replacing old inefficient appliances, by reducing the amount of appliance usage, or by managing appliance use in smarter, more effective ways. The Solution When evaluating appliance energy consumption, analysts look mainly for two things: 1. Opportunities for appliance upgrades, and 2. Appliances that carry a phantom load. The most accurate way for energy analysts to measure the energy consumption of appliances is with a wattmeter, such as a Kill-A-Watt. Watt meters can be used to determine the exact amount of power an appliance draws when it is in use. They are especially useful for measuring refrigerators, which draw varying amounts of power as they go through cycles. In this case, wattmeters are plugged in over a longer period of time, such as 24 hours, to measure the appliance s average energy consumption in one day. The industry standard for efficient appliances is the ENERGY STAR certification, administered by the Environmental Protection Agency and the Department of Energy. Typically, if any major household appliances (clothes washers and dryers, dishwashers, and refrigerators) are more than 10 years old, energy analysts recommend they be replaced with an equivalent ENERGY STAR appliance. For appliances that carry a phantom load, analysts recommend using power strips that can be turned on and off, such as Smart Strips, to control the flow of electricity to the appliance. Finally, analysts recommend routine maintenance procedures that increase the efficiency of appliance operation. Refrigerator and freezer coils (located on the back of the unit) should be cleaned once a year, freezers should be regularly defrosted and dryer vents should be cleaned on a routine basis. Electrical Systems

14 Name Date Appliances At Home Survey Directions : Energy conservation measures (ECMs ) for appliances can be classified by the acronym RUCM : Reduce, Upgrade, Control, and Maintain. Using what you know about the strategies of a Clean Energy Analysts, write your recommended ECMs in the chart below. RUCM: Appliances Reduce: How can we reduce the energy we use for appliances? Upgrade: How can we upgrade existing appliances to make them more efficient? Control: How can we control the energy we use for appliances? Maintain: How can maintenance strategies improve appliance efficiency? Now, conduct an appliance energy survey of your home. Make a list of seven appliances that you use on a daily basis and determine which potential ECM recommendations apply. Appliance ECM Recommendation(s) Electrical Systems

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