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Engineering Design and Problem Solving

Chapter4: 3 rd Design Project. Engineering Design and Problem Solving. Introduction/Description.

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Engineering Design and Problem Solving

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  1. Chapter4: 3rd Design Project Engineering Design and Problem Solving

  2. Introduction/Description • The 3rd Design Project will further allow students to apply the engineering design process (EDP), build a Grätzel cell solar system and test it using different colored dyes, and build an intermediate open or closed loop solar water heater system or an advanced feedback control loop system. • You will calculate your home’s electricity usage based on your family’s electrical utility bill, calculate the heat transfer of a solar water heater system, and create a presentation about solar energy systems documenting the steps of the (EDP) for the general public.

  3. Chapter 4: Outline Solar Energy Solar Heat Wind Energy Other Renewable Energy Sources

  4. Objectives and Results Objectives • Explain how the sun provides Earth with useful energy. • Explain how the sun's energy can be used to heat water. • Explain how the sun's energy can used to create electricity, using a Grätzel cell. • Explain the difference between temperature and heat. • Identify the features of a system. • Identify the features of open and closed loop systems. • Identify the features of a feedback and control system. • Calculate the efficiency of a process. • Calculate power used and produced by a system. • Calculate the rate of heat transfer. • Practice the design process by designing and building a solar heating or power system.

  5. Objectives and Results, cont. Results • The students will have demonstrated that they can apply the engineering design process, their knowledge of solar power and solar water heating systems, and their knowledge of control and feedback systems to design and build a solar heating or power system. • Students will demonstrate their knowledge and skills by presenting their project to the instructor and the class and by completing the quiz and meeting all of the criteria in the 3rd Design Project and presentation rubrics.

  6. Schedule of Assignments

  7. Student Project Basics Individually and in teams, you will • calculate your home’s electricity usage based on your family’s electrical utility bill, • build a Grätzel cell solar system and test it using different colored dyes, • calculate the heat transfer of a solar water heater system, • build an intermediate open or closed loop solar water heater system or an advanced feedback control loop system, and • create a presentation about solar energy systems documenting the steps of the engineering design process (EDP) for the general public.

  8. Vocabulary • Black Body Radiation • Current • Diffraction • Efficiency • Electrical Power • Electrolyte • Electromagnetic Radiation • Electromagnetic Spectrum • Frequency • Heat • Heat Conduction • Heat Convection • Heat Radiation • Kinetic Energy

  9. Vocabulary, cont. • Particle-Wave Duality • Photoelectric Effect • Photon • Photosensitive • Photovoltaic • Refraction • Solar Cell • Solar Power • Solar Water Heater • Temperature • Thermal Energy • Volt meter • Voltage • Wavelength

  10. Renewable Energy Background • Lack of electricity concerns • Supply vs. demand • Unreliable energy sources • Reliable energy sources

  11. Sun as an Energy Source • The light from the sun heats the Earth and provides energy. • Reasons to support solar energy usage include • political and economic climate, • dependence on foreign oil, and • opportunity for innovation insolar cell creation. • Solar Energy Timeline

  12. What is Sunlight? • Sunlight is visible light, but this is only part of the electromagnetic spectrum. • The Sun can be approximated as a black body source of radiation, meaning that it gives off all types of radiation in the electromagnetic spectrum. • The intensity of the radiation and its energy depend on the temperature of the black body source. Sunlight Interactive

  13. Waves and Particles in Sunlight • The wave portion of light has three main properties that are related to each other: • Wavelength (λ) • Frequency (ν) • Speed of light (c) • They are related to each other with the following equation: c =ν×λ • The speed of light is approximately 3×108 m/s. • Frequency and wavelength are inversely related to each other. • Particle-Wave Duality

  14. Light Diffraction Light diffraction happens when light scatters from a regularly repeating object, such as rain droplets, clouds, or a CD. The different wavelengths of light scatter in slightly different ways, causing the “white” light to separate.

  15. Light Refraction Light refraction happens when light travels from one material into another. Differences in the atomic structure of the material cause the light to bend. The different wavelengths of light bend at slightly different angles and cause the “white” light to separate, such as when light passes through a prism.

  16. Photoelectric Effect Photoelectric Effect Simulation

  17. How Photovoltaic Cells Work Solar Energy

  18. Grätzel Cells Grätzel Cell

  19. Calculating Power • The electrical power generated by solar cell can be found by using Joule’s Law: • P = Electrical Power = Current × Voltage = I × V • where the current is given in amps (A), the voltage is given in volts (V), and, power is reported in watts (W). • You can use a volt meter to measure the current and voltage produced by the solar cell and the multiply them together to find the power. • For example, a typical Grätzel cell can supply 2 milliamps and 0.5 volts to the circuit. Using Joule’s Law gives us the following equation for the power output of the cell: • P = 2×10-3 × 0.5 = 1 ×10-3 watts

  20. Efficiency of Solar Cell • The efficiency of a solar cell is the measure of how much electrical power is produced. Engineers use it to compare the performance of different solar cells. • For example, if a solar cell produces a power of 1×10-3 W/cm2 in sunlight, then the efficiency of that cell would be • (1×10-3)/(1×10-1)=1×10-2. • To change this to percent efficiency, multiply the answer by 100. This solar cell has a 1% efficiency.

  21. Calculate Power Usage at Home • Using your monthly power (electricity) bill and the worksheet, calculate how much power your household uses in a day. • Your energy bill reports your energy use in kilowatt hours (kWh). To calculate the power, P, in kilowatts (kW), divide the energy used by the time period, t, in hours (hr) that it was used over the billing period (usually 28 days or 672 hours): • P(kW) = E(kWh)/t(hr) • This is how much power your house hold uses in a day. • How does this relate to the typical output from a single silicon solar cell (approximately 2W)?

  22. Student Scenario • Imagine that you have been relocated to a remote rural area in which you have limited access to electricity on the normal utility grid. • You need to have regular electricity to conduct business, stay in contact with friends and family members, and have a reliable potable and hot water source. • You have to present your idea to a local zoning board and your company in order to get the funding and clearances for your systems, so you don’t have to pay the costs yourself.

  23. Design and Build a Grätzel Cell • Using the Grätzel cell kit materials, construct Grätzel cells with different plant based dyes: chlorophyll, blackberries, and raspberries. • Use a volt meter to measure the voltage and current produced with each dye, when exposed to a broad-spectrum light or sunlight as the light source. Record data for each dye-based cell. • Using the standard sunlight power per unit area of 0.1 W/cm2, calculate the efficiency of each type of dye-based solar cell and determine which dye is the most effective. • How many Grätzel cells would you need to power your house for a day?

  24. Earth as a Thermodynamic System

  25. Heat, Thermal Energy, and Temperature • Heat is the transfer of thermal energy from a system with higher thermal energy to one with lower thermal energy. • Thermal energy is the kinetic energy of atoms in a system. • In solids, it is the vibrations of the bonds between the atoms. • In liquids and gases, it is the movement of the atoms in space. • Heat is transferred by one energized particle “bumping” into another particle and giving away some of its energy to the second particle. • For solids, the “bump” is through the bond connecting the atoms. • For liquids and gases, the “bump” is the atoms colliding. Gas Properties Interactive

  26. Rate of Heat Transfer • The rate of heat transfer is how fast thermal energy is transferred into the solar heater system. This can be calculated with the following equation: Q = h × A × (Tin- Tout) where h is the heat transfer coefficient (and depends on the material being heated), and A is the internal surface area of the tubing being heated. • Using the sample data set provided in your student handout, calculate the rate of heat transfer for each experiment.

  27. Solar Water Heating Systems • Solar water heating systems collect the radiant heat from the sun and use it to heat water in your house. • There are two basic types of solar heating systems: • Open loop • Closed loop

  28. Open Loop Systems

  29. Closed Loop Systems

  30. Feedback and Control Loops

  31. Feedback and Control Loops, cont.

  32. Intermediate Open or Closed Loop • Using tubing, water, antifreeze, and tubs, design and build an open or closed loop solar water heater. • Your group should be prepared to present the following to your instructor and your class: • Problem statement and how you solved your problem using the engineering design process • Original design of your open or closed loop solar water heater system • Working model of your system • Measurement and analysis of the rate of heat transfer

  33. Advanced Feedback Control Design • In addition to the requirements for the open or closed loop system, add one of the following feedback and control systems to your design project: • Design and develop a solar water heating system that uses a feedback and control loop to switch between heating water with a solar heater and an electric element, when the temperature drops below a certain temperature. • Design and develop a solar panel system that uses a feedback and control loop to change the angle of the panel, when the power output of the solar cell drops below a level that you determine is too low.

  34. Credits • ClipArt; http://www.clipart.com/en/ • Images; http://commons.wikimedia.org/wiki/Main_Page • Slide 17 Solar Energy video; fromYouTubeuser; EngineeringTimelines; http://www.youtube.com/watch?v=he_JjrXEfN0

  35. Credits, cont. • Slide 18 Grätzel cell video; from YouTube user; Polytechpress; http://www.youtube.com/watch?v=ncsNMDgngYI • Slide 24 Earth as Thermodynamic System http://www.nasa.gov/audience/forstudents/5-8/features/F_The_Role_of_Clouds.html

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