Hydroelectric and Solar Power By: Caitlin Kelliher James Manne-Nicholas Elise McGue Amanuel Zewdie 6 th Period IBSL/AP Physics
Solar Power
Introduction When photons, light particles, collide with atoms, kinetic energy is transferred. Another method of harnessing this energy is through the photovoltaic effect, which will be expanded upon later.
Photovoltaic Cell -Photovoltaic cells, PVs, are composed of semiconductors, and two elements that have unstable valance shells. -Because of the relationship given by Ohm s law, V=IR, material possibilities are limited.
Doped (Impure) Silicon Boron Doped Silicon P-Type Phosphorus Doped Silicon N-Type Electron Acceptor Electron Donor
Photovoltaic Cell -The charge imbalance between P and N type forms an electric field. -Photons knock electrons out of their shell. -The E-field at the PN junction makes loose electrons go through a wire to fill the valance shell of Boron. -A converter turns DC into AC for household use. *N-type size is far larger in diagram than in actual use.
Example Sankey Diagram of PV Panel *All percentages relative to net energy in (solar radiation).
Solar Heating Panel -Solar radiation goes through glass and is absorbed by black material. -Reflected light is bounced back by the glass (greenhouse effect), thus trapping the thermal energy. -In this case, pipes beneath the black material heat up. Cool water is pumped through them to absorb their heat.
Distribution of Solar Energy The amount of sunlight received decreases as the angles between light rays and the ground moves away from 90.
Earth s Seasons Earth s 23.5 axis tilt causes the North pole to tilt toward the Sun part of the year and then away from it the other part of the year. This is what causes the seasons.
Example 1 Energy=(efficiency)(area)(power/area)(time) Energy=(.5)(8m^2)(1000 W/m^2)(12hr)(3600 s/hr)=1.728x10^8 J Example 2 Part a 1400 L water=1400 kg water Q=mc T Energy=(1400 kg)(4180 J*Kg/K)(30 K⁰)=175,560,000 J 1.8x10^8 J Part b Energy/time=power=(power/area)(area) (1.8x10^8 J)/(2.0 hr)=9.0x10^7 W=(9x10^2 W/m^2)(A) (9.0x10^7 W)/(9x10^2 W/m^2)=A=1.0x10^5 m^2 *Simply use dimensional analysis.
Hydroelectric Power
Hydroelectricity Electricity that is made with the force of falling or flowing water This is the most used form of renewable energy Has less output of greenhouse gases than other fossil fuel energy plants
Scheme: Run of the River Uses a turbine and generator which are on the ends of a dam or next to it The dam uses the flowing river to make hydrostatic head, or the distance that the water has to fall to the generator
Scheme: Diversion Water from the dammed river or lake moved to place with turbine and generator A canal or low-pressure tunnel is used to move the water
Pumped Storage Two reservoirs are used in this process. Electricity is used to pump the water. Water is moved from the lower basin to the upper basin. The water is then used to make power. This method is usually used when electricity is cheap and the company is interested in making the largest profit.
Scheme: Wave Power Generally a means of 2 nd hand solar energy The wind stirs the surface of open water, creating waves. Local storm waves are much harder to harness than that of a flowing river. By the time the waves reach the sore, they lose up to 60% of energy through fiction. Two Types: Floating devices Fixed devices
Energy Transformations - Potential energy - Kinetic energy (gravity does work on water) - Mechanical rotational energy - Electric energy
Example 1 Power = P = E/t = Energy/Time E=U=mgh, so P = (m/t)(g)(h) g=9.81 m/s^2, mass flow rate (mass/time) = 1.0 x 10^2 kg/s H = 15 m Thus, P= (1.0 x 10^2 kg/s)(9.81 m/s^2)(15 m) = 14715 W Since this process is experienced by five turbines, the power is five times that. P = (5)(14715 W) = 73575 W, Multiplying the power by the overall efficiency of the turbines, 70%, gives P = (73575 W)(.7) = 51502.5 W Example 2 P = (m/t)gh P =(500 kg/s)(150 m)(9.81 m/s^2)(.6)=441,450 W
Example: Sankey Diagram for Electrical energy produced from a hydroelectric scheme
Works Cited Boron Doped Silicon. Digital image. Wikibooks. Web. 6 Mar. 2010. <http://upload.wikimedia.org/wikipedia/commons/thumb/5/51/p-doped_si.svg/300px-p-doped_si.svg.png>. C, Brittany, Connie H, Igna M, and Connie W. "YouTube - Solar Photovoltaic Cells Part 1-4." YouTube - Broadcast Yourself. 9 June 2009. Web. 04 Mar. 2010. <http://www.youtube.com/watch?v=fixi-xz3u_m>. Close Up of a PV Cell. Digital image. Web. 6 Mar. 2010. <http://www.is.njit.edu/competition/2009/cat2_2_winner_group142/img/catalyst_fa05_solarpvdiagram.gif>. Earth's Titlted Axis and Light Ray Distribution. Digital image. Britannica. Web. 6 Mar. 2010. <http://media- 2.web.britannica.com/eb-media/23/72223-035-18CAA9AC.jpg>. "How Do Solar Panels Work?" WiseGEEK: Clear Answers for Common Questions. Web. 06 Mar. 2010. <http://www.wisegeek.com/how-do-solar-panels-work.htm>. Knier, Gil. "How Do Photovoltaics Work?" NASA - Science@NASA. Web. 04 Mar. 2010. <http://science.nasa.gov/headlines/y2002/solarcells.htm>. McClintock, Meredith. "YouTube - Learn about Solar Energy and Solar Panel Installation..." YouTube - Broadcast Yourself. Google Tech Talks, 12 Sept. 2007. Web. 05 Mar. 2010. <http://www.youtube.com/watch?v=cyipbiplmom>. Phosphorus Doped Silicon. Digital image. Web. 6 Mar. 2010. <http://org.ntnu.no/solarcells/pics/n-doped_si.png>. Seasons. Digital image. Areavoices. Web. 6 Mar. 2010. <http://www.areavoices.com/astrobob/images/seasons_tau%27olungasmall_1.jpg>. A Solar Array. Digital image. Speed Ace. Web. 6 Mar. 2010. <http://www.speedace.info/speedace_images/solar_cells_panels_pv_array_monocrystaline.jpg>. Solar Thermal Panel. Digital image. BBC. Web. 6 Mar. 2010. <http://www.bbc.co.uk/schools/gcsebitesize/science/images/67_solar_energy.gif>. "Solar Water Heating - Domestic Solar Panels for Heating Water - Energy Saving Trust." Energy Saving Trust - Energy Efficiency & Energy Conservation to Combat Climate Change. Energy Saving Trust. Web. 05 Mar. 2010. <http://www.energysavingtrust.org.uk/generate-your-own-energy/solar-water-heating>. The Sun. Digital image. Physics Web. Web. 6 Mar. 2010. <http://physweb.bgu.ac.il/groups/ap/ap/sun.gif>. Toothman, Jessika, and Scott Aldous. "HowStuffWorks "How Solar Cells Work"" HowStuffWorks - Learn How Everything Works! Web. 04 Mar. 2010. <http://www.howstuffworks.com/solar-cell.htm>. Woods, Melissa. "YouTube - The Power of the Sun - The Science of the Silicon Solar Cell." YouTube - Broadcast Yourself. University of California, 13 Mar. 2008. Web. 06 Mar. 2010. <http://www.youtube.com/watch?v=u0hckm8tky0>.
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