Lecture Session 2

1.Hot Pot Efficiency
2.Energy Conversion Efficiency with Popcorn

Transcript

1. Energy Education and Energy Literacy: Lecture Session No. 2 Wednesday 8.21.19 2019 International Workshop on Energy Education Tainan, Taiwan Energy System - Electricity
2. Part 1. What is an Energy System? A guided inquiry- based lesson Please have paper and pen ready so you can ‘be the student’!
3. What is an Energy System? Sample Learning Objectives Understand Basic Energy Concepts • Terms, definitions, Units • Differentiate Energy vs. Power • Define ‘energy system’ and preview a ‘lifecycle assessment’ • First and Second laws of Thermodynamics • Calculate Efficiency
4. This is an Energy System! SYSTEM: A set of components working together to achieve a common goal ENERGY SYSTEM: uses an ENERGY RESOURCE to provide a SERVICE
5. “Energy System” -- Hot Pot Question 1: What is the “SERVICE” that this system is providing? Question 2: What is the “ENERGY RESOURCE” that is providing this service?
6. “Energy System” -- Hot Pot Electricity Hot pot 800 ml cold water Hot Water
7. Hot pot 800 ml cold water Energy Resource = ELECTRICITY Energy Service = HOT WATER (NOTE: this is a BATCH system, NOT a FLOW THROUGH system) Question 3: How can we determine the ENERGY EFFICIENCY of this SYSTEM? - What do we know? - What do we need to know? - How to get the information? - What to do with the information? “Energy System” -- Hot Pot
8. Hot pot 800 ml cold water Electricity in Hot Water ENERGY EFFICIENCY = Usable Energy OUT x 100% Total Energy IN Energy in Usable Energy out ENERGY EFFICIENCY = Heat Energy absorbed by water x 100% Electric Energy in “Energy System” -- Hot Pot
9. Q = m * Cp * ΔT Q = heat energy absorbed by water (joule, J) m = mass of water (gram, g) Cp = specific heat, 4.186 j/g-˚C ΔT = change in temperature (˚C) Heat Energy Absorbed by Water (USABLE ENERGY OUT) ELECTRIC ENERGY IN = electricity used by hotpot appliance
10. Hot pot 800 ml cold water Electricity in Hot Water MEASURE: Water Temperature, initial (T1 , t = 0 seconds) = ___ Water Temperature, final (T2 , t = ___ seconds) = ___ Energy in Usable Energy out “Energy System” -- Hot Pot Electricity Consumed ?
11. WATTS KWH
12. Hot pot 800 ml cold water Electricity in Hot Water MEASURE: Water Temperature, initial (T1 , t = 0 seconds) = ___ Water Temperature, final (T2 , t = ___ seconds) = ___ Energy in Usable Energy out “Energy System” -- Hot Pot Electricity Consumed = _________ watts x seconds
13. While we wait … Definitions: Energy vs. Power My toaster uses 1200 Watts, now THAT’s a lot of ENERGY!! ??? But my cable box only uses 400 Watts, that’s not so bad…
14. Definitions: Energy vs. Power Energy: A measure of the ability to do work (“how much?” – finite quantity) Power: The rate at which energy is used (“how fast?” – variable amount)
15. Key Point ! POWER ≠ ENERGY Energy = Power x Time
16. Hot pot 800 ml cold water Electricity in Hot Water Energy in Usable Energy out Question 4: What unit would we use to describe the POWER consumed by the hotpot? (= POWER IN, at any given point in time) Question 5: What unit would we use to describe the ENERGY consumed by the hotpot? (=TOTAL ENERGY IN) “Energy System” -- Hot Pot
17. Units of ENERGY Joule (SI) calorie (heat) BTU (heat) Kilowatt-Hour (electricity) Unit of Oil Equivalent (BOE, TOE, LOE) Units of POWER Watt (electric power) Horsepower (HP) (mechanical power)
18. Hot pot 800 ml cold water, T1 Electricity in Hot Water, T2 Energy in Usable Energy out Electric energy provided = power (watts) * time (sec) = Joule Heat energy absorbed by water = mass * heat capacity * T2 -T1 = Joule “Energy System” -- Hot Pot
19. Hot pot 800 ml cold water Electricity in Hot Water Energy in Usable Energy out Question 6: Is ELECTRICITY a PRIMARY or SECONDARY energy source?? “Energy System” -- Hot Pot
20. Definitions: Primary and Secondary Energy Primary Energy Source: Exist prior to any human modification. Examples? • extracted from ground - coal, oil, gas • captured from natural resources – wind, water, solar, biomass
21. Definitions: Primary and Secondary Energy Secondary Energy Source: Obtained from transformation of primary energy source. Examples? • Electricity; gasoline or fuel oil; charcoal; hydrogen Also known as “ENERGY CARRIERS”
22. Electricity (measure) Hot pot 800 ml cold water, T1 Hot Water Large amount of heat (thermal energy) : T2 T1 = 24.2 T2 = 95.0 m = 800800g Watts = 1270 time = 196 seconds Efficiency = m * Cp * ΔT = = 91 % watts * time (s) “Energy System” – Hot Pot Final Calculations
23. Losses (thermal energy) Electricity (measure) Hot pot 800 ml cold water, T1 Hot Water Large amount of heat (thermal energy) : T2 What happened to the rest of the electric energy that went into the hot pot? “Energy System” -- Hot Pot
24. First Law of Thermodynamics ΔU = W + Q Second Law of Thermodynamics ΔS > 0 Quantity remains the same Quality constantly decreases
25. Activity guide can be found in the Google Classroom! Efficiency of an Energy System
26. Efficiency of an Energy System (Packing Peanut Efficiency Activity) • We’ll need three groups of volunteers ◦ Group 1 = 3 participants ◦ Group 2 = 5 participants ◦ Group 3 = 7 participants
27. Efficiency of an Energy System Procedure: ➢ Each bag of “energy” has been weighed and labeled in grams.
28. Efficiency of an Energy System Procedure: ➢ Define your system process ◦ Group 1: Create a simple process ◦ Group 2: Multi-step process ◦ Group 3: Complicated process
29. Efficiency of an Energy System
30. Efficiency of an Energy System Procedure: ➢ Wait for the signal to start (all teams will go at once). Your goal is to move all the packing peanuts as rapidly and efficiently as possible. ➢ When time is up, measure the mass of packing peanuts that makes it to your user. Note the amount of peanuts lost (e.g., on the floor) for each group.
31. Efficiency of an Energy System Procedure: ➢ Calculate the efficiency. peanuts peanuts
32. Efficiency of an Energy System Group System Description Peanuts In (g) Peanuts Out (g) System Efficiency % 1 Simple 6666 39.4 59.7% 2 Multi-step 6969 34.3 49.7% 3 Complex 6464 34.0 53.1%
33. Efficiency of an Energy System Example Questions For Students 1. Was any system 100% efficient? If yes, what was done to make it so? 2. Which were the least efficient systems? Why? 3. What contributed to greatest losses? Describe. 4. What happens to the “energy” (as represented by packing peanuts) that is “lost”?
34. Activity guide can be found in the Google Classroom! Efficiency of an Energy System (Popcorn Efficiency Activity)
35. Hot Pot Efficiency ... Electricity Hot Water (T2 - T1 ) Losses What is the ‘true efficiency’ of this energy system?
36. What is the “true” efficiency of our SYSTEM? “Electricity” use vs. “Energy” Use xx kW-hr Hot Pot Energy Delivered: Primary Energy Consumed: ???
37. Where does the Electricity Come From? Source: https://www.moeaboe.gov.tw/ECW/english/content/ContentLink.aspx?menu_id=1540
38. Where is the system boundary? What is the “Energy System” ?? 1000 lbs coal ~ 12,720,000 BTU 4,452,000 BTU 5,261,000 BTU 11,194,000 BTU 5,933,000 BTU
39. “True” Efficiency … “Life Cycle Efficiency” Electricity Hot Water ‘true efficiency’ of this energy system? Expands the System Boundary to include the primary resource Efficiency = energy gain in water potential energy in primary resource Efficiency ~ 35% Efficiency ~ 90% coal
40. Why do we CARE? Natural Gas flame, efficiency ~60% Electric Hot Pot, efficiency ~90% Extraction, processing, transportation Natural Gas Coal 91 MJ Extraction, transport, thermal power generation 35 MJ Use 100 MJ efficiency ~35% We know the efficiency of processes used to convert the energy from its original form to the form used by our appliance: 100 MJ Use efficiency ~91%
41. “True” Efficiency … “Life Cycle Efficiency” Electric Hot Pot: Efficiency = (0.35) x (0.90) = 0.315 -->31.5% Natural Gas Flame: Efficiency = (0.91) x (0.60) = 0.546 -->54.6% Which is the more energy efficient choice?
42. Revisit your Own Electric Bill How can you save energy on a personal level? The Taiwan Power Company has great suggestions on their website. https://www.taipower.com.tw /en/page.aspx?mid=393
43. How to reduce your energy consumption https://www.taipower.com.tw/upload/384/384_02.png F. Amount Consumption (kWh) G. Average of Daily Consumption
44. Taiwan Power Company Website Household Electricity Consumption Guide • Payment Options • Electricity Service • Your Meter • Reading Bill • Power Outage • Energy Conservation Methods • Application Form https://www.taipower.com.tw/en/page.aspx?mid=393
45. Energy Conservation Methods Air-Conditioner: • Purchase an air-conditioner with a high Energy Efficiency Ratio(EER) • Shut the window and door tightly. • Each 1℃ you raise the temperature = 6% savings of power consumption. • Set room temperature to 26~28℃ (78.8oF-82.2oF) • Clean the heat exchanger or condenser regularly. • Apply heat-insulated material and sunshade to reduce indoor heat capacity. https://www.taipower.com.tw/en/page.aspx?mid=386 https://2qaayg3yvidcn9imquz625sg-wpengine.netdna- ssl.com/wp-content/uploads/2016/05/ductless-air- conditioner.jpg
46. Energy Conservation Methods Refrigerator: • Move refrigerators at least 10 cm away from walls. • Move refrigerators away from ovens and heaters. • Keep 20 % space empty inside to let the air circulate easily. • Reduce the number of times you open the refrigerator; each time you do, the compressor must operate 10 min to return to a low-temperature. https://www.taipower.com.tw/en/page.aspx?mid=386 https://www.lg.com/us/images/refrigerators/md05130240/gallery/medium01.jpg
47. Energy Conservation Methods Lighting: • Use natural sunlight sources • Install high-efficiency LED bulbs with the HF electronic ballasts. • Paint the ceilings and walls in light colors to reflect natural sunlight https://www.taipower.com.tw/en/page.aspx?mid=386 https://target.scene7.com/is/image/Target/GUEST_2415de4b- abc2-4490-9f80-222f61348df9?wid=488&hei=488&fmt=pjpeg
48. Taiwan Power Company Website Rate Schedules When you go to their website: https://www.taipower.com.tw/en/page.aspx?mid=317 https://www.taipower.com.tw/upload/317/2018032816540459 885.pdf you find sections B1 and B2 which suggest how you can avoid using electricity during expensive times of day. This helps avoid over-use by everyone at the same time.
51. Taiwan Power Company Website The Take Away: Each of you can do your part to save energy on a personal level. https://www.taipower.com.tw/en/page.aspx?mid=317
52. Tea Break