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    kWh homework problems

    Homework:

    kWh problems:

    1. Tanya Lightov has a tea maker that boils water using 1500W.
      1. what is the current if the voltage is 120 V?
      2. what is the power in kW?
      3. how many kWh would this take if it heated the water for 10 minutes?
      4. how many hours is this?
      5. how much would it cost at $0.40/kWh?



    1. Husband and wife Mort & Fay Tality have a water heater that consumes energy at a rate of 4500 Watts.
      1. How many kW is this?
      2. If the heater is on for 2 hours in the morning, and 2 hours in the afternoon, how many kWh does this use?
      3. If the system runs at 220 Volts, how many Amperes would this take?
      4. What is the resistance of the heater?
      5. How much would this cost at $0.40/kWh?
      6. If your solar thermal system captured 3/4 of this energy, how much money would it save?
      7. If the solar thermal system cost $2000 to install, how long would it take to pay it off?
      8. If the system lasted for 30 years, what would be the total cost of ownership?


    1. Ella Fynoe lives with her husband, Bud Tuggly in beautiful downtown Fremont (of AP exam fame) where electricity costs a mere $0.10 per kWh. Ella is considering installing a PV system on her roof, where she gets a solar average of 4 hours of sunshine each day.
      1. If her system captures 10 kW of power at peak, how many kWh could she expect each day?
      2. How much money would this save Ella each year?
      3. If the system cost Ella $12,000, how long would it take her to pay it off?
      4. If the system lasted 30 years, what would be her total cost of ownership?
      5. Why would Ella and Bud not be a good target for a PPA company?


    1. Airline seat tester Wilma Butfit drives 40 miles each way from Waimea to the Kona airport every day in her Tesla, which has a 30 kWh battery, which she charges at home and at the FREE parking at the airport.
      1. Using the HELCO numbers of $0.40 per kWh, how much does it cost her to drive from Waimea to Kona one way if she only uses 25% of the battery?
      2. If her air traffic controller friend Ulanda U. Lucky drives her gas powered car, which gets 20 miles per gallon the same distance, how many gallons would this take?
      3. How much would this cost Ulanda if gas costs $4.50 per gallon?
      4. If Wilma wanted to install PV on her home, where she gets about 5 solar hours per day, how many kW would she need at least?


    From Past AP exams:

    1. The Cobb family of Fremont is looking at ways to decrease their home water and energy usage. Their current electric hot-water heater raises the water temperature to 140°F, which requires 0.20 kWh/gallon at a cost of $0.10/kWh. Each person in the family of four showers once a day for an average of 10 minutes per shower. The shower has a flow rate of 5.0 gallons per minute.
      • (a) Calculate the following. Be sure to show all your work and include units with your answers.
      • (i) The total amount of water that the family uses per year for taking showers
        (ii)The annual cost of the electricity for the family showers, assuming that 2.5 gallons per minute of the water used is from the hot-water heater
      • (b) The family is considering replacing their current hot-water heater with a new energy-efficient hot-water heater that costs $1,000 and uses half the energy that their current hot-water heater uses. How many days would it take for the new hot-water heater to recover the $1,000 initial cost?
      • (c) Describe TWO practical measures that the family could take that would reduce their overall water use at home.
      • (d) Describe TWO conservation measures (other than reducing hot water use) that the family could take to reduce the total amount of energy that they use at home.


    1. West Fremont is a community consisting of 3,000 homes. A small coal-burning power plant currently supplies electricity for the town. The capacity of the power plant is 12 megawatts (MW) and the average household consumes 8,000 kilowatt hours (kWh) of electrical energy each year. The price paid to the electric utility by West Fremont residents for this energy is $0.10 per kWh. The town leaders are considering a plan, the West Fremont Wind Project (WFWP), to generate their own electricity using 10 wind turbines that would be located on the wooded ridges surrounding the town. Each wind turbine would have a capacity of 1.2 MW and each would cost the town $3 million to purchase, finance, and operate for 25 years.
      • (a) Assuming that the existing power plant can operate at full capacity for 8,000 hrs/yr, how many kWh of electricity can be produced by the plant in a year?
      • (b) At the current rate of electrical energy use per household, how many kWh of electrical energy does the community consume in one year?
      • (c) Compare your answers in (a) and (b) and explain why you would or would not expect the numbers to be the same.
      • (d) Assuming that the electrical energy needs of the community do not change during the 25-year lifetime of the wind turbines, what would be the cost to the community of the electricity supplied by the WFWP over 25 years? Express your answer in dollars/kWh.
      • (e) Identify and explain TWO environmental benefits to West Fremont of switching from coal to wind power and TWO environmental costs to West Fremont of switching from coal to wind power.



    Comments

    /groups/apenvironmentalscience/search/index.rss?tag=hotlist/groups/apenvironmentalscience/search/?tag=hotWhat’s HotHotListHot!?tag=hot6/groups/apenvironmentalscience/sidebar/HotListadminadmin2020-08-19 15:43:59+00:002020-08-19 15:43:59updated30adminadmin2011-09-08 21:36:21+00:002011-09-08 21:36:21updated29adminadmin2011-08-24 23:20:40+00:002011-08-24 23:20:40updated28adminadmin2011-08-24 22:42:36+00:002011-08-24 22:42:36updated27adminadmin2011-08-22 02:41:09+00:002011-08-22 02:41:09updated26adminadmin2011-08-22 02:40:02+00:002011-08-22 02:40:02updated25adminadmin2011-08-21 20:39:11+00:002011-08-21 20:39:11updated24adminadmin2011-08-21 20:30:42+00:002011-08-21 20:30:42updated23adminadmin2011-08-21 20:30:13+00:002011-08-21 20:30:13updated22adminadmin2011-08-21 20:25:48+00:002011-08-21 20:25:48updated21adminadmin2011-08-21 20:25:18+00:002011-08-21 20:25:18updated20adminadmin2011-08-21 00:22:12+00:002011-08-21 00:22:12updated19adminadmin2011-08-21 00:18:56+00:002011-08-21 00:18:56updated18adminadmin2011-08-21 00:15:43+00:002011-08-21 00:15:43updated17adminadmin2011-08-21 00:12:37+00:002011-08-21 00:12:37updated16adminadmin2011-08-21 00:12:02+00:002011-08-21 00:12:02updated15adminadmin2011-08-20 23:59:41+00:002011-08-20 23:59:41updated14Added tag - hotadminadmin2011-08-20 23:59:38+00:002011-08-20 23:59:38addTag13Added tag - conservationadminadmin2011-08-20 23:59:32+00:002011-08-20 23:59:32addTag12Added tag - critical thinkingadminadmin2011-08-20 23:59:19+00:002011-08-20 23:59:19addTag11Added tag - ch1adminadmin2011-08-20 23:59:08+00:002011-08-20 23:59:08addTag10Added tag - sustainabilityadminadmin2011-08-20 23:59:05+00:002011-08-20 23:59:05addTag9adminadmin2011-08-20 20:47:39+00:002011-08-20 20:47:39updated8adminadmin2011-08-20 20:46:15+00:002011-08-20 20:46:15updated7adminadmin2011-08-20 20:43:07+00:002011-08-20 20:43:07updated6adminadmin2011-08-20 19:14:13+00:002011-08-20 19:14:13updated5adminadmin2011-08-20 19:11:26+00:002011-08-20 19:11:26updated4adminadmin2011-08-20 18:59:57+00:002011-08-20 18:59:57updated3adminadmin2011-08-20 18:56:59+00:002011-08-20 18:56:59updated2First createdadminadmin2010-11-07 01:41:28+00:002010-11-07 01:41:28created1wiki2020-08-19T15:43:59+00:00groups/apenvironmentalscience/wiki/welcomeFalseCh01 Overview/groups/apenvironmentalscience/wiki/welcome/Ch01_Overview.htmladmin30 updatesCh01 Overview Welcome to our APES wiki. You should be able to do the following after logging in with your account: To create a new page, click the ...Falseadmin2020-08-19T15:43:59+00:00adminadmin2013-02-05 02:24:03+00:002013-02-05 02:24:03updated4Added tag - hotadminadmin2013-02-05 02:24:02+00:002013-02-05 02:24:02addTag3adminadmin2013-02-05 02:05:35+00:002013-02-05 02:05:35updated2First createdadminadmin2013-02-05 02:03:35+00:002013-02-05 02:03:35created1wiki2013-02-05T02:24:03+00:00groups/apenvironmentalscience/wiki/394a8FalseEnergy notes/groups/apenvironmentalscience/wiki/394a8/Energy_notes.htmladmin4 updatesEnergy notes Week of 2.4.13: energy wrap-up e2 video: coal vs. nuclear in class AP exams: FRQ 2002.1 2004.2 2006.1 2007.2 2008.1 ...Falseadmin2013-02-05T02:24:03+00:00adminadmin2013-02-05 02:23:20+00:002013-02-05 02:23:20updated6Added tag - hotadminadmin2013-02-05 02:23:18+00:002013-02-05 02:23:18addTag5adminadmin2013-02-05 02:23:12+00:002013-02-05 02:23:12updated4adminadmin2013-02-05 02:21:48+00:002013-02-05 02:21:48updated3adminadmin2013-02-05 02:20:26+00:002013-02-05 02:20:26updated2First createdadminadmin2013-02-05 02:06:00+00:002013-02-05 02:06:00created1wiki2013-02-05T02:23:20+00:00groups/apenvironmentalscience/wiki/c360bFalseFeb-May plan/groups/apenvironmentalscience/wiki/c360b/FebMay_plan.htmladmin6 updatesFeb-May plan 1. conclusion of energy chapters (see previous wiki) 2. GCC AP questions FRQ: 2006.2 2005.3 2005.4 2007.3 ...Falseadmin2013-02-05T02:23:20+00:00adminadmin2012-03-07 05:53:55+00:002012-03-07 05:53:55updated14adminadmin2012-03-07 05:43:38+00:002012-03-07 05:43:38updated13adminadmin2012-03-07 05:41:35+00:002012-03-07 05:41:35updated12adminadmin2012-03-07 05:38:57+00:002012-03-07 05:38:57updated11Added tag - hotadminadmin2012-03-07 05:38:55+00:002012-03-07 05:38:55addTag10adminadmin2012-03-07 05:36:47+00:002012-03-07 05:36:47updated9adminadmin2012-03-07 05:22:26+00:002012-03-07 05:22:26updated8adminadmin2012-03-07 05:20:01+00:002012-03-07 05:20:01updated7adminadmin2012-03-07 05:18:58+00:002012-03-07 05:18:58updated6adminadmin2012-03-07 04:58:55+00:002012-03-07 04:58:55updated5adminadmin2012-03-07 04:57:33+00:002012-03-07 04:57:33updated4adminadmin2012-03-07 04:56:53+00:002012-03-07 04:56:53updated3adminadmin2012-03-07 04:54:20+00:002012-03-07 04:54:20updated2First createdadminadmin2012-03-07 04:53:33+00:002012-03-07 04:53:33created1weblog2012-03-07T05:53:55+00:00groups/apenvironmentalscience/weblog/de030FalseGreen Apple/groups/apenvironmentalscience/weblog/de030/Green_Apple.htmladmin14 updatesGreen Apple Team, Please watch this video about NYC: Trailer: http://www.pbs.org/e2/episodes/101_the_green_apple_trailer.html On the server: http://physics.hpa...Falseadmin2012-03-07T05:53:55+00:00adminadmin2011-09-13 19:08:24+00:002011-09-13 19:08:24updated4Added tag - hotadminadmin2011-09-13 19:08:22+00:002011-09-13 19:08:22addTag3adminadmin2011-09-13 19:08:10+00:002011-09-13 19:08:10updated2First createdadminadmin2011-09-13 19:04:30+00:002011-09-13 19:04:30created1weblog2011-09-13T19:08:24+00:00groups/apenvironmentalscience/weblog/4ecddFalseQuestions for Wednesday, wiki adds/groups/apenvironmentalscience/weblog/4ecdd/Questions_for_Wednesday_wiki_adds.htmladmin4 updatesQuestions for Wednesday, wiki adds Team, I'd like to try something for class tomorrow: each of you to create a question from chapter 3, and email it to me by this evening (Tuesday). Pl...Falseadmin2011-09-13T19:08:24+00:00hot/groups/apenvironmentalscience/search/index.rss?sort=modifiedDate&kind=all&sortDirection=reverse&excludePages=wiki/welcomelist/groups/apenvironmentalscience/search/?sort=modifiedDate&kind=all&sortDirection=reverse&excludePages=wiki/welcomeRecent ChangesRecentChangesListUpdates?sort=modifiedDate&kind=all&sortDirection=reverse&excludePages=wiki/welcome0/groups/apenvironmentalscience/sidebar/RecentChangesListmodifiedDateallRecent ChangesRecentChangesListUpdateswiki/welcomeNo recent changes.reverse5searchlist/groups/apenvironmentalscience/calendar/Upcoming EventsUpcomingEventsListEvents1Getting events…