ENVS 350 MidTerm Exam



Name: _______________________________

Student ID:_________________________

This exam consists of 12 short/medium answer questions. Questions are either worth 10, 15 or 20 points. There are a total of 160 points available on the exam.

Write Legibly and Carefully - Sloppily prepared exams will receive a point deduction. Take your time on this exam, there is no reason to hurry through it.

In all of the questions below, please confine your answers to the space that is provided for that question. For any numerical question, be sure to show your work, don't just write down an answer.



10 Point Questions

  1. Explain how levelized costs are determined.

    Need to discuss

    • capital costs
    • fixed costs
    • variable costs

    Product is then metered at relevant rate over the lifetime of the facility



  2. Explain how a basic electrical generator works to produce electricity.

    Need to discuss

    • stationary magnets
    • rotating coil or loop of wire
    • produces an alternating current of electricity


  3. Using Ohm's law, explain why tranmission lines must operate at fairly high voltage.

    Need to discuss

    • Ohms Law: V = IR
    • Power = VI I2R
    • Power losses through heat dissipitation therefore scale as current squared. At constant Power if one increases V one lowers I and correspondly I2 lowers considerably.





  4. Your best friend's eccentric Uncle insists that there are 60,000 Megawatts of harnassable wind power available on the Oregon Coast if you simply placed one wind turbine for every 5 miles of Oregon coastline. Show whether or not this claim is credible.

    Essential Elements:

    • Coastline is 400-500 miles long
    • 80 - 100 turbines
    • max Tubine capacity is about 5 MW so at most this is 500 MW (if wind blows all the time) nowhere near 60,000 !!!

  5. Suppose some sunny location has 1 KW per square meter of incident sunlight on it and you want to solve the 100,000 MW near term energy problem with PV arrays. How many square kilometers of PV array would you need? Make sure you properly account for efficiency.

    1 kw/meter x 10% efficiency = 100 watts/sq. meter

    There are 1,000,000 sq meters per square km

    So you get 100 MW per square km

    So if you want 100,000 MW you need 1000 times more collecting area or 1000 square km.

    Those of you that got 1,000,000 sq km for the answer a) need to do a reality check, and b) used 1000 sq meters in a sq km.



  6. What is the 84 Million Barrell Problem?

    This represents the maximum refining capacity on the planet. We could technically produce more oil, but that would be pointless as we can't refine and distribute more.

    15 Point Questions

  7. Explain the factors that go into determining an exponential depletion timescale. How was Hubbert able to correctly use this procedure?




    Need to discuss

    • concept of bell curve for production/consumption of oil
    • that Hubbert estimated R
    • used data from 1946-1956 to define the growth rate, k, of .03
    • Only one unique bell curve then fits R and K and that leads to the depletion timescale

  8. Explain why wind produced electricity is projected to have the lowest levelized cost of any renewable energy technology.

    Need to discuss

    • capital costs for wind are moderate
    • fixed costs are very low
    • variable costs are really non-existant
    • MW footprint on the land is increasing

  9. Describe how a solar concentrator system works and what some of its limitations might be?

    Need to discuss

    • how light is concentrated (e.g. mirrors, lens)
    • what you put at focal point (solar sterling engine, heating oil, or even PV cells)
    • if heating oil (parabolic trough) it mixes with water to produce steam so that's how the electricity gets out
    • for solar thermal, container of molten salts stays heated, that mixes with water to make steam

    Limitations:

    • requires large land use
    • low individual unit capacity
    • heat damage to components may limit lifetime
    • restricted to very sunny areas

  10. You have just purchased your whizbang new age healing device. This device generates designer ions that immediately reduce your level of stress. You really know nothing about this device other than a label on it which says "Plug me in - I require 5 amps of current". Over the course of 24 hours, how many total KWHs of energy has this device used. If you pay 10 cents per KWH, what is your monthly energy bill for this device?

    • determine Wattage: 5 x 120 = 600 Watts
    • 600 Watts x 24 hours is 14.4 KWH
    • 10 centers per KWH = $1.44 per day x 30 = about 45$ per month

    20 Point Questions
  11. Describe some of the planning steps that go into picking a site (in the American Southwest) for a large scale (1000 MW) solar concentrator facility

    Need to discuss

    • survey of incoming solar radiation
    • define a standard (6.75 KWH/sq m/day)
    • identify proxmity to transmission lines
    • identify land use issues and places were you can build
    • identify places where its flat
    • need 10-20 sq km after this selection process

  12. Critically discuss the pros and cons of having a near term (5-15 years) LNG economy? What would you propose that should be done as a subsitute given the required scale of 100,000 more MegaWatts needed by the year 2020?

    Need to discuss

    • LNG may make sense in the very near term (over next 5 years) which requires a modest increase in LNG terminals.
    • Highest ratio of MW output to input land use
    • On the short term, NG supply is still high.

    • But, increases or maintains our dependence on foreign fuel sources
    • ramping up to 50 LNG import sites is completely stupid because, by then, the resource will be running out
    • Much better to invest in large scale region wind and solar projects
    • Don't forget about conservation!