Energy & Environment I

HW#9 Revised 12/3/01

Due Wednesday, December 5, 2001

Answers in blue.

Additional information is in purple.

For the final two HW assignments (#9 due 12/5/01, and #10 due 12/12/01), the focus will be on natural gas use for electricity generation in the Pacific Northwest. You have been sent a report on this, entitled "Convergence". Additional information on electricity generation in the Pacific Northwest is contained in the Week 4 notes on the course web site – see the latter slides in "Saturday Football Lecture". Also see the national and state information on energy use on the "eia.doe.gov" web site contained in the xls spread sheet (341.01.HW9.energydata.xls) e-mailed to you.

In HW#9, given here, you will look at the amount of natural gas and electricity involved. Then in HW#10, to be assigned, you will develop a policy for natural gas use for electricity in the Pacific Northwest.

HW#9:

  1. How much natural gas are we talking about? That is:
    1. How much natural gas is currently used per year in Washington State? Express your information as trillions of std cubic feet, as quads, and as the % of natural gas used in the USA (ie, natural gas used in WA x 100/natural gas used in the USA).

      2. Answer: By the spread sheet, WA State used about 278 trillion BTUs of natural gas in 1999. This is 0.278 quads of energy. Based on 1033 BTU per std cu ft (Bodansky, p 3:7), WA State’s natural gas use in 1999 was 0.27 trillion cubic feet. The US used 22295 trillion BTUs of natural gas in 1999. Thus, WA State’s percentage was 1.25%. (For reference WA State’s population is over 5 million, about 2% of the US population. Per capita, WA State uses about 60% as much natural gas as the US.)

    2. What is breakdown on end point use? That is, for Washington State, what are the amounts and the percentages of natural gas used by residences, by commercial establishments, by industry, and by electricity generators. This information may be determined by examining the "blue" columns on the spread sheet e-mailed to you. "Percentage" means the percentage of energy provided by natural gas for each end point use. For example, what percentage of residential energy is provided by natural gas? (This is the direct use of natural gas – it does not count the electricity used by the homeowner that was generated from natural gas. This is counted under electricity.)

    Answer: The table below shows the results obtained by the spread sheet as well as additional results. Some of the additional results are based on Figure 1.4 in "Convergence". The Figure 1.4 data have been converted to trillion BTUs. Note NUG means non-utility generation of electricity.

    Trillion BTUs used in 1999 by

    WA State

    (does not include transporta-tion sector)

    WA State

    (spread sheet data)

    % of sector’s energy provided by natural gas

    % of WA State’s natural gas used by the sector

    PNW

    (Fig 1.4, Conver-gence)

    % of PNW’s natural gas used by the sector

    Residential

    75.4

    34.8%

    28.0%

    129

    24.0%

    Commercial

    53.4

    34.8%

    19.8%

    98

    18.3%

    Industrial

    133.4

    (includes NUG)

    22.5%

    49.6%

    191

    (no NUG)

    35.5%

    Electric Generators

    7.1

    Utility only

    0.6%

    2.6%

    119

    Utility+NUG

    22.2%

    Total

    269.3

    		  

    100%

    537

    100%

  2. How does Washington State compare to the rest of USA? Are our residences more or less dependent on natural gas than the rest of the USA? What about our commercial establishments? What about our industry? What about our electrical generation? This information may be determined by examining the "yellow" columns on the spread sheet.

    3. Answer: By the spread the results for 1999 are as follows:

    Residential end-use in US: 45.2% natural gas.

    Commercial end-use in US: 40.8% natural gas.

    Industrial end-use in US (includes NUGs): 36.0% natural gas.

    Utility end-use in US: 9.5% natural gas.

    For all of the end-use sectors, the US uses a greater percentage of natural than does WA State. WA State is less dependent on natural gas than the US.

    (For the US, for 1999, from Lecture #2, we note the US’s total consumption of natural gas was 22295 trillion BTUs. We also note the use on natural gas for electricity generation was 5950 billion std cu ft, which is equivalent to 6150 trillion BTUs. Thus, for the US, 27.6% of natural gas use went into the generation of electricity.)

  3. What are the projections for the future? How much natural gas is Washington State likely to use in 2010 and in 2020 for the end point sectors. What are the growth percentages? The "Convergence" document contains this information.

    4. Answer: From Figures 1.4 and 1.6 and Table 1.1 in "Convergence", one can estimate the growth in natural gas use projected for the Pacific Northwest. We assume the trends also hold for WA State. The following tables show the results:

    Billion std cu ft of natural gas used in the Pacific NW

    1999

    2010

    % increase

    average annual % increase

    Residential

    125

    180

    45%

    3.5%

    Commercial

    95

    120

    25%

    2%

    Industrial

    (no NUG)

    185

    220

    20%

    1.7%

    Electrical Gen (Utility+NUG)

    (Assuming units under construction and those permitted reach operation)

    115

    320

    180%

    10%

    Electrical Gen (Utility+NUG)

    Including all units proposed

    115

    690

    500%

    18%

    Total

    (Including units under construction and permitted)

    520

    840

    60%

    4.5%

    (Total

    Including all proposed units)

    520

    1210

    133%

    8%

    MW capacity of natural gas fired electrical gen

    MW

    MW

    cumulative

    %

    increase relative to 1999

    1999

    3069

    3069

    		  

    Under construction,

    on line in 2001-02

    1560

    4629

    50%

    Permitted

    2936

    7565

    145%

    Proposed

    8450

    16015

    420%

     

  4. From where, and from whom, do we get our natural gas? Where are the pipelines? Where do they start? Is there increasing pressure from other parts of North America for this gas? The "Convergence" document contains this information.

    5. Answer: See Figure 1.1 in "Convergence". Natural gas comes to the Pacific Northwest from two regions: 1) northwest Alberta, and 2) the Rocky Mountain Supply Basin (Wyoming, Colorado, Utah, and New Mexico). The West Coast Pipeline brings the natural gas from Alberta through British Columbia to Sumas, WA, where connection is made to the Northwest Pipeline. Natural gas from Alberta also comes into WA via the PG&E Pacific Transmission Northwest (GTN) Pipeline. This is located in eastern WA, and continues through eastern OR and northern CA to the San Francisco area. The southern leg of the Northwest Pipeline brings natural gas to WA from the Rocky Mountain Supply Basin.

    Figure 1.1 shows the Alliance and Trans Canada Pipelines, which transport natural gas from Alberta to midwestern and eastern Canada and the USA. Thus, WA State must complete with several regions for the Alberta natural gas: California, midwestern Canada and the US, and eastern Canada and the US.

  5. What type of equipment is used to generate electricity from natural gas? This has been discussed in class. Where are the new gas-fired electrical generating stations located in the Pacific Northwest? See "Convergence". How many MWs of gas-fired electrical generating capacity will be on line by the end of 2001? See "Convergence". How does this compare to the total electrical capacity in Washington State? See "Football Lecture". How does it compare to the "big 5" electrical generating sites in Washington State? See "Football Lecture".

Answer: The equipment used to generate electricity from natural gas is 1) the combined cycle combustion turbine, and 2) and the co-generation combustion turbine. Electricity can also be generated by burning natural gas in a convention Rankine cycle power-plant. However, this is not being done in the Pacific Northwest because of the inherently low efficiency of the Rankine cycle.

The natural gas-fired electrical generators in the Pacific Northwest are mainly located at the 1) oil refineries of Anacortes and Whatcom County (co-gen units), and 2) along the pipelines (combined cycle units).

The number of MWs is listed in the second table of the answer to question #3 above. If all of the units under construction are completed by the end of 2001, the capacity of the natural gas-fired electrical generators in the Pacific Northwest will be 4629 MW. Only counting those units in WA State gives 1653 MW of capacity.

The total electrical generating capacity of WA State was about 25,000 MW in 1998. The average power actually generated in 1998 was about 11,000 MW (about a 45% capacity factor). The capacities (ratings) of the big-5 generators are:
  1. Would it be more efficient to directly heat our homes and commercial establishments on natural gas, or to heat our homes on electricity generated from the natural gas? Efficiencies for residential heating systems have been discussed in class. Note the nominal transmission and distribution loss is 10% of the electrical energy generated at the power plant.

    2. Answer: If we assume a typical combined cycle power-plant efficiency of 55%, with 10% of this lost in transmission and distribution, 50% of natural gas energy content is delivered as electrical energy to the consumer. If conventional electrical resistance-type space heating equipment is used, most of the electricity purchased will be converted to heat. The overall efficiency is about 45%.

    If on the other hand, a heat pump is used, with a typical COP of 2, then the overall efficiency of the space heating will be about 50% x 2 = 100%.

    The efficiency of natural gas-fired home heating furnaces is 80-90%.

    Unless we invest in a heat pump (which has a high capital cost), the overall efficiency of heating directly with natural gas is superior to that of heating with electricity generated by a natural gas fired combined cycle.
  2. What is the recent (last few years) price history of natural gas? The current spot price of natural gas is about $2.50 per million BTUs. This can determined from "Convergence" or from the "Football Lecture". You may also wish to consult (www.eia.doe.gov).

    3. Answer: The traditional wholesale price of natural gas is $2-3 per million BTUs. However, in the winter of 2000-01, due to several factors, the price spiked to about $10 per million BTU. In CA it spiked at over $30 per million BTUs. (The "factors" were 1) low storage of natural gas at the end of the summer of 2000, 2) low drilling incentive in 1990s, 3) very cold early winter in parts of North America, and 4) growth in the economy demanding more natural gas.)

  3. What about wind turbines? Could they provide a significant amount of reasonably priced electricity compared to natural gas? See "Football Lecture".

Answer: Wind turbines are an interesting possibility for generating electricity in the PNW, and should be taken seriously. The Stateline project being built just east of the Columbia River in south central WA will have a capacity of about 300 MW when completed (soon). The average power generated will be about 100 MW, which is about 10% of Seattle’s need. Seattle City is under agreement to purchase a significant fraction of the Stateline power output, at 4.85 cents per kwh.

Bonneville Power Administration has received proposals to build a large capacity of wind turbine electrical generators in the PNW – about 1000 MW total. The wind power potential of WA may be a few 1000 MWs.