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Title: Review%20of%20Renewable%20Energy%20Course

25.0 Review of Renewable Energy
Some of the more important points
Frank R. Leslie, B. S. E. E., M. S. Space
Technology 2/23/2010, Rev. 2.0 fleslie
(321) 674-7377
In Other News . . .
  • Crude oil continues at 50/bbl
  • LAGOS (AFP) Shell cannot meet its contractual
    obligations on the delivery of crude after a fire
    on a key pipeline in Nigeria that caused a major
    production loss, a spokesman said on Thursday.
  • "We have declared a force majeur for the
    remainder of April and the month of May. The
    force majeur took effect from noon on April 14,"
    Precious Okolobo told AFP, using the term that
    releases the company from its contractual
  • "We have stopped the fire. We are investigating
    its cause while the repair of the pipeline is
    about to start."
  • The 180,000 barrels per day crude production loss
    in the volatile southern Niger Delta involves a
    range of companies 130,000 for Shell, 30,000
    barrels for French group Total and another 20,000
    barrels from various other operators, an industry
    source told AFP.
  • President Obama announced an 8B down payment of
    stimulus money to build/improve ten high-speed
    rail lines in the Northeast and California
    (AMTRACK costs more than airlines)

25 Overview of the Review
  • These slides are intended to provide the most
    important aspects of each of the sessions of the
  • Equations should be provided at the end, but you
    are responsible for knowing how to find them and
    how to use them
  • Some sections may not be fully complete at this
    time when other lecturers used transparencies

25.1 Introduction
  • The introduction at RE01 has a synopsis of the
    general content of the whole course and should be
    studied for the test
  • Not all sessions are treated equally here, but
    reflect what I believe to be most important in
    the renewable energy field and with general
    energy issues
  • I have concentrated on the conclusions of each
    session and may not have completed the one or two
    pages of the condensed version from the
    original files
  • Look at http//
    res/classpresentations.htm to select those files

25.2a Current Events
  • Light sweet crude oil futures rose from
    26/42-gallon barrel (4/26/2003) to about
    112/bbl (4/15/2008)
  • OPEC production cut-backs affect the global
  • China and India increasing demand price up
  • Key issues affecting the economy are the prices
    of gasoline and natural gas
  • Gasoline affects the price of goods delivered by
    truck, and diesel oil for trains and ships tends
    to parallel this price, also affecting farming
    and food
  • Natural gas is used for home heating and for the
    large utility plants built for natural gas or
    being converted to use it (lower pollution)
  • Hydrogen made from NG will increase that price

25.2b Pollution
  • Air and water pollution continue to drive the
    costs of energy production
  • There are other costs outside of the cost to
    consumers known as externalities
  • Military defense of oil sources (Kuwait Iraq?)
  • Public health costs of respiratory and other
    diseases caused by pollutants
  • Road traffic caused by oil truck transportation,
    and resultant exhaust fumes, which cause more
  • Renewable energies usually cause less or no
    pollution than conventional fuels
  • Making the converter also uses energy and may
    cause pollution during production

25.2b Conclusion Pollution
  • Combustion energy sources emit pollutants NOx,
    SOx, VOCs, etc. plus CO2, a green house gas (GHG)
  • Nuclear plants might rarely emit accidental
    releases of radioactivity, but safe designs
    reduce this chance
  • Wind and solar energy doesnt pollute, but there
    may have been pollution from the making of the
  • Laws effect and enforce plant changes to reduce
    pollution they remove economic incentives to
  • Emissions credit trading may help reduce
    pollution since there is an economic incentive to
    clean up
  • During the Iraq War, Hussein did not have time to
    set oil wells on fire as in the Persian Gulf War
    of 1991

25.3 Climate Change
  • Climate change is controversial, as many or most
    scientists believe that increased combustion of
    fuels by civilization and industry releases green
    house gases (like CO2) that change the earths
    temperature balance
  • The level of atmospheric CO2 and population have
    both grown over the last 150 years is one the
    cause of the other?
  • A classic statistics example is that the sales of
    liquor and the number of Baptist ministers (who
    presumably claim to eschew alcohol) are
    positively correlated
  • They are correlated to the increasing population,
    not necessarily to each other! Be wary of those
    who say correlation proves cause and effect!

25.3 Climate Change
  • An argument is made that most of the Worlds
    scientists agree that global warming is caused by
  • In somewhat earlier days, most scientists
    agreed that the earth was flat, and only
    extremists thought otherwise! Koreshans thought
    Earth was hollow!
  • Science is not democracy, and most doesnt make
    right! Public opinion doesnt determine science
  • About 1950, there was concern about global
  • On the other hand, now glaciers are melting and
    receding over a period of years indicating a
    warmer average weather change
  • Solar dimming due to pollutants reduces global
    warming do we need more pollution to fight GW?

25.4 Fuel Hydrogen
  • There is much talk of the Hydrogen Economy,
    where hydrogen (an energy carrier) will replace
    fossil fuels
  • See Amory Lovins, Rocky Mountain Institute for
    early espousal of the concept Romm for the
  • There are no hydrogen wells, so hydrogen isnt a
    fuel in the usual sense, but an energy carrier
  • To get hydrogen, electrolysis of water, pyrolysis
    of fossil fuels, or bacterial action is required
  • Nuclear and fossil fuel base-load power plants
    produce energy to support the lowest daily load
    or more
  • This cycle peaks in mid-afternoon and/or
    dinnertime and is lowest at 3 a.m.
  • If the electrolysis is done off-peak, is the
    resultant hydrogen clean? Depends upon energy

25.4 Fuel
  • Fossil fuels are of limited extent known,
    suspected, and possible
  • Hubbert predicted the depletion of US oil about
    1970 (it peaked in 1974)
  • World oil production may peak about 2005 to 2020
  • After the peak, lots of money chasing a
    diminished supply increases the price (has the
    price increased lately?)
  • When fossil fuel prices exceed the cost of
    renewable energy, a shift will occur, slowly at
    first, then accelerating

25.4.3 Fuels Conclusion
  • Fuel usage is determined by cost and convenience
  • Fuel density is critical for transportation
  • Cost of fossil fuels and nuclear energy will keep
    these in predominance for several decades
  • Renewable energy provides small contributions
    now, but diversity is critical as transition

25.5 Conservation and Efficiency
  • Conservation of energy is the cheapest way to cut
    energy costs, but there is a tradeoff against the
    benefits of using the energy
  • Automatic air conditioning thermostats can manage
    temperatures without human intervention,
    simplifying life while saving energy
  • Motion-sensor lights only use electricity when
    someone is moving in the field of view
  • The time to pay off the investment is zero, and
    savings begin immediately

25.5 Conservation and Efficiency
  • Efficiency means getting the desired result for
    less money effectiveness means doing the right
  • Lighting must be bright enough for the task and
    yet not present when unneeded
  • Bright local lighting is better than bright
    general lighting since less power is needed to
    produce it
  • Compact fluorescent lights (CFLs) produce good
    light intensity with about 1/4 the power
  • Timers or motion detectors can turn off lights
    when they are not needed
  • Better building insulation conserves heating in
    winter and keeps summer heat out

25.5.3 Cons. Efficiency Conclusion
  • Conservation by reducing loads or shortening
    duration of use will save money, reduce
    pollution, and extend the time that fossil fuels
  • Greater efficiency in generating, transmitting,
    and using energy will yield the same utility for
    lower cost
  • Energy not used reduces the need for utility
    plant construction or delays it
  • Efficient use of fuels will save still more money
    and prolong their economical use
  • While conservation and efficiency are valuable
    practices, they only delay the depletion of
    fossil fuels

25.6 Prof. Odum, EROEI, and Emergy
  • Emergy addresses the amount of energy that is
    required to make energy conversion systems and to
    obtain and process the fuel for them
  • Energy Return on Energy Invested (EROEI) shows
    worth of an approach or product
  • This subject is well-known, but only to a few
    --- Miles E. Hall, 1958

25.7 Thermal Systems
  • Steam boiler systems require fuel to heat the
    water, making steam for turbines that spin
    generators that produce electricity
  • Solar parabolic and paraboloidal collectors have
    been developed to heat water into steam or to
    power Stirling engines
  • Simple flat plate collectors moderately heat
    water or air for household or industrial use
  • Thermocouple systems generate very-low-voltage
    electricity from heat on metals of different
  • Used in radioactive thermal generators (RTGs)
    for space probes or undersea work

25.7.3 Conclusion
  • Thermal energy conversion remains the predominant
    use of fuel
  • Since fossil fuels are still perceived as cheap,
    there isnt much clamor to change to renewables,
    which are still more expensive
  • As the price of conventional fuels increases and
    renewable energy decreases, a shift will occur
  • There must be a long overlapping period of the
    two technologies to permit development of
    renewable resources before conventional fuels
    become difficult to obtain at a reasonable price

25.8 Coal
  • The most available and least expensive fuel in
    the US, coal has many pollution issues
  • The so-called Clean Coal program reduces
    pollution by washing the coal first, controlling
    burn temperature, and then cleaning the stack
    gases afterwards sequestration is next
  • Powerful marketing forces and lobbies clamor for
    maintaining coal predominance in the energy
  • Utilities say coal diversifies their fleet of
  • Many union jobs depend upon coal production and
    transport, thus many block-votes drive
    politicians to retain coal rather than fund the
    renewable energy area
  • There arent many renewable energy unions

25.8.3 Conclusion Coal
  • Coal is the most abundant fuel in the United
    States and is estimated to last about 100 to 200
    to 400 years
  • Coal will last several hundred years longer than
    oil or NG
  • Coal will continue to be a primary fuel close to
    coal mines
  • Coal is most suited to fixed energy plants while
    mobile use requires oil or natural gas for
    density and convenience
  • Coal is cheap, and may be chemically processed to
    yield natural gas, liquids, or hydrogen, but
    taking heat and water to do so
  • Is hydrogen clean (green) if it is processed from
    coal or coal-generated electricity? No, really

25.9 Oil and Natural Gas
  • Oil and the natural gas often found with it are
    of limited extent NG aids oil production by its
  • Estimates of the remainder vary greatly since
    detection of more deposits is somewhat limited
  • Production in the United States peaked in 1974,
    resulting in oil imports as demand increased
  • World production will possibly peak in 2005 to
    2010 as China and India develop needs
  • Natural gas is a relatively clean-burning fuel
    and is the choice for new fossil-fuel power
    plants, but the price is volatile
  • Competition for the diminishing supply will drive
    prices still higher

25.9 Natural Gas Decline
Note declines are getting steeper!
25.9.3 Conclusion Oil Natural Gas
  • Oil is energy-dense and easy to transport and
    use, and thus it works well in vehicle tanks
  • Many chemicals and materials are made from oil,
    thus burning it may restrict or prevent a better,
    higher use
  • Choices are made from the economics and cost of
    doing business in the short term
  • The future value of oil in ANWR is difficult to
    predict, but it will be far more valuable in
    constant dollars a hundred years from now than it
    is right now

25.10 Nuclear Energy
  • Nuclear energy is not well understood by many
    the mysteriousness leads to fear (and loathing)
  • Nuclear energy has many radioactive concerns in
    mining, preparation, transportation and disposal
  • At the end of the fuel cycle, the spent fuel
    must be dealt with to avoid a concentration of
    plutonium in the fuel that might be misused by
  • Yucca Mountain AZ will eventually be a storage
    site for spent fuel, yet the fuel must be taken
    there from many locations by rail or truck
  • Some complain that storage must last 250,000
  • Human failure remains the largest concern
  • More outcry is raised about the possibility of
    nuclear contamination than about the statistical
    health problems caused by fossil fuel plants

25.10 Nuclear Energy
  • Future hydrogen may be produced by nuclear energy
    for electrolysis of water is this what we want?
  • In many cases, what we want is instant
    gratification and cheap, not-a-care energy its
    just there for us
  • The Age of Terrorism brings a new level of
    uncertainty to the problem, as the potential of
    attacks on nuclear plants cause widespread
    anxiety and outcry
  • The first nuclear truck bomb exploding in the US
    will bring incredible social changes
  • If there were 1 billion of lawsuit payouts per
    year for plant errors, that much would have to be
    set aside each year risk consequence
  • Money spent to reduce the risk would cut the
    amount needed as insurance premiums

25.11.1 Solar Energy
  • Available solar energy changes with the seasons,
    thus collectors may need adjustment to receive
    maximum energy
  • There are four important astronomical epochs or
  • The vernal equinox about Mar. 21 (equal day and
    night hours equi nox ? night equals day)
  • The summer solstice about Jun. 21 (longest day)
  • The autumnal equinox about Sep. 23 (equal day and
    night hours)
  • The winter solstice about Dec. 22 (shortest day)
  • These sometimes drift into an adjacent date
  • Solstices are at the extremes of angular sun

25.11.1 Solar Energy
  • Since the earth axis is tilted 23.45 degrees from
    the plane of revolution, the Northern Hemisphere
    is tipped towards the sun in summer, which occurs
    because the suns rays strike more directly than
    in winter
  • Since the direction of the sun at solar noon
    changes throughout the year, a fixed collector
    works best if aimed parallel to the equatorial
    plane (latitude angle)
  • The sun is too high in summer too low in winter
  • Setting the collector angle to the latitude angle
    thus allows the sun angle to be equal and
    opposite at the solstices
  • To heat water in the winter, an extra tilt to the
    south (north) of 15 degrees may be added since
    the cold air around the collector cools the
    collector in winter

25.11 Conclusion Solar Energy
  • Received solar energy varies widely as evidenced
    by climate records and vegetation (deserts and
    rain forests) that average growth to match solar
  • This variability affects the economic viability
    of a system
  • Solar energy systems are simple, robust, and easy
    to install
  • Solar modules are still expensive, approximately
    3.50/W for large arrays to 16/W for small
    modules, depending upon size
  • Organic process might yield 0.20/W!?!?
  • Installation adds another 5 per watt of cost

25.11.2 Solar Electric
  • A PV module may produce 30 volts with no load,
    yet produce maximum power at 17 volts
  • If it produces 17 volts and 5 amperes, the power
    is 17 5 85 watts (instantaneous power not
    per day, etc.)
  • Typical sun-hours might be only 5 hours/day
  • If it does this for 5 hours, the energy produced
    is 85 watts 5 hours 425 watt-hours (both the
    values and the units are multiplied)
  • If it produces 425 watt-hours in one day (24
    hours), the average power is 425 watt-hours / 24
    hours 17.7 watts over that day including
  • Clearly (or cloudily), the average power varies
    with the weather

25.11.2 Solar Electric Batteries
  • Batteries are comprised of primary
    (nonrechargeable like dry cells) and secondary
    (rechargeable) types
  • Primary batteries dont recharge well but
    chargers are sold since people will buy them
  • Only secondary batteries (groups of cells) are
    used for renewable energy storage
  • A battery with a 300 ampere-hour capacity based
    upon 25 hours specified time can deliver 300
    ampere-hours/25 hours 12 amperes current to a
    load for 25 hours
  • For 30 hours, 10 A for 100 hours, 3 A 300
    hours, 1 A, etc.
  • But these arent quite linear relations, and
    lower currents yield even more ampere-hours
  • Engine-cranking currents of 500 A are for 30
    seconds periods and then the alternator recharges
    the auto battery

25.11.2 Conclusion
  • Solar PV cells tend to lose capacity (10) due
    to some darkening of the cover glass use more
    area than needed to compensate
  • While PV is expensive at 3.50/W to 14/W, the
    low installation costs (5/W) reduce the overall
    cost as compared to a diesel generator
  • Research similar installations to gain
  • Evaluate intended loads closely
  • Use spreadsheets to change system parameters
  • Make these into a report format
  • Isolated remote sites have no alternative utility
    power, and some assumptions are warranted

25.11.3 Solar Thermal
  • Solar thermal energy for water heating is simply
    done with uncomplicated materials
  • To get higher temperatures (gt180 degrees F), the
    suns rays must be concentrated on the collector
  • Parabolic single-curved surfaces are inexpensive
    and increase the energy by the ratio of the
    sunlight interception area to the collector pipe
  • Paraboloidal (dish) surfaces are more expensive
    to make but increase the temperatures still
  • The SEGS solar thermal plants near Barstow CA use
    long rows of parabolic reflectors to heat oil to
    700F, which then heats water to steam to spin a

33 Conclusion Solar Thermal
  • Solar thermal systems are cost effective at low
  • Solar water heaters are energy savers, but
    initial cost dissuades many from using them
  • Power tower (Solar Two) electricity cost is at
    6/W peak
  • Not competitive
  • Massive power tower yields 10 MWe, while a
    typical utility plant is 500 MWe
  • Power towers arent likely to be economically

25.12.1 Wind Energy
  • Expensive wind turbines require good assessment
    of the local site winds to determine where to
    place the turbine
  • A 10 increase in wind speed can yield a 33
    increase in power
  • Obstructions that interrupt a smooth laminar flow
    of wind will greatly hamper power production
  • Long-term local wind studies ensure an optimal
    positioning of a turbine

35 Wind Energy
  • Distant forests will have little influence on
    wind speed while a nearby building will have a
    great influence
  • The width and height of a blocking object
    determines how much wind-slowing effect will
  • A flagpole upwind is cylindrical and narrow, thus
    the wind stream will reconverge 5 to 10 pole
    diameters behind the pole to resume smooth, fast
    flow as before
  • A rule of thumb is that the wind turbine should
    be 500 feet from the nearest large object and at
    least 15 feet above it rules vary

25.12.1 Conclusion Wind Resources 1
  • Wind resources vary greatly with latitude,
    season, and terrain
  • Extensive data and wind maps exist for wind
  • At the mesoscale level, topographic information
    is being used to create predictions of wind speed
    from widely scattered measured data
  • Anemometers can be erected to obtain wind speeds
    in a likely locale
  • An alternative is to erect a small wind turbine
    to sample the energy and to help determine where
    a large turbine should be placed
  • Wind resources may be excellent, but there is
    much more to installing a turbine

25.12.2 Wind Energy 2
  • Wind energy is a statistical variable that is
    usually much more time-variable than sunshine
  • We traditionally quantify wind energy in bins
    or ranges of various speeds
  • A probability density function (p.d.f. left) and
    cumulative distribution function (c.d.f. right)
    define these variations and make revealing graphs

080415 sum3fly.htm
38 Wind Energy 2
  • The probability of a certain wind speed times the
    energy of that speed yields the probable energy
    add each of these products to get the 100
    probable energy
  • Proportional averaging means multiply the percent
    of time a value occurs by the value, sum each of
    these products to get the overall average (all of
    them 100)
  • Average (A B)/2 (0.5 A) (0.5 B)
    (50 A) (50 B)
  • So 20 10 80 40 2 32 34
  • For a wind problem, winds under 6 mph cause zero
    output and dont turn the rotor because of
    bearing resistance
  • The top 30 of the winds likely produce the
    majority of the energy, but too much requires
    turbine shutdown
  • http//
    n3/eda362.htm is a good statistics reference

25.12.2 Conclusion Wind Theory
  • The theory of wind energy is based upon fluid
    flow, so it also applies to water turbines water
    density is 832 times more
  • While anemometers provide wind speed and usually
    direction, its data processing that converts the
    data into information
  • Because of the surface boundary drag layer of the
    atmosphere, placing the anemometer at a
    standard height of 10 meters above the ground
    is important for comparisons
  • Turbine anemometers are often placed at 150
    meters above ground --- anticipated hub height is
  • The erroneous average of the speeds is not the
    same as the correct average of the speed cubes!
  • The energy extracted by a turbine is proportional
    to the summation of (each speed cubed x the time
    that it persisted)

25.12.3 Wind Turbines
  • Vertical axis turbines are simple but dont work
    very well
  • The wind forces reverse on the blades with each
    half turn of the rotor and cause mechanical
    stress failure
  • Three-bladed horizontal axis turbines have good
    performance and appear to have the best future
    chances of success (this common style works!)
  • The turbine power is proportional to the cube of
    the wind speed, thus a 20 mph wind has eight
    times the power of a 10 mph wind
  • This means a wind speed of 20 mph (eight times
    the power as 10 mph wind) for an hour yields the
    same energy as a 10 mph wind for eight hours!
  • The longer gusts are very important for high

41 Wind Turbines
  • Large companies investing in renewable energy
    usually choose wind or solar as offering the best
    return on investment
  • Wind power is about one-fifth the solar cost per
  • Florida doesnt have very high winds (ignoring
    hurricanes), yet GE Power Systems builds wind
    turbines near Pensacola, while FPL (formerly
    known as Florida Power and Light) is the largest
    owner of utility size wind turbines in the US,
    all elsewhere
  • Many turbines were developed in Nordic countries
  • Europe has good ocean winds and strong incentives
    for renewable energy, thus many turbines

42 Conclusion Wind Turbine Theory 1
  • The turbine rotor must be matched to the
    generator or alternator to maximize the extracted
    power at lowest cost
  • Although most turbines wont rotate until the
    wind speed reaches 6 mph, there is no significant
    energy lost below this speed remember the cube
  • If better placement (siting) can increase the
    wind speed by just 10, the power increases by
  • All parts must be designed to survive high winds,
    say 140 mph
  • Large turbines use yaw motors to aim the nacelle
    into the wind small turbines steer by wind
    forces on the tail

25.12.4 Wind Turbines 2
  • The exact site determines the annual power
  • Rows of turbines are placed at right angles to
    the usual power wind direction so they dont
    block each other
  • Rows are spaced some eight rotor diameters apart
    to allow wind speed to re-increase between rows
  • Turbines are often remotely controlled from a
    central operations site
  • Offshore turbines have free access to the
    unhindered wind from any direction and yield high
    energy over a year

44 Conclusion Wind Turbine Siting and
  • Turbine siting is somewhat of an art, but science
    is providing tools that speed that site selection
  • Accurate siting strongly determines the economic
    and energy success of the system
  • Energy storage is likely to be in batteries for
    the foreseeable future more exotic methods are
    slow in reaching a cost-effective market entry
  • 2 MW batteries for wind farms are available
  • Since wind energy is the fastest developing
    energy source, the economic fall of prices will
    speed its adoption where the wind is powerful

25.13 Bioenergy
  • Biomass collects solar energy to build more
  • Energy crops that maximize the energy absorption
    can be grown for biomass combustors or reactors
  • Biomass has less pollution than fossil fuels but
    still emits pollution
  • Biomass is CO2 neutral since it absorbs CO2 in
  • The Southeast US has more biomass energy than
    other kinds of renewable energy
  • Biomass can yield fuels like ethanol, or with
    still more processing, methane gas
  • Methane also can be produced from agricultural
    wastes and manure

25.13.3 Conclusion Biomass
  • Renewables are a very small contributor to
    current Florida energy sources
  • Biomass energy is the predominant renewable
    energy source available in Florida
  • Unfortunately, most of present production is from
    municipal solid waste (MSW) that should be
    avoided or phased out due to heavy metal

25.14 Hydropower
  • The large hydroelectric dams of the US West were
    built to bring the economy out of depression, put
    people to work, and provide cheap energy to spur
    (pun intended) the development of the West
  • Once installed, the hydro plants had a short time
    to pay off and produced cheap energy that
    attracted high users of electricity (aluminum
  • Boulder Dam (now Hoover) was built to supply Los
    Angeles, where many of the dam-haters live
  • The Columbia River of Washington State has many
    dams, raising the controversy of fish migration
    and kills
  • Some extremists want to breach dams to let the
    river run free this would cause extensive
    economic damage to the Nation as power systems

25.14 Conclusion Hydropower
  • The majority of logical, large US hydropower
    sites were developed in the 1930s
  • Hydropower provides inexpensive electricity in
    the US Northwest, primarily from the huge
    Columbia River
  • There are still some in construction, like
    Chinas Three Gorges 18 GW dam
  • Africa has only 7 hydro potential developed
  • Hydropower in the US West was a result of
    President Roosevelts work program to increase
    employment during a depression and also to
    provide cheap electricity to spur commerce
  • Small hydropower on the scale of remote home
    energy is still developing

25.15 Ocean Energy
  • Because of water density, energy is 826 times
    more dense than for wind energy (power is
    directly proportional to density)
  • Momentum of water flow can stabilize the flow
    speed, so the range of variation is not as great
    as for wind
  • Tidal energy is primarily lunar driven its not
    renewable but the time to depletion is when the
    earth-moon angular momentum decays a great deal
    the moon is receding about 3.8 cm per year per
    NASA laser ranging
  • Wave energy varies more than tidal energy and
    thus requires greater strength in extraction
  • Current flow requires deep water work that
    increases the cost

25.16 Geothermal Energy
  • Geothermal energy is categorized into three (3)
  • Low 0 to 250 degrees F
  • Air conditioning or heating
  • Medium 250 to 450 degrees F
  • Industrial or processing industry
  • High 450 or higher degrees F
  • High temperature energy generation, testing,
    cutting, missile nosecone testing

25.16 Conclusion Geothermal
  • Geothermal energy is limited in extent as
    extracting the heat usually exceeds the
    replenishment rate
  • Hot, dry rock (HDR) is widespread and offers new
    resources in areas where geyser activity is
  • Direct low-temperature heat transfer for home
    heat pump systems is practical as long as low
    maintenance is designed into the system
  • Sources of high temperature water or steam are
    limited and the cost of extraction, maintenance,
    and operation will remain high in comparison with
    other sources of energy
  • Geothermal energy likely to remain at 1 world
    energy Kruger, 1973

25.17 Transmission of Energy
  • Electric currents flowing through wires lose
    energy as heat, and there may also be leakage
    currents across insulators (especially when it
  • Power lost in the wire is P I2R
  • This power loss can be reduced by sending the
    power at high voltage and low current P V
    times I
  • A step-up transformer has heavy windings on the
    primary input and many more windings of lighter
    conductor on the secondary or output side
  • The turns ratio of 101 will increase voltage 10
    times and reduce current to 1/10 of the input
    (for an ideal transformer)
  • The process is reversed at the distribution end

25.17 Conclusion Energy Transmission
  • Installation of new power lines and pipelines is
    usually met with opposition by NIMBYs
  • Doubling of conductors on an existing line
    doubles the possible current flow and is not met
    with vocal opposition
  • The Hydrogen Economy will require
    hydrogen-grade pipelines to bring the gas from
    wherever it is made to the sales points
  • The only alternative is to carry the hydrogen in
    tank trucks in groups of bottles like those used
    for welding gases
  • Direct radiation of electrical power is unlikely
    despite Nikola Teslas experiments due to radio

25.18 Energy Storage
  • Energy may be produced when not needed or be
    needed when not available
  • Storage of energy allows use at a different time
    than when it was produced
  • Electricity is more valuable during prime time
    than during the middle of the night
  • The most common form is the storage battery, but
    other types are flywheels, compressed air,
    hydraulic lifting, chemical storage (like
    hydrogen), high temperature oil, or

25.18 Energy Storage Batteries
  • Storage batteries are rated differently for
    starting engines (continuous cranking amperes,
    CCA) than for powering lesser loads like lights
  • Reserve capacity (RC) is defined as the time in
    minutes to supply a 25 ampere load until the
    voltage falls to 10.5 volts for a nominal 12 volt
  • Lesser loads can receive energy longer, while
    heavier loads drain the battery faster
  • The battery capacity (BC) is approximately 25
    amperes RC if RC 180 minutes, then BC 25
    180 4500 ampere-minutes or 75 ampere-hours
  • As an approximation, multiply the RC by 25A and
    divide by the actual current drain say 180
    minutes 25 A/20 amperes 225 minutes until
    10.5 V

25.18 Conclusion Energy Storage
  • Energy storage is to be avoided due to the losses
    of energy storage and removal, but may be
    economic when load time-shifting is possible
  • Energy must be stored in vehicles since they
    cannot obtain sufficient power from wind or sun
    on the vehicle
  • Special student SunRayce PV cars are fragile and
    light (built about as strongly as a model
    airplane), and cannot be used at normal highway
    speeds without a significant death rate
  • Newer technologies may increase energy storage
    density at a lower cost both are needed for a
    viable product

25.19.1 Transportation Energy
  • Transportation by steel wheel on steel rails is
    most efficient because of the low deformation of
  • These vehicles can only go where the rails are
  • Car and truck are less restricted, and the low
    cost allows people to move wherever they desire
  • Changing from rail to cars requires extensive
    road systems that form an area of transport
    instead of the linear corridors of rail systems
  • As population growth expanded, service of the
    people by train was more difficult since they
    still had to get to the station
  • High-speed rail is touted as a better way to move
    people medium distances

58 Transportation Energy
  • Florida voters changed the state constitution to
    mandate high-speed trains to service the major
  • While the cost wasnt specified to distract them,
    maglev trains reaching 300 mph were implied
  • The cost of such systems was so great that a
    first link from Tampa to Orlando is projected to
    cost nearly 4 billion dollars and will likely be
    conventional rail running at a speed just over
    100 mph
  • The fares cant be made high enough to pay off
    such a system or passengers would seek other ways
  • A just fare might be 2000 for Tampa to Orlando
  • Public subsidy will be required indefinitely, so
    the nonpassengers can pay for the few passengers!

59 Transportation Energy
  • Airline travel requires jet fuel to power the
  • Some experiments with hydrogen and even
    electric/fuel cell engines are possible
  • The high energy density of liquid fuels cannot
    readily be replaced by highly compressed gas
  • Compressing gas costs energy
  • A return to synfuel made from coal may be
    necessary (the Germans did this during World War
    II), or possibly transcontinental flights will
    require more stops for refueling

60 Conclusion Transportation
  • Changes in lifestyles have led to a highly mobile
    US society
  • Public transportation declined as more people
    drove a car and were disinclined to wait for a
    bus or a train
  • In high density areas, exorbitant parking charges
    (20/day at New York City Days Inn), traffic
    delays, and convenient trains or light rail shift
    public use back to public transportation
  • Long-haul trains, ships, and barges carry
    freight, having a decline in passenger travel
  • Still, short-term ships carry tourists, as do
    AMTRAC trains
  • The heavily congested Northeast US has the most
    use of fast trains for commuting to work or school

25.19.2 Transportation Energy Cars, Etc.
  • Alternative fuel vehicles (AFVs) use ethanol,
    methanol, compressed natural gas, propane, or
  • The alternative is other than gasoline or diesel
  • Some hydrogen-fuel-cell cars are being tested in
    Los Angeles, California the manufacturer
    furnishes the hydrogen
  • Electric cars use utility energy stored in
  • Where did the electricity come from?
  • Electric cars are being discontinued since hybrid
    electric cars are more widely accepted by the

25.19.2 Transportation Energy
  • The DOE Clean Cities Program has a local group,
    the Florida Space Coast Coalition, that is based
    at the Florida Solar Energy Center (FSEC) in
  • About twenty-six years after the energy crisis,
    were still sending money about a billion
    dollars a week somewhere else Dan Reicher,
    Assistant Secretary for Energy Efficiency and
    Renewable Energy, DOE

63 Conclusion Transportation 2
  • Introduction of alternate fuel vehicles will
    require a long period of adjustment by the public
  • At one time, full service gas stations seemed
    necessary, but most people now found they could
    pump their gas in order to pay a lower cost
  • Perhaps CNG stations will need full-service at

64 Conclusion Transportation 2
  • Current hybrid vehicles are user-friendly, thus
    will be rapidly accepted by the market if price
  • In transition over 10 years, they may be the
    common vehicle before some other type dominates
    the market
  • Now, the Plug-in Hybrid Electric Vehicle (PHEV)
    seems the most likely in the future
  • Vehicle changes are driven by cost above all
    else if costs increase due to government
    pollution or carbon taxes, an economic shift will
    begin to occur

25.20 Distributed Generation
  • Distributed generation (DG) is diffuse and
    consists of many small sources interconnected by
    the power grid
  • Central utilities plants are often rated at 800
    MW per section, and they often have two or three
  • Distributed plants are perhaps 3 kW to 30 MW, but
    there are many of them
  • Since the plants feed the grid as well as supply
    their own loads, there is a robust energy supply
    that resists outages

25.20 Conclusion Distributed Generation
  • Distributed generation is less vulnerable to
    outages since there are so many local sources of
  • Winter ice storms can stop electrical power over
    a much wider area than a terrorist attack
  • Critical loads are better protected when nearby
    multiple sources are available
  • Computer and industrial processes require backup
    power to prevent secondary problems caused by
    loss of power
  • Independent energy systems can use
    failure-resistant sources like multi-day fuel
    tanks or natural gas pipelines
  • Islanding of multiple power sources is a concern
    for power line workers, yet this robustness
    ensures power stability

25.21 Economics of Energy
  • Sustainable energy is essentially renewable
  • If an amount of coal took a million years to
    form, using a millionth of that amount each year
    would be sustainable (that amount would be
    pathetically small)
  • Great amounts of solar energy strikes the earth
    each day, and recovery would satisfy human needs
    without depleting it
  • Ethically, we should use only enough energy that
    we are neither better off nor worse off than some
    distant future generation
  • The present value of money can be computed to
    evaluate the risk of a project

25.21 Conclusion
  • The cost of money must be included in economic
    decisions since, generally, inflation will occur
    in the future
  • Limited resources should be used with an amount
    set aside for future generations
  • While the use isnt sustainable, the result and
    benefit to a future period should be equivalent
    to that for this period
  • Eventually, costs will rise until a different
    type of renewable energy becomes a better choice

25.22 Tradeoffs and Decisions
  • Tradeoffs provide a systematic way to evaluate
    choices and select the best one
  • Uncertainty in various estimates may tend to be
    forgotten but should not be!
  • The square root of the sum of the squares of
    uncertainties yields the uncertainty of the total
  • Weighted scoring allows the importance of various
    parameters to be adjusted
  • Adjustment of the weights will greatly affect the
  • Be wary of forcing the outcome to be what you
    want it to be

25.22 Conclusion Trades
  • Renewable energy is faced with the same types of
    problems that affect other areas of daily living
  • Getting permission to do something different than
    what is codified in law or local ordinances
  • Convincing the public or government officials
    that the project is not a nuisance and will be
    beneficial to the community
  • Trade studies that produce a well-written report
    documenting the situation, goals, choices, and
    selections may help to sway those with the power
    to approve or disapprove your proposal
  • Practice these trade studies on small projects to
    be prepared to do the large projects

25.23 Legal Considerations
  • Energy projects are constrained by laws,
    regulations, and ordinances
  • Compliance is mandatory to avoid fines or
  • Design of an energy project must include the
    costs of licensing, inspection, and pollution
    prevention, etc.
  • Comprehensive plans define the uses for various
    geographic areas or districts
  • Code compliance is necessary for the public good
  • Codes written by professional organizations are
    often recognized in law or ordinances by
    reference shall comply with Sect. Xxx of the
    National Electrical Code . . . phraseology

25.23 Conclusion Legal
  • Legal restrictions enforce many things that
    people should do, but perhaps would not due to
    cost or bother
  • The public good is protected by these laws and
  • Without legal requirements, there would be no
    possibility of recovery for loss or injury
  • Renewable energy installations should be designed
    to comply with these restrictions
  • Oh, yes --- ethics is what you do when no one is
    watching and no one will ever know but you

24 Conclusion Review
  • This review synopsizes the key points of the
    Renewable Energy course, ENS4300
  • Study of this presentation provides a good
    starting point for mastering the final test, but
    you will find study of the original presentations
    also is helpful
  • Where additional presenters assisted, you may
    need to study your class notes if no PowerPoint
    slides were available
  • Good luck on your exam and in your career!Frank

25.1 Some Interesting Facts
  • Earths axial tilt 23.5 degrees
    (23.45) Earth-sun distance 92 M miles
    92,955,820.5 miles 149,597,892 kmEarth
    Equatorial Radius 6378137 m (WGS-77)
  • Wind Turbine Power, P ?/2A U3 watts, where ?
    (rho) is 1.225 kg/m3, A is area p r2 m2, r
    blade radius in m, U wind speed in m/s.
  • P 0.5 ? A Cp V3 Ng Nb
  • whereP power in watts (746 watts 1 hp)
    (1,000 watts 1 kilowatt)? air density (about
    1.225 kg/m3 at sea level, less higher up)A
    rotor swept area, exposed to the wind (m2)Cp
    Coefficient of performance (.59 Betz limit is
    the maximum theoretically possible, .35 for a
    good design) V wind speed in meters/sec (20
    mph 9 m/s, or 2.24 mph 1 m/s)Ng generator
    efficiency (50 for car alternator, 80 or
    possibly more for a permanent magnet generator or
    grid-connected induction generator)Nb
    gearbox/bearings efficiency (depends, could be as
    high as 95 if good)
  • (from AWEA, the American Wind Energy Association)

25.2 Some Interesting Facts
  • Average wind power density, P/m2 6.1x10-4 v3
    watt/m2, where v is m/s
  • Locations Arctic Circle is 66.55º N Big Blow,
    Texas is 31º N, 103.73º W Colon, Panama is 9.7º
    N, 80º W Cicely, Alaska is 66.55º N, 145º W
    Florida Tech, Melbourne FL, 28.2º N, 80.6º W
    Panama City, Panama 8.97º N, 79.53º W Paris,
    France is 48.8º N, 2.33º E
  • Area of sphere 4 p r2 Volume of a sphere is 4/3
    p r3 PEIE2/RI2R E or VIR
  • Typical computer/monitor power is 150 watts.
    Standard 40 W fluorescent ceiling lamps
    were/are being replaced by newer T8, 32 W lamps.
  • The Link Building power meter (SE corner)
    indicates a typical weekday power load to be 60
    kW, and nights/weekends, it is 35 kW.
  • A copy machine is on only during office hours (8
    to 5) weekdays and usually draws 190 W. When
    copying, it draws 900 W.
  • FPL charges 0.10/kWh for electricity (ignore
    demand charge and billing charge, taxes, etc.)

25.3 Some Interesting Facts
  • Melbourne FL, Dec. 24-hour radiation on a
    horizontal surface is 150 W/m2 (?) and annual
    direct normal energy is 2.5 to 3.0 kWh/m2. Direct
    normal often is 1000W/m2
  • Air density is 1.225 kg/m3 Kinetic energy 0.5
    mv2 joules, where v is in m/s
  • K.E. also p / (RT), where p pressure, T
    Kelvin, and R gas constant 287.05 Joule/Kg/K
    for air
  • Snells Law Angle of Incidence Angle of
  • Altitude of the sun 90º -latitude sun
    declination azimuth is the horizontal angle
    clockwise from north
  • (declination is the varying solar
    latitude/-23.45 degrees)

Olin Engineering Complex 4.7 kW Solar PV Roof
References Books
  • Boyle, Godfrey. Renewable Energy, Second Edition.
    Oxford Oxford University Press, 2004, ISBN
    0-19-26178-4. (my preferred text)
  • Brower, Michael. Cool Energy. Cambridge MA The
    MIT Press, 1992. 0-262-02349-0, TJ807.9.U6B76,
  • Duffie, John and William A. Beckman. Solar
    Engineering of Thermal Processes. NY John Wiley
    Sons, Inc., 920 pp., 1991
  • Gipe, Paul. Wind Energy for Home Business.
    White River Junction, VT Chelsea Green Pub. Co.,
    1993. 0-930031-64-4, TJ820.G57, 621.45
  • Patel, Mukund R. Wind and Solar Power Systems.
    Boca Raton CRC Press, 1999, 351 pp. ISBN
    0-8493-1605-7, TK1541.P38 1999, 621.312136
  • Sørensen, Bent. Renewable Energy, Second Edition.
    San Diego Academic Press, 2000, 911 pp. ISBN
  • Tester, Jefferson W. , Elisabeth M. Drake,
    Michael J. Driscoll, Michael W. Golay and William
    A. PetersSustainable Energy Choosing Among
    Options. Boston MIT Press, 870 pp. July 2005

References Websites, etc.
  • Wind Energy elist
  • Wind energy home
    powersite elist
  • on geothermal energy
    ml PNNL wind energy map of CONUS Elist
    for wind energy experimenters
  • Site devoted to the decline of
    energy and effects upon population
  • Federal Energy Regulatory
    on OTEC systems