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25.0 Review of Renewable Energy

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 @fit.edu; (321) 674-7377 www.fit.edu/~fleslie. In Other News . . . . Crude oil continues at ~$50/bbl

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25.0 Review of Renewable Energy

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  1. 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 @fit.edu; (321) 674-7377 www.fit.edu/~fleslie

  2. 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 obligations. • "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) 090416

  3. 25 Overview of the Review • These slides are intended to provide the most important aspects of each of the sessions of the course • 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 070424

  4. 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://my.fit.edu/~fleslie/CourseRE/ClassPres/classpresentations.htmto select those files 050428

  5. 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 market • 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 080415

  6. 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 ailments • Renewable energies usually cause less or no pollution than conventional fuels • Making the converter also uses energy and may cause pollution during production 080415

  7. 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 doesn’t pollute, but there may have been pollution from the making of the equipment • Laws effect and enforce plant changes to reduce pollution; they remove economic incentives to pollute • 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 050428

  8. 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 earth’s 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! 080415

  9. 25.3 Climate Change • An argument is made that most of the World’s scientists agree that global warming is caused by mankind • 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” doesn’t make right! Public opinion doesn’t determine science • About 1950, there was concern about global cooling • 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? 080415

  10. 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 opposite • There are no hydrogen wells, so hydrogen isn’t 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 source 050428

  11. 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 080415

  12. 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 occurs 050428

  13. 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 050428

  14. 25.5 Conservation and Efficiency • Efficiency means getting the desired result for less money; effectiveness means doing the right thing • 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 080415

  15. 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 last • 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 080415

  16. 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 080415

  17. 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 types • Used in radioactive thermal generators (RTGs) for space probes or undersea work 080415

  18. 25.7.3 Conclusion • Thermal energy conversion remains the predominant use of fuel • Since fossil fuels are still perceived as cheap, there isn’t 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 080415

  19. 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 market • Utilities say coal diversifies their “fleet” of plants • 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 aren’t many renewable energy unions 080415

  20. 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 dirty 080415

  21. 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 pressure • 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 080415

  22. 25.9 Natural Gas Decline Note declines are getting steeper! http://www.eogresources.com/investors/stats/us_decline_curve.jpg 070424

  23. 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 080415

  24. 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 terrorists • 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 years • 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 070424

  25. 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 – it’s 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 * prob(consequence) • Money spent to reduce the risk would cut the amount needed as insurance premiums 080415

  26. 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 transitions: • 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 travel 070424

  27. 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 sun’s 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 080415

  28. 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 energy • 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 070424

  29. 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 nighttime • Clearly (or cloudily), the average power varies with the weather 080415

  30. 25.11.2 Solar Electric: Batteries • Batteries are comprised of primary (nonrechargeable like dry cells) and secondary (rechargeable) types • Primary batteries don’t 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 aren’t 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 080415

  31. 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 understanding • Evaluate intended loads closely • Use spreadsheets to change system parameters readily • Make these into a report format • Isolated remote sites have no alternative utility power, and some assumptions are warranted 080415

  32. 25.11.3 Solar Thermal • Solar thermal energy for water heating is simply done with uncomplicated materials • To get higher temperatures (>180 degrees F), the sun’s 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 area • Paraboloidal (dish) surfaces are more expensive to make but increase the temperatures still further • 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 turbine 080415

  33. 25.11.3.3 Conclusion: Solar Thermal • Solar thermal systems are cost effective at low temperatures • 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 aren’t likely to be economically practical 080415

  34. 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 030426/080415

  35. 25.12.1.1 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 occur • 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 080415

  36. 25.12.1 Conclusion: Wind Resources 1 • Wind resources vary greatly with latitude, season, and terrain • Extensive data and wind maps exist for wind prospecting • 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 080415

  37. 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 http://www.weibull.com/Articles/RelIntro/data_a3.gif 080415 www.pnl.gov/ces/analysis/ sum3fly.htm

  38. 25.12.2.1 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 don’t 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://www.itl.nist.gov/div898/handbook/eda/section3/eda362.htm is a good statistics reference 080415

  39. 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, it’s 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 ideal • 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) 080415

  40. 25.12.3 Wind Turbines • Vertical axis turbines are simple but don’t 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 energy 080415

  41. 25.12.3.1 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 watt • Florida doesn’t 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 070424

  42. 25.12.3.2 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 won’t rotate until the wind speed reaches 6 mph, there is no significant energy lost below this speed; remember the cube law? • If better placement (siting) can increase the wind speed by just 10%, the power increases by 33% • 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 080415

  43. 25.12.4 Wind Turbines 2 • The exact site determines the annual power available • Rows of turbines are placed at right angles to the usual “power” wind direction so they don’t 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 070424

  44. 25.12.4.3 Conclusion: Wind Turbine Siting and Installation • 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 080415

  45. 25.13 Bioenergy • Biomass collects solar energy to build more biomass • 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 growing • 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 070424

  46. 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 contaminants http://www.eia.doe.gov/cneaf/electricity/st_profiles/florida/fl.html#t1 070424

  47. 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 plants) • 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 fail 070424

  48. 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 China’s Three Gorges 18 GW dam • Africa has only 7% hydro potential developed • Hydropower in the US West was a result of President Roosevelt’s 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 080415

  49. 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; it’s 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 090504

  50. 25.16 Geothermal Energy • Geothermal energy is categorized into three (3) qualities: • 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 070424

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