RE250Review

Slide1 : 25.0 Review of Renewable Energy Frank R. Leslie, B. S. E. E., M. S. Space Technology 4/24/2007, Rev. 1.7 fleslie @fit.edu; (321) 674-7377 www.fit.edu/~fleslie Some of the more important points


25 Overview of the Review : 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


25.1 Introduction : 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.htm to select those files 050428


25.2a Current Events : 25.2a Current Events “Light sweet” crude oil futures rose from $26/42-gallon barrel (4/26/2003) to about $65/bbl (4/24/2007) 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 the price 070424


25.2b Pollution : 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 pollution than conventional fuels Making the converter also uses energy and may cause pollution 070424


25.2b Conclusion: Pollution : 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


25.3 Climate Change : 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 correlated They are correlated to the increasing population, not necessarily to each other! Be wary! 050428


25.3 Climate Change : 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 weather change Solar dimming due to pollutants reduces global warming 070424


25.4 Fuel: Hydrogen : 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


25.4 Fuel : 25.4 Fuel Fossil fuels are of limited extent: known, suspected, and possible Hubbert predicted the depletion of oil in the US 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 070424


25.4.3 Fuels Conclusion : 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


25.5 Conservation and Efficiency : 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


25.5 Conservation and Efficiency : 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 not present when not needed Bright local lighting is better than bright general lighting since less power is needed 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 070424


25.5.3 Cons. & Efficiency Conclusion : 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 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 040413


25.6 Prof. Odum, EROEI, and Emergy : 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 shows worth of an approach or product This subject is “well-known, but only to a few” --- Miles E. Hall, 1958 070424


25.7 Thermal Systems : 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 collectors have been developed to heat water into steam or to power Stirling engines Simple flat plate collectors moderately heat water for household or industrial use Thermocouple systems generate low-voltage electricity from heat on metals of different types Used in radioactive thermal generators (RTGs) for space probes or undersea work 070424


25.7.3 Conclusion : 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 As the price of conventional fuels increase and renewables decrease, 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 070424


25.8 Coal : 25.8 Coal The most available and most inexpensive 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 Powerful marketing forces and lobbies clamor for maintaining coal predominance in the energy market Utilities say coal diversifies their “fleet” 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 070424


25.8.3 Conclusion: Coal : 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 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 070424


25.9 Oil and Natural Gas : 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 Natural gas is a relatively clean-burning fuel and is the choice for new power plants Competition for the diminishing supply will drive prices higher 070424


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


25.9.3 Conclusion: Oil & Natural Gas : 25.9.3 Conclusion: Oil & Natural Gas Oil is energy-dense and easy to transport and use, and thus it works well in vehicles 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 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 070226


25.10 Nuclear Energy : 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


25.10 Nuclear Energy : 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 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 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 050428


25.11.1 Solar Energy : 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


25.11.1 Solar Energy : 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 070424


25.11 Conclusion: Solar Energy : 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


25.11.2 Solar Electric : 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) 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 070424


25.11.2 Solar Electric: Batteries : 25.11.2 Solar Electric: Batteries Batteries are comprised of primary (nonrechargeable) and secondary (rechargeable) types Primary batteries don’t recharge well Only secondary batteries (groups of cells) are used for renewable energy work 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 battery 070424


25.11.2 Conclusion : 25.11.2 Conclusion Solar PV cells tend to lose capacity 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 Isolated remote sites have no alternative utility power, and some assumptions are warranted 070424


25.11.3 Solar Thermal : 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 simply-curved surfaces are inexpensive and increase the energy by the ratio of the sunlight interception area to the collector 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 and spins a turbine 070424


25.11.3.3 Conclusion: Solar Thermal : 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 070424


25.12.1 Wind Energy : 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 30% increase in power Obstructions that interrupt a smooth laminar flow of wind will greatly hamper power production Long-term wind studies ensure an optimal positioning of a turbine 030426


25.12.1.1 Wind Energy : 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 effect will occur A flagpole upwind is cylindrical and narrow, thus the wind stream will reconverge ~5 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 object and at least 15 feet above it; rules vary 070424


25.12.1 Conclusion: Wind Resources 1 : 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 real 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 050428


25.12.2 Wind Energy 2 : Wind energy is a statistical variable that is usually much more 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 25.12.2 Wind Energy 2 050428 www.pnl.gov/ces/analysis/ sum3fly.htm http://www.weibull.com/Articles/RelIntro/data_a3.gif


25.12.2.1 Wind Energy 2 : 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 The top 30% of the winds likely produce the majority of the energy, but too much requires shutdown http://www.itl.nist.gov/div898/handbook/eda/section3/eda362.htm is a good statistics reference 070424


25.12.2 Conclusion: Wind Theory : 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 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 the summation of (each speed cubed x the time that it persisted) 070424


25.12.3 Wind Turbines : 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 070424


25.12.3.1 Wind Turbines : 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


25.12.3.2 Conclusion: Wind Turbine Theory 1 : 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 tail wind forces 070226


25.12.4 Wind Turbines 2 : 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


25.12.4.3 Conclusion: Wind Turbine Siting and Installation : 25.12.4.3 Conclusion: Wind Turbine Siting and Installation 070424 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 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 : 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


25.13.3 Conclusion: Biomass : 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 070424 http://www.eia.doe.gov/cneaf/electricity/st_profiles/florida/fl.html#t1


25.14 Hydropower : 25.14 Hydropower 070424 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


25.14 Conclusion: Hydropower : 25.14 Conclusion: Hydropower The majority of logical, large US hydropower sites were developed in the 1930s 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 Hydropower provides inexpensive electricity in the US Northwest, primarily from the huge Columbia River 070424


25.15 Ocean Energy : 25.15 Ocean Energy 070424 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 moon crashes into the earth due to frictional drag diminishing its orbital height above Earth 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 : 25.16 Geothermal Energy 070424 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


25.16 Conclusion: Geothermal : 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 unknown Direct low-temperature heat transfer for home 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] 030327


25.17 Transmission of Energy : 25.17 Transmission of Energy 030427 Electric currents flowing through wires lose energy as heat, and there may also be leakage currents across insulators Power lost in the wire is P = I2R This power loss can be reduced by sending the power at high voltage and low current 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 10:1 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 : 25.17 Conclusion: Energy Transmission Installation of new power lines and pipelines may by 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 Tesla’s experiments 030426


25.18 Energy Storage : 25.18 Energy Storage 040415 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), or ultracapacitors


25.18 Energy Storage Batteries : 25.18 Energy Storage Batteries 030427 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 battery 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 : 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 040415


25.19.1 Transportation Energy : 25.19.1 Transportation Energy 040415 Transportation by steel wheel on steel rails is most efficient because of the low deformation of steel These vehicles can only go where the rails are located 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


25.19.1.1 Transportation Energy : 25.19.1.1 Transportation Energy 040415 Florida voters changed the state constitution to mandate high-speed trains to service the major cities While the cost wasn’t 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 can’t 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!


25.19.1.1 Transportation Energy : 25.19.1.1 Transportation Energy 040415 Airline travel requires jet fuel to power the engines 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


25.19.1.3 Conclusion: Transportation : 25.19.1.3 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 030412


25.19.2 Transportation Energy: Cars, Etc. : 25.19.2 Transportation Energy: Cars, Etc. 030427 Alternative fuel vehicles (AFVs) use ethanol, methanol, compressed natural gas, propane, or hydrogen 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 batteries Where did the electricity come from? Electric cars are being discontinued since hybrid electric cars are more widely accepted by the public


25.19.2 Transportation Energy : 25.19.2 Transportation Energy 030427 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 Cocoa http://www2.fsec.ucf.edu/env/fsccities/spccst.htm About “twenty-six years after the energy crisis, we’re still sending money – about a billion dollars a week – somewhere else” – Dan Reicher, Assistant Secretary for Energy Efficiency and Renewable Energy, DOE


25.19.2.3 Conclusion: Transportation 2 : 25.19.2.3 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 first 030409


25.19.2.3.1 Conclusion: Transportation 2 : 25.19.2.3.1 Conclusion: Transportation 2 Current hybrid vehicles are user-friendly, thus will be rapidly accepted by the market if price falls 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 070424


25.20 Distributed Generation : 25.20 Distributed Generation 030427 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 sections 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 : 25.20 Conclusion: Distributed Generation Distributed generation is less vulnerable to outages since there are so many local sources of supply 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 040415


25.21 Economics of Energy : 25.21 Economics of Energy Sustainable energy is essentially renewable energy 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 030427


25.21 Conclusion : 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 isn’t 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 030419


25.22 Tradeoffs and Decisions : 25.22 Tradeoffs and Decisions 030427 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 outcome Be wary of forcing the outcome to be what you want it to be


25.22 Conclusion: Trades : 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 (variance) 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 040415


25.23 Legal Considerations : 25.23 Legal Considerations 030427 Energy projects are constrained by laws, regulations, and ordinances Compliance is mandatory to avoid fines or imprisonment 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 : 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 regulations 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 070424


24 Conclusion: Review : 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 Leslie 040415


25.1 Some Interesting Facts : 25.1 Some Interesting Facts Earth’s axial tilt = 23.5 degrees (23.45) Earth-sun distance = 92 M miles = 92,955,820.5 miles = 149,597,892 km Earth Equatorial Radius = 6378137 m (WGS-77) Wind Turbine Power, P = ρ/2·A· U3 watts, where ρ (rho) is 1.225 kg/m3, A is area = π r2 m2, r= blade radius in m, U = wind speed in m/s. “P = 0.5 · ρ · A · Cp · V3 · Ng · Nb where: P = power in watts (746 watts = 1 hp) (1,000 watts = 1 kilowatt) ρ = 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) 030419


25.2 Some Interesting Facts : 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 π r2 Volume of a sphere is 4/3 π r3 P=E*I=E2/R=I2R; E or V=IR 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.) 070424


25.3 Some Interesting Facts : 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 / (R·T), where p = pressure, T = Kelvin, and R = gas constant = 287.05 Joule/Kg/K for air Snell’s Law: Angle of Incidence = Angle of reflection 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) 040415


References: Books : References: Books Brower, Michael. Cool Energy. Cambridge MA: The MIT Press, 1992. 0-262-02349-0, TJ807.9.U6B76, 333.79’4’0973. 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, 621.4’5 Patel, Mukund R. Wind and Solar Power Systems. Boca Raton: CRC Press, 1999, 351 pp. ISBN 0-8493-1605-7, TK1541.P38 1999, 621.31’2136 Sørensen, Bent. Renewable Energy, Second Edition. San Diego: Academic Press, 2000, 911 pp. ISBN 0-12-656152-4. 030331


References: Websites, etc. : References: Websites, etc. awea-windnet@yahoogroups.com. Wind Energy elist awea-wind-home@yahoogroups.com. Wind energy home powersite elist geothermal.marin.org/ on geothermal energy mailto:energyresources@egroups.com rredc.nrel.gov/wind/pubs/atlas/maps/chap2/2-01m.html PNNL wind energy map of CONUS windenergyexperimenter@yahoogroups.com. Elist for wind energy experimenters www.dieoff.org. Site devoted to the decline of energy and effects upon population www.ferc.gov/ Federal Energy Regulatory Commission www.hawaii.gov/dbedt/ert/otec_hi.html#anchor349152 on OTEC systems telosnet.com/wind/20th.html www.google.com/search?q=%22renewable+energy+course%22 solstice.crest.org/ dataweb.usbr.gov/html/powerplant_selection.html 030412