Paul M. Jones
Spin generator, spin!
Electricity is the flow of charged particles. Students can draw on prior knowledge of atomic structure, to understand that electricity is essentially electrons moving down a wire. Our energy consumption is tied to the simplification of Newton's law that "energy cannot be created or destroyed"; hence, we do not make electricity, we convert energy in one form (fuel) to energy in a usable form (electricity) (Trainer, 5).
All power plants, traditional fuel or nuclear, use their fuels to boil water to create steam. The steam is compressed and piped along the fans of a turbine, which is connected to a generator. As the generator spins, a series of magnets excites coils of wire to move electrons. In the case of a coal fired power plant, chemical energy is converted to heat, heat converted to mechanical energy, finally to electricity. Only photovoltaic systems do not require the use of a coil generator. All of our electricity needs are as simple as finding innovative, clean, sustainable ways of spinning the generator to create electricity.
Sustainable vs. Renewable vs. Green Energy
Whenever energy is a topic, alternative forms of energy to fossil fuels are often referred to as renewable, sustainable, or green. Though used so, these words are not interchangeable. Sustainability is a concept referring to the long-term viability of fuel option; it will not run out, and have minimal or zero environmental or ecological impact, and, thus, will be available to future generations. The most natural forms of energy, such as wind, tidal, and solar, will never run out as long as our planet receives solar energy (Elliot, pg xvii).
Use of the word renewable can cause some confusion. Energy sources can be renewable, such as from bio-fuels, but not sustainable or environmentally fiscal. It could be argued that fuels made from intensively farmed plants, such as corn to make ethanol, could be as environmentally harmful as burning coal it you take into consideration the water requirements, transportation needs, petrochemical fertilizer requirements, soil degradations, farmland that could be devoted to growing food, and subsequent emissions. Though the fuel itself won't run out, and for the most part can be grown indefinitely as long as it is replanted, it is not sustainable.
Green energy is often used to describe energy sources that are environmentally safe. In the current media, much attention has been paid to CO
2
emissions and their roll in global climate change, and the term green is often used to describe something that does not cause excess production of CO
2
.
All sustainable energy forms are renewable and green. They will not cause long term or extensive environmental damage, their fuel source will not run out, and will be available to future generations.
Potential for Renewable Energy in Connecticut
When students are considering sustainable energy options, they will most likely apply the viability to their surroundings. Students having been raised in view of the Long Island Sound will no doubt be most curious about (and most anxious to exploit) tidal and wind energy. The reality is that with the appropriate leadership and infrastructure, all forms of sustainable energy are available to everyone in some capacity. It is important that students are familiar and comfortable with the concepts of electricity as the needs of society change. Below, background information for each form of sustainable energy will be discussed, followed by a brief description of its viability in Connecticut. In the teacher resources will be a list of websites and resources allowing this educational unit to be applied to other states.
There are intentional omissions or brevity of certain possible sustainable energies. Hydrogen power is generally regarded as non-feasible and is an inappropriate topic of study for this grade level. Niche hydropower is unrealistic as a large energy source and is discussed in this unit for the teacher's discretion. Solar power is discussed in the background to bring the teacher up to speed for classroom discussion. Geothermal energy in most locations in the United States is sparse and unattainable besides small local projects and is omitted. Any of the sustainable energy forms may not be relevant to certain geographic, demographic and ability level competencies, and should be developed or omitted accordingly to facilitate learning and discussion. For 9
th
grade science national standards, an understanding of the overall function and use of renewable energies, especially wind and solar, is considered the goal of learning, and being able to forecast use, pros and cons, and realistic applications of them is advanced for the grade level (Trainer, 97).
How much is that? The watt, megawatt, terawatt, and the oil equivalent
Before embarking on comparisons of energy sources, developing units of measurement as part of the curricula language is imperative. It is up to the individual instructor to decide if actual comparisons in real terms are realistic for the student base. Simple ways to discuss power sources would be to consider them in their oil equivalent. But even this is difficult for most students to consider, and looking at global figures often distance students further. Looking at a household, however, may be more realistic and providing students with workable numbers and letting them extrapolate these to larger regions, states, and countries (even if the total figures don't quite work out correctly) makes the data more accessible.
A watt (W) is a unit of measurement for power, used internationally, to measure electricity use. Watts are a present tense unit, whereas watt hours are used to measure energy use over time. A 50 watt bulb is using 50 watts of electricity each instant and 50 watt hours each hour. Utility services bill in kilowatt hours (kWh), with each kilowatt hour being 1000 watt hours. Power plants generate electricity in megawatts (MW), or 1000 kilowatts. 1000 megawatts can be measured in gigawatts (GW), some large scale power plants produce several GW; a nation's output of power from a particular source may be several GW. 1000 GW is measured in terawatts (TW), the total power consumptions by humans in 2005 was roughly 16 TW, with the United States accounting for 1.6 TW of consumption alone. All of these can be put in terms of watt hours. Sustained generation of a gigawatt for one hour is a gigawatt hour. A home using 5 kilowatts continuously for one hour will be billed by the utility company for 5 kWh (Nersesian 16; Hoffman 63).
How much his ours?
As human society becomes more and more of a global society, it should be noted that there is still a strong distinction between the haves and have-nots. Human use of fossil fuels having an effect on global climate is no longer debated, and its results will certainly be a global issue, yet distribution and use of fossil fuels is not equal globally.
The developed nations of the world use the lion's share of fossil fuels, and besides petroleum which is used predominantly for transportation, these energy sources are used to make electricity. The United States in particular uses roughly 10% of the global energy output with only 4% of the world's population, while one third of the world's population does not have in-home electricity. Furthermore, our current fossil fuel based energy policy is by no means sustainable. Not only do we depend on depleting fossil fuel reserves, we must import much of the petroleum need for transportation. It is in our nation's best environmental and fiscal interest to lessen our dependency on unsustainable energy use, and be a global leader in environmental stewardship by converting as much of electricity generation as possible to renewable and sustainable energy sources (U.S. EIA).
For students to consider these facts and figures in terms of change of practice and conservation can be unreasonable. Adolescents do not often consider themselves a part of community let alone a national or planetary movement. But redesigning the practice at home, and looking at the state they live in, makes these ideas accessible. An examination of electricity use and its method of generation is the obvious point of change for a movement towards sustainability. Reduction in energy use through change of habit and consumption choices such as efficient appliances can result in obvious reduction in power use. Since electricity accounts for a large part of total energy consumption, focusing on electricity generation at the students' state level and how sustainable practices could be applied offers a realistic path to study energy and electricity generating resources.
The Non-Renewables
Fossil Fuels
Millions of years ago carbon in the form of plants and animals, often micro-organisms, was buried under layers of sediments. After being subjected to immense heat and pressure, the organic carbon in the organisms, trapped in layers of non-porous rock formed oil, coal, and natural gas, depending on the conditions and ingredients. The carbon atoms stored in the bodies of ancient organisms, can provide an energy rich fuel when burned. Currently, our society is almost entirely fossil fuel dependent. The amount of energy that can be obtained from burning fossil fuels is immense considering they are essentially free; they only need to found and removed from the ground. It could be said that life as we know it could not be maintained without the use of unsustainably harvested energy from fossil fuels. The human population has been growing nearly exponentially since coal became widely used.
Once fossil fuels became the main source for generating electricity, their use continues to grow. Remember that in order to make electricity, source energy must be used to spin in a generator. In the cases of oil, coal, and natural gas, all three are used as source energy to heat water to create steam. The compressed steam is used to spin the turbine attached to the generator. Most of the coal use in this country is for electricity generation, while natural gas is mostly used as a heat source for buildings, and oil is mostly refined for use as a motor vehicle fuel. All three are used for electricity, and all three emit carbon dioxide when burned contributing to the greenhouse effect.
Coal naturally has a high sulfur content; how much depends on the content, source location, and formation process. This sulfur contributes to acid rain and the particulate content in its emission is a heavy contributor to smog and particulate pollution. In Connecticut, coal represents around 5% of the total energy used, but nearly all of that is used to generate electricity. As this unit is focusing on alternative sources of electricity, coal should be targeted as not only a polluter but as an energy source that needs to be reduced. Coal's availability and its high energy content make it the ideal source for our society to wean onto long term sustainable projects, and the vast stores found in the United States make its intensive use practical in the short term. The idea that electricity must be readily available, and cannot be readily stored, lends itself to the likelihood that coal fired electricity power plants are a necessity in the immediate future.
The conservation minded student will quickly attribute oil as the fossil fuel we are most dependent on, and the one that will be hardest to reduce or eliminate from our society. While it does not play as major a role in electricity generation, it is hard to find anything that does not owe it existence to oil. Polymer based plastics are made from oil, and nearly all transportation is fueled by oil. Most personal vehicles run on gasoline refined from oil, and the chemicals we use to fertilize our crops are petroleum based. It is gasoline that represents the largest sink of oil use, especially in Connecticut. Diesel fuel is used by most commercial vehicles and public transportation, but the automobile and SUVs, are the vehicles that are using most of the fuel. Any practice in changing the way we think about the car, a mere 10% reduction in driving, would substantially impact the amount of petroleum used in our country.
The cost of oil, and gasoline, is hard to fathom and is not represented at the pump. We simply do not pay the true cost of oil. The environmental impact of the millions of barrels per day consumed is often ignored. The 2010 Gulf of Mexico oil spill is a glaring reminder that our reliance on oil is often blameless, with no particular entity to bill for the damages caused. Security for oil exploration in often hostile areas of the world is financed by the United States Government and not at the gas pump. Hugely increased asthma rates in our country, often attributed to pollution from combustion, and the increased medical cost is not included in price per gallon of unleaded gasoline. These factors, coupled with the fact that we use more each year of a finite resource, show that our reliance on oil can only be temporary. It is unreasonable to think that through change of habit we can curtail oil use any time soon, but not unreasonable to see that our reliance on oil will be forcibly reduced because of its scarcity in the coming years, certainly within the lifetime of current high school students.
Nuclear
The often misunderstood nuclear power is sometimes considered to be a sustainable energy source. It is often billed as a cheap and clean form of energy. It must be noted that nuclear power is capable of generating huge amounts of electricity that is carbon free. The benefit of nuclear power is its capability of generating massive amounts of electricity from a single plant. In 2004, the United States represented 24% of the world's electricity usage. That year the typical peak demand was about 800 gigawatts, with a base demand at any time of 500 gigawatts. A single nuclear power plant can handle the base-load needs of a 600,000 person city at any time. This means fewer plants are need in the long run, and only supplemental energy is need at time of peak use (Nersesian, 275).
Nuclear power has the drawback that, while it can produce large amounts of power, it is not fail safe. A single nuclear power accident, though rare and unlikely, can be devastating. The fuel needed to make the nuclear reaction, to boil water to make steam similar to a fossil fuel fired plant, is not easily obtained. Though not considered rare, uranium is not so voluminous that it could be considered sustainable. 25,000-100,000 tons of ore must be mined to produce the required 200 tons of uranium to run a typical 1 gigawatt nuclear reactor for one year. This will produce an annual waste of 25-30 tons of highly toxic, radioactive material. The immense cost and risk of transporting and storing nuclear waste, and the risks (albeit low but possibly costly ones) of a nuclear accident, make nuclear power far from sustainable. Reserves of uranium could last for over a century, but as with other forms of power, reserves empty faster as use and need increases with population. IF typical base-load electricity needs of the United States were satisfied with nuclear power alone, it would require more than 500 large-scale nuclear reactors producing 15,000 tons of nuclear waste each year. Waste and effluent from mining operations would be measured in millions of tons, and waste water pollution at non-point source locations is nearly immeasurable. Connecticut relies on nuclear power for almost 50% of its electricity power needs, with natural gas, coal, with fuel oil picking up the balance in order of most used. With only one small reactor operating in state, nearly all of the inherited risks and cost are outsourced to other locations for waste disposal, making this an irresponsible and in no way a sustainable source of energy (EIA, 2010; Nersesian, 277; Sweet, 181).
Solar
All sources of energy can be traced to the sun. Fossil fuels are derived from plants that stored solar energy and organisms that consumed plants. Wind, water and tides move because of weather and water cycles that are ultimately powered by the sun. As our needs grow for sustainable energy, it only makes sense that we should be looking for ways to exploit a nearly limitless supply of energy that enters our atmosphere daily. One of the most difficult aspects of providing electricity to millions of people is the fact that it must be produced instantly as it is needed, cannot be easily stored, and does not transport well. Using solar power can overcome some of these challenges, and certainly offset the costs of using fossil fuels in the immediate future.
Most student texts provide information on solar power being used either actively or passively by the individual homeowner. Passive solar designs have no mechanical parts, buildings can be designed to provide warmth and light from the sun by positioning the building to allow light to enter while reducing heating cost. Designs often account for shade during the summer months to aid in home cooling. Active solar power refers to a more extensive use of the energy, sometimes making electricity directly (Pahl, 34).
Active solar power is comes in two primary types, using solar energy to heat water for heating or to make steam to generate electricity, and the direct conversion to electricity. Using photovoltaic cells, panels of layers of semiconductor elements, often silicon, whose electrons excite when irradiated by the sun engaging the flow of electrons through a conductor, can convert solar energy directly to electricity. Currently, photovoltaic cells are expensive and not incredibly efficient, but once installed can generate significant amounts of electricity to a local user. Technological advancements in photovoltaic cells have allowed them to convert upwards of 15% of incoming solar radiation to electricity. Though unrealistic to think every home could become its own power plant, looking at data suggests that even small solar panels installed on rooftops could significantly reduce importation of electricity from large-scale power plants (Pahl, 38).
Solar power as a large scale industry is using several emerging technologies. Large mirrors that move to catch the sun and direct it to a receiver that heats water for steam can produce power in the 100 megawatt range. Solar power towers that direct sunlight to melt salts to "store" energy for late use are becoming more common in the western United States. Solar chimneys, large tubes that move are upwards dues to temperature differences, spin turbine-generator apparatus to conventionally make electricity. By using mirrors to direct and intensify solar power, Brayton and Stirling engines can turn generators and make electricity, only limited by space for mirrors and availability of sunlight. The idea of using solar power to assist the hydrogen fuel cell bring hope that solar efficacy can be increased by the ability to store usable energy (Trainer, 100).
The limitations of solar power are largely based on geographic location and climate. True solar power plants, or solar farms, can be constructed to make large amounts of power that rival conventional power plants. But even these are limited if cloud cover is significant. Covering the American desert in photovoltaic cells is not the answer to the questions of sustainable energy as the transportation of power and energy lost in the form of heat (some estimates put 1/3 of all electricity generated as losses in transmission) as it is transmitted. Again, large plants of photovoltaic panels will reduce the efficiency by location alone: places where they could be sensibly put where there is room and sunlight are often not where the power is most needed, and energy lost in transmission reduces the efficacy of large solar farms as a significant power source, especially in the northern climes and densely populated eastern United States (Elliot, 109).
Solar power in Connecticut is an under utilized source of power. Obviously, the climate in the northeastern United States is not conducive to large-scale solar power plants, but the population and housing of Connecticut gives it a serious advantage. Individual homes can be heated using solar power effectively, and photovoltaic cells on rooftops can provide power during peak daytime energy periods. Large scale solar farms are not necessary in the state for solar power to be utilized, and the space and climate needs do not make large scale solar a viable option. The Department of Energy reports that less than 1% of Connecticut's power comes from renewable resources and far less than 1% if biomass and hydropower are removed from that figure. When considering how Connecticut can move towards sustainability, solar power should be impressed upon to meet these needs.
Wind
Like any source of power that is considered sustainable, Wind power can make electricity from a source that is essentially free, has little or no chemical pollution, and is hampered only by a large initial investment that can be recouped through generation of electricity with next to no overhead costs besides routine maintenance. Wind turbines, both large and small, operate by harnessing the wind on the blades of a propeller and using the kinetic energy of moving air to spin a turbine and a generator to make electricity. Besides the low impact nature of this power source, it is simple and readily available. While being mostly benign environmentally, wind power has many opponents citing wind turbines as unsightly, noisy and dangerous to migrating populations of birds, not to mention as unreliable as the wind. This aside, used in conjunction with other renewable forms of energy, wind power can great reduce reliance on fossil fuels.
The largest problem with wind turbines is that the wind must be in the optimum range to reliably produce power. Too much or too little wind and efficiency can be reduced to zero, and variability minute by minute means all of the wind is not going to be converted to electricity. A single wind turbine can be at best an erratic source of power, but the erratic nature is reduced when several turbines are spaced in an area of high average wind-speed. Spacing of wind turbines near, but not to close to, developed areas make them ideal in that power is not lost significantly in transmission (Trainer, 21).
Large-scale wind power plants generally require Class 4 wind power density (13 mph sustained yearly average) to be considered viable, and any smaller project to be connected to the grid must be between Class 2 and Class 3 (greater than 11 mph sustained yearly average). Roughly one third of Connecticut sits in Class 3 Wind Power Density. Even if large-scale wind farms are impractical, small wind projects can offset electricity production (DOE, 2010).
Hydro
The concepts of potential and kinetic energy should be familiar to high school students. Hydroelectric power works by harnessing water and storing it in a dam (potential energy) to release it through a turbine to spin a generator (kinetic energy). This source of electricity is clean and renewable, producing no greenhouse pollution, though not without environmental opposition. It is unlikely that any new hydroelectric power projects will be attempted. Not only are dams obtrusive and potentially devastating to downstream ecology, they are expensive and most sites that have potential to provide large amounts of energy have already been tapped. In 2002, 7% of United States electricity generation came from hydroelectric power. This figure will not continue to grow due to no planned major projects, but hydroelectric power is not removed from being a major player in power production (Pahl, 7).
The reality with hydroelectric power is that what is developed is all that will be developed. As our energy needs grow, hydroelectric dams will represent a smaller and smaller portion of our power needs. There are ways to still tap the energy stored in water in less conventional ways.
Micro-hydro
Mini generators placed in small streams, or small scale water diversions are becoming popular mechanisms for electrical generation in remote areas. Small systems that can generate 1 kW of power from a small stream head can be set up in almost any moving stream. Though this by no means will ever be a source of power that can wean an energy hungry society from fossil fuels, it can contribute to public energy systems, municipal and public power needs such as street or public space lighting or other application removing some drain from the grid. As students work on a culminating project, they should look at ways to get more and more power from renewable means. Micro-hydro represents an electricity generating system that they can relate to, and even build; and it should be presented to students. The small generating capacity of these projects helps in realizing how much power we need and how small scale renewable energy sources will not take the place of fossil fuel generated power plants on our energy budget (Pahl, 119, 122).
In Connecticut, many towns have old mill ponds that were used to operate machinery such as mills and grind stones. These dams hold a substantial amount of water head that could be retrofitted with electricity generators. If each town possessing a mill pond would invest in the retrofit process, upwards of one hundred 10 to 500 kilowatt generators could be functioning in Connecticut. Targeting dams that are in place but non-functioning would not add ecological stress to the environment, while delivering clean and reliable power to the states energy budget (U.S. EIA).
Tidal and Wave
The mere fact that the ocean covers roughly 70 seventy percent of the Earth's surface and is constantly absorbing solar radiation suggests that it must contain vast stores of usable energy. True, kinetic energy in tides, currents, and waves and thermal energy in temperature differentials are vast, but do not currently represent a significant form of attainable energy.
Tidal power can be used by damming incoming tides to create a head of water when tides recede. As the tide goes out, trapped water can be channeled through a hydroelectric dam and electricity can be generated. Technology using floats to catch the up and down motion of waves, propellers to harness the ebb and flow of tides at channels, and various forms of sluice gates to channel moving water have been developed (Pahl, 131).
The main drawback to all of these technologies is that they must be in areas of a large tidal differential to create a large enough flow to be significant, and in coastal areas that are otherwise likely to be developed. There is one significant source of tidal power in France currently in use producing 240 megawatts of power. Most other tidal sources are in the 0.5 megawatt range and indicative of the problems faced by tidal power. Though Connecticut has a little over 100 miles of coastline on the Long Island Sound, there is little if any undeveloped waterfront property with space suitable for tidal technology. The five main rivers in Connecticut could present the opportunity for small-scale hydro-tidal propeller generators with upwards of 10 megawatts peak production if technology were fully invested (Neirsesian, 324).
Biomass-Can it be sustainable and is it renewable?
Until the industrial revolution, and most specifically the introduction of coal as a fuel source, most of the world's energy came from biomass in the form of burning wood. Reliance of biomass on an energy source has been relegated mainly to niche communities and the less developed nations until recently, when interest in liquid bio-fuels has surged forward as a replacement for transportation fuel.
Energy from biomass, living or once living parts of plants, often lumped together with agricultural and municipal waste, presents itself as renewable form energy. If managed correctly fuels from biomass can be quite sustainable or tragically not so. For students this concept presents itself as an excellent topic for moral or ethical debate: If enough energy could be yielded from the land and any carbon emissions neutralized by the intake of the following years' crop, at what expense are you willing to sacrifice potential food sources to satisfy energy needs?
The idea of introduction of biomass to 9
th
graders as a reliable energy source may be the most daunting aspect of this unit because of the variable nature from species to species and the different applications and processes. Yields per acre vary among species and clime. Currently, sugarcane and corn present the most likely candidates in ethanol production. Wastes from the fermentation/distillation process can be burned in biomass incinerators, and add to the energy yield per acre yet reduce the fertility of the soil. When considering biomass and bio-fuel production, one must consider the costs of fossil fuel expenditure in transportation, processing, harvesting, and petrochemical application. It is safe to assume that without some fossil fuel resource, production of enough energy per acre is not possible to make the expenditure viable; especially considering the volume of fossil fuel needed to support our transportation system would require a substantial portion of arable land to grow the equivalent crops necessary (Nersesian, 48).
Students in urban areas will relate directly to the idea of municipal solid waste as a fuel. People living in densely populated areas produce large volumes of waste that is highly visible. Burning municipal solid waste to produce electricity is not a new idea, but an emerging one as a sustainable practice. Even the most optimistic recyclers know that large amounts of energy are wasted by burying our garbage and incineration presents an opportunity for energy recovery. Ash waste after incineration is a reduction in volume, though more volatile and technology in scrubbers to prevent air pollution has improved to make this an important use of resources. Certainly waste is a renewable fuel.
Connecticut currently farms one half million acres of its 3.5 million acre area. Devoting this land to the production of biomass is unlikely, but properly managed cropland can add to the energy budget. Streamlining the waste flow and managing waste collectively, after building a statewide infrastructure for recycling and waste management while maintaining EPA protocol on waste incineration makes biomass a major aspect of the renewable energy slate.
What works for us, what won't, and how to digest it all…
The idea behind this unit is to make students aware of renewable energy, while considering global energy use. Students can understand straight facts of energy use easily and even the reluctant learner can grasp what millions of barrels of oil per day or tons of coal means. Gaining an enduring understanding that no one renewable energy source can sustain current practices is the ultimate goal, that adopting an all of the above strategy for energy while changing habits and practices is the only way to wean our society of non-renewable, unsustainable energy.
Connecticut can represent a microcosm of what is to come. Many people living in a small area make it obvious that all of the resources used cannot possibly come from the area occupied. Only from diligent use of resources, and a reduction of that use, can several million people hope to live sustainably in an area of several thousand square miles.
