Ch 16 Quiz
How are hydrothermal reservoirs of geothermal energy used to provide energy in geothermal power plants?
(For more info: https://www.energy.gov/eere/geothermal/how-geothermal-power-plant-works-simple) We have also learned to tap into deeper, more concentrated hydrothermal reservoirs of geothermal energy, as Iceland has done for decades. Wells are drilled into these reservoirs to extract their dry steam, wet steam, or hot water, which are used to heat buildings, provide hot water, grow vegetables in greenhouses, raise fish in aquaculture ponds, and spin turbines to produce electricity. Cool water left over can be pumped back into the reservoirs to be reheated.
What is a geothermal heat pump?
(For more info: http://energy.gov/energysaver/geothermal-heat-pumps) Naturally cools or heats a home using underground-surface temperature differences. Below approximately 10 ft under the ground surface, the temperature stays around 50-60 degrees F. Heating and cooling buildings and to produce electricity. Can be installed on an individual building/property. Used in/involve power plants. Exploiting the temperature differences between the earth's surface and underground, almost anywhere in the world at a depth of 3-6 meters. In winter, a close loop of buried pipes circulates a fluid (usually water or an antifreeze solution), which extracts heat from the ground and carries it to a heat pump, which transfers the heat to a home's heat distribution system (usually a blower and air ducts). In summer, this system works in reverse, removing heat from a home's interior and storing it in the ground. These systems can also be modified to provide hot water. Key to more sustainable future. According to the EPA, after super-insulation, a well designed geothermal heat pump system is the most energy-efficient, reliable, environmentally clean, and cost-effective way to heat or cool a space. It produces no air pollutants and emits no CO2. Installation costs are recouped after 3-5 years, and then such systems save their owners money. Scientists estimate that using just 1% of the heat stored in the uppermost 5 kilometers (8 miles) of the earth's crust would provide 250 times more energy than that stored in all the earth's oil and natural gas reserves. Currently, about 40 countries (most of them in the developing world) extract enough energy from hydrothermal reservoirs to produce about 1% of the world's electricity, enough to meet the needs of 60 million people and equal to the electrical output of all 104 nuclear power plants in the United States. Geothermal energy has two main problems. One is that the current cost of tapping large-scale hydrothermal reservoirs is too high for all but the most concentrated and accessible sources, although new drilling and extraction technologies may bring these costs down. The other is that some dry- or wet-steam geothermal reservoirs could be depleted if their heat is removed faster than natural processes can renew it. Recirculating the water back into the underground reservoirs for reheating could slow such depletion.
Be able to explain why biodiesel/ethanol are not great alternatives to fossil fuels
(This article gives a good overview: https://www.nytimes.com/2015/01/29/science/new-report-urges-western-governments-to-reconsider-reliance-on-biofuels.html?_r=0) Biodiesel takes a lot of land to produce, and it is more expensive and inefficient. Increased NOx emissions/smog, higher environmental cost not, low net energy yield for soybean crops, loss of biodiversity, and difficulty for engines in cold weather. Expensive process, not widely consumed, require huge areas of land and some crops have low yield, runoff, increased greenhouse gas emissions, threat to biodiversity. There are some major disadvantages of using ethanol. For example, it is not that great for the environment. It is very energy-intensive to grow corn and extract energy from it. This is because fossil fuels are used to make fertilizer and pesticides to help corn grow and are also needed to ferment corn sugar. Some critics claim it takes more energy to make ethanol than we get out of ethanol. While others caution that we can never grow enough corn to meet demands. It is also more expensive and can make food made from the crop more expensive (e.g. corn goods). Also, harvesting of corn and conversion to ethanol to use as biofuel emits nearly the same amount of carbon dioxide as its external bioproducts. Finally, it may cause a loss of biodiversity through deforestation to grow more crops to build crop plantations and it takes land away from solar panels that could produce more energy.
How does hydropower work? How can energy be obtained from tides/waves?
1. Tidal streams 2. Tidal barrages 3. Tidal lagoons Used for homes and businesses. Dams are pretty common and we get lots of energy from them. Must be located on coastlines. Utilize turbines (electrical electrical energy generated by kinetic energy moving a turbine which then works a generator).
What are the CAFE standards? How do these standards compare to those of other countries and Europe?
Between 1973 and 1985, average fuel efficiency for new vehicles sold in the United States rose sharply because of government-mandated corporate average fuel economy (CAFE ) standards. However, since 1985, the average fuel efficiency for new vehicles sold in the United States decreased to about 9 kilometers per liter (kpl) (21 miles per gallon (mpg)). This was mostly because there was no increase in the CAFE standards until 2008, and because mileage standards for popular trucks and SUVs are not as high as those for cars. Fuel economy standards in Europe, Japan, China, and Canada are much higher than those in the United States. A 2008 law raised CAFE standards in the United States to 15 kpl (35 mpg) to be attained by 2020. This will still put U.S. fuel efficiency standards much lower than those of the other countries.
Understand the differences in environmental impact when ethanol is derived from different sources (ex: sugar cane vs corn)
Currently, this method of energy generation works by growing corn. However, growing and extracting corn is very energy-intensive because fossil fuels are used to make fertilizer and pesticides that help to grow the corn and are also needed to ferment corn sugar. Moreover, only the corn seeds are used for ethanol and the rest is thrown away. However, if we use a different part of corn or a different plant to obtain cellulosic biomass, it can be better. For Brazil, where they use sugarcane to produce ethanol, ethanol yields 8 times the amount of energy taken to produce it while gasoline takes 4.1. Whereas in the United States where they use corn ethanol, it only produces 1.1-1.5 net energy which isn't very efficient compared to fossil fuels. Corn is very space and resource intensive, 1 bushel of corn = 3 gallons of fuel. To cover, US needs of 130 billion gallons of fuel, so would need the entire country to convert completely to biofuel made from corn. Ethanol produces twenty-five percent fewer greenhouse emissions. Currently, fossil fuels are used to make fertilizer and pesticides to help corn grow and are also needed to ferment corn sugar. However, if cellulosic ethanol can be manufactured without burning fossil fuel, such as by using switchgrass, net carbon emissions can essentially be zero.
What are some concerns/ drawbacks to using any type of solar energy?
Disadvantages of Solar Energy 1. Cost: The initial cost of purchasing a solar system is fairly high. This includes paying for solar panels, inverter, batteries, wiring, and the installation. Nevertheless, solar technologies are constantly developing, so it is safe to assume that prices will go down in the future. 2. Weather-Dependent: Although solar energy can still be collected during cloudy and rainy days, the efficiency of the solar system drops. Solar panels are dependent on sunlight to effectively gather solar energy. Therefore, a few cloudy, rainy days can have a noticeable effect on the energy system. You should also take into account that solar energy cannot be collected during the night. On the other hand, if you also require your water heating solution to work at night or during wintertime, thermodynamic panels are an alternative to consider. 3. Solar Energy Storage Is Expensive: Solar energy has to be used right away, or it can be stored in large batteries. These batteries, used in off-the-grid solar systems, can be charged during the day so that the energy is used at night. This is a good solution for using solar energy all day long but it is also quite expensive. In most cases, it is smarter to just use solar energy during the day and take energy from the grid during the night (you can only do this if your system is connected to the grid). Luckily your energy demand is usually higher during the day so you can meet most of it with solar energy. 4. Uses a Lot of Space: The more electricity you want to produce, the more solar panels you will need, as you want to collect as much sunlight as possible. Solar PV panels require a lot of space and some roofs are not big enough to fit the number of solar panels that you would like to have. An alternative is to install some of the panels in your yard but they need to have access to sunlight. If you don't have the space for all the panels that you wanted, you can opt for installing fewer to still satisfy some of your energy needs. 5. Associated with Pollution: Although pollution related to solar energy systems is far less compared to other sources of energy, solar energy can be associated with pollution. Transportation and installation of solar systems have been associated with the emission of greenhouse gases. There are also some toxic materials and hazardous products used during the manufacturing process of solar photovoltaic systems, which can indirectly affect the environment. Nevertheless, solar energy pollutes far less than other alternative energy sources.
What is a wind farm? Why are some countries planning on building offshore wind farms?
Electricity and specific tasks. Wind, rotates propellers, and powers generators. Utilize turbines (electrical energy generated by kinetic energy moving a turbine which then works a generator). Can be installed on an individual building/property. Advantages are that it is cleaner and renewable compared to fossil fuels and other sources. Renewable, no pollutants, ocean, efficient technology, prevent hurricane damage, and cost efficient. Cost low once gets going. Fossil fuels used in building. Offshore wind farms have a higher potential for power generation due to faster and more constant winds, also providing energy at a more stable rate. There are no visual or noise pollution disadvantages as those caused by onshore wind farms.
What byproduct do hydrogen fuel cells produce?
Electricity, heat, and water. When hydrogen is sued in a hydrogen fuel cell, the fuel cell emits H2O.
What incentives do people have in Japan and Europe to conserve fuel?
Gasoline prices are much higher in Japan and most European nations, because their governments have set higher fuel-efficiency standards and imposed high gasoline taxes to encourage greatly improved fuel efficiency.
Where in the world can geothermal heat pumps be installed? Where can geothermal power plants be installed? Why?
Geothermal heat pumps can be installed on an individual building/property. Almost anywhere in the world. Geothermal wells that supply geothermal power plants are drilled to depths of approximately, for a horizontal loop you only need to dig between 6 - 8 feet deep and for a vertical loop you need to drill between 250 and 300 feet deep feet.
What is the LEED program?
Green building certification standards now exist in 21 countries, spurred by the World Green Building Council, established in 1999. Since 2001, the U.S. Green Building Council's Leadership in Energy and Environmental Design (LEED) program has accredited more than 25,000 building professionals in energy and environmental design. It has established guidelines, and it awards its much-coveted silver, gold, and platinum standard certifications to buildings meeting certain standards. One platinum standard building is China's Ministry of Science and Technology in Beijing. Its surrounding area is paved with porous bricks made of fly ash left over from burning coal. These bricks allow water to flow through them and to help replenish the city's aquifer. Solar cells made in China provide about 10% of the building's electricity, and it has a solar hot water heating system also made in China. A soil substitute used in its energy-saving roof garden is 75% lighter and holds three to four times more water per cubic meter than dirt can hold. The use of concrete building blocks filled with insulating foam also saves energy. This is an impressive showcase building, but China lags far behind other countries in energy-efficient building design. Nevertheless, within 20 years, China expects to be the world's leader in this area and to sell its innovative designs and materials in the global marketplace.
What are some concerns with wind power?
Harm/kill birds and bats, lots of space, unreliable, the manufacture of turbines emits CO2, they can generate noise pollution, and strong winds are isolated (steady winds are intermittent). Zero emission, proximity of protected birds, and environmental disruption.
What is passive solar heating? How can buildings be heated & cooled naturally?
Makes houses more energy efficient. Passive solar technologies use design features to capture and distribute the sun's heat. The sun heats house based on specific angle of sun. Can be installed on an individual building/property.
How do solar thermal systems (aka high-temperature heat and electricity or concentrated solar power) work?
Mirrors point towards boiler towers causing them to create steam and power a turbine. At night, tanks of salt heated during day work at night to turn turbines. Transmission lines. Reflect light to big tower and concentrate to salt. Used in/involve power plants.
What are some drawbacks to using hydrogen as an energy source? How could it become a viable energy source in the future?
More expensive, will always have a negative net energy yield, and production can be harmful. Cost (expensive in beginning but saves a lot in the long run), new policies, and fossil fuels can be used in electrolysis. Before you can use hydrogen as an energy source, you must get it into its pure form by separating it from other elements.
How could recycling save energy in industry?
Recycling materials such as steel and other metals is a third way for industry to save energy and money. Producing steel from recycled scrap iron in an electric arc furnace uses 75% less energy than producing steel from virgin iron ore. Switching three-fourths of the world's steel production to such furnaces would cut energy use in the global steel industry by almost 40% and sharply reduce its CO2 emissions. Similarly, if all of the world's energy-intensive cement producers used today's most energy-efficient dry kiln process, the global cement industry could cut its energy use by 42% and greatly reduce its CO2 emissions.
What is cogeneration?
Some companies save energy and money by using cogeneration, or combined heat and power (CHP), systems. In such a system, two useful forms of energy (such as steam and electricity) are produced from the same fuel source. For example, the steam produced in generating electricity in a CHP system can be used to heat the plant or other nearby buildings, rather than released into the environment and wasted. The energy efficiency of these systems is as high as 80% (compared to 30-40% for coal-fired boilers and nuclear power plants), and they emit one-third as much CO2 per unit of energy produced as do conventional coal-fired boilers. Cogeneration has been widely used in Europe for years and its use in the United States and in China is growing.
What is biomass? What is biofuel? biodiesel? ethanol? What is the main difference in the composition of biodiesel vs ethanol?
The dry weight of all organic matter contained in its organisms. Burning biomass has not net CO2 emissions only if it is replenished with new plant growth faster than it is used. In a food chain or web, chemical energy stored in biomass is transferred from one trophic level to another. Mass of living organic material. Biofuel is any fuel that is derived from biomass—that is, plant or algae material or animal waste. Since such feedstock material can be replenished readily, biofuel is considered to be a source of renewable energy, unlike fossil fuels such as petroleum, coal, and natural gas. Biodiesel is used for gas for cars and combustion engines, transportation, biogas for cooking, electricity, and petroleum-based diesel fuel and gasoline substitute. Use diesel combustion engines. Can be used in motor vehicles. Algae is substitute and corn for petroleum and biofuels. Indirect solar energy because it is combustible organic compounds made from photosynthesis. Oil part. Ethanol, on the other hand, uses sugars. Soy is another source. Involves burning things. It burns cleaner than fossil fuels. Reduced CO and CO2 emissions (still produces CO2), high net energy yield, reduced hydrocarbon emissions, better gas mileage, renewable. Takes a lot of land to produce, and it is more expensive and inefficient. Increased NOx emissions/smog, higher environmental cost, low net energy yield for soybean crops, loss of biodiversity, and difficulty for engines in cold weather. Expensive process, not widely consumed, requires huge areas of land and some crops have low yield, runoff, increased greenhouse gas emissions, threat to biodiversity. Ethanol is used for motor vehicles, corn-based ethanol is used in blends with gasoline to reduce air pollution, ethanol can be used as a replacement for gasoline. Currently, this method of energy generation works by growing corn. However, growing and extracting corn is very energy-intensive because fossil fuels are used to make fertilizer and pesticides that help to grow the corn and are also needed to ferment corn sugar. Moreover, only the corn seeds are used for ethanol and the rest is thrown away. However, if we use a different part of corn or a different plant to obtain cellulosic biomass, it can be better. The process begins with microorganisms. The microbes tear the cellulose apart, releasing sugar compounds locked within. In fermentation tanks, another microbial species turns that sugar into ethanol. The long-term goal is to combine genetic material from the two species into a single microbe that can make ethanol from cellulose in one efficient step. Turning two steps into one step is such a big deal because it would be revolutionary from an economic point of view. The carbon dioxide is captured at the source, compressed for transport, and then injected deep into rock formations at carefully selected, safe locations where it is stored permanently. Ethanol has to be taken from plants such as corn or bagasse, whose residue is fermented, and distilled to produce ethanol. This ethanol is burned and acts as a sort of fuel, similar to gasoline. Ethanol = distilled corn; used as a biofuel; alternatives are expensive, but ecologically friendly. Compares to fossil fuels and other energy sources by depending on which plants you use and the method of creating the ethanol. For Brazil, where they use sugarcane to produce ethanol, ethanol yields 8 times the amount of energy taken to produce it (the most efficient form of ethanol) while gasoline takes 4.1. Whereas in the United States where they use corn ethanol, it only produces 1.1-1.5 net energy which isn't very efficient compared to fossil fuels. Corn is very space and resource intensive, 1 bushel of corn = 3 gallons of fuel. US needs 130 billion gallons of fuel, so would need the entire country to convert completely to biofuel made from corn. Ethanol produces twenty-five percent fewer greenhouse emissions. Currently, fossil fuels are used to make fertilizer and pesticides to help corn grow and are also needed to ferment corn sugar. However, if cellulosic ethanol can be manufactured without burning fossil fuel, such as by using switchgrass, net carbon emissions can essentially be zero. Advantages and disadvantages are, depending on the way ethanol is harvested, a major advantage of using this energy source is that it produces twenty five percent fewer greenhouse emissions. Additionally, flex-fuel vehicles that can burn ethanol and gasoline do not cost much more than conventional cars. Moreover, it has a lot of potential because it is great motor fuel, it is just a matter of how inexpensive we can make it and how much of it we can make. Ethanol's potential can be fulfilled by using other parts of corn and other plants such as switchgrass (which can be grown on land without nitrogen fertilizers) and turning the two steps used to produce ethanol from ground-up corn stalks into one. Finally, we have the land to grow enough biomass to replace at least a quarter of the gas we now consume with cellulosic ethanol. Also, ethanol could replace gasoline altogether if cars were more efficient. And, so long as less fossil fuels are used in the process and there is a decreased amount of deforestation to plant more crops to produce ethanol, it could be considered a renewable resource. However, there are some major disadvantages of using this energy source as well. For example, it is not that great for the environment. It is very energy-intensive to grow corn and extract energy from it. This is because fossil fuels are used to make fertilizer and pesticides to help corn grow and are also needed to ferment corn sugar. Some critics claim it takes more energy to make ethanol than we get out of ethanol. While others caution that we can never grow enough corn to meet demands. It is also more expensive and can make food made from the crop more expensive (e.g. corn goods). Also, harvesting of corn and conversion to ethanol to use as biofuel emits nearly the same amount of carbon dioxide as its external bioproducts. Finally, it may cause a loss of biodiversity through deforestation to grow more crops to build crop plantations and it takes land away from solar panels that could produce more energy. Involves burning things and can be used in motor vehicles. Produces CO2.
How is energy conservation considered a source of energy?
The world will rely increasingly on a mix of renewable energy resources. In addition, however, many analysts urge us to make much greater use of a strategy not usually thought of as a source of energy—that is, energy conservation, a decrease in energy use based primarily on reducing unnecessary waste of energy.
What are the differences between plug-in hybrids and conventional hybrid cars?
There is growing interest in developing superefficient and ultralight cars that could eventually get 34-128 kpl (80- 300 mpg). One of these vehicles is the energy-efficient, gasoline-electric hybrid car, invented by Ferdinand Porsche in 1900 and improved with modern technology by Japanese automobile companies such as Toyota and Honda. It has a small traditional gasoline-powered motor and an electric motor used to provide the energy needed for acceleration and hill climbing. The most efficient models of these cars get up to 20 kpl (46 mpg) on the highway and emit about 65% less CO2 per kilometer driven than a comparable conventional car emits. The next step in the evolution of more energy-efficient motor vehicles will probably be the plug-in hybrid electric vehicle—a hybrid with a second and more powerful battery that can be plugged into a standard outlet and recharged. By running primarily on electricity, they could easily get the equivalent of at least 43 kpl (100 mpg) for ordinary driving and up to 430 kpl (1,000 mpg), if used only for trips of less than 64 kilometers (40 miles). Manufacturers hope to have a variety of plug-in hybrids available by 2010, and some analysts project that they could dominate the motor vehicle market by 2020. The key is to develop a battery that will have enough range and be strong, safe, reliable, and affordable enough to use in a mass auto market. Replacing the current U.S. vehicle fleet with highly efficient plug-in hybrid vehicles over 2 decades, would cut U.S. oil consumption by 70-90%, eliminate the need for oil imports, save consumers money, and reduce CO2 emissions by 27%, according to a 2006 Department of Energy study. If the batteries in this national car fleet were recharged mostly with electricity generated by wind, solar energy, hydropower, and geothermal energy instead of by coal-burning power plants, U.S. emissions of CO2 would drop by 80-90%, which would greatly help to slow global warming and projected climate change.
What strategies can governments use to facilitate a shift toward sustainable energy sources?
To most analysts, economics, politics, and consumer education hold the key to making a shift to a more sustainable energy future. It will require maintaining consistent and sustained energy policies at the local, state, and national levels so that businesses can make long-range plans. Governments can use three strategies to help stimulate or dampen the short-term and longterm use of particular energy resources. First, they can keep the prices of selected energy resources artificially low to encourage use of those resources. They do this by providing research and development (R&D) subsidies and tax breaks to encourage the development of those resources, and by enacting regulations to favor them. For decades, this approach has been employed to stimulate the development and use of fossil fuels and nuclear power in the United States and in most other developed countries. The U.S. oil industry received almost half of the $600 billion in R&D subsidies provided by taxpayers between 1950 and 2003, according to the U.S. Department of Energy and the Congressional Budget Office. And in 2007, the Department of Energy allocated $159 million for solar energy R&D. At the same time, it allocated nearly double this amount, $303 million, for nuclear energy R&D and $427 million for coal R&D. For decades, this sort of policy has created an uneven economic playing field that encourages energy waste and rapid depletion of nonrenewable energy resources, while it discourages improvements in energy efficiency and the development of renewable energy resources. To many energy analysts, one of the most important steps governments can take to level the economic playing field is to phase out the $250-300 billion in annual subsidies now provided worldwide for fossil fuels and nuclear energy—both mature industries that could be left to stand on their own, economically. These analysts call for greatly increasing subsidies for developing renewable energy and energy-efficiency technologies. If this had been done beginning in 1980, they say, the world probably could have greatly increased its energy sustainability, sharply decreased its dependence on imported oil, avoided two wars in the Middle East, and be well on the way to slowing global warming and projected climate change. The second major strategy that governments can use is to keep energy prices artificially high for selected resources to discourage their use. They can do this by eliminating existing tax breaks and other subsidies that favor use of the targeted resource, and by enacting restrictive regulations or taxes on its use. Canada, in 2007 introduced rebates for hybrid vehicles, a tax on gas-guzzlers, and subsidies for development of renewable fuels. China is also taxing gas-guzzlers and raising energy-efficiency requirements for homes and office buildings. Such measures can increase government revenues, encourage improvements in energy efficiency, reduce dependence on imported energy, and decrease use of energy resources that have limited supplies. To make such changes acceptable to the public, analysts suggest that governments can offset energy taxes by reducing income and payroll taxes and providing an energy safety net for low-income users. Third, governments can emphasize consumer education. Even if governments offer generous financial incentives for energy efficiency and renewable energy use, people will not make such investments if they are uninformed—or misinformed—about the availability, advantages, disadvantages, and relative costs of energy resources. For example, cloudy Germany has more solar water heaters and solar cell panels than sunny France and Spain, mostly because the German government has made the public aware of the environmental benefits of these technologies. It has also provided consumers with substantial economic incentives for using them. The good news is that we have the technology, creativity, and wealth to make the transition to a more sustainable energy future within your lifetime, as the state of California is proving. Making this transition depends primarily on education and politics—on how well individuals understand ecological and environmental problems, and on how they vote and then influence their elected officials. People can also vote with their pocketbooks by refusing to buy inefficient and environmentally harmful products and by letting company executives know about their choices.
What are photovoltaic cells? How do they work (generally)?
Used for the production of energy. Comes from solar towers or panels. Convert sunlight into electrical energy. When the sunlight hits these panels, they create an electrical field converting energy to power homes. Lots of mirrors that concentrate rays. Very similar to power plants. Series of cells electrons can flow through. Can be installed on an individual building/property. Advantages are that it is environmentally friendly compared to fossil fuels, although some small emissions. High net energy yield, low environmental impact, easily exempt or moved, last 20-40 years. Low environmental impact, low air pollution, and very cheap. Disadvantages are that nearby trees can shade solar panels, low efficiency, relies on electricity storage system or backup.
How can we make new and existing buildings more efficient?
We can realize huge savings in energy by designing and building for energy efficiency and retrofitting existing buildings to make them more energy efficient. In fact, a 2007 U.N. study concluded that better architecture and energy savings in buildings could save 30-40% of the energy used globally. For example, orienting a building so it can get more of its heat from the sun can save up to 20% of heating costs and as much as 75% when the building is well insulated and airtight—a simple application of the solar energy principle of sustainability. The 13-story Georgia Power Company building in the U.S. city of Atlanta, Georgia, uses 60% less energy than conventional office buildings of the same size use. The largest surface of the building faces south to capture solar energy. Each floor extends out over the one below it. This blocks out the higher summer sun to reduce air conditioning costs but allows the lower winter sun to help light and heat each floor during the day. In the building's offices, energy-efficient compact fluorescent lights focus on work areas instead of illuminating entire rooms. Such green buildings have been used widely in Europe for almost 2 decades, especially in Germany and the Netherlands, and are beginning to catch on in the United States. Green architecture, based on energy-efficient and money-saving designs, makes use of natural lighting, passive solar heating, geothermal heat pumps for heating and cooling, cogeneration, solar hot water heaters, solar cells, fuel cells, natural ventilation, recycled building materials, energy-efficient appliances and lighting, motion sensors for lighting, rainwater collection, recycled waste water, waterless urinals, composting toilets, and nontoxic paints, glues, and building materials. Some green designs also include living roofs, or green roofs, covered with soil and vegetation. They have been used for decades in Europe and are becoming more common in the United States. Another important element of energy-efficient design is superinsulation. A house can be so heavily insulated and airtight that heat from direct sunlight, appliances, and human bodies can warm it with little or no need for a backup heating system, even in extremely cold climates. An air-to-air heat exchanger prevents buildup of indoor air pollution. The building cost for such a house is typically 5% more than that for a conventional house of the same size. The extra cost is paid back by energy savings within about 5 years, and the homeowner can save $50,000-100,000 over a 40-year period. Superinsulated houses in Sweden use 90% less energy for heating and cooling than typical American homes of the same size use. Since the mid-1980s, there has been growing interest in straw bale houses. The walls of these superinsulated houses are made by stacking compacted bales of low-cost straw (a renewable resource) and then covering the bales on the outside and inside with plaster or adobe.
How much energy is wasted unnecessarily in the US? What are some ways that it is wasted?
You may be surprised to learn that 84% of all commercial energy used in the United States is wasted. About 41% of this energy is wasted unavoidably because of the degradation of energy quality imposed by the second law of thermodynamics. The other 43% is wasted unnecessarily, mostly due to the inefficiency of incandescent lights, furnaces, industrial motors, coal and nuclear power plants, most motor vehicles, and other devices. Another reason is that many people live and work in leaky, poorly insulated, badly designed buildings.
Some study ideas for wrapping your brain around all these energy sources:
• Try grouping the alternative energy sources into different categories, such as: -sources that can be used for motor vehicle fuel -sources that can be used for heating -sources that can be used for electricity -sources that utilize turbines -sources that can be installed on your house -etc • Compare & contrast the energy sources in each category (which one do you think is best in each category?) • Identify which types of alterative energy are indirect forms of solar energy (& explain how this is true!)