Electricity Production - Ecological Perspective - Lecture Slides, Slides of Ecology and Environment

Download Electricity Production - Ecological Perspective - Lecture Slides and more Slides Ecology and Environment in PDF only on Docsity! We can concentrate sunlight to produce high- temperature heat and electricity • Solar thermal systems use different methods to collect and concentrate solar energy in order to boil water and produce steam for generating electricity • The net energy yield for solar thermal systems is only about 3%, which means that they need large government subsidies or tax breaks in order to compete in the marketplace with alternatives that have higher net energy yields. • Inexpensive solar cookers focus and concentrate sunlight for cooking food and sterilizing water. Docsity.com We can use sunlight directly to produce electricity • Solar energy can be converted directly into electrical energy by photovoltaic cells, commonly called solar cells. • Solar cells have no moving parts, are safe and quiet, and produce no pollution or greenhouse gases during operation. • The material used in solar cells can be made into paper-thin rigid or flexible sheets that can be incorporated into roofing materials and attached to a variety of surfaces such as walls, windows, and clothing. • Generating electricity with solar cells could become nearly as efficient as using coal-burning power plants without producing the air pollutants and climate-changing CO2 emitted by those plants. Docsity.com Using wind to produce electricity is an important step toward sustainability • Wind turbines have been erected in large numbers at favorable sites to create wind farms • Since 1990, wind power has been the world’s second fastest-growing source of energy after solar cells. • Wind turbines can be interconnected in arrays of tens to hundreds. These wind farms or wind parks can be located on land or offshore. • In 2009, a Harvard University study estimated that wind power has the potential to produce 40 times the world’s current use of electricity. Docsity.com Using wind to produce electricity is an important step toward sustainability • Benefits: – Wind is widely distributed and inexhaustible – Wind power is mostly carbon-free and pollution-free. – A wind farm can be built within 9 to 12 months and expanded as needed. – Homeowners can also use small and quiet wind turbines to produce their own electricity. – Wind power has a moderate-to-high net energy ratio. Docsity.com Using wind to produce electricity is an important step toward sustainability • Areas with the greatest wind power potential are often far from cities so may require controversial upgrading and expansion of electrical grid systems. • Winds can die down and thus require a backup source of power, such as natural gas, for generating electricity. • Some people in populated areas oppose wind farms as being unsightly and noisy. • In windy parts of the U.S. Midwest and in Canada, farmers and ranchers are paid royalties for each wind turbine located their land and can still grow crops or graze cattle. Docsity.com We can convert plants and plant wastes to liquid biofuels • Liquid biofuels such as biodiesel (produced from vegetable oils) and ethanol (ethyl alcohol produced from plants and plant wastes) are being used in place of petroleum-based diesel fuel and gasoline. • Advantages of biofuels: – While oil resources are concentrated in a small number of countries, biofuel crops can be grown almost anywhere, and thus they help countries to reduce their dependence on imported oil. Docsity.com We can convert plants and plant wastes to liquid biofuels – If these crops are not used faster than they are replenished by new plant growth, there is no net increase in CO2 emissions, unless existing grasslands or forests are cleared to plant biofuel crops. – Biofuels are easy to store and transport through existing fuel networks and can be used in motor vehicles at little or no additional cost. • The two most water-intensive ways to produce a unit of energy are irrigating soybean crops to produce biodiesel fuel and irrigating corn to produce ethanol. Docsity.com We can convert plants and plant wastes to liquid biofuels • An alternative to corn ethanol is cellulosic ethanol, which is produced from inedible cellulose that makes up most of the biomass of plants. – In this process, enzymes are used to help convert the cellulose from widely available inedible cellulose materials such as leaves, stalks, and wood chips to sugars that are processed to produce ethanol. – A plant that could be used for cellulosic ethanol production is switchgrass, a tall perennial grass native to North American prairies that grows faster than corn. – Affordable chemical processes for converting cellulosic material to ethanol are still being developed and are possibly years away. Docsity.com We can get energy by tapping the earth’s internal heat • Deep geothermal energy stored in hot, dry rock found 5 or more kilometers (3 or more miles) underground almost everywhere. – Tapping just 2% of this source of geothermal energy in the U.S. could produce more than 2,000 times the country’s current annual use of electricity. – Digging so deep into the earth’s crust is costly. Docsity.com Will hydrogen save us? • Focus is on fuel cells that combine H2 and oxygen gas (O2) to produce electricity and water vapor (2 H2 + O2→2 H2O). • Use of hydrogen as a fuel would eliminate most of our outdoor air pollution problems. • Greatly reduce the threat of projected climate change as long as the H2 is not produced with the use of fossil fuels or nuclear power. Docsity.com Will hydrogen save us? • Three challenges in turning the vision of widespread use of hydrogen as a fuel into reality. – Hydrogen gas must be produced from elemental hydrogen (H), which requires using other forms of energy; the amount of energy it takes to make this fuel will always be more than the amount we can get by burning it. – Fuel cells are the best way to use H2 to produce electricity. – Whether or not a hydrogen-based energy system produces less outdoor air pollution and CO2 than a fossil fuel system depends on how the H2 is produced. Docsity.com Choosing energy paths – What government research and development subsidies and tax breaks will be needed to help develop the resource? – How will dependence on the resource affect national and global economic and military security? – How vulnerable is the resource to terrorism? – How will extracting, transporting, and using the resource affect the environment, the earth’s climate, and human health? How will these harmful costs be paid and by whom? – Does use of the resource produce hazardous, toxic, or radioactive substances that must be safely stored for very long periods of time? Docsity.com Choosing energy paths • Hard energy paths are based on increasing use of nonrenewable fossil fuels and nuclear energy. • Soft energy paths are based on improving energy efficiency and increasing the use of various renewable energy resources. Docsity.com Choosing energy paths • Three general conclusions of experts who have evaluated energy alternatives: – There will likely be a gradual shift: • from large, centralized power systems such as coal and nuclear power plants to smaller, decentralized power systems such as household and neighborhood solar-cell panels, rooftop solar water heaters, and small natural gas turbines. • from gasoline-powered motor vehicles to hybrid and plug-in electric cars. • to fuel cells for cars and to stationary fuel cells for houses and commercial buildings. 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