Energy Related Free Response Questions

Transcription

1 Energy Related Free Response Questions Electric vehicles often have been proposed as an environmentally sound alternative to the gasoline engine for transportation. In response to state initiatives, several car manufacturers now include electric vehicles among their available models. In spite of these state initiatives, the penetration of electric vehicles into the transportation sector of the United States, as well as other countries, remains modest. (a) Identify and describe two environmental benefits to using electric vehicles in place of gasolinepowered engines for transportation. (b) Estimate the potential reduction in petroleum consumption (in gallons of gasoline per year) that could be achieved in the United States by introducing electric vehicles under the following assumptions: 1. The mileage rate for the average car is 25 miles per gallon of gasoline. 2. The average car is driven 10,000 miles per year. 3. The United States has 150 million cars percent of United States cars could be replaced with electric vehicles. (c) Some people have suggested that electric vehicles only shift the emission of air pollutants from dispersed sources to point sources. Explain and defend or refute this statement. (d) Propose two potential new United States government policies that would encourage the widespread use of electric vehicles. Explain.

2 West Fremont is a community consisting of 3,000 homes. A small coal-burning power plant currently supplies electricity for the town. The capacity of the power plant is 12 megawatts (MW) and the average household consumes 8,000 kilowatt hours (kwh) of electrical energy each year. The price paid to the electric utility by West Fremont residents for this energy is $0.10 per kwh. The town leaders are considering a plan, the West Fremont Wind Project (WFWP), to generate their own electricity using 10 wind turbines that would be located on the wooded ridges surrounding the town. Each wind turbine would have a capacity of 1.2 MW and each would cost the town $3 million to purchase, finance, and operate for 25 years. (a) Assuming that the existing power plant can operate at full capacity for 8,000 hrs/yr, how many kwh of electricity can be produced by the plant in a year? (b) At the current rate of electrical energy use per household, how many kwh of electrical energy does the community consume in one year? (c) Compare your answers in (a) and (b) and explain why you would or would not expect the numbers to be the same. (d) Assuming that the electrical energy needs of the community do not change during the 25-year lifetime of the wind turbines, what would be the cost to the community of the electricity supplied by the WFWP over 25 years? Express your answer in dollars/kwh. (e) Identify and explain TWO environmental benefits to West Fremont of switching from coal to wind power and TWO environmental costs to West Fremont of switching from coal to wind power.

3 Radioactive isotopes are widely used in the field of medicine, in the generation of electricity, and in the military. The use of radioactive isotopes has increased significantly over the past fifty years, leading to a corresponding increase in the amount of radioactive waste produced. The question of how to deal with radioactive waste is a topic of ongoing environmental concern. (a) Explain how the properties of low-level radioactive waste differ from those of high-level radioactive waste and how these properties lead to different storage requirements. For one of the two types of radioactive waste, give an example of a specific isotope that may be present in the waste, and explain how human activity generates the waste. (b) The United States Department of Energy recently chose Yucca Mountain in Nevada as the site for the deep underground burial of high-level radioactive waste. Describe THREE characteristics of an ideal deep underground storage site for high-level radioactive waste. (c) Identify TWO other options that have been suggested for the long-term management of radioactive waste. Discuss the feasibility of each method. (d) Exposure to high levels of ionizing radiation has adverse effects on human health and can result in immediate death. Identify one sublethal adverse effect on human health that can result from exposure to ionizing radiation, and explain how this effect is caused by the radiation.

4 Most of the coal mined in the United States today comes from surface (strip) mines. In surface mining, the vegetation, soil, and rock covering the coal (referred to as overburden) are removed and set aside. After the coal has been hauled away, good conservation practices require that the overburden be replaced and the surface be restored to its original condition. Land restoration may be difficult in some regions, due to factors such as the local climate, the thickness of the coal seam, the extent of the overburden, and the sulfur content of the coal. (a) Describe the steps that should be taken to restore the land after the overburden has been replaced. (b) Explain why the restoration of the land would likely be more difficult in an arid climate (less than ten inches of precipitation per year). (c) Describe one environmental impact that the sulfur content of the remaining coal and the tailings would have on the reclamation process and suggest a possible remedy. (d) Other than mining and reclamation, describe TWO environmental impacts of using coal for energy. (e) Explain why per capita coal consumption in the United States is likely to increase.

5 The Alaskan National Wildlife Refuge (ANWR) on Alaska s North Slope is frequently in the news because petroleum geologists estimate that there are billions of barrels of economically recoverable oil beneath the surface of its frozen tundra. According to a 1998 United States Geological Survey (USGS) estimate, ANWR could contain up to 10 billion barrels of technically recoverable oil. Oil company officials advocate opening the refuge to oil exploration and the subsequent development of its petroleum resources. Environmentalists argue that oil exploration and development will damage this fragile ecosystem and urge Congress to protect ANWR by designating it as a wilderness area. (a) The United States consumes approximately 20 million barrels of oil per day. According to the USGS estimate, for how many days would the technically recoverable oil resource in ANWR supply the total United States demand for oil? (b) Describe TWO characteristics of arctic tundra that make it fragile and explain how these two characteristics make the tundra particularly susceptible to damage from human impacts. (c) Identify TWO activities that would be associated with the development of ANWR petroleum resources and describe a substantial environmental impact of each in ANWR. (d) Identify and describe TWO major end uses of the 20 million barrels of oil that the United States consumes each day and for each use describe a conservation measure that would substantially reduce United States consumption.

6 Upon receiving notice from their electric utility that customers with solar power systems are permitted to sell excess power back to the utility, an Arizona family is considering the purchase of a photovoltaic solar energy system for their 2,700-square-foot suburban home. The initial costs of the systems they are considering range from $7,000 to $30,000. While gathering information prior to making a decision, the homeowners find the following information at the Web site of the United States Department of Energy. Stand-Alone vs. Grid-Connected Systems Stand-alone systems produce power independently of the utility grid. In some off-the-grid locations as near as one-quarter mile from the power lines, stand-alone photovoltaic systems can be more costeffective than extending power lines. Direct-coupled systems need no electrical storage because they operate only during daylight hours, but most systems rely on battery storage so that energy produced during the day can be used at night. Some systems, called hybrid systems, combine solar power with additional power sources such as wind or diesel. Grid-connected photovoltaic systems supply surplus power back through the grid to the utility and take from the utility grid when the home system s power supply is low. These systems remove the need for battery storage, although arranging for the grid interconnection can be difficult. In some cases, utilities allow net metering, which allows the owner to sell excess power back to the utility. (a) Describe one environmental benefit and one environmental cost of photovoltaic systems. (b) From the two types of solar systems described on the government Web site, select the system (either stand- alone or grid-connected) that you think best meets the needs of the homeowners. Write an argument to persuade them to purchase the system you selected. Include the pros and cons of each system in your argument. (c) Describe TWO ways that government or industry could promote the use of photovoltaic power systems for homeowners in the future. (d) Describe TWO ways that homeowners could use passive solar designs and/or systems and, for each way, explain how it would reduce the homeowners energy costs.

7 The Cobb family of Fremont is looking at ways to decrease their home water and energy usage. Their current electric hot-water heater raises the water temperature to 140 F, which requires 0.20 kwh/gallon at a cost of $0.10/kWh. Each person in the family of four showers once a day for an average of 10 minutes per shower. The shower has a flow rate of 5.0 gallons per minute. (a) Calculate the following. Be sure to show all your work and include units with your answers. (i) The total amount of water that the family uses per year for taking showers (ii) The annual cost of the electricity for the family showers, assuming that 2.5 gallons per minute of the water used is from the hot-water heater (b) The family is considering replacing their current hot-water heater with a new energy-efficient hotwater heater that costs $1,000 and uses half the energy that their current hot-water heater uses. How many days would it take for the new hot-water heater to recover the $1,000 initial cost? (c) Describe TWO practical measures that the family could take that would reduce their overall water use at home. (d) Describe TWO conservation measures (other than reducing hot water use) that the family could take to reduce the total amount of energy that they use at home.

8 Read the article below and answer the questions that follow.

9 (a) Calculate the number of acres required to produce 1,000 gallons of oil in one year from (i) microalgae (ii) soybeans (b) Describe TWO environmental advantages that biodiesel production from microalgae offers over biodiesel production from the other crops listed in the table. (c) Explain why burning biodiesel fuel has a different impact on atmospheric CO 2 concentrations than does burning fossil fuels. (d) Discuss TWO benefits, other than those related to atmospheric impacts, of increased reliance on biodiesel fuels over the next 50 years. (e) Describe TWO economic or societal problems associated with producing fuel from corn.

10 Anaerobic methane digesters have been used for many years to reduce energy costs on farms throughout Europe and on some large farms in the United States. The digesters operate by using anaerobic bacteria to break down animal waste. During the process, which typically uses a tank heated to about 100 F (38ÁC) to speed the reactions, raw manure is broken down and methane is produced. The methane can then be used to generate electricity or produce heat. For a certain dairy farm with 500 cows, the cost of installing a digester is approximately $400,000. Assume that the farm uses 800,000 kilowatt-hours (kwh) of electricity each year at a cost of $0.10 per kwh. The waste from a single cow can produce 3.0 kwh of electricity each day. (a) Describe the steps by which methane produced in the digester can be used to generate electricity. (b) Discuss TWO environmental benefits that may result from the installation of an anaerobic methane digester. (c) Assuming that the cost of electricity remains constant and the farmer starts using the manure from the cows in an anaerobic digester to produce electricity on the farm, calculate: (i) The number of kwh of electricity that can be produced in one year (ii) The amount of money the farmer can save in one year, NOT counting the installation cost of the digester. (You may round your answer to the nearest $1,000.) (iii) The amount of time, in years, that it will take to recover the cost of installing an anaerobic digester on the farm. (You may round your answer to the nearest whole number of years.) (d) Calculate the minimum number of cows the farm would need to produce 800,000 kwh of electricity per year.

11 Shown above is a graph of the gross domestic product (GDP) per capita versus the annual electrical energy consumption per capita for nine countries in (a) Iceland s position on the graph is due in part to its access to geothermal energy sources. Describe how electricity is generated from a geothermal source. (b) Despite its low GDP per capita and low annual electrical energy consumption per capita, China has become the world s largest emitter of CO 2. Explain this apparent contradiction. (c) In addition to contributing to increased atmospheric CO 2 concentrations, China is facing other air pollution issues related to the generation of electricity. Identify one such issue and describe the impact it has on human health. (d) Two countries shown on the graph have developed domestic energy sources: sugarcane in Brazil and tar sands in western Canada. (i) Choose EITHER sugarcane or tar sands, then briefly describe the process of fuel production from that energy source. (ii) Describe TWO disadvantages of using the energy source that you chose in part (d)(i). (iii) Which of the two energy sources is more sustainable? Justify your answer with an explanation.

12 The Fremont School District uses oil to heat school buildings. Go Green! is a new project the district will implement. The superintendent has declared that the district will dedicate itself to reducing its carbon footprint. In addition to taking serious energy-conservation measures, the district is planning to help offset its carbon dioxide emissions by raising money to help conserve a portion of a large tract of forest land adjacent to the high school campus. (a) Describe one alternative energy source that would reduce the carbon footprint of the school district. Discuss one environmental benefit (other than reduced CO 2 emissions) and one environmental drawback of using the alternative source instead of fuel oil. (b) Identify TWO ecological benefits provided by intact forest ecosystems (other than reducing CO 2 levels in the atmosphere). (c) Use the assumptions below to answer the questions that follow. For each calculation, show all work. The biomass of the forest increases at an annual rate of kg/ha. The forest biomass is 50 percent carbon by mass. Each year the district uses gallons of fuel oil for heating and hot water. 10 kg of CO 2 is produced when 1 gallon of fuel oil is burned. 1.0 kg of CO 2 contains 0.27 kg of carbon. The cost of putting 1 ha of the forest into conservancy is $12,000. (i) Calculate the mass of carbon, in kg, that is accumulated and stored in 1.0 ha of forest in one year. (ii) Calculate the mass of carbon, in kg, that is emitted by the school as a result of its fuel-oil consumption in one year. (iii) Calculate the number of hectares of forest the school district needs to conserve in order to offset the carbon released in one year by the school burning its fuel oil. (iv) Calculate the amount of money the school district must raise for the conservation project.

13 Read the following article from the Fremont Gazette and answer the questions that follow. (a) Identify and describe TWO water-related environmental problems associated with fracking. (b) Natural gas is considered to be a better fossil fuel for the environment than coal is. Discuss TWO environmental benefits of using natural gas as a fuel compared to using coal. (c) Describe TWO environmental drawbacks, not related to water use, of using the fracking process to extract natural gas from shale. (d) Describe one economic benefit to society of using fracking to obtain natural gas from shale. (e) Nuclear power is an alternative to using natural gas or coal as a fuel for generating electricity. However, there are also problems associated with nuclear power plants. Describe TWO negative environmental impacts associated with nuclear power.

14 Battery electric vehicles (BEVs) have been introduced to consumers as an alternative way to reduce the environmental effects caused by use of internal-combustion engine (ICE) vehicles. A comparison of both vehicle types can help determine whether the use of BEVs would be beneficial in the future. Where calculations are required, show your work. (a) Identify THREE strategies that the federal government could implement to encourage the use of BEVs. (b) Assume that the fuel efficiency of the ICE vehicle is 25 miles per gallon (mpg) and that gasoline costs $3.75 per gallon (gal). Calculate the cost of gasoline per mile. (c) The charger supplies energy to the BEV battery at an average rate of 4.0 kilowatts (kw) and fully charges the BEV battery in 7.0 hours. The car will run for 100 miles on a full charge. The cost of electricity is $0.11 per kilowatt-hour (kwh). i. Calculate the cost of the electricity to fully charge the battery. Assume that the battery is not charged to begin with. ii. Calculate the cost of electricity per mile to drive the BEV. When it is driven 100 miles, the ICE vehicle contributes 72.8 pounds (lb) of CO 2 from the burning of the gasoline. The drilling, refining, and transportation costs of getting the gasoline to the gas station add an additional 17.7 lb of CO 2 per 100 miles. The BEV does not emit any CO 2 itself, but the extraction, transportation, and combustion of the coal that produced the electricity at the power plant add 63.6 lb of CO 2 for the same 100 miles. (d) Calculate the difference in the amount of CO 2 that would enter the atmosphere if both cars were driven 100 miles. (e) Describe TWO economic impacts (excluding costs related to climate change resulting from CO 2 or the cost of gasoline at the pump) that result from an increased number of BEVs on the road.

15 Read the article below and answer the questions that follow. (a) State whether you agree or disagree with each of the following remarks made by Dr. Kull. For each remark, provide one justification for your position. (i) Nuclear power plants produce no dangerous solid waste. (ii) Using nuclear power avoids the release of greenhouse gases. (b) If the plan for a nuclear power plant in Fremont is approved, it will take several years for the plant to be built. Describe TWO environmental problems that could result from the construction of the plant (i.e., prior to operation). (c) Suppose that the nuclear power plant is constructed on the Fremont River site. (i) Identify the most likely pollution threat that the plant will pose to the Fremont River as a result of the plant s normal daily operation. (ii) Discuss one potential ecological consequence of the pollution threat that you identified in part (i). (iii) Identify a system often used in nuclear power plants to reduce the pollution you identified in part (i). (d) Describe TWO specific steps that Fremont residents and/or businesses could take to reduce the use of electricity. (e) Identify a specific nuclear power plant at which a major accident has occurred. Explain one environmental consequence (other than effects on human health) of a nuclear power plant accident.