We use energy to grow our food, power our vehicles, and run the appliances in our homes, schools, and workplaces. Over the past two centuries, industrial societies have used inexpensive, and readily available, sources of energy to fuel urbanization and economic development. This growth has created, at least in some countries, the highest level of human development in the history of civilization. A question to ponder, though, is if this level of development can be sustained indefinitely. Many of the great civilizations of the past declined, at least in part, due to environmental change caused by human activities.
Starting in the late 18th century with the Industrial Revolution, the global economy has increasingly relied on fossil fuels such as coal, petroleum, and natural gas. In the future, the global economy will run out of these fuels. In the meantime, some scientists argue that dependence on fossil fuels has contributed to global warming. The Intergovernmental Panel on Climate Change (IPCC), founded in 1988 by the World Meteorological Organization and the United Nations Environment Programme, argues that measurable global warming has occurred, and that humans are at least partially to blame.
Some scientists and commentators from across the political spectrum downplay the significance of global warming—especially the role humans might play in climate change. However, even famous skeptics such as author Michael Crichton, or contrarian scientist Bjorn Lomborg, agree that the Earth is getting warmer, but do not believe that humans are to blame. The heavy reliance on fossil fuels raises several questions. First, how long into the future will these resources last? Second, to what extent do fossil fuels contribute to climate change? Third, are there alternative fuels that are less likely to influence the climate and that will last into the foreseeable future? Alternative energy strategies based on wind, biomass, geo-thermal, solar and photovoltaics (PV), hydrogen fuel cells, and improved fuel efficiencies could ameliorate climate change.
ALTERNATIVES TO FOSSIL FUELS
The phrase Alternative energy implies that these energy sources are alternatives to nuclear and traditional fossil fuels such as coal, petroleum, or natural gas. Alternative energy, therefore, is a catchall category of energy sources that proponents argue can replace traditional fossil fuels in daily life, while causing less harm to the environment.
Alternative energy is increasingly important for at least three reasons. First, fossil fuels are nonre-newable; eventually, they will be exhausted. The United States is already witnessing a decline in its petroleum production. In 1950, the United States was largely self-sufficient in fossil fuels, producing 32,562,667 billion Btus of energy. At the same time, Americans consumed 31,631,956 billion Btus of fossil fuels. The United States therefore enjoyed a slight fossil fuel surplus. Now, fossil fuel consumption in the United States far outstrips production. In 2006, the United States produced 56,032,329 billion Btus of fossil fuels, but consumed 84,760,343 billion Btus. Advocates of alternative energy argue that alternative energy sources need to be developed now, so that when fossil fuels are gone, there will be other dependable energy resources.
Second, many advocates of alternative energy argue that as oil production declines, Americans and others around the world will become increasingly reliant on foreign sources of oil. This will require heavy investments in the military to ensure that fossil fuels continue to flow, especially from politically unstable regions of the world such as the Middle East.
Third, alternative energy has received increased attention because of a scientific consensus that the average temperature of the planet is rising. Scientists argue that a leading cause of global warming is the emission of so-called greenhouse gases such as carbon dioxide, methane, various nitrous oxides, hydro-fluorocarbons, sulfur oxides, and particulate matter.
These gases come from the combustion of fossil fuels in vehicles, in the production of electricity from coal or natural gas, and in many other processes.
Carbon dioxide and other greenhouse gases are not inherently bad. In fact, these gases naturally occur in the atmosphere and help moderate the global climate to support living organisms, including humans. In this process, the Earth’s surface is first warmed directly during the day by incoming solar radiation. At night, this energy is radiated back into the atmosphere as latent heat energy, some of which is absorbed by atmospheric gases such as carbon dioxide. The problem, say many scientists, is that the growing use of fossil fuels is increasing the concentrations of carbon dioxide, methane, and other gases, which, in turn, increase the capacity of the atmosphere to absorb latent heat energy. The National Aeronautical and Space Administration (NASA) notes that the atmospheric concentration of carbon dioxide has increased 35 percent 1750-2007. At the same time, the Earth’s average temperature has increased between 1.1 degrees F to 1.6 degrees F (0.6 degrees C to 0.9 degrees C) and that warming continues at an accelerating rate. The only way to slow global warming is to reduce greenhouse gases. This means that the use of fossil fuels will have to be reduced.
Reducing the reliance on fossil fuels will not be easy. The United States relies on fossil fuels for 85 percent of its energy needs. Nuclear energy accounts for another 8 percent. Hence, only 7 percent of the energy consumed in the United States comes from renewable sources such as biomass, hydroelectric, wind, or solar power. Another way to look at the heavy reliance on fossil fuels is to see the amount of energy consumed in absolute terms—data show that Americans consumed more fossil fuels in 2006 than they did in 2002. However, renewable energy is playing a slightly larger role in the U.S. energy portfolio.
DEFINITIONS
To maintain the current standard of living in the industrial world, and promote human and economic development in the less prosperous regions of the world, alternative forms of energy must be found. Some scientists use the phrases alternative energy and renewable energy interchangeably. International agencies such as the IPCC and World Bank, as well as government agencies such as the U.S. Department of Energy (DOE) or the U.S. Environmental Protection Agency (EPA), offer separate, but somewhat overlapping definitions for alternative versus renewable energy.
The word alternative can be seen as somehow marginalizing the importance of the concepts it embodies. However, an argument can be made for its use because of the need for a clear distinction between the various forms of energy. In the future, alternative energy may, in fact, become the dominant form of energy used. Maybe a better term is sustainable energy, to focus on its potentially mainstream status and renewable nature. However, for the time being, these energy sources represent only a small fraction of the energy used.
Use of alternatives
The World Bank definition for alternative versus renewable energy differs. It uses a hierarchical strategy to categorize energy forms. Alternative energy represents the broadest category of energies that are not based on fossil fuels or nuclear energy. These energy forms are thought to produce fewer greenhouse gases than the fossil fuels they are intended to replace. Within this broad category, there are two subcategories of energy sources or strategies for greenhouse gas reduction: renewable energy and improved energy efficiencies.
A hyrdoelectric plant in Tennessee. Once the water level reaches a high enough level, a gate is opened in the dam, allowing gravity to carry water down toward the generator. The force of the water falling spins the turbine and generator, creating electricity.
Renewable energies can be further sorted into energies used to generate electricity and energies used for transportation. While there is certainly overlap between these two categories (for example, solar energy can generate electricity for distributed use in homes and it can also be used to power vehicles), it makes sense to examine the efficacy of renewable energies by starting with these two categories.
Electricity is produced by finding a way to convert kinetic energy (energy associated with movement) into electrical energy. A generator typically does this. A generator consists of a rotating magnet, called a rotor, and a stationary coil of copper wires known as a stator. By turning the rotor continually past the stator, an electrical current is generated. The challenge is to find a source of energy to move the rotor. In simplified form, a rotor is attached to some type of turbine or propeller that is forced to turn by some external force, usually water, steam, or air. Fossil fuels such as coal, natural gas, and oil, and nuclear fission can be used to generate heat. This heat is used to convert water into steam within a confined space. As steam is created, it expands, creating pressure. This pressure can be directed at a turbine, and when released in a controlled manner, can cause the turbine to turn.
The problem with using fossil fuels for generating electricity is that the combustion of fossil fuels to create the heat needed to rotate turbines creates carbon dioxide and other greenhouse gases. Furthermore, these forms of energy are nonrenewable, and the extraction of fossil fuels through mining and oil drilling itself requires considerable amounts of fossil fuels. The process also transforms the landscape in profoundly destructive ways.
HYDROELECTRICITY
The major renewable forms of energy include hydroelectric, solar, and wind power. These energies produce electricity, but do not use the combustion of fuels to spin a turbine. For example, hydroelectric-ity works by converting potential energy into kinetic energy. A hydroelectric generating station uses a dam on a river to create a reservoir. As the reservoir fills up with water behind the dam, the water level rises above the turbine, which is located on the downstream side of the dam. There is a large pipe called a penstock, which connects the reservoir above to the turbine below. Once the water level reaches a high enough level, a gate is opened in the dam, allowing gravity to carry water down the penstock toward the generator. The force of the water falling from the height of the reservoir spins the turbine and generator, creating electricity.
A similar mechanism operates to generate electricity from tidal power. In places where there are large tides, such as the Bay of Fundy in Canada, the rapid flow of incoming and outgoing tides can be used to spin a turbine. Annapolis, Nova Scotia, hosts an operating example of a tidal power plant generating electricity from tides that fluctuate 40 or more ft. between low and high tide. The tidal plant operates using a reversible turbine that generates electricity as the tide rises. The turbine then reverses to generate power as the tide goes back out.
From a global warming perspective, hydroelectric-ity and tidal power are low-impact ways to generate electricity. However, they have limitations. They only work in certain geographic and climatic areas. Hydroelectricity can only be generated where there is sufficient precipitation to keep the reservoirs full. It also works better in areas of rugged topography where rivers flow through steep valleys. This makes the construction of dams and reservoirs more cost-effective. Reservoirs also cause considerable damage, as land previously occupied by towns, or used for agriculture, is flooded. This is a particularly sensitive topic in countries such as India and China that have rapidly-expanding energy needs, but also have large populations that will be displaced by any large-scale hydroelectric project.
Tidal power may be even more restricted in the places where it can work economically. In many parts of the world, daily tidal variations may be only a few feet, which is too small to merit large-scale investments in tidal power. Furthermore, the tidal power plants require that dams or so-called "barrages" be built across estuaries in order to channel the force of the tides through the generator. Barriers of this sort can disrupt ocean ecosystems and hinder boat navigation.
WIND POWER
Electricity generated by wind power relies on air moving past a propeller to spin a turbine. Wind is created as a result of the differential heating of the earth’s surface of the sun. Air masses move from areas of high atmospheric pressure to low atmosphere pressure. Wind energy creates very few greenhouse gases and will exist as long as the sun shines and winds blow. There are challenges to implementing wind energy, though. Wind energy, like other forms of renewable energy, operates effectively only in certain geographic areas and climates. Wind speeds and direction can vary hourly, daily, and seasonally. For example, winds are typically stronger during the day than at night. In temperate climates, the wind tends to be stronger during the winter than during the summer. Hence, a wind turbine only makes economic sense if, on average, the wind blows at a certain minimum average velocity, usually at least 10 to 12 mi. (16 to 10 km.) per hour for much of the calendar year. Winds lower than that cannot move the large propellers to spin the turbine.
A wind turbine also needs a relatively open space, so that trees or buildings do not affect wind speeds. Critics of wind farms also argue that wind turbines can harm migrating birds and bats, are an aesthetic blight on the landscape, and cause irritating "flicker" as sunlight reflects off of the rotating propeller blades.
SOLAR POWER
Solar power can reduce greenhouse gases in several ways. First, passive solar energy can be used for heating. Dark surfaces absorb energy from the sun better than light surfaces. This principle can be used to heat water or warm a house. Water stored in a dark container or cistern on the roof of a house can become very hot. This water can be used for showers, laundry, or cleaning. Similarly, a dark exterior on the roof or walls of a house can help warm the house on a cold winter day. This helps reduce greenhouse gases, because like all renewable energies, its use offsets the use of fossil fuels.
Second, active solar energy can generate electricity through the use of photovoltaic cells. This technology relies on semiconductors to take direct light from the sun and convert it into electricity. This form of energy production is renewable.
However, it has several limitations, including the daily fluctuations in light, as well as regional variations in the amount of annual sunshine received. Solar energy is more economical in the American southwest, where sunshine is abundant. It is less viable in areas that have more cloud cover. However, solar energy is viable in most parts of tropical and mid-latitude regions.
Geothermal energy can be used to offset fossil fuels in several ways. First, the energy can be used to heat and cool buildings. Typically, a residential geothermal system relies on the fact that the Earth’s temperate remains constant at about 55 degrees F (12.7 degrees C) at about 12 ft. (3.6 m.) below the surface. During the summer, the heat from the house is drawn down into the ground through a closed system, where it dissipates into the cool ground. During the winter, the relatively warm temperature of the ground is brought to the surface and used to help heat the house on a cold day.
HYDROGEN AND BIOMASS
Many researchers tout hydrogen as the ultimate renewable energy source, because it is the most common element in our universe. Hydrogen-based fuel cells operate by reacting pure hydrogen with oxygen to generate electricity. Energy is released that is then converted into electricity, with water as the only by-product. Unfortunately, pure hydrogen must be created through the hydrolysis of water. This is an expensive process that relies largely on conventional energy sources. Hence, there are significant technological barriers to the widespread adoption of hydrogen power.
Biomass, or plant material, can also be a significant source of energy for the production of electricity and for transportation. The DOE identifies three biomass sources: wood, waste, and biofuels. Wood can be cut and burned directly for home heating. The by-products of processing wood into paper products can also be co-fired with fossil fuels to make coal-fired electrical plants burn cleaner. Combustible biomass can also come from municipal solid waste, industrial waste, and landfill gas. Biomass can be used to create alcohol fuels such as ethanol, or diesel fuels, such as soy diesel. Advocates of these fuels, used largely for transportation, argue that their production and use creates fewer greenhouse gases than conventional fossil fuels.
Critics argue that biofuels must still be burned and therefore still generate greenhouse gases. They also argue that the increased production of corn and soybeans for ethanol or soy diesel will increase food prices, while degrading soil quality. This will require more use of petroleum-based fertilizers. Finally, skeptics suggest that biofuels are not a viable alternative because the energy it takes to produce ethanol is more than the energy contained in the fuel.
COST OF ALTERNATIVES
The high cost of production and related technological barriers affect all alternative energy sources. A comparison of production costs shows that fossil fuels are simply cheaper to produce than alternative fuels, which often need government subsidies to make them economically feasible. For example, it costs approximately 4.0 cents per kilowatt hour ($/ kWh) and around 5.0 C/kWh to produce electricity from natural gas and coal, respectively. Electricity from large-scale hydroelectric generators can cost between 5.0 and 12.0 C/kWh. Electricity from nuclear fission can cost between 11.0 and 15.0 C/kWh.
Great technological strides have been made in the advance of renewable fuels. Electricity from wind, which cost over 40.0 C/kWh in 1980, now costs in the range of 4.0 to 6.0 C/kWh. However, that makes it barely competitive with coal. Electricity from solar photovoltaics still costs almost 20.0 C/kWh, while that from hydrogen-powered fuel cells costs $4.00 per kWh. That is why some scientists suggest that while research is done over the long term to reduce the costs of producing energy from wind, solar, bio-mass, or hydrogen, the focus should be on increasing the efficiency of current systems. Environmentalist Amory Lovins argues that existing technologies can help reduce energy needs. Examples include more fuel-efficient vehicles, homes with better insulation to reduce heating and cooling costs, and more efficient appliances. The refrigerator exemplifies this progress in energy efficiency. In 1980, a 20 cu. ft. refrigerator used about 1,300 kWh of electricity per year. In 2001, a comparably sized unit used 500 kWh of electricity per year.
Alternative energy can be an important part of a strategy to reduce global warming if the commitment to energy efficiency can be increased in the short term, with continued research on alternative energy technologies in the long term. It may also mean combining energy types to maximize the amount of work that can be done. Increasing investments by the public and private sector in research and development can help make this happen.
