Geothermal energy is natural heat from the interior of the Earth that is converted to heat buildings and generate electricity. The idea of harnessing Earth’s internal heat is not new. As early as 1904, geothermal power was used in Italy. Today, Earth’s natural internal heat is being used to generate electricity in 21 countries, including Russia, Japan, New Zealand, Iceland, Mexico, Ethiopia, Guatemala, El Salvador, the Philippines, and the United States. Total worldwide production is approaching 9,000 MW (equivalent to nine large modern coalburning or nuclear power plants)-double the amount in 1980. Some 40 million people today receive their electricity from geothermal energy at a cost competitive with that of other energy sources. In El Salvador, geothermal energy is supplying 30% of the total electric energy used. However, at the global level, geothermal energy supplies less than 0.15% of the total energy supply.
Geothermal energy may be considered a nonrenewable energy source when rates of extraction are greater than rates of natural replenishment. However, geothermal energy has its origin in the natural heat production within Earth, and only a small fraction of the
vast total resource base is being utilized today. Although most geothermal energy production involves the tapping of high heat sources, people are also using the low-temperature geothermal energy of groundwater in some applications.
The average heat flow from the interior of the Earth is very low, about 0.06 W/m2. This amount is trivial compared with the 177 W/m2 from solar heat at the surface in the United States. However, in some areas, heat flow is sufficiently high to be useful for producing energy. For the most part, areas of high heat flow are associated with plate tectonic boundaries. Oceanic ridge systems (divergent plate boundaries) and areas where mountains are being uplifted and volcanic island arcs are forming (convergent plate boundaries) are areas where this natural heat flow is anomalously high.
The environmental impact of geothermal energy may not be as extensive as that of other sources of energy, but it can be considerable. When geothermal energy is developed at a particular site, environmental problems include on-site noise, emissions of gas, and disturbance of the land at drilling sites, disposal sites, roads and pipelines, and power plants. Development of geothermal energy does not require large-scale transportation of raw materials or refining of chemicals, as development of fossil fuels does. Furthermore, geothermal energy does not produce the atmospheric pollutants associated with burning fossil fuels or the radioactive waste associated with nuclear energy. However, geothermal development often does produce considerable thermal pollution from hot waste-waters, which may be saline or highly corrosive, producing disposal and treatment problems.
In paragraph 1, the author introduces the concept of geothermal energy by
A. explaining the history of this energy source worldwide
B. arguing that this energy source has been tried unsuccessfully
C. comparing the production with that of other energy sources
D. describing the alternatives for generating electric power
What is true about geothermal energy production worldwide?
A. Because it is a new idea, very few countries are developing geothermal energy sources
B. Only countries in the Southern Hemisphere are using geothermal energy on a large scale
C. Until the cost of geothermal energy becomes competitive, it will not be used globally
D. Geothermal energy is already being used in a number of nations, but it is not yet a major source of power