GEOTHERMAL ENERGY Distribution of geothermal resources in the United States Favourability of deep Enhanced Geothermal Systems EGS Most favourable Least favourable Regions not assessed for deep EGS potential No data 2012 Encyclopædia Britannica Inc Source National Renewable Energy Laboratory This map shows geothermal energy resources in the United States As you can see some areas have far more geothermal resources than others do crust hot spots such as Yellowstone National Park and the Hawaiian Islands Areas near volcanic activity often have features that bring heat from deep inside Earth right to the surface such as lava flows geysers geysers or hot springs In other places the extraction
INTRODUCTION of geothermal energy can be more challenging For successful extraction geothermal reservoirs must have adequate permeability or faults that allow fluids to rise close to the surface and an impermeable caprock caprock to prevent the escape of heat In addition such reservoirs must be economically accessible that is within the range of drills The annual heat flow to the surface averages between 50 and 70 milliwatts mW per square meter worldwide In contrast incoming solar radiation striking striking Earth’s surface provides 342 watts per square meter annually The estimated amount of geothermal geothermal energy that can be recovered and utilized on the surface is roughly three times the world’s annual consumption of all types of energy Geothermal energy is an alternative energy source That means that it is one of several renewable renewable power sources that can be used in place of fossil fuels and other traditional sources of energy which are limited in supply and produce pollution and other environmental problems Other alternative alternative energy sources include solar power wind power and waterpower 7
Chapter One HEAT FROM INSIDE EARTH Heat from Earth’s interior is produced mainly by the radioactive decay of elements in Earth’s crust and mantle and also by friction generated along the margins of continental plates It generates surface phenomena such as lava flows geysers fumaroles hot springs and mud pots INSIDE EARTH Earth is made up of three layers the core mantle and crust Temperatures and pressures rise with increasing increasing depth inside the planet At roughly 50 miles 80 kilometers below the surface the rock of the mantle is at about 2,500 degrees Fahrenheit 1,370 degrees Celsius and becomes partly molten Below about 150 to 200 miles 250 300 km the mantle is under 8
HEAT FROM INSIDE EARTH mantle 1 800 miles so much pressure that it becomes more rigid again Beneath the mantle the material becomes much denser and liquefies core Scientists believe that this 4 300 miles crust layer called the outer core 3 19 miles consists of up to 90 percent molten iron and nickel with some other elements such as sulfur mixed in Finally below about 3 200 miles 5 100 km is the inner core This hottest layer is estimated to be between 8 000°F and 12 000°F Earth's interior has three main about 4 400°C 6 600°C layers a relatively thin rocky Some of the heat in crust a thick mantle and a largely Earth's interior is left over molten core The measurements from the planet's formation provided are averages formation and some is released from the outer core as iron and nickel slowly solidifies Most of the heat though is believed to result from the decay of long lived radioactive elements such as potassium thorium and uranium 2014 Encyclopædia Britannica Inc
