Geothermal Energy. History of Geothermal Energy Usage. - For thousands of years, civilizations have used naturally warm spring water for various purposes - This hot water was mostly used for bathing and cleaning, but was also used to heat living spaces. Ancient Rome
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- For thousands of years, civilizations have used naturally warm spring water for various purposes
- This hot water was mostly used for bathing and cleaning, but was also used to heat living spaces
-The scientific study and measurement of geothermal energy first began in 1740, when a researcher measured temperatures at various locations along a mineshaft in France. He, and others began to notice that, generally, the deeper one goes, the higher temperature one finds.
The first district heating system came online in the 14th century and continues to operate to this day.
- Geothermal energy usage was first found in the United States in Boise, Idaho in 1892
- 40 businesses and 200 homes were heated
- 450 homes continue to be heated today
Geothermal energy was first used to produce electricity in Italy in the early 20th century. The first working prototype was small and constructed by Prince Gionori Conti in 1905.
- This experimental unit paved the way for the first commercially viable unit, which in 1913 began producing 250kWe
In 1755, natural scientists drilled the first holes for hot water wells
In 1930, the first Icelandic buildings were heated using geothermal energy
In 2008, 52 water heating wells were in operation, providing 2,400 liters per second of water ranging from 62 to 132C
- Today, 24% of Iceland’s electricity is produced from Geothermal sources
Wairakei was the site of the nation’s first geothermal site for electricity production
- The site utilized different turbine types for efficient electricity production from varied steam pressures.
- The once magnificent Geyser Valley has been reduced to a stream
1st: The heat from impacts with large bodies such as meteors and asteroids was trapped in surrounding rock of the planet, and may have been enough in certain circumstances to completely melt the early Earth.
2nd: Remnant heat of an early Earth event known as the Iron Catastrophe. With much of early Earth still molten, denser metals, particularly iron and nickel, migrated to the center of the planet. Tremendous amounts of frictional heat was created.
3rd: Compression due to gravity.
Detailed understanding of the nature of heat below the Earth’s surface occurred when scientists began to understand the various origins of subterranean heat.
Radiogenic heat was discovered by nuclear physicists in the 1950’s.
- Radiogenic heat is generated by the decay of radioactive isotopes of uranium, potassium, and thorium, which are found deep under the Earth’s surface, and significantly contributes to the presence of subterranean heat.
- Once radiogenic heat was understood, along with other sources, the creation, dissipation, and movement of underground heat was better understood.
In some instances, passive heat extraction is used.
- In places with “hot rocks” at the surface electricity is created without the need for heat extraction.
- Active heat extraction requires energy input but allows for power production at many more locations
- Heat is drawn from the depths either actively or passively through the movement of hot water
The heat is then used to boil water
The steam produced then is fed to a turbine
The turbine converts the geothermal heat energy into mechanical energy
- The turbine spins a generator which converts mechanical energy into electrical energy
Horizontal Closed Loop
Source: Geothermal Resources Council
Geothermal Field - A geothermal system provides heating and cooling for the building, making use of the ground’s constant temperature (approximately 55°F 6 feet below grade). In summer, excess heat from the building is pumped into the cooler ground; in winter, heat from the ground is pumped into the building.
Example of a ground-source heat pump.