Download Geothermal Energy

Geothermal Energy
First of all, I would like to deeply thank our honorable Sir to let me choose my own topic for my
presentation today. To be honest, I personally found the topic “Geothermal Energy as a Source of
Electricity” very interesting as a means of producing electricity to meet our ever increasing electricity
need.
Good afternoon everybody.
Well who can deny that we are experiencing terrible shortage of electricity especially during the
summer when we need it the most? Over the past few decades or so it has gotten out of control and
various steps have been undertaken or supposedly to be taken as a solution to this problems in the past
and in current time. But we have failed miserably each time due to the lack of sincere approach to
finding the correct solution to it. In this case, my little research on “Geothermal Energy” seems a
promising solution to the problem.
The people of world today are facing irreversible damages and consequences to our environment due to
continuous unwise use of our natural resources especially that of fossil fuels. The natural resources that
we have are limited and they are depleting day by day. However, these days, people are getting more
conscious and are inclined to the use of various renewable energy sources for power generation which is
very admirable and optimistic. However, unlike, the solar energy, wind power and other renewable
sources, the geothermal energy is very much less-discussed or less-implemented.
Let’s now try to find out what geothermal energy is and how it can play a vital role in solving a million
dollar question and that is what could be the most efficient way of producing electricity without
impacting adversely our world’s environment and our world climate.
What is Geothermal Energy?
The word geothermal comes from the Greek words geo (earth) and thermos (heat). So, geothermal
energy is heat from within the Earth. We can recover this heat as steam or hot water and use it to
generate electricity. Geothermal energy is a renewable energy source because the heat is continuously
produced inside the Earth.
Worldwide, geothermal plants have the capacity to generate about 10 gig watts of electricity as of 2007,
and in practice supply 0.3% of global electricity demand. An additional 28 gig watts of direct geothermal
heating capacity is installed for district heating, space heating, spas, industrial processes, desalination
and agricultural applications.
Geothermal power is cost effective, reliable, sustainable, and environmentally friendly, but has
historically been limited to areas near tectonic plate boundaries. Recent technological advances have
dramatically expanded the range and size of viable resources, especially for applications such as home
heating, opening a potential for widespread exploitation. Geothermal wells release greenhouse gases
trapped deep within the earth, but these emissions are much lower per energy unit than those of fossil
fuels. As a result, geothermal power has the potential to help mitigate global warming if widely
deployed in place of fossil fuels.
The Earth's geothermal resources are theoretically more than adequate to supply humanity's energy
needs, but only a very small fraction of it may be profitably exploited. Drilling and exploration for deep
resources costs tens of millions of dollars, and success is not guaranteed. Forecasts for the future
penetration of geothermal power depend on assumptions about technology growth, the price of energy,
subsidies, and interest rates.
Using Department of Energy Geothermal Data, we see that if you could dig 4,000 miles below the
surface of the Earth, you would reach the core of our planet. It is estimated to be 7,200 degrees F or
higher at that depth. The heat exists in part because of the heat created when billions of tons of hot
mass collided and collapsed under continuing bombardment from yet more hot mass that fell when our
world was in the process of creation.
By most accounts, that was over 4 billion years ago and the core would have cooled down by now unless
something else contributed to the heat. It turns out that the largest contributor to the heat below our
feet is the decay of radioactive particles. We stand on nothing less than a planet-sized nuclear reactor
that promises to continue generating heat for billions of years in the future. Getting closer to the surface
of our planet, if you drill a hole 50 to 60 miles deep, you hit hot molten rock of 1200 to 2200 F.
About 3 to 4 miles below the surface of the Earth, you find hot dry rock ranging in temperature from
about 300F to 400F.
Geothermal Energy Is Generated Deep Inside the Earth
Geothermal energy is generated in the Earth's core. Temperatures hotter than the sun's surface are
continuously produced inside the Earth by the slow decay of radioactive particles, a process that
happens in all rocks. The Earth has a number of different layers:
The core itself has two layers: a solid iron core and an outer core made of very hot melted rock, called
magma.
The mantle surrounds the core and is about 1,800 miles thick. It is made up of magma and rock.
The crust is the outermost layer of the Earth, the land that forms the continents and ocean floors. It can
be 3 to 5 miles thick under the oceans and 15 to 35 miles thick on the continents.
The Earth's crust is broken into pieces called plates. Magma comes close to the Earth's surface near the
edges of these plates. This is where volcanoes occur. The lava that erupts from volcanoes is partly
magma. Deep underground, the rocks and water absorb the heat from this magma. The temperature of
the rocks and water gets hotter and hotter as you go deeper underground.
People around the world use geothermal energy to heat their homes and to produce electricity by
digging deep wells and pumping the heated underground water or steam to the surface. We can also
make use of the stable temperatures near the surface of the Earth to heat and cool buildings.
Where Geothermal Energy is found
Naturally occurring large areas of hydrothermal resources are called geothermal reservoirs. Most
geothermal reservoirs are deep underground with no visible clues showing above ground. But
geothermal energy sometimes finds its way to the surface in the form of:
Volcanoes and fumaroles (holes where volcanic gases are released)
Hot springs
Geysers
Most Geothermal Resources Are Near Plate Boundaries. The most active geothermal resources are
usually found along major plate boundaries where earthquakes and volcanoes are concentrated. Most
of the geothermal activity in the world occurs in an area called the Ring of Fire. This area encircles the
Pacific Ocean.
When magma comes close to the surface, it heats ground water found trapped in porous rock or water
running along fractured rock surfaces and faults. These features are called hydrothermal. They have two
common ingredients: water (hydro) and heat (thermal). Geologists use various methods to look for
geothermal reservoirs. Drilling a well and testing the temperature deep underground is the most reliable
method for finding a geothermal reservoir.
Use of Geothermal Energy
Some applications of geothermal energy use the Earth's temperatures near the surface, while others
require drilling miles into the Earth. The three main uses of geothermal energy are:




Direct use and district heating systems use hot water from springs or reservoirs near the
surface.
Electricity generation power plants require water or steam at very high temperature (300° to
700°F).
Geothermal power plants are generally built where geothermal reservoirs are located within a
mile or two of the surface.
Geothermal heat pumps use stable ground or water temperatures near the Earth's surface to
control building temperatures above ground.
Geothermal Power Plants
Geothermal power plants use hydrothermal resources that have two common ingredients: water
(hydro) and heat (thermal). Geothermal plants require high temperature (300°F to 700°F) hydrothermal
resources that may come from either dry steam wells or hot water wells. We can use these resources by
drilling wells into the Earth and piping the steam or hot water to the surface. Geothermal wells are one
to two miles deep.
Types of Geothermal Plants
There are three basic types of geothermal power plants:



Dry steam plants use steam piped directly from a geothermal reservoir to turn the generator
turbines. The first geothermal power plant was built in 1904 in Tuscany, Italy, where natural
steam erupted from the Earth.
Flash steam plants take high-pressure hot water from deep inside the Earth and convert it to
steam to drive the generator turbines. When the steam cools, it condenses to water and is
injected back into the ground to be used over and over again. Most geothermal power plants
are flash steam plants.
Binary cycle power plants transfer the heat from geothermal hot water to another liquid. The
heat causes the second liquid to turn to steam which is used to drive a generator turbine.
Resources
The Earth's internal heat naturally flows to the surface by conduction at a rate of 44.2 terawatts, (TW,)
and is replenished by radioactive decay of minerals at a rate of 30 TW. These power rates are more than
double humanity’s current energy consumption from all primary sources, but most of it is not
recoverable. In addition to heat emanating from deep within the Earth, the top ten meters of the
ground accumulates solar energy (warms up) during the summer, and releases that energy (cools down)
during the winter.
Beneath the seasonal variations, the geothermal gradient of temperatures through the crust is 25–30 °C
per kilometer (km) of depth in most of the world. The conductive heat flux is approximately 0.1
MW/km2 on average. These values are much higher near tectonic plate boundaries where the crust is
thinner. They may be further augmented by fluid circulation, either through magma conduits, hot
springs, hydrothermal circulation or a combination of these.
Enhanced geothermal system
1: Reservoir 2: Pump house 3: Heat exchanger 4: Turbine hall 5: Production well 6: Injection well
7: Hot water to district heating 8: Porous sediments 9: Observation well 10: Crystalline bedrock
Pros and Cons:
Like every other energy resource, however, geothermal energy utilization brings with it a number of
issues. The four main areas of discussion about the pros and cons of geothermal energy are:





Environmental Friendliness
Reliability
Cost
Availability
Sustainability
Environmental Friendliness:
1. Geothermal energy use does entail some environmental impact, but it is safe to say that the
environmental benefits far outweigh the costs.
2. Most geothermal facilities operate virtually emission free. Some even reduce sulfur emissions
that would have occurred from natural venting if these sites had been left untapped. A few do
produce some silica and sulfur dioxide, both of which are largely removed from the vapors and
either returned to the hydrothermal well or processed and sold for industrial uses.
3. Almost 100% of the visible, airborne effluent seen rising from geothermal plants is water vapor.
4. Geothermal energy has the smallest land use of any major power generation technology. A
typical geothermal facility occupies about the same space as a gas fired plant of the same
capacity. But the geothermal facility does not require miles of buried pipeline to carry fuel to
keep it running. Geothermal has minimal land and freshwater requirements. Geothermal plants
use 3.5 square kilometers per gig watt of electrical production (not capacity) versus 32 and 12
square kilometers for coal facilities and wind farms respectively. They use 20 liters of freshwater
per MW-h versus over 1000 liters per MW-h for nuclear, coal, or oil.
5. Geothermal facilities also have no coal or nuclear fuel to mine and transport, no radioactive
wastes or ash wastes to deal with, and no emissions of carbon dioxide, particulates, or other
combustion byproducts.
6. Geothermal power plants do not burn fuel to generate electricity, so their emission levels are
very low. They release less than 1% of the carbon dioxide emissions of a fossil fuel plant.
Geothermal plants use scrubber systems to clean the air of hydrogen sulfide that is naturally
found in the steam and hot water. Geothermal plants emit 97% less acid rain-causing sulfur
compounds than are emitted by fossil fuel plants. After the steam and water from a geothermal
Reservoir have been used, they are injected back into the Earth.
In other words, geothermal energy is one resource that can be universally celebrated for its contribution
to a cleaner, safer environment.
Reliability:
Once in operation, geothermal plants may be the most reliable of all energy production methods. Since
they are fundamentally simpler than most other power systems, there is less to go wrong.
Other factors that contribute to the impressive reliability of geothermal systems:
1. They require no purchase or transport of fuel. They require no waste disposal.
2. They can be used either as base load systems or swing with demand.
3. They have no intermittency or dispatch ability problems.
It’s noteworthy that every geothermal energy facility that has been built in the last 100 years is still in
production.
Cost:
In geologically suitable areas, geothermal energy is currently cost competitive with conventional
generation methods. Geothermal power plants do have high initial costs to drill and construct new
facilities. But relatively high construction costs are paid back because there are no fuel costs. As shown
in this Department of Energy Geothermal Report geothermal power costs are currently competitive with
coal power plants, making them among the cheapest power providers around and getting cheaper with
every project. But current cost figures are based on projects that are located at the best geothermal
sites.
The key to economically exploiting geothermal resources using current technologies is finding the best
producing hydrothermal wells.
Sustainability:
Geothermal resources may outlast the sun. There is enough thermal nuclear energy in our Earth to fuel
the engines of civilization for billions of years.
Beneath our feet we have more usable geothermal energy resources than oil, coal, gas, and mineable
nuclear fuels combined.
Geothermal Resource Council Data shown below compares global continental (not including deep ocean
resources) geothermal energy resources to global oil reserves.
Units: Billions of barrels of oil equivalent
Crustal Heat-----------------79,000,000
Thermal Aquifers--------------------130
Oil Reserves-----------------------5,300
*Annual Global Energy Consumption----70
A Stanford University Wind Power Study shows total annual global Btu consumption from all sources of
49 to 70 billion barrels of oil equivalent.
Thermal aquifers are the primary source of geothermal electrical power using current technology. Those
130 billion barrels of oil equivalent masks the fact that geothermal resources are a form of nuclear
power and can continue to provide those energy supplies year after year, decade after decade, century
after century.
Fossil fuel reserves, on the other hand, may be gone in a few decades.
Energy from thermal aquifers (hydrothermal) has a couple of problems, though.
Conclusion:
I am not talking about Star Wars gizmos. All that’s needed is a hole, a really deep hole about 4 miles
down, water, and generating equipment. Drill a couple of holes, fracture the rock between the holes,
pour water down one hole, and harvest steam from the other to drive turbines for electrical generators.
That’s it. The technology already works; it’s only a matter of improving costs to the extent that deep
geothermal energy becomes competitive with existing power generation technologies. We are close to
doing just that. And when we do, we can move forward with the very reasonable expectation that
geothermal energy resources can permanently and economically provide a million times more usable
energy than we consume.