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Geothermal power plant (Sources, History, Diagram and types)

May 12, 2018
Geothermal power plant (Sources, History, Diagram and types)

Geothermal power plant

It’s not the first time to hear about geothermal power plant as we illustrate in types of power plants that geothermal plant is the station where we use (geothermal energy) hydrothermal resources to produce electricity and this plant requires high temperature (300ᵒF to 700ᵒF).

Geothermal power plant

Geo (earth) and thermal (heat) which means that we use drilling wells to pipe hot water or steam from the earth to pass through the turbine which turns to produce the electric power.

Sources of geothermal energy:

Geothermal energy is a relatively clean inexhaustible source which doesn’t depend on any external conditions (supply, weather, etc.). So this energy can be:

1- Shallow geothermal energy:

It’s the energy from the few meters below the ground’s surface with a constant temperature all the year; we use one or more vertical probe at a depth of about 120-150 meters to draw this energy from the subsoil where the temperature is about 12ᵒ-15ᵒC.

And we inject the liquid into a U-shaped tube where it’s heated up with the heat of the subsoil; then it’s risen to the surface where it’s used.

Sources of geothermal energy

2- Deep geothermal energy:

Exploitation in this form is a technique of recovery of this energy which produces from a depth  1_4 KM where the water temperature reaches 40ᵒ to 130ᵒ C.

We use a borehole (production) to recover the water presented in this soil to inject the energy of this water into another liquid to a remote heating network where the temperature kept sufficiently for producing electricity.  After that, we re-injected the water into the basement into a lake.

3- Geothermal energy of great depth:

The temperature of the rocks between 4000_6000 meter reaches 200ᵒC which allows the recovery of this energy to make it possible to produce heat and electricity. We use drills to reach the rocks.

then we carry out stimulation with water under high pressure to improve the rocks’ permeability.

after that, we inject water via a borehole into fissures; whereby the contact with rocks water will be heated; then it’s pumped to the surface where it’s used.

History of geothermal energy:

It’s very important to know when we discover the energy we use and how it’s improved to withstand our requirements; so it’s the time to know everything about the geothermal energy.

  • There are some rumors from more than 20000 years ago that the first use of the geothermal energy occurred in North America when people used water from hot springs for bathing; cleaning, and cooking.
  • But the first use of geothermal energy in the industry began in the late 18th century near Pisa where they used steam from natural vents to extract boric acid from the hot pools.
  • And Piero Ginori invented the first geothermal power plant in 1904 and he used to generate a power capable to switch on  5 light bulbs. In 1922 the USA started its first geothermal plant with a capacity of 250 KW. And in 1946 in Portland the first ground source geothermal heat pump installed in commonwealth building.
  • In 1960 in San Francisco the first large-scale used for operating pacific (gas and electric) and it produces 11 MW.
  • The geothermal heat pumps started by 1980 to gain popularity to reduce heating and cooling costs.
  • We use the geothermal power in 2009 to supply less than 1% of the world’s energy; we also use it in 2013  to install capacity of 3400 MW in the USA; today about 20 countries depend on it for producing power, and it’s probably to supply 10-20% of the world’s energy by 2050.

I think it isn’t a big history, but it means that using geothermal energy and geothermal power plant isn’t so hard or difficult like other sources of energy.

Geothermal power plant diagram:

The layout of the geothermal power plant illustrates the whole process from heated water and steam in the depths until electricity powering our homes.

The steam was extracted from the different layers of the earth and channeled into steam-pipelines to be forward to the turbines.

In the turbine, the kinetic energy of the steam transformed into a rotational mechanical power; and as we know the axis of the turbine connected to the rotor of the alternator which rotates to transfer the mechanical energy into alternating electric current.

Geothermal power plant diagram

After that, we use transformers to raise the voltage of the electric power to transfer it to the distribution networks. And the steam exits from the turbine returns to the condenser in the same time; the gases that don’t condense dispersed into the atmosphere.
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And we use the cooling tower to cool water produced from steam condensation process; the condensed water then dispersed into the deep rock layers by a re-injecting.

Types of geothermal power plants:

Depending on how much geothermal energy we have and how hot is the source we use; we can classify the geothermal power plant into three main categories which are:

1- Dry steam plants:

In dry plants; the geothermal fluid passes through a heat exchanger where it’s transferred to another fluid circulating in a closed system and vaporized to steam used to drive the turbine; after that, it’s condensed again to liquid to re_begain the cycle.

Dry steam plants

These plants are the oldest types as the first plant was constructed in 1904 in Larderello, Italy; and they are only used where the temperature underground is higher because they require the highest temperature.

but they also require the least fluid flow and they virtually eliminate pollution.

2- Flash cycle steam plants:

Flash plants are the most common types and they use geothermal reservoirs of water with a temperature higher than 360ᵒF to flow up through wells in the ground under its pressure.

When the very hot water flows upward its pressure decreases and it boils into the steam that used to power the turbine and the generator to produce the electric power.

Flash cycle steam plants

After that, the water and the condensed steam reinjected into the reservoir to be used again as a sustainable resource. This plant needs higher costs due to the more complex parts needed. And the first constructed plant was built in 1958 in New Zealand.

3- Binary cycle plants:

Binary plants instead operate with a low-temperature water of about 225-360ᵒF.

this plant uses the heat from the water to boil the used working fluid which vaporized in the heat changer to be used to turn the turbine and produce electricity.

Binary cycle plants

Then the water is injected back into the ground; we try to keep the water and the fluid separated during this process so there is little or no air emissions. And the first used plant constructed in 1967 in Russia.

What is geothermal energy used for:

We use geothermal energy  in numerous applications as:

  • In heating systems to provide hot water or steam that used for heating and cooling of private and commercial buildings (homes; offices, and shops).
  • With greenhouses as it has an industrial potential to grow the plants; on fish farms to heat water, and for drying crops.
  • We can also use this energy in fish farms to warm water to spur the growth of animals as alligators; tropical fish; shellfish; catfish; amphibians, or trout.

What is geothermal energy used for

  • And in industrial applications; as it uses vary from drying vegetables; drying fruits; drying wool, and drying wood to extract silver and gold from ore.
  • The cold countries use geothermal energy in the winter to heat sidewalks and roads to prevent freezing.
  • We can also use it in fermentation; distillation; balenological utilization; desalination that depends on the sources’ temperature.

Advantages of geothermal energy:

Geothermal energy is one of the most advantageous sources of energy around the world

  • It’s economically-friendly as it only gives off few amounts of greenhouse gasses because it doesn’t involve any combustion.
  • Geothermal is a renewable power source which means it’s available 24/7 despite weather changing.
  • It’s widely available around the world.
  • Maintenance required and costs are low.
  • We don’t need fossil fuels to operate the plant so it minimizes the dependence of fossil fuel sources.
  • Geothermal systems use the same principle as a refrigerator, it operates quietly without any noise.
  • Also, geothermal heat pumps are high efficiency as they use 25% to 50% electric power for heating and cooling.

Disadvantages of geothermal energy:

  • Geothermal plants can cause earthquakes.
  • The geothermal power becomes only sustainable when we properly manage the reservoirs.
  • And the initial costs required for construction are high.
  • Sometimes geothermal energy releases some harmful and poisonous gases escaping through holes drilled during construction.
  • The construction of the plant may affect the stability of the land around it.
  • There are only handful areas around the world able to benefit from the placement of highly efficient geothermal plants.