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Geothermal Power Plant

July 11, 2020

The geothermal plant is the station where we use (geothermal energy) hydrothermal resources to produce electricity and this plant requires high temperature (300ᵒF to 700ᵒF).

Geo (earth) and thermal (heat) mean 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 that 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.

Liquid is injected into a U-shaped tube where it’s heated up with the heat of the subsoil; then it rises to the surface.

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.

A borehole (production) is used to recover the water presented in this soil and it inject the energy of this water into another liquid.

This is sent to a remote heating network where the temperature is 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 meters 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;

Thus, the contact with rocks water will be heated; and then it’s pumped to the surface where it’s used.

History of geothermal energy

Bathing, cleaning and cooking were the first uses of geothermal energy in North American

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 at Portland, the first ground-source geothermal heat pump installed in commonwealth building.

Operating pacific gas and electric were the first large scale of geothermal energy in 1960 at San Francisco

The geothermal heat pumps were started by 1980 to gain popularity to reduce heating and cooling costs.

The geothermal power was used in 2009 to supply less than 1% of the world’s energy;

It was also used 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; the axis of the turbine connected to the rotor of the alternator which rotates to transfer the mechanical energy into alternating electric current.

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.

And we use the cooling tower to cool water produced from the 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.

Then a vaporized steam is used to drive the turbine; after that, it’s condensed again to liquid to re-begin the cycle.

These plants are the oldest. The first plant came into existence in 1904 at Larderello, Italy;

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.

After that, the water and the condensed steam is reinjected into the reservoir to be used again as a sustainable resource. This plant needs higher costs due to the more complex parts needed.

The first came into being in 1958 at New Zealand.

3- Binary cycle plants:

Binary plants instead operate with 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.

This turns the turbine to produce electricity

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.

Uses of geothermal energy

We use geothermal energy in numerous applications. For instances:

  • It generates hot water and steam 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.
  • 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 a 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 a handful of areas around the world able to benefit from the placement of highly efficient geothermal plants.