Geothermal Energy Systems Overview
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Questions and Answers

What does the term 'geothermal' primarily refer to?

  • Energy derived from the Earth’s heat (correct)
  • Energy sourced from tidal movements
  • Energy generated from solar radiation
  • Energy derived from wind

What is the typical temperature rise of rock for every 100 m below the Earth's surface?

  • 3ºC (correct)
  • 1ºC
  • 4ºC
  • 2ºC

Which of the following is NOT a method of geothermal power generation?

  • Binary cycle power generation
  • Direct steam power generation
  • Combined solar power generation (correct)
  • Flash-steam power generation

What is a primary advantage of geothermal energy?

<p>It is renewable and reliable (C)</p> Signup and view all the answers

Which application is NOT a typical use of geothermal resources?

<p>Electric vehicle charging (A)</p> Signup and view all the answers

What can the temperature of hot water in geothermal systems exceed?

<p>150ºC (C)</p> Signup and view all the answers

What is the general range of current prices for geothermal energy per kWh?

<p>5-8 cents (A)</p> Signup and view all the answers

Which term describes the process of generating power by using heat from geothermal steam?

<p>Flashing process (D)</p> Signup and view all the answers

What is the primary purpose of the turbine in the steam power cycle?

<p>To convert thermal energy into mechanical work (D)</p> Signup and view all the answers

What does the term 'double-flash' refer to in a double-flash steam power plant?

<p>Flashing the remaining hot fluid to generate additional steam (A)</p> Signup and view all the answers

In the given process, what condition does 'x1 = 0' indicate?

<p>The steam is fully condensed (A)</p> Signup and view all the answers

How does double-flash steam production compare to single-flash steam production?

<p>It produces 10-20% more power (C)</p> Signup and view all the answers

Which condition must be true during the flashing process?

<p>Pressure and temperature must decrease in sequence (A)</p> Signup and view all the answers

What does the notation 'm1 = m2' signify in the flashing process?

<p>The mass flow rates are equal at different stages (C)</p> Signup and view all the answers

In the context of steam properties, what does '0 < x2 < 1' imply?

<p>The steam is a mixture of liquid and vapor (B)</p> Signup and view all the answers

What is the significance of 'ex1 = ex2 + exdest' in the flashing process?

<p>It balances the energy between two states (C)</p> Signup and view all the answers

What is a defining characteristic of a single-flash steam power plant?

<p>It is the most common type of geothermal power plant. (C), It produces electricity from high-pressure steam by flashing liquid. (D)</p> Signup and view all the answers

In the energy balance equations, what does MBE represent?

<p>Mass Balance Equation (C)</p> Signup and view all the answers

For energy efficiency calculation without re-injection, which equation is used?

<p>$ rac{ar{W}_T}{ar{m}_1 h_1}$ (A)</p> Signup and view all the answers

What happens to the steam in a flash-steam power plant?

<p>It is produced by reducing the pressure of the liquid. (D)</p> Signup and view all the answers

Which of the following is true about the energy balance equations for the turbine?

<p>The energy input equals the energy output plus work done. (D)</p> Signup and view all the answers

What is the primary function of the separator in a flash-steam power plant?

<p>To separate steam from the remaining liquid. (C)</p> Signup and view all the answers

What determines the efficiency of a geothermal power plant in relation to reinjection?

<p>The temperature and pressure of the entering fluid. (C)</p> Signup and view all the answers

What does the ExBE in the energy balance equations signify?

<p>Exergy Balance Equation (C)</p> Signup and view all the answers

Which equation is critical for analyzing the condenser's performance in a steam power plant?

<p>$ar{m}_5 h_5 = ar{m}<em>6 h_6 + ar{Q}</em>{con}$ (C)</p> Signup and view all the answers

In the mass balance equation for the condenser, which mass flow rates equal each other?

<p>ṁ 4 and ṁ 5 (B)</p> Signup and view all the answers

What does the energy balance equation (EBE) for the turbine express?

<p>The relationship between mass flow rates and specific enthalpy (B)</p> Signup and view all the answers

Which of the following represents the mass balance equation for Separator 1?

<p>ṁ 2 = ṁ 3 + ṁ 6 (C)</p> Signup and view all the answers

Which of the following equations represents the exergy balance equation (ExBE) for the condenser?

<p>ṁ 4 ex 4 + ṁ 8 ex 8 = ṁ 5 ex 5 + ṁ 9 ex 9 + Eẋ dest,c (D)</p> Signup and view all the answers

In the mass balance equation for the circulation pump, what does ṁ 1 equal?

<p>ṁ 2 (B)</p> Signup and view all the answers

What is the primary purpose of the EnBE (Energy Balance Equation) in the context of the turbine?

<p>To determine work output from the turbine (C)</p> Signup and view all the answers

In the equation for efficiency without re-injection, what factor impacts the total work output?

<p>ṁ 10 h10 (D)</p> Signup and view all the answers

What does the term Ẇ CP represent in the energy balance equation for the circulation pump?

<p>Input work required by the circulation pump (C)</p> Signup and view all the answers

In the energy balance equation for the production pump, what is included along with mass flow rate and specific enthalpy?

<p>Work input to the production pump (A)</p> Signup and view all the answers

Which energy balance equation correctly describes the interaction in Flash Chamber 2?

<p>ṁ 6 h6 = ṁ 7 h7 + Q̇ con (D)</p> Signup and view all the answers

Which term in the energy balance equation for the condenser indicates heat loss?

<p>Q̇ con (D)</p> Signup and view all the answers

What is indicated by the term EnBE in the mass and energy balance equations?

<p>Entropy balance equation (D)</p> Signup and view all the answers

What parameter is represented by ṁ 3 + ṁ 8 in the turbine's mass balance equation?

<p>The total input mass flow (C)</p> Signup and view all the answers

In the mass balance equation for the production pump, what does ṁ 6 represent?

<p>The outlet mass flow rate (B)</p> Signup and view all the answers

What condition must be met for the Exhaust Energy Balance Equation (ExBE) to be valid?

<p>Net energy in must equal net energy out (D)</p> Signup and view all the answers

What does Eẋ dest,Sep2 in the ExBE for Separator 2 represent?

<p>The energy losses during the separation process (C)</p> Signup and view all the answers

Which of the following describes the impact of re-injection on energy efficiency?

<p>It increases the total mass flow rate into the system. (C)</p> Signup and view all the answers

What does the term Ṡ gen,FC in the Energy Balance Equation for Flash Chamber indicate?

<p>Entropy generation within the flash chamber (A)</p> Signup and view all the answers

What does the mass flow balance equation state in a heat exchanger?

<p>ṁ 2 = ṁ 3 (B)</p> Signup and view all the answers

Which equation represents the energy balance for the heat exchanger?

<p>ṁ 2 h2 + ṁ 6 h6 = ṁ 3 h3 + ṁ 7 h7 (A)</p> Signup and view all the answers

In the context of energy efficiencies, what does the symbol ηele represent?

<p>Useful work produced (B)</p> Signup and view all the answers

What is the role of a separator in a binary geothermal power plant?

<p>To separate steam from liquid (C)</p> Signup and view all the answers

Which efficiency measurement does not involve re-injection?

<p>Work output minus losses over energy input (C)</p> Signup and view all the answers

What is one main benefit of geothermal or ground source heat pump systems?

<p>They provide consistent heating and cooling. (D)</p> Signup and view all the answers

Which equation is used for the exergy balance in a heat exchanger?

<p>ṁ 2 ex 2 + ṁ 6 ex 6 = ṁ 3 ex 3 + ṁ 7 ex 7 + Eẋ d,Sep (A)</p> Signup and view all the answers

How does the presence of reinjection impact energy efficiency in geothermal systems?

<p>Enhances overall system efficiency (B)</p> Signup and view all the answers

In terms of geothermal energy use, what is a primary application of ground source heat pumps?

<p>Heating or cooling buildings (B)</p> Signup and view all the answers

Which parameter is essential for determining the efficiency of a geothermal power plant?

<p>Temperature difference between input and output (D)</p> Signup and view all the answers

Flashcards

Geothermal Energy

Energy derived from the Earth's internal heat.

Geothermal Resources

Sources of geothermal energy, like hot water and steam.

Flash Steam Power Generation

A geothermal method to generate power by flashing high-temperature geothermal water.

Direct Steam Power Generation

A method of using geothermal steam directly to turn turbines and generate electricity.

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Geothermal Heat Pumps

Systems harnessing geothermal energy for space heating and cooling.

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Geothermal Maps

Maps indicating areas with high geothermal resource potential.

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Geothermal District Heating

Using geothermal energy to heat multiple buildings/areas.

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Binary Cycle Power Generation

A geothermal power plant type that uses working fluid to drive a turbine.

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Steam Power Plant Equation

The equation that describes the power output of a steam turbine, considering the mass flow rate and enthalpy of steam entering and leaving the turbine.

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Flashing Process

A process where high-pressure, high-temperature water suddenly drops in pressure, causing some of the liquid to vaporize into steam.

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Enthalpy (h)

The total energy content of a substance, including internal energy, pressure, and volume.

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Double-Flash Steam Power Plant

A geothermal power plant design that utilizes two flashing stages to produce steam at different pressures, resulting in higher power output compared to single-flash systems.

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Separator

A device used in a double-flash power plant to separate the steam produced from the flashed water.

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Primary Steam

The steam generated in the first flashing stage of a double-flash power plant.

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Double Flash Advantages

Double-flash power plants offer higher power output compared to single-flash systems, typically increasing power generation by 10-20%.

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Flashing Stage

A specific point within a geothermal power plant where flashing occurs, leading to steam generation.

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Dry Steam Power Plant

A geothermal power plant that uses naturally occurring steam to drive a turbine and generate electricity. This type of plant doesn't require further processing or flashing.

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Flash Steam Power Plant

A geothermal power plant where high-pressure, hot water is suddenly reduced in pressure, causing it to flash into steam. The steam then drives a turbine to generate electricity.

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Single-Flash Steam Plant

A type of Flash Steam Power Plant where the geothermal liquid is flashed only once. This single flash creates steam that drives the turbine.

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Flash Chamber

A component in a Flash Steam Power Plant where high-pressure hot water is rapidly depressurized, causing it to flash into steam.

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Turbine

A device in a geothermal power plant that is rotated by the force of steam, converting its energy into mechanical energy.

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Condenser

A component in a geothermal power plant that cools the steam exhausted from the turbine, converting it back into water.

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Reinjection Well

A well used to pump the cooled water back into the geothermal reservoir after it has been used in the power plant.

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Production Well

A well that extracts hot water or steam from the geothermal reservoir to be used in the power plant.

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Energy Efficiency

The ratio of the useful energy output from the power plant to the total energy input. It measures how effectively the plant converts geothermal energy into electricity.

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Mass Balance Equation (MBE)

An equation that shows the conservation of mass in a system, meaning the total mass entering equals the total mass leaving.

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Energy Balance Equation (EBE)

An equation that shows the conservation of energy in a system, meaning the total energy entering equals the total energy leaving.

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Entropy Balance Equation (EnBE)

An equation that shows the increase in entropy within a system due to irreversible processes, like friction and heat transfer.

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Exergy Balance Equation (ExBE)

An equation that shows the exergy loss due to irreversibilities and the production of useful work in a system.

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Work Done by Turbine (ẆT)

The power generated by a turbine as a result of the steam expanding and driving the turbine blades.

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Work Done by Pump (ẆPP)

The power required to move the working fluid (water) from a low-pressure state to a high-pressure state.

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Heat Transfer (Q̇)

The rate of heat transfer between two bodies at different temperatures. In this case, it's the heat absorbed by the water in the condenser.

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Entropy Generation (Ṡgen)

The increase in entropy within a system due to irreversible processes, like friction and heat transfer. This represents energy loss in the system.

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Flashing

The rapid vaporization of liquid into steam when pressure drops below its saturation pressure.

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Re-injection

The practice of injecting spent geothermal fluid back into the subsurface, maintaining reservoir pressure and minimizing environmental impact.

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Flashing (in geothermal power)

The rapid conversion of high-pressure, high-temperature liquid water into steam by reducing pressure.

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Binary Cycle Power Plant

A geothermal power plant that utilizes a working fluid (like isobutane) to transfer heat from geothermal water to turbines.

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Study Notes

Geothermal Energy Systems Overview

  • Geothermal energy represents Earth's heat, a renewable, reliable, and efficient energy source.
  • Current prices range from 5-8 cents/kWh.
  • Temperature increases approximately 3°C for every 100 meters below the ground's surface.
  • Hot water or steam can be generated deep underground when water comes into contact with heated rock.
  • Temperatures exceeding 150°C are typical and facilitate various applications.

Geothermal Resources and Applications

  • Geothermal resources are categorized by reservoir temperature.
  • High-temperature (>220°C) reservoirs are suitable for power generation.
  • Intermediate (100-220°C) temperatures are used for power generation and direct use applications.
  • Low-temperature (50-150°C) reservoirs are ideal for direct use applications (heating, industrial processes).
  • Technologies employed for geothermal power generation include flash steam, combined flash/binary cycles, binary cycles, and direct use.

Geothermal Power Generation

  • Common methods of geothermal power generation include direct steam, flash steam, binary cycle, flash binary, and combined geothermal power generation.
  • Radioactive decay in the Earth's mantle produces heat.
  • Cool water is injected into the ground and heated.
  • Hot water is extracted.
  • Steam is produced and used to drive turbines and generate electricity.

Geothermal Maps of Canada

  • Canada has significant geothermal resource potential, though less utilized.
  • Key resource areas are shown on maps.
  • Geothermal resource potentials are assessed based on heat flow rates.
  • Assessments map hot dry rock and high heatflow areas.

Geothermal Power Plants

  • Different types of geothermal power plants exist, including dry steam, flash steam, and binary cycle plants.

Geothermal Resources and Applications (Specific Examples)

  • Geothermal resources are used in various applications: district heating, geothermal heat pumps, and industrial processes.
  • Some countries lead in geothermal power production: the US, Indonesia, the Philippines.

Geothermal Maps (Specific Examples)

  • Maps highlight areas with high geothermal potential (areas with heat flow).
  • Examples of geothermal field locations (e.g., Western Canada, etc.) are located on diagrams and maps.

Geothermal Data Summary (Specific Examples)

  • The United States holds the most electricity production from geothermal resources.
  • Significant geothermal-related projects are present in the US, with capacity measured in MW.

Geothermal Energy Technologies (Specific Examples)

  • A schematic diagram shows how systems (e.g., Tuzla geothermal power plant) operate
  • Diagrams illustrate components of different geothermal systems.

Additional Notes on Geothermal Power Production

  • The diagram for a dry steam plant shows turbines, steam generation and use, and a condenser system.
  • The diagram for a flash steam plant highlights steam flashing and associated components.
  • The diagram for a binary plant demonstrates how a working fluid operates in a heat exchanger. Multiple plants, both integrated and independent, are shown for various types of geothermal systems.
  • Diagrams show the processes for combined geothermal power plants.

Closing Remarks

  • Geothermal energy is a sustainable and environmentally friendly energy source.
  • Multiple operating system options exist.
  • Geothermal systems offer cost-effective power production.
  • Applications exist for heating, cooling, power generation, district heating, drying and integrated hydrogen production systems.
  • Ground-source heat pumps are widespread.

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Geothermal Energy Systems (PDF)

Description

This quiz explores the principles of geothermal energy, including its sources, temperature classifications, and applications. It covers how geothermal systems harness Earth's heat for power generation and direct use, as well as the technologies involved. Test your knowledge on this renewable energy resource and its practical uses.

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