Notes on Geothermal Energy and Hydropower (Outline for Exam)
GEOTHERMAL ENERGY
ENERGY RESOURCES overview: energy resources are all forms of fuels used for heating, generation of electrical energy, or for other energy conversion processes. They are categorized into two main types: Geothermal energy and Hydropower energy.
ETYMOLOGY of geothermal: from the Greek words geo (earth) and therme (heat).
WHY geothermal is renewable: heat is continuously produced inside the Earth, making geothermal energy a renewable source.
PRIMARY USES of geothermal energy: bathing, heating buildings, and generating electricity.
SOURCE of geothermal energy inside the Earth: the slow decay of radioactive particles in the Earth's core (a process that happens in all rocks) produces geothermal energy.
TYPES OF GEOTHERMAL POWER PLANTS (3 main types):
DRY STEAM PLANTS
FLASH STEAM PLANTS
BINARY CYCLE PLANT
HOW GEOTHERMAL POWER PLANTS WORK (overview):
In a dry steam plant, underground steam is brought to the surface, directed to a turbine which spins a generator to produce electricity.
In a flash steam plant, high-temperature geothermal water (above a certain temperature) is brought to the surface; a drop in pressure causes some water to flash into steam which then drives a turbine connected to a generator.
In a binary cycle plant, a closed-loop system uses a secondary, low-boiling-point working fluid to capture heat from the geothermal resource via a heat exchanger and drive a turbine, instead of using steam directly from the reservoir.
TYPES OF GEOTHERMAL POWER PLANT details:
DRY STEAM PLANTS
Steam from reservoir → turbine → generator → electricity.
Production well brings steam to surface; injection well returns condensate/fluids back.
FLASH STEAM PLANTS
Hot geothermal water is flashed to steam when pressure drops; steam drives turbine → generator; residual water re-injected.
BINARY CYCLE PLANTS
Heat exchanger transfers heat from geothermal water to a secondary working fluid with a lower boiling point; the secondary fluid vapor drives a turbine → generator.
ADDITIONAL GEOTHERMAL POWER PLANT DIAGRAM COMPONENTS (for context):
Rock layers, production well, injection well, turbines, generators, heat exchangers, flash tanks, and binary cycle heat exchangers.
SOURCES OF GEOTHERMAL ENERGY (4 main categories): 1) HYDROTHERMAL SYSTEMS – hot water or steam near the Earth’s surface; most accessible and well-known.
Examples: hot springs, geysers, fumaroles.
2) MAGMA AND HOT DRY ROCK (HDR) – magma heat or proximity to magma heats rock; hot dry rock formations can be heated by proximity to magma or radioactive decay. Access via drilling; water can be injected to create steam for power generation (Enhanced Geothermal Systems, EGS).Key terms: MAGMA, HOT DRY ROCKS, Enhanced Geothermal Systems (EGS).
3) OLD MINESHAFTS AND CANALS – existing infrastructure repurposed to extract geothermal heat for direct heating or shallow geothermal applications.
4) TECTONIC PLATE BOUNDARIES – reservoirs are prevalent along plate boundaries due to volcanic and seismic activity.
EXAMPLES / IMPLEMENTATIONS:
Leyte Geothermal Plant, Philippines (illustrative example of a geothermal power project).
Netherlands and Turkey use geothermal energy for vegetables and flowers (aquaculture and greenhouse applications discussed later).
USES OF GEOTHERMAL ENERGY – broad applications beyond electricity generation:
HEATING AND COOLING OF BUILDINGS (Geothermal heat pumps)
Principle: uses the relatively constant near-surface earth temperature to heat in winter and cool in summer.
Applications: homes, schools, malls, office buildings; district heating/cooling systems in some cities.
Benefits: reduces heating/cooling bills by up to ; year-round operation with minimal maintenance; reduces greenhouse gas emissions.
AGRICULTURE (greenhouses)
Geothermal heat keeps a warm, stable environment for crops; hot water from wells or surface heat exchangers heats radiators or underfloor systems in greenhouses.
Benefits: increases plant growth and yield; saves fuel for heating; enables farming in cold climates.
Global examples: Netherlands and Turkey use geothermal for vegetables and flowers.
AQUACULTURE
Geothermal water warms fish tanks or ponds to species-specific temperatures (tilapia, catfish, shrimp, etc.).
Methods: direct use (if temperature/minerals allow) or heat exchangers to transfer heat to tank water.
Benefits: stable year-round temperatures; faster fish growth; reduces disease caused by cold water.
Examples: exploratory studies in Southern Negros (Philippines) for small-scale fish farms; New Zealand uses geothermal heat for trout hatcheries.
INDUSTRIAL APPLICATIONS
Geothermal heat used in dehydrators, ovens, dryers, sterilizers to process food.
Delivery: steam or hot water from reservoirs piped directly or via heat exchangers.
Benefits: cuts fuel and electricity costs; eco-friendly option for heat-intensive industries; reduces carbon footprint.
Examples of processing uses include drying crops (fruits, herbs, grains), pasteurizing milk, sterilizing containers or packaging, and other food processing tasks.
SIGNIFICANCE AND IMPLICATIONS (summary):
Geothermal energy offers a diverse set of applications beyond electricity, enabling direct heating/cooling, agricultural optimization, aquaculture, and industrial processing.
It provides near-constant, low-emission energy with potential cost savings and resilience benefits (e.g., year-round operation, reduced reliance on fossil fuels).
Environmental and logistical considerations include resource temperature, location relative to plate tectonics, and the need for drilling or repurposing infrastructure.
HYDROPWR/HYDROELECTRICITY
INTRODUCTION AND DEFINITION
Hydropower (also known as hydroelectric power) is the process of generating electricity using the energy of moving water.
It is a renewable energy source that harnesses the natural flow of water, typically from rivers or reservoirs, to drive turbines connected to generators.
The kinetic energy of flowing water spins turbines, converting mechanical energy into electricity.
Hydropower is a significant contributor to many countries’ energy grids and is considered a clean energy source.
TYPES OF HYDROPOWER/HYDROELECTRICITY FACILITIES: 1) IMPOUNDMENT FACILITIES (DAMS)
A dam creates a large reservoir of water.
Electricity is generated when water passes through turbines in the dam.
2) PUMPED STORAGE FACILITIESTwo reservoirs are used: an upper and a lower reservoir.
Water is pumped from the lower to the upper reservoir when excess electricity is available, storing energy for later release.
3) RUN-OF-RIVER FACILITIESRely on natural water flow rates, diverting a portion of river water through turbines.
Often operate with little to no reservoir; can be less environmentally disruptive but may depend more on seasonal flow.
CORE COMPONENTS OF HYDRO PLANTS (conceptual):
Reservoir or channel, dam or diversion structure, intake, penstock or tunnel, turbine, generator, transformer, power house, discharge (tailrace).
SOURCES OF HYDRO POWER (where the water comes from):
RIVERS AND STREAMS: flowing water is the most common source; dams/reservoirs regulate flow.
RAINFALL: replenishes rivers, lakes, and reservoirs that drive plants.
LAKES AND RESERVOIRS: stored water behind dams can be released to meet demand.
TIDAL ENERGY: some plants use tidal movements in oceans/seas to generate power.
SNOWMELT: melting snow from mountains contributes to river flow, especially in warmer seasons.
USES OF HYDROPOWER/HYDROELECTRICITY
ELECTRICITY GENERATION
Water flows through turbines → spins turbines → activates generators → electricity.
Benefits: renewable and clean energy; reduces dependence on fossil fuels; provides reliable base-load power.
IRRIGATION SUPPORT
Dams store and release water for farmland; reservoirs supply irrigation canals; dams support agricultural fields.
Benefits: boosts crop production; reduces dependence on unpredictable rainfall; supports food security.
WATER SUPPLY & DRINKING WATER SYSTEMS
Reservoirs store freshwater; treated and supplied to households and industries.
Benefits: provides clean drinking water; ensures year-round availability; supports urban and industrial growth.
FLOOD CONTROL & WATER MANAGEMENT
Dams regulate river flow by holding excess water during heavy rains and releasing it gradually to prevent flooding.
Benefits: protects communities; preserves ecosystems by maintaining steady water flow; prevents property and crop damage.
RECREATIONAL & ECONOMIC ACTIVITIES
Reservoirs and dam sites support boating, fishing, tourism, and related local revenue.
SIGNIFICANCE (summary):
Hydropower provides a versatile, scalable, and often reliable source of renewable electricity with broad societal benefits including irrigation, water security, flood control, and recreation.
Trade-offs include environmental and social impacts of damming rivers and altering ecosystems; careful site planning and management are essential.
CONNECTIONS TO GEOTHERMAL ENERGY:
Both are renewable energy sources that reduce fossil fuel use and greenhouse gas emissions.
They differ in resource location, technological implementation, and primary applications (electricity generation with ancillary uses for hydro vs. heating, direct use, and electricity generation for geothermal).
PRACTICAL TAKEAWAYS (for exam):
Geothermal energy uses Earth’s internal heat; three main plant types are dry steam, flash steam, and binary cycle.
Geothermal sources include hydrothermal systems, magma/hot dry rock (HDR/EGS), old mineshafts/canals, and tectonic plate boundaries.
Hydropower utilizes impoundment, pumped storage, and run-of-river configurations; sources include rivers, rainfall, lakes/reservoirs, tides, and snowmelt.
Common uses beyond electricity for geothermal: heating/cooling with geothermal heat pumps, greenhouse heating, aquaculture, and industrial processing; beyond electricity for hydropower: irrigation, municipal water supply, flood control, and recreation.
Key numerical references from the transcript to remember:
Hot geothermal water threshold for flash steam processes:
Heating/cooling cost savings with geothermal heat pumps: up to reduction in bills.
Temperature and process notes: dry steam, flash steam, and binary cycle distinctions; closed-loop binary systems use a secondary working fluid rather than direct steam.
Geographic and tectonic context: geothermal reservoirs commonly occur near plate boundaries due to volcanic and seismic activity.
Real-world example: Leyte Geothermal Plant, Philippines (illustrative case).