Q.f - Geothermal Energy Applications

f 6 Marks

Discuss about application of geothermal energy.

Answer: Applications of Geothermal Energy

1. Introduction

Geothermal Energy is thermal energy generated and stored within the Earth, originating from the planet's formation (~20%) and ongoing radioactive decay of minerals (~80%). It is a reliable, renewable, and largely untapped energy source available 24/7 regardless of weather conditions.

The Earth's interior temperature increases with depth at approximately 25-30°C per kilometer. At depths of 3-5 km, temperatures can reach 150-200°C, sufficient for power generation. Geothermal resources range from shallow ground (10-16°C year-round) to deep hot water/steam reservoirs (>200°C).

Global Capacity (2023): ~16 GW installed power generation capacity | Top countries: USA (3.7 GW), Indonesia (2.4 GW), Philippines (1.9 GW), Turkey, New Zealand

2. Major Applications of Geothermal Energy

A. Electricity Generation

Geothermal power plants convert underground heat into electricity using three main technologies:

Plant Type	Resource Temperature	Working Principle	Efficiency
Dry Steam Plants	>235°C	Steam directly from wells drives turbines	Oldest technology, high efficiency where available
Flash Steam Plants	>180°C	Hot water "flashed" to steam in low-pressure tank	Most common type (60% of capacity)
Binary Cycle Plants	100-180°C	Hot water heats secondary fluid (lower boiling point) to drive turbine	Expands usable resources, zero emissions

Key Features of Geothermal Power:

Baseload Power: Unlike solar/wind, provides stable 24/7 electricity generation
High Capacity Factor: 90%+ compared to 25-35% for wind/solar
Small Footprint: Requires less land per MW than other renewables
Long Lifespan: Plants operate for 30-50 years
Low Emissions: 45 g CO2/kWh vs 820 g for coal

B. Direct Use Applications

Geothermal heat can be used directly without conversion to electricity, which is more efficient:

Application	Temperature Range	Description	Examples
District Heating	60-90°C	Heating buildings, communities through hot water pipes	Reykjavik (95% of buildings), Paris
Greenhouse Heating	40-80°C	Year-round crop cultivation in cold climates	Netherlands, Iceland vegetable farms
Aquaculture	20-30°C	Fish farming in temperature-controlled ponds	Tilapia, catfish, prawns farming
Industrial Processing	50-200°C	Drying, pasteurization, chemical processes	Paper manufacturing, food drying, textile processing
Agricultural Drying	40-100°C	Dehydrating crops, fruits, vegetables	Grain drying, fruit preservation
Spa/Balneology	30-45°C	Therapeutic bathing, health tourism	Japan onsen, Iceland Blue Lagoon
Snow Melting	40-60°C	Heating roads, sidewalks, runways	Iceland airports, parking lots

C. Geothermal Heat Pumps (Ground Source Heat Pumps)

How Ground Source Heat Pumps Work:

Principle: Exploit stable underground temperatures (10-16°C year-round below frost line)
Heating Mode (Winter): Extract heat from ground, amplify with heat pump, deliver to building
Cooling Mode (Summer): Extract heat from building, reject to ground (which acts as heat sink)
Efficiency: 3-5 times more efficient than conventional HVAC (COP of 3-5)
Types: Horizontal loops, vertical boreholes, pond/lake loops, open loop systems

Applications of GHPs:

Residential heating and cooling
Commercial buildings (offices, hotels, hospitals)
Schools and universities
Industrial facilities
Swimming pool heating

Energy Savings: GHPs reduce energy consumption by 25-50% compared to conventional systems. Over 1.4 million units installed in USA alone.

3. Advanced/Emerging Applications

Enhanced Geothermal Systems (EGS): Creating artificial reservoirs in hot dry rock by hydraulic fracturing - expands usable resources significantly
Geothermal Desalination: Using geothermal heat for seawater desalination
Hydrogen Production: High-temperature geothermal for green hydrogen via electrolysis
Mineral Extraction: Recovering lithium, silica, zinc from geothermal brines
Carbon Capture: Injecting CO2 into geothermal formations for permanent storage

4. Advantages of Geothermal Energy

Advantage	Details
Reliability	24/7 availability, not weather-dependent unlike solar/wind
Low Emissions	Minimal GHG emissions, no combustion required
Small Footprint	Requires 1-8 acres per MW vs 5-10 for solar
Long Lifespan	Plants operate 30-50 years, wells last 20-30 years
Domestic Resource	Reduces energy import dependence
Baseload Power	Provides stable grid support
Cascaded Use	Same resource can serve multiple applications at different temperatures

5. Geothermal Energy in India

India's Geothermal Potential:

Estimated Potential: ~10,000 MW (mostly low-medium temperature)
Hot Springs: 340+ locations identified across India
Key Regions:
- Puga Valley, Ladakh (temperature >150°C, most promising)
- Tattapani, Chhattisgarh (90-95°C)
- Manikaran, Himachal Pradesh (94°C)
- Cambay Basin, Gujarat (150-175°C at depth)
- West Coast Hot Springs
Current Status: No commercial power plants yet; ONGC exploring projects
Direct Use: Hot springs for bathing, small greenhouse heating

6. Limitations and Challenges

Location Specific: High-temperature resources limited to certain geological areas
High Upfront Costs: Drilling and exploration expensive (40-60% of project cost)
Resource Risk: Uncertainty until wells are drilled
Induced Seismicity: EGS projects may trigger minor earthquakes
Water Use: Some systems require water for reinjection
Technical Expertise: Specialized skills required for development

Conclusion

Geothermal energy offers diverse applications from large-scale power generation to direct heating and efficient ground-source heat pumps. Its reliability, low emissions, and small land footprint make it valuable for sustainable energy portfolios. While India's geothermal sector remains underdeveloped compared to global leaders, regions like Ladakh offer significant potential. With technological advances in EGS expanding accessible resources, geothermal energy is poised to play an increasingly important role in the global clean energy transition.