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QI047- Energías Alternativas
Ivan Rafael Quevedo Partida
4.1-Energía Geotérmica
Otoño 2024
What is Geothermal Energy?
• Utilize temperature of the earth’s core.
• Direct use: District Heating System
• Electricity generation
• Heat pumps
Boyle: Renewable Energy, 3e
Map of the Earths Lithospheric
Plates
Boyle: Renewable Energy, 3e
Campos Geotérmicos en Mexico
Boyle: Renewable Energy, 3e
Essential Characteristics of a
Geothermal Site
Boyle: Renewable Energy, 3e
Relationship between grain size,
shape and porosity
Boyle: Renewable Energy, 3e
Conceptual Model of a Typical
Volcanic Geothermal System
Boyle: Renewable Energy, 3e
Thermal Gradient and Heat Flow
Boyle: Renewable Energy, 3e
Boyle: Renewable Energy, 3e
Main Types of Geothermal Electrical
Energy Production
Boyle: Renewable Energy, 3e
Direct Use of Geothermal Energy
Boyle: Renewable Energy, 3e
Total Heat in Place
Boyle: Renewable Energy, 3e
Geothermal Well
Boyle: Renewable Energy, 3e
Geothermal Drilling
Boyle: Renewable Energy, 3e
Electricity Demand Supplied by
Geothermal Energy
Boyle: Renewable Energy, 3e
Environmental Impacts
• Almost no negative
impact
on
the
environment.
• Release about 1 to 3
percent of the carbon
dioxide emissions of
a fossil fuel plant.
Boyle: Renewable Energy, 3e
Summary
• Appropriate technologies have been developed to
allow the economic exploitation of geothermal
sources.
• Its major advantage is that it is continuously
available irrespective of climate or daylight.
• While the impact of geothermal energy is still
minor in most countries, geothermal electricity is
already a key component of the supply system
Boyle: Renewable Energy, 3e
Problems
1. Evaluate the amount of the thermal resource available in
a specific location under the assumption that the thermal
gradient (G) is constant with depth z. Suppose that z1 is
the minimum depth needed to reach temperatures of
T1=150 C, and z2 is the maximum depth at which current
technology allows wells to be drilled.
2. Assume that the thermal gradient in a given location is
not constant but rather a function of depth of the form G=
Go(1+az). Find by integration the thermal energy per unit
area between two depths z1 and z2.
Boyle: Renewable Energy, 3e
Conversion Technology
High
Enthalpy
T 150 C
Geothermal
Reservoirs
• Single Flash Steam
(Evaporación Súbita)
Medium
Enthalpy
•
T : 90 150 C
Low
Enthalpy
T : 30 90C
Boyle: Renewable Energy, 3e
• Dry Steam
(Conversión Directa)
•
•
Binary Cicle
(Ciclo Rankine)
Heat Pump (Calefacción)
Ammonia Refrigeration
Conversion Technology
Medium
Enthalpy
Binary Cycles
Working Fluid
Benzene
Toluene
Butane
Isobutane
Pentane
Isopentane
Hexane
R113
R114
R115
R123
R124
R218
R227ea
Isohexane
R236ea
Cyclohexane
R245ca
Heptane
R245fa
Octane
RC318
Nonane
Decane
Boyle: Renewable Energy, 3e
Thermodynamics Review
Carnot Cycle
What about “real world heat engines”?
Carnot
T1 T2
T1
Analysis of Ideal Heat
Engines
A heat engine is a device or machine that converts heat into work by a cyclic
process.
Q1 Q2 T1 T2
C
Q1
T1
Two combinations of continuous heat and work flows between a high
temperature (T1) and a low temperature (T2) heat reservoir, allowed by the laws
of Thermodynamics. The ellipse represents a device that can produce work
from heat or utilize work to move heat from a lower to a higher temperature. We
have in (a) Carnot Heat Engine, and in case (b) Carnot heat pump.
Real (Irreversible) Heat Engines
In real world, many factors degrade the performance of heat
engines:
• Heat losses in the reservoir
• Pressure losses due to friction
• Chemical Reactions
Wheat_produ ced Wrev
Wnet
cycle
Qin
Wnet
u
WCarnot
T1 T2
cycle u Carnot u
T1
Cycle efficiency (cycle)
Thermodynamic utilization efficiency (u)
Rankine Cycle
in
in
in
out
Qin Qout QBC
QCD
QDE
QFA
(H E H B ) (H F H A )
Rankine
in
in
in
Qin
QBC QCD QDE
(H E H B )
Neglecting the work needed to compress the liquid: HB=HA
Rankine
(H E H F )
(H E H A )
Problems
3. A geothermal power plant produces 11.5 MW
of power utilizing a liquid resource (brine) at 170
C. If the mass flow rate of geothermal water is
210 Kg/s and the environmental temperature in
the area is 20 C, determine the thermal
efficiency of this power plant.
Problems
4. A heat pump with refrigerant 134a as the working fluid is used
to maintain a room at 25 C by absorbing heat from geothermal
water that enters the evaporator at 60 C at a rate of 0.065 kg/s
and leaves at 40 C. The refrigerant enters the evaporator at 12 C
with a quality of 15% and leaves at the same pressure as
saturated steam. If the compressor consumes 1.6 KW of power,
determine: a) The mass flow of the refrigerant; b) the heat supply
rate; c) the COP (Coefficient of Performance).
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