GEOTHERMAL ENERGY Jen Eden ME 258 Fall 2012
Dec 22, 2015
GEOTHERMAL ENERGYJen Eden
ME 258
Fall 2012
LOCATION REQUIREMENTS
Traditional Geothermal Plant Hottest reservoir regions
Volcanic areas Recent tectonic activity
High Permeability Discovered by visible hot springs or other
industries Hydrocarbon
Enhanced Geothermal Systems Low enthalpy reservoirs Near the end user
EGS PLANT
U.S. Department of Energy: http://www1.eere.energy.gov
WHAT SETS EGS APART
1. Man-made reservoirs Created where there is hot rock but little to no
natural permeability or fluid saturation
2. Fluid is injected into the subsurface At low pressures
Causes less damage to fractures Which causes pre-existing fractures to re-open
3. Increased permeability Allows fluid to circulate throughout the rock Transport heat to the surface where electricity
can be generated.
2. DRILLING INJECTION WELL
Understand Geology Rock permeability
Depth to target temperature is important Heat at shallow depth is desired
3. RESERVOIR ENHANCEMENT
Thermal Stimulation Increases Permeability
Hydraulic Fracture Increases Permeability
Chemical Stimulation Dissolves Rock
Induced Seismicity Opening existing fractures Or creates new ones
EXTRACTION WELL
Needs to intersect as many fractures as possible
Can have multiple production wells Hot fluid (brine) is pumped out of the well and
into the power plant
TYPES OF POWER PLANTS
1. Dry Steam First type of plant built Hydrothermal fluids are primarily steam
2. Flash Steam Most common type of plants today Fluid greater than 360°F (182°C) is
pumped at high pressure into a tank The tank is held at a much lower pressure,
causing the fluid to rapidly vaporize, "flash”
3. Binary Cycle The future Brine below 400°F Uses secondary fluid with lower
vaporization temperature Binary cycle power plants are closed-loop
systems and virtually nothing
U.S. Department of Energy: http://www1.eere.energy.gov
BINARY POWER PLANT DIAGRAM
Power Generation From Low-Enthalpy Geothermal Resources. by Maghiar and Antal
BINARY POWER PLANT SCHEMATICUNIVERSITY OF OREDEA, ROMANIA
Power Generation From Low-Enthalpy Geothermal Resources. by Maghiar and Antal
PAPER 1: ROCK SPECIFIC HYDRAULIC FRACTURING AND MATRIX ACIDIZING TO ENHANCE A GEOTHERMAL SYSTEM-CONCEPTS AND FIELD RESULTS A major aspect of EGS is enhancing the
geothermal reservoir. This is done on a site–to–site basis taking into
account unique geological features. This paper focused on the Groß Schönebeck
field, a key site for EGS research in the North German Basin Has 2 lithological units:
volcanic rock on bottom Siliciclastics on top (from conglomerates to fine-
grained sandstone)
PAPER 1: ROCK SPECIFIC HYDRAULIC FRACTURING AND MATRIX ACIDIZING TO ENHANCE A GEOTHERMAL SYSTEM-CONCEPTS AND FIELD RESULTS
Treatments were performed over 6 days Needed multiple hydraulic treatments done
at various depths in order to initiate cross-flow.
Multiple acid treatments were also performed to avoid iron scaling of the injected water and keep the pH at 5.
Additionally, quartz was added in low concentrations to maintain sustainable fracture performance.
PAPER 1: ROCK SPECIFIC HYDRAULIC FRACTURING AND MATRIX ACIDIZING TO ENHANCE A GEOTHERMAL SYSTEM-CONCEPTS AND FIELD RESULTS
Must sustain fracture openings mostly tensile fractures without shearing
displacement: add meshed sand or proppants to support the fracture opening
Higher flow rates lead to an increase in fracture length, lower flow rates lead to an increase in width and height.
Acid stimulation dissolved the residual drilling mud increased productivity by 30-50% lead to a total increase in productivity by a factor
between 5.5 and 6.2
PAPER 2: ENVIRONMENTAL ANALYSIS OF PRACTICAL DESIGN OPTIONS FOR ENHANCED GEOTHERMAL SYSTEMS(EGS) THROUGH LIFE-CYCLE ASSESSMENT Analysis of EGS in central Europe based on
life cycle assessment (LCA) of 10 significant design options
Annual electricity output of 10 power plants in central Europe corresponding to different sets of parameters were calculated. number of wells well depth and geothermal fluid temp at
production wellhead flow rate production flow rate reinjection flow rate induced seismicity risk
PAPER 2: ENVIRONMENTAL ANALYSIS OF PRACTICAL DESIGN OPTIONS FOR ENHANCED GEOTHERMAL SYSTEMS(EGS) THROUGH LIFE-CYCLE ASSESSMENT 2 well cases: 5 risk categories:
Human Health Ecosystem Quality Climate Change Resources Seismicity Risk
PAPER 2: ENVIRONMENTAL ANALYSIS OF PRACTICAL DESIGN OPTIONS FOR ENHANCED GEOTHERMAL SYSTEMS(EGS) THROUGH LIFE-CYCLE ASSESSMENT EGS achieves environmental performances
comparable to other renewable energies (Despite the high amount of energy and resources required to build it)
Drilling has the highest environmental impact because of its use of fossil fuels Alternative: is to connect to the grid to improve
environmental performance. Without appropriate reinjection strategy, the
risk of induced seismicity increases. Design of the plant and reservoir conditions
can greatly change the environmental performance.
PAPER 3: EGS USING CO2 AS WORKING FLUID
Problems with water use: water is a sparse commodity and loss of it can be
an economic liability water is a powerful solvent which brings
precipitants to the surface
Aim: Utilize supercritical CO2 instead of water as heat transmission fluid to reduce CO2 emissions by
PAPER 3: EGS USING CO2 AS WORKING FLUID
Wellbore flow: gravity contribution to pressure gradient is
dominant friction and inertial gradients are decidedly small at lower depths, temperature increases by
surrounding rock and by pressure increase, from compression, of the fluid
this is small for water but higher for CO2. Difference in wellhead pressures are:
230.7 bar CO2
61.2 bar water
Indicates a stronger buoyancy drive from CO2
PAPER 3: EGS USING CO2 AS WORKING FLUID
Benefits of CO2: CO2 is superior to water in its ability to mine heat
and with its larger compressibility and expansive
properties its large buoyancy force would reduce power consumption with respect to the wellbore hydraulics,
its lower viscosity would yield higher velocities, it’s a less effective solvent than water
Thermal extraction rate 50% larger for CO2 than water CO2 flow rates are larger than water by a factor of
3.7(This is a result of the enhanced mobility of CO2 at lower temperatures near the injection well.)
PAPER 4: PERFORMANCE ANALYSIS OF HYBRID SOLAR-GEOTHERMAL CO2 HEAT PUMP SYSTEM FOR RESIDENTIAL HEATING
Aim: to develop a solar-CO2 geothermal hybrid heating system
The performance of a heat pump using CO2 is lower than that using a subcritical cycle refrigerant due to irreversibilities, so system performance needs to be investigated.
Previous studies have used CFC or HCFC refrigerant, so it’s important to analyze the performance of a hybrid solar-geothermal CO2 heat pump system.
PAPER 4: PERFORMANCE ANALYSIS OF HYBRID SOLAR-GEOTHERMAL CO2 HEAT PUMP SYSTEM FOR RESIDENTIAL HEATING
Setup: A solar heat unit A CO2 heat pump unit. The heat is collected and stored in a thermal
heat storage tank at a specified operating temperature, when the temperature drops below this, the heat pump starts to operate and supplies heat to the tank
PAPER 4: PERFORMANCE ANALYSIS OF HYBRID SOLAR-GEOTHERMAL CO2 HEAT PUMP SYSTEM FOR RESIDENTIAL HEATING
Performance of the hybrid system was analyzed under varying operating conditions Elevation of ground temp can significantly reduce the
refrigerant temperature at the outlet of the compressor, thereby improving the system performance and reliability. When the heat pump operating temperature increases from
40 C to 48 C, the pressure ratio between the inlet and the outlet of the compressor rises by 19.9% and the compressor work increases from 4.5 to 5.3 kW.
The performance of the solar hybrid heat pump is very sensitive to pump operating conditions.
Therefore, design of proper indoor temperature for variable outdoor conditions is very important to maintain high system performance and reliability in the pump system.
PAPER 5: SHALLOW GEOTHERMAL ENERGY APPLIES TO A SOLAR-ASSISTED AIR-CONDITIONING SYSTEM IN SOUTHERN SPAIN
Aim: to determine the viability of a shallow geothermal system used in place of a cooling tower for a solar assisted AC system. Specifically an aquifer thermal storage to solar
assisted AC system Main goal is to propose the application of a
new alternative heat dissipation system for the absorption chiller installed in the CIESOL building in Spain
PAPER 5: SHALLOW GEOTHERMAL ENERGY APPLIES TO A SOLAR-ASSISTED AIR-CONDITIONING SYSTEM IN SOUTHERN SPAIN
First analyzed the solar-assisted AC system with cooling tower, then with the geothermal system applied. Cooling Tower:
The water in it can cause corrosion if not treated The tower circuit is vulnerable because its an open circuit
susceptible to scaling from precipitation of dissolved solids and algae growth and microorganisms
Causes Legionella outbreak if not properly maintained. Also requires a storage tank and distribution pump to provide
the needed permanent flow. Shallow Geothermal System:
Purpose is to provide cooling water to the absorption chiller. No risk of Legionella. Does not involve any water consumption or rigorous
maintenance. Requires less space and eliminates outdoor noise levels
PAPER 5: SHALLOW GEOTHERMAL ENERGY APPLIES TO A SOLAR-ASSISTED AIR-CONDITIONING SYSTEM IN SOUTHERN SPAIN
Operating for 2 years 2010-2012. During Summer: Used 31% less electrical energy Consumed none of the water the cooling tower
needed Saves 116m3 of water in one cooling period.
QUESTIONS?