Geothermal Power Generation: Developments and Innovation–a Review

Geothermal energy is one of the dark horses of renewable energy. Few “renewable energy advocates” know much—if anything—about it. They don’t know what geothermal contributes today and have no clue what its role could be in a 100% renewable energy future. This is a grave mistake.

Where the resource exists—and there’s a lot more of it out there than most people realize—geothermal should be an essential part of the generation mix.

I’ve always kept an eye on geothermal’s role in California. In 2016 geothermal produced 12 TWh or 4% of California’s generation. This is nearly as much as the more well known contribution by wind energy. And geothermal has been producing steadily at this level far longer than wind has.

Iceland, of course, is famous for geothermal energy, sitting as it does on the Mid-Atlantic Ridge. The island generates one-quarter of its electricity (4 TWh) from geothermal power plants. That’s not the whole story. 85% of homes in Iceland use geothermal heating. All told geothermal provides two-thirds of Iceland’s primary energy.

That’s why I was happy to get a copy of Geothermal Power Generation: Developments and Innovation by Ron DiPippo. The book is a tour de force for geothermal engineers. DiPippo, Chancellor Professor Emeritus of Mechanical Engineering and the former Associate Dean of Engineering at the University of Massachusetts in Dartmouth, Mass.

The 854-page tome is a companion to DiPippo’s previous Geothermal Power Plants, one of the definitive texts on geothermal technology. The new book is a continuation of his work, this time in collaboration with other experts in the field.

As a generalist, I found Part Four the most useful. There are eight case studies, beginning with the birthplace of geothermal: Larderello in Tuscany. This is followed by a review of geothermal in California, including the Geysers, a giant field in Northern California. Famous fields in New Zealand, Mexico, Indonesia, and Central America are also covered.

Italy’s Larderello

I was hooked as soon as I opened up the book to the chapter on Larderello. The subtitle described the history of the “boraciferous region” in what the Italians call the Colline Metallifere between Pisa and Florence. It was here geothermal fluids boiled to the surface carrying solutions of borates.

It’s obscure, very obscure, but borates from Tuscany’s geothermal fields are linked to the history of California and specifically the region where I live.

Borates are one of the major mineral products of California and the mining for borates—the search for them, and their exploitation–are integral to many famous tales from California’s period of European settlement.

Death Valley National Park is a direct result of the borate boom as is the famous 20 mule team wagon trains that carried the borates from Death Valley to Mojave, California. One of the world’s largest borate mines is not far from Mojave—well within view of the thousands of wind turbines that line the Tehachapi Pass.

And it was competition from California’s abundant borates that led inexorably to the collapse of Larderello’s borate industry and the rise of geothermal power generation. As the Italians continued to refine their mining of the borate solutions to stay competitive with California, they began drilling deeper and deeper wells. They also began using the hot geothermal fluids for the industrial process of concentrating the borates. Subsequently, they began electrifying the fields and when they could no longer sell the borates they turned to selling the electricity that they generated from geothermal energy. Today, the geothermal plants in and around Larderello generate from 5 TWh to 7 TWh per year for almost 2% of Italy’s total generation.

California’s Geysers

The “Geysers,” as they are called, remain one of the world’s largest geothermal fields. The region in Northern California has been producing electricity from geothermal energy since the 1960s!

I’d written about the Geysers long ago—in the mid-1980s. See Geysers Loosing Steam: a Finite Resource After All? At the time the field was in steep decline. As geologist Carl Austin said at the time, there were simply too many “straws in the bottle” for the field to maintain its pressure. The solution was known: reducing the number of wells and the extraction rate.

Two authors from California’s geothermal industry describe in this case study how the solutions were eventually implemented and thoroughly document the results.

While the field has never recovered its previous glory, the steps taken in the 1990s have arrested its rapid decline. The field’s depletion rate has dropped from a high of 4.8% per year in the 1980s to 2% per year in the 2000s. Nevertheless, steam production has been halved from its peak in the late 1980s, illustrating how much the field had been overdeveloped.

The data in this case study is the most succinct and up-to-date I’ve found for production from the Geysers. Companies operating in California are notoriously secretive about their generation. It was a sign of how serious the problem had become that the companies “mining” the geothermal resource in the Geysers had to share data and work together to prevent a complete collapse of the industry—and their costly investments.

Though the case study on the Geysers doesn’t disprove whether or not geothermal energy is a finite resource, it does address the question—with 55 years of stats—of how to successfully manage the resource with an eye toward sustainability.

DiPippo and his co-authors have produced a comprehensive reference work for those working in the geothermal industry and should be a reference work on the shelf of every environmental organization pursuing a 100% renewable energy supply.

Ron DiPippo, editor. Geothermal Power Generation: Developments and Innovation. London: Woodhead Publishing, 2016. 854 pages. ISBN: 9780081003374 cloth. $210.00, ISBN: 9780081003442, epub. $210.00. 9.5 x 6.25 x 1.75 inches. 1.5 lbs. Printed in England.

Table of Contents

Related titles
Woodhead Publishing Series in Energy
Author biographies
Preface
1. Introduction to geothermal power generation
Part One. Resource exploration, characterizationand evaluation

2. Geology of geothermal resources

2.1. Introduction
2.2. Heat flow and plate tectonics
2.3. Geologic techniques
2.4. Hydrothermal alteration
2.5. Volcanic-hosted systems
2.6. Sediment-hosted geothermal systems
2.7. Extensional tectonic geothermal systems
2.8. Unconventional geothermal resources
2.9. Conclusions

3. Geophysics and resource conceptual models in geothermal exploration and development

3.1. Introduction
3.2. Geophysics in the context of geothermal decision risk assessment
3.3. Geothermal resource conceptual models
3.4. Geothermal resource models with elements that differ from those in Fig. 3.1
3.5. Formation properties and geophysical methods
3.6. Choosing geophysical methods and designing surveys for geothermal applications
3.7. Resistivity methods
3.8. MT surveys
3.9. TEM resistivity sounding for correction of MT static distortion
3.10. Awibengkok MT model and validation
3.11. Using MT to build conceptual models and define resource areas and targets
3.12. Deep low-resistivity zones
3.13. Gravity methods for exploration and development
3.14. Magnetic methods
3.15. Seismic monitoring
3.16. Reflection/refraction seismic methods
3.17. Borehole wireline logs
3.18. SP method
3.19. Geophysics management issues

4. Application of geochemistry to resource assessment and geothermal development projects

4.1. Introduction
4.2. Early-phase resource assessment
4.3. Contributions to conceptual models
4.4. Geochemical contributions to geothermal power project design
4.5. Geochemical tools for geothermal reservoir operation and maintenance
4.6. Summary

5. Geothermal well drilling

5.1. Introduction
5.2. Getting started
5.3. Casing design
5.4. Mud program
5.5. Directional program
5.6. Wellhead design and blow-out preventer systems
5.7. Cementing program
5.8. Cement placement
5.9. Hydraulic and bit program
5.10. Drilling curve
5.11. Mud logging
5.12. Drilling rig selection and special considerations
5.13. Cost estimate

6. Characterization, evaluation, and interpretation of well data

6.1. Upward convective flow in reservoirs
6.2. Pressure and temperature profile analysis
6.3. Injection testing
6.4. Discharge tests
6.5. Pressure transient tests
6.6. Wellbore heat loss
6.7. Summary

7. Reservoir modeling and simulation for geothermal resource characterization and evaluation

7.1. Review of resource estimation methods
7.2. Computer modeling methodology
7.3. Computer modeling process
7.4. Recent modeling experiences
7.5. Current developments and future directions

Part Two. Energy conversion systems

8. Overview of geothermal energy conversion systems: Reservoir-wells-piping-plant-reinjection

8.1. Introduction
8.2. It begins with the reservoir
8.3. Getting the energy out of the reservoir
8.4. Connecting the wells to the power station
8.5. Central power station
8.6. Geofluid disposal
8.7. Conclusions and a look ahead

9. Elements of thermodynamics, fluid mechanics, and heat transfer applied to geothermal energy conversion systems

9.1. Introduction
9.2. Definitions and terminology
9.3. First law of thermodynamics for closed systems
9.4. First law of thermodynamics for open steady systems
9.5. First law of thermodynamics for open unsteady systems
9.6. Second law of thermodynamics for closed systems
9.7. Second law of thermodynamics for open systems
9.8. Exergy and exergy destruction
9.9. Thermodynamic state diagrams
9.10. Bernoulli equation
9.11. Pressure loss calculations
9.12. Principles of heat transfer applied to geothermal power plants
9.13. Example analyses for elements of geothermal power plants
9.14. Conclusions
Sources of further information

10. Flash steam geothermal energy conversion systems: Single-, double-, and triple-flash and combined-cycle plants

10.1. Flash steam cycles
10.2. Mixed and combined cycles
10.3. Cogeneration and coproduction from flashed brines
10.4. Equipment research and development
10.5. Summary

11. Direct steam geothermal energy conversion systems: Dry steam and superheated steam plants

11.1. Introduction
11.2. Power cycle
11.3. Steam quality
11.4. Steam systems
11.5. Turbine-generators
11.6. Condensers
11.7. Gas removal systems
11.8. Cooling systems
11.9. Plant auxiliaries
11.10. Engineering materials
11.11. Summary

12. Total flow and other systems involving two-phase expansion

12.1. Total flow
12.2. Alternative systems for power recovery based on two-phase expansion

13. Binary geothermal energy conversion systems: Basic Rankine, dual–pressure, and dual–fluid cycles

13.1. Introduction
13.2. Binary power cycle
13.3. Binary cycle performance
13.4. Types of binary cycles
13.5. Selection of working fluid
13.6. Cycle performance comparison
13.7. Design considerations
13.8. Economic considerations

14. Combined and hybrid geothermal power systems

14.1. Introduction and definitions
14.2. General thermodynamic considerations
14.3. Combined single- and double-flash systems
14.4. Combined flash and binary systems
14.5. Geothermal-fossil hybrid systems
14.6. Geothermal-solar hybrid systems
14.7. Conclusions
Nomenclature

Part Three. Design and economic considerations

15. Waste heat rejection methods in geothermal power generation

15.1. Introduction: overview and scope
15.2. Condensers in geothermal power plants
15.3. Water-cooled condensers
15.4. Air-cooled condensers
15.5. Evaporative (water- and air-cooled) condensers
15.6. Concluding summary and future trends

16. Silica scale control in geothermal plants—historical perspective and current technology

16.1. Introduction
16.2. Geochemistry of silica
16.3. Thermodynamics of silica solubility
16.4. Silica precipitation kinetics
16.5. Silica scaling experience in geothermal power production
16.6. Historical techniques for silica/silicate scale inhibition
16.7. Current scale control techniques at high supersaturation
16.8. Case study for scale control in a combined-cycle plant design
16.9. Pilot-plant testing for bottoming cycle optimization
16.10. Guidelines for optimum pH-mod system design
16.11. Summary

17. Environmental benefits and challenges associated with geothermal power generation

17.1. Introduction
17.2. Environmental, social, and cultural benefits and challenges of geothermal power generation
17.3. Developing an environmentally sound and socially responsible project
17.4. Geothermal energy in the context of sustainable development
17.5. Conclusions

18. Project permitting, finance, and economics for geothermal power generation

18.1. Introduction
18.2. Finance background
18.3. Recent evidence in geothermal drilling and construction
18.4. Cost and financing issues
18.5. Permitting land use and interconnection
18.6. Long-term economic and financing security
18.7. Conclusions

Part Four. Case studies

19. Larderello: 100years of geothermal power plant evolution in Italy

Prologue: historical outline on geothermal development in Italy up to 1960, with particular reference to the boraciferous region
19.1. Introduction: background of geothermal power generation
19.2. 1900–1910: first experiments of geo-power generation and initial applications
19.3. 1910–1916: first geothermal power plant of the world, experimental generation, and start of geo-power production at the commercial scale
19.4. 1917–1930: consolidation of geoelectric power production at the industrial scale and start of a new technology: the direct-cycle geo-power units
19.5. 1930–1943: toward a balanced economic importance of chemical production and geo-power generation
19.6. 1944–1970: destruction, reconstruction, relaunching, and modification of the geo-power system
19.7. 1970–1990: from reinjection of spent fluids and processing of steam to the renewal of all power units and remote control of the whole generation system
19.8. 1990–2014: recent technological advancements, with special regard to the “AMIS Project,” new materials, and environmental acceptability
19.9. Other geothermal areas

20. Fifty-five years of commercial power generation at The Geysers geothermal field, California: The lessons learned

20.1. Introduction
20.2. Background
20.3. The fledgling years (1960–69)
20.4. Geothermal comes of age (1969–79)
20.5. The geothermal rush (1979–86)
20.6. The troubled era (1986–95)
20.7. The watershed years (1995–98)
20.8. Stability at last (1998–2004)
20.9. Renewed optimism (2004–15)
20.10. The future (beyond 2015)
20.11. Lessons learned

21. Indonesia: Vast geothermal potential, modest but growing exploitation

21.1. Introduction
21.2. Geological background
21.3. Vast geothermal potential
21.4. History of geothermal development in Indonesia
21.5. Geothermal law and other geothermal regulations
21.6. National energy condition and policy
21.7. Geothermal energy role in the National Energy Mix
21.8. Geothermal development plan
21.9. Geothermal exploitation growth
21.10. Challenges in geothermal development
21.11. Future planning of geothermal development
21.12. Conclusions

22. New Zealand: A geothermal pioneer expands within a competitive electricity marketplace

22.1. Reform of the NZ electricity generation and supply industry
22.2. Geothermal resource management
22.3. Geothermal: a Maori treasure being actively and innovatively used
22.4. Geothermal developments—2000 to 2015
22.5. Field review of geothermal power, tourism, and direct use developments
22.6. Geothermal outlook

23. Central and South America: Significant but constrained potential for geothermal power generation

23.1. Central America
23.2. South America
23.3. Final remarks

24. Mexico: Thirty-three years of production in the Los Azufres geothermal field

24.1. Geothermal power in Mexico
24.2. Main features of the Los Azufres field
24.3. Geothermal production
24.4. Power plants and output
24.5. Perspectives

25. Enhanced geothermal systems: Review and status of research and development

25.1. Introduction
25.2. Characterization of geothermal energy systems
25.3. Reservoir types applicable for EGS development
25.4. Treatments to enhance productivity of a priori low-permeable rocks
25.5. Environmental impact of EGS treatments
25.6. Sustainable operation
25.7. Outlook

26. Geothermal energy in the framework of international environmental law

26.1. Introduction
26.2. Environmental international law and geothermal energy
26.3. Environmental features in public and private companies developing geothermal projects; green sells
26.4. Global interest in geothermal energy
26.5. Conclusion

Index