SUPERHOT CP FA NOFO (DE-FOA-0003556) - Mod 03.pdf

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AR-311-10.24

FINANCIAL ASSISTANCE

NOTICE OF FUNDING OPPORTUNITY

ADVANCED RESEARCH PROJECTS AGENCY – ENERGY (ARPA-E)

U.S. DEPARTMENT OF ENERGY

STIMULATE UTILIZATION OF PLENTIFUL ENERGY IN ROCKS

THROUGH HIGH-TEMPERATURE ORIGINAL TECHNOLOGIES

(SUPERHOT)

Announcement Type: Modification 02 Modification 03 Notice of Funding Opportunity No. DE-FOA-0003556

Assistance Listing Number 81.135

Mod. No. Date Description of Modifications 03 2/6/2026 • Removed indirect cost cap at 15% of Total Project Costs (Section I.G.15).

02 1/28/2026 • Inserted certain deadlines and updated dates, including the deadlines for submitting questions and Full Applications (Basic Information, Section IV.C).

• Clarified Full Application requirements for Subcategory 1.3 (Section I.E.)

• Inserted indirect cost cap at 15% of Total Project Costs (Section I.G.15).

• Updated definition of ‘Project Team’ and ‘Participation’ (Section II.A); updated definition of ‘Covered Individuals’ (Section IX).

• Inserted information about Entity of Concern Prohibition (Sections II.A.6, IX).

• Updated guidance on submitting components of the Full Application, including SciENcv

Biosketches and CPS Common Forms for Covered Individuals (Sections III.C, III.C.1, III.C.5, III.C.6, III.C.7., III.C.8).

• Added information on Artificial Intelligence Application Use (Section IV.E).

• Updated Technical Responsiveness Requirements and Program Policy Factors (Sections

V.A.1, V.C).

• Inserted information about Due Diligence Review for Research, Technology, and

Economic Security (Section V.H).

• Updated details about Other Transactions Authority (Section VI.D.3).

• Inserted information about Presidential Memo on Simplifying Funding of Energy

Infrastructure and Critical Mineral and Material Projects (Section VIII.E).

01 2/7/2025 • Clarified the meaning of the Program Policy Factors in Section V.C

All modifications to the Notice of Funding Opportunity (NOFO) are highlighted in yellow in the body of the NOFO.

NOFOs are posted on ARPA-E eXCHANGE (https://arpa-e-foa.energy.gov/), Grants.gov (http://www.grants.gov/), and FedConnect (https://www.fedconnect.net/FedConnect/). Any modifications to the NOFO are also posted to these websites. You can receive an e-mail when a modification is posted by registering with FedConnect as an interested party for this NOFO. It is recommended that you register as soon as possible after release of the NOFO to ensure that you receive timely notice of any modifications or other announcements.

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TABLE OF CONTENTS

BASIC INFORMATION ......................................................................................................................................... - 5 -

I. FUNDING OPPORTUNITY DESCRIPTION ..................................................................................................... - 6 -

A. AGENCY OVERVIEW ........................................................................................................................................... - 6 - B. PROGRAM OVERVIEW........................................................................................................................................ - 8 - C. PROGRAM OBJECTIVES ................................................................................................................................ - 13 - D. TECHNICAL CATEGORIES OF INTEREST ............................................................................................................. - 14 - E. TECHNICAL PERFORMANCE TARGETS .................................................................................................................. - 17 - F. STATEMENT OF SUBSTANTIAL INVOLVEMENT ....................................................................................................... - 21 - G. FUNDING RESTRICTIONS .............................................................................................................................. - 22 -

1. ALLOWABLE COSTS .................................................................................................................................... - 22 -

2. PRE-AWARD COSTS ................................................................................................................................... - 22 -

3. PATENT COSTS .......................................................................................................................................... - 22 -

4. CONSTRUCTION ......................................................................................................................................... - 23 -

5. FOREIGN TRAVEL ....................................................................................................................................... - 23 -

6. PERFORMANCE OF WORK IN THE UNITED STATES............................................................................................ - 23 -

7. PURCHASE OF NEW EQUIPMENT .................................................................................................................. - 23 -

8. TECHNOLOGY TRANSFER AND OUTREACH ...................................................................................................... - 24 -

9. LOBBYING ................................................................................................................................................ - 24 -

10. CONFERENCE SPENDING ............................................................................................................................. - 25 -

11. INDEPENDENT RESEARCH AND DEVELOPMENT COSTS....................................................................................... - 25 -

12. BUY AMERICA REQUIREMENT FOR PUBLIC INFRASTRUCTURE PROJECTS .............................................................. - 26 -

13. REQUIREMENT FOR FINANCIAL PERSONNEL .................................................................................................... - 26 -

14. PARTICIPANTS, COLLABORATING ORGANIZATIONS, AND CURRENT AND PENDING SUPPORT ................................... - 26 -

15. MAXIMUM LIMIT ON INDIRECT COSTS .......................................................................................................... - 27 -

II. ELIGIBILITY INFORMATION ...................................................................................................................... - 28 -

A. ELIGIBLE APPLICANTS ....................................................................................................................................... - 28 -

1. INDIVIDUALS ............................................................................................................................................. - 28 -

2. DOMESTIC ENTITIES ................................................................................................................................... - 28 -

3. CONSORTIA .............................................................................................................................................. - 29 -

4. FOREIGN NATIONAL PARTICIPATION FROM COUNTRIES OF CONCERN ................................................................. - 29 -

5. FOREIGN PARTICIPATION CONSIDERATIONS ................................................................................................... - 30 -

6. ENTITY OF CONCERN PROHIBITION ............................................................................................................... - 30 -

B. COMPLIANCE AND RESPONSIVENESS ................................................................................................................... - 30 - C. LIMITATION ON NUMBER OF SUBMISSIONS ..................................................................................................... - 31 - D. COST SHARING ........................................................................................................................................... - 31 -

1. BASE COST SHARE REQUIREMENT ................................................................................................................ - 31 -

2. INCREASED COST SHARE REQUIREMENT ........................................................................................................ - 31 -

3. REDUCED COST SHARE REQUIREMENT .......................................................................................................... - 32 -

4. LEGAL RESPONSIBILITY ............................................................................................................................... - 32 -

5. COST SHARE ALLOCATION ........................................................................................................................... - 33 -

6. COST SHARE TYPES AND ALLOWABILITY ........................................................................................................ - 33 -

7. COST SHARE CONTRIBUTIONS BY FFRDCS AND GOGOS .................................................................................. - 34 -

8. COST SHARE VERIFICATION ......................................................................................................................... - 34 -https://arpa-e.energy.gov/faqs mailto:ARPA-E-CO@hq.doe.gov mailto:ExchangeHelp@hq.doe.gov

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III. APPLICATION CONTENTS AND FORMAT .............................................................................................. - 35 -

A. GENERAL APPLICATION CONTENT REQUIREMENTS ................................................................................................ - 35 -

1. MARKING OF CONFIDENTIAL INFORMATION ................................................................................................... - 35 -

2. EXPORT CONTROL INFORMATION ................................................................................................................. - 35 -

B. CONCEPT PAPERS ............................................................................................................................................ - 36 -

1. FIRST COMPONENT: CONCEPT PAPER............................................................................................................ - 36 -

2. SECOND COMPONENT: SUMMARY SLIDE ....................................................................................................... - 36 -

C. FULL APPLICATIONS .................................................................................................................................... - 37 -

1. FIRST COMPONENT: TECHNICAL VOLUME ...................................................................................................... - 37 -

2. SECOND COMPONENT: SF-424 ................................................................................................................... - 38 -

3. THIRD COMPONENT: BUDGET JUSTIFICATION WORKBOOK/SF-424A ................................................................ - 38 -

4. FOURTH COMPONENT: SUMMARY FOR PUBLIC RELEASE .................................................................................. - 39 -

5. FIFTH COMPONENT: SUMMARY SLIDE ........................................................................................................... - 39 -

6. SIXTH COMPONENT: BUSINESS ASSURANCES & DISCLOSURES FORM .................................................................. - 39 -

7. SEVENTH COMPONENT: BIOGRAPHICAL SKETCHES (BIOSKETCH) ........................................................................ - 39 -

8. EIGHTH COMPONENT: CURRENT, PENDING, AND PAST SUPPORT ....................................................................... - 40 -

D. REPLIES TO REVIEWER COMMENTS ................................................................................................................ - 42 -

IV. SUBMISSION REQUIREMENTS AND DEADLINES ................................................................................... - 43 -

A. UNIQUE ENTITY IDENTIFIER AND SAM REGISTRATION ........................................................................................... - 43 - B. USE OF ARPA-E EXCHANGE .......................................................................................................................... - 43 - C. REQUIRED DOCUMENTS CHECKLIST AND DEADLINES ......................................................................................... - 44 - D. COMPLIANCE ............................................................................................................................................. - 45 - E. ARTIFICIAL INTELLIGENCE (AI) APPLICATION USE .................................................................................................. - 46 - F. INTERGOVERNMENTAL REVIEW ......................................................................................................................... - 46 -

V. APPLICATION REVIEW INFORMATION ..................................................................................................... - 47 -

A. RESPONSIVENESS ............................................................................................................................................ - 47 -

1. TECHNICAL RESPONSIVENESS REVIEW ........................................................................................................... - 47 -

2. SUBMISSIONS SPECIFICALLY NOT OF INTEREST ................................................................................................. - 48 -

B. REVIEW CRITERIA ............................................................................................................................................ - 48 -

1. CRITERIA FOR CONCEPT PAPERS ................................................................................................................... - 48 -

2. CRITERIA FOR FULL APPLICATIONS ................................................................................................................ - 49 -

3. CRITERIA FOR REPLIES TO REVIEWER COMMENTS ............................................................................................ - 50 -

C. PROGRAM POLICY FACTORS ......................................................................................................................... - 50 - D. REVIEW AND SELECTION PROCESS ................................................................................................................. - 52 -

1. CONCEPT PAPERS ...................................................................................................................................... - 52 -

2. FULL APPLICATIONS ................................................................................................................................... - 52 -

3. REPLY TO REVIEWER COMMENTS ................................................................................................................. - 52 -

4. PRE-SELECTION CLARIFICATIONS AND “DOWN-SELECT” PROCESS ...................................................................... - 52 -

5. SELECTION FOR AWARD NEGOTIATIONS ........................................................................................................ - 53 -

E. ARPA-E REVIEWERS ....................................................................................................................................... - 53 - F. ARPA-E SUPPORT CONTRACTORS ..................................................................................................................... - 53 - G. RISK REVIEW.............................................................................................................................................. - 54 - H. DUE DILIGENCE REVIEW FOR RESEARCH, TECHNOLOGY AND ECONOMIC SECURITY ................................................. - 55 -https://arpa-e.energy.gov/faqs

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VI. AWARD NOTICES AND AWARD TYPES ................................................................................................. - 56 -

A. AWARD NOTICES ............................................................................................................................................ - 56 -

1. REJECTED SUBMISSIONS ............................................................................................................................. - 56 -

2. CONCEPT PAPER NOTIFICATIONS .................................................................................................................. - 56 -

3. FULL APPLICATION NOTIFICATIONS ............................................................................................................... - 56 -

B. PRE-AWARD COSTS ......................................................................................................................................... - 58 - C. RENEWAL AWARDS ..................................................................................................................................... - 58 - D. FUNDING AGREEMENT TYPES ....................................................................................................................... - 58 -

1. COOPERATIVE AGREEMENTS........................................................................................................................ - 58 -

2. FUNDING AGREEMENTS WITH FFRDCS/DOE LABS, GOGOS, AND FEDERAL INSTRUMENTALITIES .......................... - 59 -

3. OTHER TRANSACTIONS AUTHORITY .............................................................................................................. - 59 -

VII. POST-AWARD REQUIREMENTS AND ADMINISTRATION ...................................................................... - 61 -

A. NATIONAL POLICY REQUIREMENTS .................................................................................................................... - 61 -

1. NATIONAL POLICY ASSURANCES ................................................................................................................... - 61 -

2. ENVIRONMENTAL IMPACT QUESTIONNAIRE ................................................................................................... - 61 -

B. ADMINISTRATIVE REQUIREMENTS ...................................................................................................................... - 62 -

1. COST SHARE PAYMENTS ............................................................................................................................. - 62 -

2. INTELLECTUAL PROPERTY AND DATA MANAGEMENT PLANS ............................................................................. - 62 -

3. U.S. COMPETITIVENESS .............................................................................................................................. - 63 -

4. NONDISCLOSURE AND CONFIDENTIALITY AGREEMENTS REPRESENTATIONS .......................................................... - 64 -

5. INTERIM CONFLICT OF INTEREST POLICY FOR FINANCIAL ASSISTANCE .................................................................. - 65 -

6. COMPLIANCE AUDIT REQUIREMENT .............................................................................................................. - 65 -

7. RESEARCH SECURITY TRAINING REQUIREMENT ............................................................................................... - 65 -

C. REPORTING................................................................................................................................................ - 66 -

1. FRAUD, WASTE, AND ABUSE ....................................................................................................................... - 66 -

2. COMMERCIALIZATION PLAN AND SOFTWARE REPORTING ................................................................................. - 66 -

VIII. OTHER INFORMATION ......................................................................................................................... - 67 -

A. TITLE TO SUBJECT INVENTIONS .......................................................................................................................... - 67 - B. GOVERNMENT RIGHTS IN SUBJECT INVENTIONS.................................................................................................... - 67 -

1. GOVERNMENT USE LICENSE ........................................................................................................................ - 68 -

2. MARCH-IN RIGHTS .................................................................................................................................... - 68 -

C. RIGHTS IN TECHNICAL DATA ......................................................................................................................... - 68 - D. PROTECTED PERSONALLY IDENTIFIABLE INFORMATION ...................................................................................... - 69 - E. PRESIDENTIAL MEMORANDUM ON SIMPLIFYING FUNDING OF ENERGY INFRASTRUCTURE AND CRITICAL MINERAL AND

MATERIAL PROJECTS ................................................................................................................................................ - 69 -

IX. GLOSSARY ........................................................................................................................................... - 71 -https://arpa-e.energy.gov/faqs

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BASIC INFORMATION

KEY DATES:

Notice of Funding Opportunity (NOFO) Issue Date: January 16, 2025 Deadline for Concept Paper Questions to ARPA-E-CO@hq.doe.gov: 5 PM ET, February 7, 2025 Submission Deadline for Concept Papers: 9:30 AM ET, February 19, 2025 Anticipated Date for Encourage/Discourage Notifications: 5 PM ET, April 7, 2025 Deadline for Full Application Questions to ARPA-E-CO@hq.doe.gov: 5 PM ET, February 23, 2026 Submission Deadline for Full Applications: 9:30 AM ET, March 5, 2026 Expected Reviewer Comment Release Date: 5 PM ET, March 26, 2026 Submission Deadline for Replies to Reviewer Comments: 5 PM ET, March 31, 2026 Anticipated Timeframe for Selection Notifications: April 2026 Anticipated Timeframe for Award: July 2026 Anticipated Period of Performance: July 2026 – July 2029

BASIC INFORMATION:

Total Amount to Be Awarded

Approximately $30 million, subject to the availability of appropriated funds to be shared between NOFOs DE-FOA-0003556 and DE-FOA-0003557.

Anticipated Number and Value of Awards

ARPA-E anticipates making approximately 5-15 awards between NOFOs DE-FOA- 0003556 and DE-FOA-0003557. ARPA-E may issue one, multiple, or no awards under this NOFO. The Federal share of awards under this NOFO may vary between $250,000 and $10 million.

Agency Contact Information

• Questions and answers (Q&As) about ARPA-E and this specific NOFO:

http://arpa-e.energy.gov/faq.

• Send other questions about the NOFO to: ARPA-E-CO@hq.doe.gov.

• Send questions about use of ARPA-E eXCHANGE to:

ExchangeHelp@hq.doe.gov.

Upon the issuance of a NOFO, only the Grants Officer via ARPA-E-CO@hq.doe.gov may communicate with Applicants. This “quiet period” remains in effect until ARPA-E’s public announcement of project selections. Emails sent to other email addresses will be disregarded.

The SUPERHOT program will support the research and development of technologies that enable the production of geothermal energy from super-hot reservoirs (>375 oC and >22 MPa) for 15 years or more.

This program seeks to fund the development of novel technologies for well construction, enhance testing facilities, and optimize reservoir heat extraction to make super-hot geothermal production a reality. The program will have two categories:

• Category 1: Technologies related to the construction of robust super-hot wells and validation services for quality assurance of new well designs and materials. This focus will involve new materials, novel well solutions, and state-of-the-art testing facilities to assess these new approaches.

• Category 2: Technologies related to the extraction of heat from the reservoir to the well. The focus of this category is to develop fracture based and non-fracture-based methods for extracting heat from a super-hot reservoir (potentially composed of ductile rocks) to a working fluid in a well.

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I. FUNDING OPPORTUNITY DESCRIPTION

A. AGENCY OVERVIEW

The Advanced Research Projects Agency – Energy (ARPA-E), an organization within the Department of Energy (DOE), is chartered by Congress in the America COMPETES Act of 2007 (P.L. 110-69), as amended by the America COMPETES Reauthorization Act of 2010 (P.L. 111- 358), as further amended by the Energy Act of 2020 (P.L. 116-260):

“(A) to enhance the economic and energy security of the United States through the development of energy technologies that—

(i) reduce imports of energy from foreign sources;

(ii) reduce energy-related emissions, including greenhouse gases;

(iii) improve the energy efficiency of all economic sectors;

(iv) provide transformative solutions to improve the management, clean-up, and disposal of radioactive waste and spent nuclear fuel; and

(v) improve the resilience, reliability, and security of infrastructure to produce, deliver, and store energy; and

(B) to ensure that the United States maintains a technological lead in developing and deploying advanced energy technologies.”

ARPA-E issues this Notice of Funding Opportunity (NOFO) under its authorizing statute codified at 42 U.S.C. § 16538. The NOFO and any cooperative agreements or grants made under this NOFO are subject to 2 C.F.R. Part 200 as supplemented by 2 C.F.R. Part 910.

ARPA-E funds research on, and the development of, transformative science and technology solutions to address the energy and environmental missions of the Department. The agency focuses on technologies that can be meaningfully advanced with a modest investment over a defined period of time in order to catalyze the translation from scientific discovery to early-stage technology. For the latest news and information about ARPA-E, its programs and the research projects currently supported, see: http://arpa-e.energy.gov/.

ARPA-E funds transformational research. Existing energy technologies generally progress on established “learning curves” where refinements to a technology and the economies of scale that accrue as manufacturing and distribution develop drive improvements to the cost/performance metric in a gradual fashion. This continual improvement of a technology is important to its increased commercial deployment and is appropriately the focus of the private sector or the applied technology offices within DOE. In contrast, ARPA-E supports transformative research that has the potential to create fundamentally new learning curves.

ARPA-E technology projects typically start with cost/performance estimates well above the level of an incumbent technology. Given the high risk inherent in these projects, many will fail to progress, but some may succeed in generating a new learning curve with a projected cost/performance metric that is significantly better than that of the incumbent technology.

ARPA-E will provide support at the highest funding level only for submissions with significant https://arpa-e.energy.gov/faqs mailto:ARPA-E-CO@hq.doe.gov http://arpa-e.energy.gov/

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- 7 -technology risk, aggressive timetables, and careful management and mitigation of the associated risks.

ARPA-E funds technology with the potential to be disruptive in the marketplace. The mere creation of a new learning curve does not ensure market penetration. Rather, the ultimate value of a technology is determined by the marketplace, and impactful technologies ultimately become disruptive – that is, they are widely adopted and displace existing technologies from the marketplace or create entirely new markets. ARPA-E understands that definitive proof of market disruption takes time, particularly for energy technologies. Therefore, ARPA-E funds the development of technologies that, if technically successful, have clear disruptive potential, e.g., by demonstrating capability for manufacturing at competitive cost and deployment at scale.

ARPA-E funds applied research and development (R&D). The Office of Management and Budget defines “applied research” as an “original investigation undertaken in order to acquire new knowledge…directed primarily towards a specific practical aim or objective” and defines “experimental development” as “creative and systematic work, drawing on knowledge gained from research and practical experience, which is directed at producing new products or processes or improving existing products or processes.”1 Applicants interested in receiving financial assistance for basic research (defined by the Office of Management and Budget as “experimental or theoretical work undertaken primarily to acquire new knowledge of the underlying foundations of phenomena and observable facts”)1 should contact the DOE’s Office of Science. Office of Science national scientific user facilities (http://science.energy.gov/user-facilities/) are open to all researchers, including ARPA-E Applicants and awardees. These facilities provide advanced tools of modern science including accelerators, colliders, supercomputers, light sources and neutron sources, as well as facilities for studying the nanoworld, the environment, and the atmosphere. Projects focused on early-stage R&D for the improvement of technology along defined roadmaps may be more appropriate for support through the DOE applied energy offices including: the Office of Critical Minerals and Energy Innovation, the Hydrocarbons and Geothermal energy Office, the Office of Nuclear Energy, and the Office of Electricity.

ARPA-E encourages submissions stemming from ideas that still require proof-of-concept R&D efforts as well as those for which some proof-of-concept demonstration already exists.

Submissions can propose a project with the end deliverable being an extremely creative, but partial solution.

1 OMB Circular A-11 (https://www.whitehouse.gov/wp-content/uploads/2018/06/a11_web_toc.pdf), Section 84,

pg. 3.

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B. PROGRAM OVERVIEW

1. SUMMARY

The Stimulate Utilization of Plentiful Energy in Rocks through High-temperature Original Technologies (SUPERHOT) program aims to boost America’s supply of baseload power by enabling future power production from superhot, geothermal resources, defined as temperatures greater than 375 °C and pressures greater than 22 megapascals (MPa). As the demand for power in the U.S. increases, driven by the rise in data centers and increasing electrification, superhot geothermal power can play an important role in addressing this critical need.2 The amount of energy in the Earth’s subsurface is immense, with estimates of at least 15,000 gigawatts (GW) of producible electricity from depths of at most 10 kilometers (km) within the U.S. alone.3 Unfortunately, access to this resource has been constrained by the limited extent of natural hydrothermal systems, which currently only provide about 4 GW of utility-scale power.

Expansion beyond natural hydrothermal systems is now possible by recent advances in Enhanced Geothermal Systems (EGS) and in Advanced Geothermal Systems (AGS), which essentially create artificial geothermal reservoirs.4 The combination of highly productive superhot wells with the expanded geographic availability provided by EGS or AGS technology can accelerate the widespread development of gigawatt-scale geothermal facilities across much of the U.S., with the possibility of 10-20 GW of baseload power with a levelized cost of electricity (LCOE) less than $30 per megawatt hour (MWh) by 2040.5

The goal of the SUPERHOT program is to support research and development of new technologies to enable scalable superhot geothermal by addressing the major technical challenges affecting geothermal well life and the ability to harvest subsurface energy effectively.6 Consequently, the focus is on the following subject areas: 1) robust well construction, and 2) transfer of heat from the surrounding geologic formation to the well.

2 How data centers and the energy sector can sate AI’s hunger for power [Online]. Available at https://www.mckinsey.com/industries/private-capital/our-insights/how-data-centers-and-the-energy-sector-can-sate-ais-hunger-for-power.

3 Augustine, Chad. Update to enhanced geothermal system resource potential estimate. No. NREL/CP-6A20-66428.

National Renewable Energy Lab. (NREL), Golden, CO (United States), 2016.

4 Norbeck, Jack and Timothy Latimer, 2023, Commercial-scale demonstration of a first-of-a-kind enhanced geothermal system, [online], Available at https://eartharxiv.org/repository/view/5704/ 5 Superhot Rock Energy A Vision for Firm, Global Zero-Carbon Energy, https://cdn.catf.us/wp-content/uploads/2022/10/21171446/superhot-rock-energy-report.pdf 6 Kruszewski, Michal, and Volker Wittig. "Review of failure modes in supercritical geothermal drilling projects."

Geothermal Energy 6, no. 1 (2018): 28. https://geothermal-energy-journal.springeropen.com/articles/10.1186/s40517-018-0113-4.

https://arpa-e.energy.gov/faqs mailto:ARPA-E-CO@hq.doe.gov mailto:ExchangeHelp@hq.doe.gov https://www.mckinsey.com/industries/private-capital/our-insights/how-data-centers-and-the-energy-sector-can-sate-ais-hunger-for-power https://www.mckinsey.com/industries/private-capital/our-insights/how-data-centers-and-the-energy-sector-can-sate-ais-hunger-for-power https://cdn.catf.us/wp-content/uploads/2022/10/21171446/superhot-rock-energy-report.pdf https://cdn.catf.us/wp-content/uploads/2022/10/21171446/superhot-rock-energy-report.pdf https://geothermal-energy-journal.springeropen.com/articles/10.1186/s40517-018-0113-4 https://geothermal-energy-journal.springeropen.com/articles/10.1186/s40517-018-0113-4

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2. TECHNICAL DESCRIPTION

State of the Art and Challenges

EGS and AGS technology (Figure 1) create engineered geothermal systems wherever hot rock exists either by creating subsurface fracture networks or drilling long boreholes. Unfortunately, the highest temperatures that can be accessed are about 220 °C due to the lack of commercial off-the-shelf equipment capable of handling higher temperatures.7 This relatively low temperature limits the power production for EGS to about 10 megawatts-electric (MWe) per well site. The ability to access superhot reservoirs will increase the electrical power per well, potentially up to 30-50 MWe, as both available subsurface heat and thermal-to-power efficiency increase.8

Figure 1. Types of geothermal production (closed loop is also known as AGS).9

7 Fercho, Steven, Jack Norbeck, Emma McConville, Nick Hinz, Irene Wallis, Aleksei Titov, Saurabh Agarwal et al.

"Geology, state of stress, and heat in place for a horizontal well geothermal development project at Blue Mountain, Nevada." In Proc., 48th Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, CA. 2023.

8 Petty, Susan, Trenton Cladouhos, Jill Watz, and Geoffrey Garrison. "Technology Needs for SuperHot EGS Development." Proc., 45th Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, February 10-12, 2020 SGP-TR-216.

9 Figure taken from Blankenship, Doug, Charles Gertler, Mohamed Kamaludeen, et. al. Pathways to Commercial Liftoff: Next-Generation Geothermal Power [online], Available at https://negpa.org/wp-content/uploads/2024/08/LIFTOFF_DOE_NextGen_Geothermal_v14.pdf https://arpa-e.energy.gov/faqs mailto:ARPA-E-CO@hq.doe.gov mailto:ExchangeHelp@hq.doe.gov https://negpa.org/wp-content/uploads/2024/08/LIFTOFF_DOE_NextGen_Geothermal_v14.pdf https://negpa.org/wp-content/uploads/2024/08/LIFTOFF_DOE_NextGen_Geothermal_v14.pdf

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High temperature subsurface rocks exist everywhere but vary greatly in depth. In volcanic regions with a high geothermal gradient (e.g., parts of Hawaii, Alaska, and the West Coast) temperatures of 375 °C may be found at depths as shallow as 5 km. Elsewhere, it will be necessary to drill to depths of 10 km (or more). Drilling wells greater than 9 km has been possible for decades in areas with lower geothermal gradients, although none reached superhot temperatures.10

Well Construction

Previous attempts have been made to produce geothermal power from superhot reservoirs.

Roughly 20 vertical and near-vertical boreholes have been drilled to temperatures as hot as 500 °C and to depths up to 5 km.11,12 Most wells failed rapidly, and none are currently producing power (Table 1).

Table 1. Partial compilation of superhot (hydrothermal) wells and failures.13

10 Zhamaletdinov, A. A. "Fiftieth anniversary of the Kola SG-3 superdeep borehole." Izvestiya, Atmospheric and Oceanic Physics 56 (2020): 1401-1422.

11 Kruszewski, Michal, and Volker Wittig. "Review of failure modes in supercritical geothermal drilling projects."

Geothermal Energy 6, no. 1 (2018).

12 Reinsch, Thomas, Patrick Dobson, Hiroshi Asanuma, Ernst Huenges, Flavio Poletto, and Bernard Sanjuan.

"Utilizing supercritical geothermal systems: a review of past ventures and ongoing research activities." Geothermal Energy 5, no. 1 (2017): 1-25.

13 Suryanarayana, P.V., Ravi M Krishnamurthy, and Daniel Bour, “Bridging the Gaps: A Survey of Methods, Challenges, and Pathways Forward for Superhot Rock Well Design and Construction”, https://cdn.catf.us/wp-content/uploads/2024/10/01162900/shr-well-design-construction.pdf

Well Year Temp °C Cause of Failure Location

NJ-11 1985 380 Supercritical flows, Inability to control well, leaks, blow-out. Well abandoned. Iceland

IDDP-1 2008 450 Casing failure, suspected to be due to quenching. Possible high temperature hydrogen attack. Iceland

IDDP-2 2016 427

Damaged casing due to cement gap at roughly 2,300 m depth, number of collapse and tensile failures, wellhead failure.

Iceland

KJ-39 2008 386 Well construction not adequate for supercritical point. Iceland

HE-53 2009 N/A Blowout and failure of production casing (connections) after quenching, flow from shallower depths. Iceland

San Pompeo-2 1979 394 Blow-out, well not suitable for superhot, abandoned. Italy

Sasso-22 1980 380 High well temperatures, corrosive fluids, damaged casing. Italy

San Vito-1 1980 419 Well architecture not rated above 300°C. Italy

Venelle-2 2017 517 Cementing failure, well abandoned. Italy

WD-1A 1994 500 Safety concerns of high temperatures for its architecture. Japan https://arpa-e.energy.gov/faqs mailto:ARPA-E-CO@hq.doe.gov mailto:ExchangeHelp@hq.doe.gov https://cdn.catf.us/wp-content/uploads/2024/10/01162900/shr-well-design-construction.pdf https://cdn.catf.us/wp-content/uploads/2024/10/01162900/shr-well-design-construction.pdf

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Superhot geothermal facilities must be constructed in a cost-effective manner and should have a life of approximately 15 years. The materials used in the construction and the construction procedure itself must be suitable for an environment with high temperatures, rapid changes in temperature, and corrosive fluids.14 Current geothermal wells typically consist of steel casing and liners combined with a Portland cement variant.15 This conventional design appears inadequate for superhot wells. Two possible approaches exist: 1) modification of conventional well designs (e.g., casing and cement-based designs) with new materials to survive superhot conditions, or 2) completely novel designs (and possibly new materials or materials systems) that satisfy superhot requirements. An essential component for both approaches is comprehensive testing and validation, both via numerical models and experiments at laboratory scale in the expected operating conditions. Thorough testing prior to implementation is critical as operational failures in superhot wells are catastrophic and expensive to repair.

Several key factors make construction of superhot wells difficult: high-performance metal alloys and materials are expensive for the quantities needed for kilometers of geothermal casing;16 installation and deployment require well-vetted procedures; and superhot geothermal

14 Suryanarayana, P.V., Ravi M Krishnamurthy, and Daniel Bour, “Bridging the Gaps: A Survey of Methods, Challenges, and Pathways Forward for Superhot Rock Well Design and Construction”, [Online] Available at:

https://cdn.catf.us/wp-content/uploads/2024/10/01162900/shr-well-design-construction.pdf 15 Finger, John Travis, and Douglas A. Blankenship. Handbook of best practices for geothermal drilling. No.

SAND2011-6478. Sandia National Lab.(SNL-NM), Albuquerque, NM (United States), 2012. [Online]. Available at https://www.osti.gov/biblio/1325261 16 Lowry, Thomas S., John T. Finger, Charles R. Carrigan, Adam Foris, M. Kennedy, T. Corbet, C. Doughty, Stephen Pye, and E. Sonnenthal. "GeoVision Analysis Supporting Task Force Report: Reservoir Maintenance and Development." SAND2017-9977. Albuquerque, NM: Sandia National Laboratories. [Online]. Available:

https://www.osti.gov/biblio/1394062

Well Year Temp °C Cause of Failure Location

H-43 2007 395 Corrosion, precipitation, and erosion from superheated steam. Mexico

Wilson No.

1 1981 400 Casing collapse. Abandoned. USA

KS-13 2005 N/A Encountered magma, problems recovering, well abandoned. USA

IID-14 1990 390 Abandoned due to concerns about well controllability. USA

Prati-32 2010 400 Used as injection well in a pair. USA

Nisyros-1 1982 400 Initial production casing damaged at several locations during test, remedial tieback also experienced buckling and collapse.

Greece

OW-740A 2018 >300 Parted casing at shallow depths, quenching/ high thermal stresses. Kenya

MW 1-6 2011 325-400 Circulation loss / stuck pipe / encountered magma. Kenya https://arpa-e.energy.gov/faqs mailto:ARPA-E-CO@hq.doe.gov mailto:ExchangeHelp@hq.doe.gov https://cdn.catf.us/wp-content/uploads/2024/10/01162900/shr-well-design-construction.pdf https://www.osti.gov/biblio/1325261 https://www.osti.gov/biblio/1394062

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- 12 -technology experiences extreme conditions including high temperatures, high-pressure corrosive fluids, and repeated thermal cycling.

Exposure to corrosive fluids over the course of the well lifetime will result in degradation to the well casing and the cement; therefore, reliability of well components is a significant factor in well design. In an EGS, water is injected into one well and then flows through fractures to the nearby production well while reacting with the surrounding rock. The final composition of the fluid in the production well depends on the lithology of the rock and on the temperature, pressure, and phase state (sub- or supercritical) of the water. AGS fluids may have less direct interaction with host rock and fluids may not be as corrosive. The effects will be exacerbated at the supercritical point due to the changes in both physical properties (e.g., density, viscosity, enthalpy) and chemical properties (polar to a non-polar solvent).17,18 The temperature and pressure of the supercritical point will vary with the concentration of solutes. Precipitation (scaling) of dissolved solids may also be an issue as the fluids cool or change phase and may obstruct flow in the borehole or surface facilities.

Multiple factors will impact the mechanical stability of the well. Thermal cycling, which may cause temperature changes up to 350 °C in the wellbore, creates significant stress on the casing due to expansion or contraction. Hydraulic stimulation procedures will impose additional stress variations. The stress variations may pose problems at connections and regions where the cement integrity is poor.17

Addressing these issues will require a combination of design, procedures, and advanced materials. The designs and materials must undergo extensive reliability testing and be validated for superhot conditions prior to deployment. This will require testing facilities capable of handling superhot temperatures, pressures, and potentially corrosive fluids both in a subcritical and supercritical state. Facilities for testing water at supercritical temperatures and pressures exist in other industries, but they typically do not include highly corrosive fluids. Most thermal-hydraulic-mechanical-chemical (THMC) numerical codes used in reservoir engineering do not include ductile rock behavior or equation-of-state for supercritical water as required to model superhot reservoir and well behavior.

Heat Extraction

The heat transfer from a superhot reservoir to a working fluid within the borehole needs to be effective over the 15 year or more expected lifetime of the reservoir. EGS extracts heat by forcing water through artificially created fracture systems in hot, brittle rock between two wells. The fractures are created by injecting water at high pressure into the well, similar to

17 Galli, Giulia, and Ding Pan. "A closer look at supercritical water." Proceedings of the National Academy of Sciences 110, no. 16 (2013): 6250-6251.

18 Bröll, Dirk, Claudia Kaul, Alexander Krämer, Petra Krammer, Thomas Richter, Matthias Jung, Herbert Vogel, and Peter Zehner. "Chemistry in supercritical water." Angewandte Chemie International Edition 38, no. 20 (1999):

2998-3014.

https://arpa-e.energy.gov/faqs

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- 13 -hydraulic fracturing in gas shales. AGS extracts heat by flowing water only through the borehole rather than fracture systems, which may require extended boreholes.

None of the superhot wells drilled to date have attempted EGS-type fracture stimulation.

Hydraulic fracturing in brittle rocks is well-proven, but at high temperatures rocks begin to display ductile deformation (rather than brittle) depending on the strain rate and lithology (Table 2). The fractures may form a diffuse cloud in partially ductile rock which may be more favorable for heat extraction.19 Fracture flow rates for supercritical water will differ from subcritical water. It is essential to model and verify fracture geometry, longevity, and flow rates.20 The effectiveness of proppants should be investigated. An associated risk of EGS is the possibility of induced seismicity, which is associated with hydraulic stimulation at lower temperatures.