Green Therma’s Fifth Generation Geothermal Technology Targets Heat Markets Image : Kimm Gunn Maver , Chief Geologist at Green Therma The geothermal industry has historically depended on favourable geological conditions, naturally permeable reservoirs and the availability of underground fluids. Although conventional hydrothermal systems have enabled commercial geothermal electricity generation across several countries, their dependence on specific geological characteristics has limited the number of locations where projects can be developed successfully. A new generation of engineered geothermal technologies is seeking to address these limitations by changing how heat is extracted from the subsurface. Green Therma is advancing what it describes as Generation 5 geothermal technology , centred on Enclosed Loop Geothermal (ELG). Unlike conventional hydrothermal systems and Enhanced Geothermal Systems (EGS), the technology uses a fully enclosed engineered piping arrangement that prevent...
Green Therma’s Fifth Generation Geothermal Technology Targets Heat Markets
Image : Kimm Gunn Maver , Chief Geologist at Green Therma
A new generation of engineered geothermal technologies is seeking to address these limitations by changing how heat is extracted from the subsurface.
Green Therma is advancing what it describes as Generation 5 geothermal technology, centred on Enclosed Loop Geothermal (ELG). Unlike conventional hydrothermal systems and Enhanced Geothermal Systems (EGS), the technology uses a fully enclosed engineered piping arrangement that prevents circulating fluids from coming into contact with geological formations.
Through its Heat4Ever™ technology and DualVac™ insulation, Green Therma aims to improve heat extraction and transportation while reducing dependence on naturally occurring reservoir conditions.
The proposed approach could have important implications for industrial heat, district heating and regions where geothermal temperatures are available but conventional geothermal development faces geological constraints.
In this exclusive Q&A with Alphaxioms, Kimm from Green Therma explains the evolution of geothermal technology, the engineering behind Generation 5, its commercial potential, environmental characteristics and opportunities in emerging geothermal markets.
1. The Evolution of Geothermal Technology
Alphaxioms: Your publication introduces a framework categorising geothermal development into five generations. What technological limitations in previous generations motivated this classification?
Kimm, Green Therma:
Initially, geothermal was very geology-dependent, severely limiting the number of sites where it was commercially viable and resulting in a low success rate.
This issue was addressed through increasingly complex well designs, which have proven both expensive and difficult to execute.
Our fifth-generation fully engineered geothermal system will always work, and the well design is simple.
The classification therefore reflects the industry's continuing efforts to overcome geological dependence and improve the predictability of geothermal development.
2. Understanding Generation 5: Enclosed Loop Geothermal
Alphaxioms: What fundamentally distinguishes Enclosed Loop Geothermal (ELG) from conventional hydrothermal, EGS and earlier closed-loop systems?
Kimm, Green Therma:
The key feature with ELG is that the system is completely enclosed through an engineered piping solution. No fluids will be in contact with or flow through the geological formations.
As a result, a completed well will always produce heat.
In hydrothermal systems, you need a reservoir with unique properties to flow a fluid through.
EGS requires that the tight reservoir is first stimulated or fractured and, secondly, that a fluid can flow through the stimulated reservoir.
Finally, some closed-loop systems flow the fluid partly through a tight but still open hole.
ELG takes a different approach by maintaining an enclosed circulation system, separating the working fluid from the surrounding geological formation.
This distinction is central to Green Therma's Generation 5 proposition: extracting geothermal heat through an engineered system rather than relying on the natural movement of fluids through underground formations.
3. The Engineering Breakthrough: Heat4Ever™ and DualVac™
Alphaxioms: How does Green Therma's Heat4Ever™ technology and DualVac™ insulation address the longstanding challenge of heat loss in deep closed-loop geothermal systems?
Kimm, Green Therma:
DualVac™, which transports heat back to the surface, is a pipe-in-pipe solution. Between the two pipes there is a vacuum.
It is a continuous vacuum for the full length of the installation.
The vacuum is created once after installation. However, a vacuum pump is available at the surface if the vacuum needs to be partly recreated over time.
The vacuum reduces heat loss from 30–40% to a few percent, depending on the length of the well and the circulation speed.
Heat transportation is an important consideration in closed-loop geothermal development. Heat extracted at depth must be transported to the surface efficiently enough to support commercially useful temperatures.
Green Therma's DualVac™ arrangement is designed to address this challenge through vacuum insulation, reducing thermal losses along the transportation pathway.
The company's stated objective is to improve the amount of usable heat delivered to the surface, supporting the economics of engineered geothermal installations.
4. Geological Accessibility and Scalability
Alphaxioms: Could Generation 5 technology genuinely expand geothermal development into regions without naturally permeable reservoirs or sufficient hydrothermal resources? What geological limitations remain?
Kimm, Green Therma:
Yes, that is completely possible.
As the system only depends on thermal conductivity, it is independent of permeability, porosity and naturally occurring water.
If a well is successfully completed, it will always produce heat.
The heat production depends on the geothermal temperature gradient and the thermal conductivity of the rock surrounding the well.
This approach potentially changes the geographical boundaries of geothermal development.
Conventional geothermal projects often require a combination of suitable temperatures, permeability, fluid availability and reservoir characteristics. By contrast, ELG is designed to extract heat without requiring fluids to circulate through the geological formation.
However, the distinction between producing heat and producing commercially competitive quantities of heat remains important.
Temperature gradients, rock thermal conductivity, well depth, drilling costs and the engineering performance of the installation will continue to influence project economics.
For countries with geothermal resources but limited conventional reservoir productivity, engineered closed-loop systems could introduce another development pathway.
5. Commercial Viability and Economics
Alphaxioms: What are the principal cost drivers of Generation 5 geothermal projects, and how competitive could this technology become against conventional geothermal, natural gas and other sources of industrial heat?
Kimm, Green Therma:
The principal cost driver is drilling cost and the number of days it takes to drill the well, which have been proven to be reducible drastically.
In general, the solution can compete on Levelised Cost of Heat (LCOH) when written off over 30 years.
With an expected system lifetime of more than 50 years, it becomes a very attractive solution.
Drilling economics are therefore central to the commercial proposition.
The cost of constructing a geothermal well can represent a substantial proportion of the initial project investment. Reducing drilling time and improving the rate of penetration could consequently have a significant impact on capital expenditure.
The long operating life proposed by Green Therma also introduces an important consideration when comparing geothermal heat with alternative energy sources.
Rather than assessing project economics only through initial investment, developers must consider the lifetime cost of producing and delivering heat.
For industrial users, district heating networks and other heat-intensive applications, the relevant comparison is the cost of reliably supplying heat over the project's operating life.
Nevertheless, commercial competitiveness will ultimately depend on actual drilling performance, installation costs, operating expenses, delivered temperatures, system efficiency and the financing structure of individual projects.
6. Environmental Performance and Risk
Alphaxioms: How does a fully enclosed geothermal circulation system change the industry's approach to water consumption, induced seismicity, reservoir management and environmental protection?
Kimm, Green Therma:
That is the beauty of an enclosed solution: it removes all the concerns.
The well only needs water once at the onset of heat production.
As there is no fluid circulation into the geological formation, seismicity is not induced.
The Earth is one big "reservoir" as the system relies on thermal conductivity that is continuously being replenished.
It circulates the same fluid (water) in the enclosed loop as is used in district heating, and therefore there are no environmental concerns.
The enclosed configuration is intended to reduce several environmental challenges associated with conventional geothermal operations.
In conventional hydrothermal and EGS developments, managing underground fluids, reservoir pressures and injection operations can be important aspects of project design and environmental management.
By keeping the working fluid within an engineered circulation system, ELG seeks to avoid the need for fluid injection into the geological formation as part of normal heat extraction.
This could be particularly relevant in areas where water availability, reservoir management or concerns about induced seismicity influence the development of geothermal projects.
The actual environmental performance of individual installations will still depend on drilling practices, construction materials, surface infrastructure, operational requirements and the management of the complete project lifecycle.
7. Global Deployment and Emerging Markets
Alphaxioms: What opportunities do you see for Generation 5 geothermal in emerging geothermal markets such as Kenya, Indonesia, Ethiopia and other East African countries?
Kimm, Green Therma:
An enclosed system will work anywhere in the world.
The listed countries are very fortunate to have very high geothermal temperatures where hydrothermal solutions producing electricity are possible.
But if there are places where heat is the required energy resource and a hydrothermal solution cannot work, an enclosed system is possible.
This perspective is particularly relevant for emerging geothermal markets.
Kenya, Indonesia and Ethiopia have significant geothermal resources and established interest in developing geothermal electricity. However, not every location within these countries possesses the geological conditions required for conventional geothermal power production.
Generation 5 technology could potentially complement existing geothermal development strategies by targeting locations where the resource is better suited to direct heat applications than conventional hydrothermal electricity generation.
Potential applications include industrial process heat, district heating, agricultural processing and other sectors requiring dependable thermal energy.
For East Africa, the opportunity is particularly interesting because geothermal resources extend beyond established electricity-generation fields.
The possibility of developing geothermal heat without depending on naturally permeable reservoirs could broaden the range of locations considered for geothermal investment.
However, project-specific assessments would remain essential to establish suitable well depths, temperatures, thermal conductivity, drilling requirements and the cost of delivering usable heat.
A General Comment on the Enclosed Solution from Kim Gunn Maver
Why an engineered enclosed loop co-axial geothermal well solution only dependent on thermal conductivity and applicable everywhere is a true democratic energy source:
Found and developed locally. There is always geothermal heat beneath your feet that can be produced
Have multiple usages in the local society including district heating. Heated water in the 60 to 120 degrees range have many applications
Serves the local community. Secure, minor surface footprint, no environmental impact, nearly removing heat production from an overstretched electrical grid
- 8. The Future of Geothermal: What Comes After 2030?
Alphaxioms: Looking towards 2030 and beyond, do you believe engineered closed-loop systems could become a major part of the global geothermal industry, and what milestones must the industry achieve to make this possible?
Kimm, Green Therma:
As the enclosed-loop system can practically be implemented everywhere, it will become a cornerstone in the renewable energy transition and become a major supplier of heat.
Remember that more than half the world's energy demand is for heat.
The speed of enclosed-loop deployment will largely be driven by reduction in well costs as a result of increased drilling speed (Rate-of-Penetration).
The future expansion of geothermal energy may therefore depend not only on electricity generation but also on the industry's ability to supply reliable and competitive heat.
Industrial decarbonisation, district heating and the replacement of fossil-fuel-based thermal energy represent substantial opportunities for geothermal technologies.
For Generation 5 systems, demonstrating drilling efficiency, maintaining insulation performance, validating long-term system reliability and establishing competitive LCOH will be important milestones.
The ability to replicate installations across different geological environments will also be important in establishing confidence among developers, investors and industrial heat consumers.
Alphaxioms Analysis: Could Generation 5 Change the Geothermal Market?
Green Therma's Generation 5 proposition introduces an important question for the geothermal industry: can engineered systems make geothermal heat commercially accessible beyond locations with naturally productive hydrothermal reservoirs?
The company's approach is based on separating the working fluid from the geological formation and relying on heat transfer through engineered piping and the surrounding rock.
This differs fundamentally from conventional geothermal production, where the characteristics of the underground reservoir play a central role in determining project success.
Three areas deserve particular attention.
First, geological independence. By reducing dependence on natural permeability and underground fluid movement, enclosed-loop systems could expand the geographical range of geothermal heat development.
Second, drilling economics. Green Therma identifies drilling speed and well construction costs as the principal determinants of commercial competitiveness. Improving the rate of penetration could therefore be critical to scaling the technology.
Third, the global heat market. Geothermal development has traditionally attracted significant attention for electricity generation. However, industrial heat and district heating offer another major market, particularly as industries seek alternatives to fossil fuels.
There are also important questions that will need to be answered through commercial demonstrations and independently verified performance data.
These include sustained heat output, thermal drawdown, well lifetime, vacuum insulation durability, pumping requirements, delivered temperatures and actual levelised cost of heat.
The distinction between a system that can technically extract heat and one that can deliver commercially competitive heat at scale will ultimately determine its market position.
Nevertheless, Green Therma's Generation 5 framework contributes to a wider technological shift towards engineered geothermal systems that seek to make subsurface heat more accessible.
Conclusion
The next phase of geothermal development may be shaped by technologies that reduce the industry's dependence on naturally favourable geological conditions.
Green Therma's Enclosed Loop Geothermal concept represents one approach to this challenge, combining engineered circulation, Heat4Ever™ technology and DualVac™ insulation to improve heat extraction and transportation.
Its long-term commercial potential will depend on drilling performance, engineering reliability and the ability to demonstrate competitive heat production across different geological environments.
For emerging geothermal markets such as Kenya, Indonesia and Ethiopia, the technology could provide an additional pathway for expanding geothermal applications beyond conventional electricity-generation fields.
As the global energy transition increasingly focuses on industrial heat, the question facing the geothermal industry may no longer be limited to where electricity can be generated, but also where underground heat can be economically accessed.
Alphaxioms will continue tracking the technologies, companies and investments shaping the next generation of geothermal development.
Related: Unlocking Impermeable Geothermal Reservoirs: Hydraulic Stimulation, Menengai and Olkaria
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