Unlocking Geothermal Potential:
The Potential of GreenLoop Systems

Jakarta, Indonesia - May 16, 2024

Article by Ericko L.

Geothermal energy, utilized from the Earth's heat, has long been recognized as a sustainable and reliable source of power. Traditional geothermal power generation relies on the extraction of geothermal fluid from subsurface reservoirs, typically characterized by high temperature, benign fluid composition, and sufficient permeability. However, not all wells drilled meet these criteria, leading to the classification of some as non-commercial wells due to tight permeability or other limitations. These wells are often deemed unsuitable for conventional geothermal power generation, thus creating challenges for resource utilization.

In recent years, advancements in technology have expanded the possibilities for geothermal energy utilization, with closed-loop systems emerging as a promising solution for unlocking previously untapped geothermal resources. Closed-loop geothermal systems offer a novel approach to utilizing geothermal energy, avoiding the need for high-permeability reservoirs. Closed Loop Geothermal System (CLGS) is a method to extract geothermal energy by circulating a working fluid continuously into a sealed/closed wellbore and the closed system to avoid fluid leakage and reservoir blockage (Muir, J. R., 2020).

GreenFire Energy Inc. (GFE) has been pioneering the development of Closed-Loop Geothermal (CLG) technology since 2014, notably with its GreenLoop system (Figure 1). GreenLoop is a downbore heat exchanger (DBHX) comprising a tube-in-tube setup installed within existing wells, offering a straightforward yet highly effective solution for immediate application. The system features a liner with a sealed end at the base to prevent the working fluid from escaping into the wellbore.

GreenLoop’s system uses a liquid that moves through the bottom of the DBHX. The liquid goes into the space between the inner and outer parts of the DBHX and the plugged liner. This helps transfer heat from the source to the cold liquid that goes back up to the surface through the insulated tube. Hot liquids from the reservoir touch the outer part of GreenLoop with convection transfer, heating the liquid inside the DBHX. The liquid used can be water, supercritical carbon dioxide (sCO2), or other working fluids.

The hot working fluid goes back up to the surface. There, the heat turns into electricity using steam condensing turbines. These condensing turbines are connected to a special system called an Organic Rankine Cycle (ORC) power unit. The heat can also be used directly for things like heating or cooling large areas. When it is running, water collects on the outside of a special part of the system. This water goes down to the bottom of a hole, adding pressure with other liquids to push the hot liquid back into the ground.

GreenFire Energy Inc. successfully installed GreenLoop in Coso, California. The project used  DBHX to extract heat from an unused well. Tested using water and sCO2 as fluids, both can be effectively used as a transfer fluid for closed-loop geothermal. The DBHX installed can produce ~1.2 MW of net electric power.

Indonesia, located in the Pacific Ring of Fire, has a lot of geothermal power potential. One big problem in finding geothermal energy in Indonesia is finding a resource that has high temperature and permeability. A closed-loop geothermal system is a way to use existing unused wells in Indonesia to generate electricity. By retrofitting existing wells with closed-loop geothermal systems, Indonesia could significantly expand its geothermal power generation capacity.