Week 44 Geothermal: Supercritical CO2 brings us heat from beneath our feet

Hot Springs- Photo Credit - emosaidis & Free Images - Pixabay

Welcome to the forty-fourth edition of my weekly blog where I take a closer look at the policies adopted by individual countries in their efforts to meet the requirements of the Paris Agreement. Particular attention is paid to the role that Carbon Capture, Utilisation, and Storage (CCUS) research and technologies are playing in the drive to meet these requirements.

Introduction
This week I take a look at how advances in carbon capture and utilization technologies are being exploited to enhance geothermal systems and also to provide permanent storage site for CO2.

Geothermal Energy
Geothermal energy is generated naturally when heat from the Earth’s crust warms underground water reservoirs and the subsequent steam that is formed breaks through the surface at ground level (hydro-geothermal). This typically occurs in regions of the world where two tectonic plates have collided.

Geysers are a well-known type of geothermal energy located close to volcanoes. Iceland is famous for its geysers. Geysers are also found in other areas of the world such as Chile and Yellowstone National Park in the US.

Enhanced Geothermal Systems (EGS)
The Pembina Institute (PI) defines enhanced Geothermal systems as the transfer of geothermal heat through supercritical CO2 or the direct generation of power from supercritical CO2 turbines. Supercritical CO2 is a fluid and occurs when CO2 is held at or above its critical temperature and pressure. In the context of CO2, water is replaced by supercritical CO2 and is injected into man-made underground reservoirs in a closed loop. The vapour rising from the heating of the CO2 reaches the surface and turns turbines to generate electricity.

PI highlights permanent storage capability and improving the efficiency of geothermal energy as benefits accruing from EGS. Limitations included the length of time to make it commercially viable, supercritical CO2 transportation costs, and a requirement for grid connection on site.

Iceland and United Nations University
Iceland was featured in week 19 of this blog, what we learned then was that approximately 90% of Icelandic homes are heated naturally with energy sourced from their geothermal plants.

We also found out that the United Nations University has trained over 500 scientists at their geothermal training programme in Iceland on how geothermal energy can be implemented in their countries.

Just to provide an idea of the potential for geothermal energy, Kenya who sent scientists to the United Nations University in Iceland built the first geothermal plant in Africa in the Olkaria fields in Southwestern Kenya, 120 km North West of Nairobi. Roughly 50% of Kenyan electricity now sourced from geothermal energy.

KenGen operates the geothermal plants, and say the plants have the potential to increase electricity generation to 1,000 megawatts, almost double the existing levels. This would mean that the geothermal plants could support the energy needs of the population of Kenya, similar to Iceland. KenGen says that each new wells costs approximately USD$6m to install, however, the benefits can be realized immediately at a geothermal plant that is already connected to the grid.

Summary
Geothermal energy is not new, it occurs naturally in places like Iceland where the local inhabitants have reaped its benefits for centuries. Enhanced Geothermal Systems is a clever innovation on this that can help boost the efficiency of clean energy produced and also find a permanent storage site for CO2.

Countries like Kenya are taking advantage of this technology are able to generate electricity during drought periods, reducing their reliance on diesel generators.

Next week’s blog will profile Luxembourg and their efforts to meet their CO2 emissions reduction targets.
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If you liked this article you might enjoy reading some recent articles in the series:
Week 43 Ireland: Dear Leo, by the time you read this letter we’ll all be gone
Week 42 Austria: New Government, same renewable energy goal
Week 41 Enhanced Oil Recovery: extracting oil more efficiently and replacing it with CO2.