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Details of Grant 

EPSRC Reference: EP/Y009568/1
Title: Recovery of metals from geothermal brines
Principal Investigator: Blundy, Professor JD
Other Investigators:
O'Hare, Professor D Wood, Professor BJ
Researcher Co-Investigators:
Dr A Gion
Project Partners:
Clean Resources GEORG Geothermal Research Cluster Inst of Geological and Nuclear Sciences
Parker Wellbore Tohoku University University of Calgary
Department: Earth Sciences
Organisation: University of Oxford
Scheme: Standard Research
Starts: 01 May 2024 Ends: 30 April 2028 Value (£): 934,132
EPSRC Research Topic Classifications:
Earth Engineering Properties Of Earth Materials
EPSRC Industrial Sector Classifications:
Related Grants:
Panel History:  
Summary on Grant Application Form
The need to transition from a society powered by fossil fuels to one powered by renewable resources is a globally-recognized, urgent problem. One attractive source of base-load renewable energy is geothermal energy, although high capital and production costs mean that in many parts of the world geothermal energy is not economically competitive against fossil fuel alternatives. In Japan, for example, geothermal electricity costs 2-4 times as much to generate per kWh as that from gas-fired power plants.

One strategy to increase the power output of geothermal plants is through accessing even hotter and deeper 'supercritical' fluids, with temperatures in excess of 400 Celsius and depths over 3 km. Such fluids can carry up to ten times more enthalpy than conventional geothermal fluids, and trial supercritical projects are underway in USA, Mexico, Japan, Iceland, Italy and New Zealand. However, the greater contribution of magmas (silicate melts) to supercritical fluids means that they can have significantly higher solute loads, making them much more likely to cause well-bore scaling, a perennial problem in geothermal systems. On the other hand, the higher solute load brings with it opportunities if the dissolved metals can be recovered commercially alongside the heat. This provides a second value stream that could greatly reduce the costs of geothermal power generation. Many of the metals dissolved in supercritical fluid are those commonly used in batteries and electric vehicles capable of producing scales with metal concentrations comparable to high-grade ores. The total polymetallic value of supercritical fluids is estimated to be up to ten times that of their contained energy, giving a sense of the considerable economic benefit to recovering metals alongside geothermal energy.

To date, the co-production of geothermal energy and metals is limited to lower temperature, relatively solute-poor fluids and has not yet been considered for supercritical systems. Currently, most metals present in geothermal fluids are either lost to scale downhole, which also reduces the efficiency of the well, or left in solution and lost as waste. The aim of this project is to develop novel functional materials that selectively remove metals from saline, supercritical geothermal fluids. These materials will not only enable metals recovery, but also help inhibit problematic scale growth on the well-bores. The use of minerals to recover metals is in contrast to the more common use of immiscible solvents whose selectivity between different metals is consistently less. We will build upon our long experience of metal-fluid partitioning of metals in geologic systems to select the optimum metal-sequestering minerals for geothermal fluids.

The objectives will be accomplished in several stages. The initial stage will involve characterisation of geothermal scale found in active geothermal wells. Metal contents and scale mineralogy will be determined. This step will help inform which materials can be used to selectively remove the metals of interest from the geothermal fluid. Hydrothermal experiments will then be performed at small-scales and in novel flow-through reactors to determine the efficiency at which the chosen materials can remove metals from supercritical fluids. During the last stage of the project, strategies for synthesising the materials downhole, as well as recovery of metals at the surface, will be developed through collaboration with industry partners.

The project represents translational science whereby an understanding of element partitioning in geological and engineered systems is used to bridge a fundamental knowledge gap between the mining and geothermal energy sectors in the development of a novel approach to the Net Zero transition. Our choice of project partners from the global geothermal research, drilling and metals processing community will facilitate scale-up and commercial uptake at this new research frontier.
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Organisation Website: http://www.ox.ac.uk