Fri, 22 May, 2020
Geothermal resources are naturally aggressive environments due to inherent high temperature conditions and scaling effects of the geothermal fluids, which pose a major threat to the integrity of various components of power plants. The geothermal fluids often contain high proportions of components like carbonates, silicates, sulphates and chlorides, causing extensive surface damage via corrosion, erosion and scaling mechanisms. These damage mechanisms can vary widely based on the thermomechanical properties of the geothermal fluid as well as on the design of the plant components, including material selection and dimensions. Click here to find out what the experts say on current challenges and opportunities in geothermal.
Funded under the European Commission ‘s H2020 programme in 2017 (Grant agreement number 764086), project Geo-Coat, part of the low carbon energy call to develop next generation technologies for renewable electricity and heating/cooling, was commissioned to design the new high performance coatings to resist the threats posed by the aggressive geothermal environments.
A Consortium of Complimentary Expertise
Led by TWI’s experience and knowledge in coatings, material properties (how materials and components behave and degrade), the Geo-Coat consortium had the complementary expertise to deliver innovations with socio-economic and environmental impacts. With technological advancements tailored to meet the differing needs of specific geothermal environments, the project was aimed at improving the growth and exploitation of geothermal energy by significantly reducing the environmental impact of installation as well as operational expenditure (Opex) and capital expenditure (Capex).
Following the kick-off in February 2018 at TWI, the project has been working on materials that offer the advantage of allowing the resistant coating materials to be applied to a cheaper substrate than the resistant alloy material, such as titanium or nickel alloys, which would be otherwise used in an un-coated form. Coating deposition parameters have been optimised, leading to the development of corrosion- and erosion- resistant coatings, based on selected High Entropy Alloys (HEAs) and Ceramic/ Metal mixtures (Cermets). These are applied through thermal powder coating techniques (primarily high-velocity oxygen fuel spray / laser cladding) developed ad-hoc to provide the required bond strength, hardness and corrosion resistance for the harsh geothermal service conditions. One of the many advantages of the Geo-Coat technology is that the new materials can be applied as coatings at specific failure points rather than the whole component, thus leading to an extension of the components’ lifetime at a relatively low cost.
After 2 years of exhaustive lab-based work, the project has now entered its final phase, where the Geo-Coat test coupons are being tested in the simulated geothermal environment and field tests undertaken to confirm their performance in service applications. “The developed coatings show remarkable improvements in terms of lab-based corrosion, erosion and cost performance compared to state-of-the-art alloys, and we are currently testing the coatings in-situ within geothermal power plants in order to further prove their efficiency. We expect the project to provide new materials to help geothermal power plant operators to reduce both operational and capital investment through initial material cost reduction and reduced production downtime”, explains Francesco Fanicchia, Senior Project Leader and coordinator of project Geo-Coat completes two successful years.
To find out more about the role of materials science in geothermal, read our insight “Materials Science: Opportunities for Geothermal Technology”.
To discover more about the project’s latest activities, check out the latest edition of the Geo-Coat Newsletter, Issue 4.