The corrosion behaviour of a new titanium-based alloy, with nickel, molybdenum and zirconium as the main alloying elements, was studied in a simulated geothermal environment at various phase conditions of a corrosive fluid. Corrosion testing of carbon steel was also conducted for comparison. Both materials were tested at an elevated temperature between 180 and 350 °C and at a 10 bar gauge pressure in H₂O containing HCl, H₂S, and CO₂ gases with an acidic condensate of pH = 3. The study found that the titanium alloy demonstrated good corrosion resistance in a single- and multiphase geothermal environment. In the testing volume, where the boiling of testing fluid occurred, the carbon steel was prone to localized damage of oxide, sulphide and chloride corrosion products. In the superheated testing volume, a homogeneous oxide corrosion layer was observed on the carbon steel. In the testing volume where condensation of the testing fluid occurred, a sulphide layer with an oxide sublayer was formed on the carbon steel.

Recurrent influxes of pelagic Sargassum seaweed along Caribbean coastlines pose growing environmental and socio-economic challenges while offering an underutilised renewable biomass resource. This study examines the feasibility of converting Caribbean Sargassum into a solid biofuel through pelletisation, focusing on energy performance and process efficiency. Pellets were produced at laboratory scale using four feedstock compositions containing 0–100% Sargassum, providing the first systematic experimental assessment of full-range Sargassum co-pelletisation combined with an energy balance. Pellets were characterised for density, mechanical strength, moisture and ash contents, and higher heating value, and an energy balance was developed for the full processing chain, including collection, preprocessing, drying, and pelletisation. Results show that Sargassum can be densified into mechanically robust pellets with high particle and bulk densities. However, increasing Sargassum content sharply increased ash content and reduced heating value, with pure Sargassum pellets exhibiting ash contents near 47% and heating values below 8 MJ kg−1. Drying was the dominant energy consumer, rendering net energy returns marginal for 100% Sargassum pellets. Co-pelletisation with woody biomass at 50–75% Sargassum provided a more favourable balance between energy yield and biomass utilisation. Overall, Sargassum pelletisation is best suited to industrial-scale renewable and waste-to-energy systems integrated with efficient drying strategies.

Intermittent drying (ID) is often reported to be more energy-efficient than continuous drying (CD), although prior studies frequently lack consistent comparison conditions. A recent meta-analysis suggested a probable correlation between material thickness, initial water content, and the specific energy savings of ID. The present study was conducted to experimentally validate these findings under controlled and comparable conditions. Drying experiments were performed using a porous sponge model, with thicknesses ranging from 12 to 48 mm and initial water contents from 30% to 70% (wet basis), while maintaining identical operating conditions and total drying time for both ID and CD. Results show that the energy advantage of ID is condition-dependent rather than universal. For thin or low-moisture samples, the specific energy consumption ratio (ĒCD/ĒID) remained close to unity (~0.97–1.00), indicating negligible differences. In contrast, for thicker (≳36 mm) and wetter (≳60%) samples, the ratio reached ~ 1.05, corresponding to energy savings of up to 4–5%. These findings support a threshold-like behavior governed by internal moisture redistribution during tempering. The study provides experimentally validated criteria for selecting drying strategies and highlights the importance of fair comparison under equal drying duration

Currently, there are several deep drill geothermal projects that aim to discharge superheated or supercritical geothermal fluid for sustainable power production. In geothermal power utilisation, the well casing steel and surface equipment is susceptible to corrosion due to corrosive species in the geothermal fluid. The temperature and the phase state of the fluid greatly affect the extent and the forms of corrosion that can occur. To mitigate corrosion damage in the casing and surface equipment, the recently developed production method Extra High-speed Laser Application (EHLA) cladding is proposed as a solution. To simulate application of carbon steel and EHLA clads in superheated geothermal wells, the materials were tested in a superheated steam containing CO₂ and H₂S at 450 °C temperature and 150 barG pressure. Microstructural and chemical analysis was performed with SEM, EDX and XRD, and corrosion rate was analysed with the weight loss method. The carbon steel was prone to corrosion with a double corrosion layer but the corrosion of the EHLA clads was insignificant. The results show that the EHLA clads tested have good corrosion resistance in the test environment, and the study can aid in the selection of casing and clad materials for future deep geothermal wells. Furthermore, this study shows that the EHLA clads increase the variety of corrosion mitigation solutions for future geothermal projects.

Carbon steel casing material in high-temperature deep geothermal wells can be prone to severe corrosion and premature failure due to the oxidation capacity of H₂O, H₂S, CO₂, and more corrosive species in geothermal fluid. Due to the higher temperature and pressure and phase state of fluid in high-temperature deep geothermal wells, the rate and extent of corrosion can be expected to be different than in low-temperature geothermal wells. To reduce the extent of corrosion damage and corrosion rate, and increase the lifetime of geothermal wells, one mitigation method is to clad the internal surface of the geothermal casing with a more noble, corrosion-resistant material. Conventional cladding, however, has been an expensive and time-consuming process up to the current date, but recently, a more economical and productive method has been established, i.e., EHLA cladding. In this study, a 14-day corrosion performance test was conducted on stainless steel and nickel-based alloy clads on a carbon steel substrate in a 262 °C and 95 bar geothermal well in the Hellisheidi geothermal field (SW Iceland). Samples were partially or fully cladded, and some samples were stressed to investigate the clads’ susceptibility to general corrosion and stress corrosion cracking, as well as the substrate’s vulnerability to galvanic corrosion. Corrosion analysis of pure carbon steel substrate was also investigated for comparison. Samples were microstructurally analysed with SEM, and chemical analysis was performed with EDX. The results indicated that the clad materials have good corrosion resistance in the geothermal environment tested, suggesting that EHLA cladding is a more feasible option for strengthening the corrosion resistance of geothermal casing and equipment.