Speaker
Description
The Geothermal Village project addresses community exploitation of geothermal resources, which in Africa are commonly found along the East African Rift System and typically off-grid (Varet et al. 2014). The H2020 LEAP-RE program (Grant Agreement 963530) co-funds feasibility studies at 4 sites now ready for demo financing. This abstract focuses on the resources.
At Era Boru, Ethiopia, in the Afar triangle, steam emerges from open faults, used for millenia to source fresh water by condensation. Infra-red drone surveys show the hottest areas along fault systems, where drilling to 300m, likely with a modified water-drilling rig, should provide ~150°C steam for electricity as well as direct heat and condensed fresh water.
Lake Abhe Village, Djibouti, lies on the E. side of Lake Abhe, on basaltic ridges formed by ENE-trending normal faults. To the west, on exposed lake beds, fields of hydrothermal chimneys, steam vents and hot springs (71-99.7°C) are inferred sources from a buried N-trending fault system bounding the lake basin, consistent with electric resistivity tomography, induced polarity and magnetotelluric (ERT, IP, MT) mapping of the 3D hydrothermal plumbing. Well doublets would spud on the basalt about 1km distant from fractured-basement targets 800m beneath the unconsolidated lake beds, providing ~135°C brine, for ORC electricity, heat and fresh water.
Homa Hills, Kenya, at the NE corner of Lake Victoria, is underlain by a carbonatite volcano complex (12-1.3 Ma). Hot spring temperatures range from 88 to 43°C. MT soundings identify both shallow (200m) and deep (4 km) low resistivity zones but no connection between. The spring water indicates a deep high-temperature (up to 200°C) source. Relatively shallow drilling (500m) for 130° brine should allow village-scale ORC electricity and direct-use heat, likely at several locations.
The Mashyuza hot springs, in the Bugarama valley, Rwanda, lie between the Tanganyika and Kivu rifts. They emit 51°C carbonate-rich water and gas (99% CO2), depositing travertine and carbonate mud in excess of 50m thickness. Flow from natural springs is approximately 140l/s; a 60°C shallow source is inferred. The springs are adjacent to a NE-trending oblique-slip fault bounding the N-trending graben. ERT, IP and MT delineate low-resistivity zones inferred to be fluid-rich basement faults. Targeting these zones at 200m depth with doublets would allow high-flow rate 60° water for direct use while maintaining natural spring heads.
