Geothermal development in Tanzania - status report

Abstract

Tanzania is among East African countries that are traversed by the East African Rift System. The geological settings for the occurrences of geothermal resource in Tanzania is variable and include potentials that are likely to be associated with typical young volcanic provinces in the north, intersection of eastern and western arms (triple junction) in the south west, faulted granites areas in central Tanzania (craton), and intrusive in young coastal sedimentary formation. This makes the occurrence of geothermal resource in Tanzania quite different from other countries. In addition the eastern arm and western arms tend to have different geological conditions that need to be differently considered during the exploration of geothermal energy resources in Tanzania. Tanzania has a total grid installation capacity of 1,583MW from three main sources. These are hydro (37%), gas (47%) and HFO, diesel (16%). Previously, the national power system was mostly relying on hydropower. Long and frequent periods of drought which might have been due to the climate change between 2003 and 2006; 2009 and 2010 lead to shortfalls in electricity supply from the hydropower stations; thus, the government of Tanzania resorted to thermal based generation sources as a short term solution. As a long term power development strategy the government intends to diversify the country’s energy generation mix and is focusing on increasing the proportion of renewable energy generation, whereby geothermal development is ranked high on the list. Other renewable sources being considered are wind, nuclear and solar.

Geothermal resource studies in Tanzania date back to 1949 but have been limited to surface studies mainly, measurements of surface temperature, water and gas sampling and analyses of the hot springs. The only study that has gone beyond preliminary surface studies is on Ngozi-Songwe geothermal field that was undertaken between 2006 and 2012 by the Ministry of Energy and Minerals (MEM) in collaboration with the Geological Survey Tanzania (GST), Tanzania Supply Company Limited (TANESCO) and the Federal Institute for Geosciences and Natural Resources (BGR) of Germany. This study comprised geological, geochemical and geophysical investigations and culminated in locating three sites for drilling of temperature gradient wells. The drilling of temperature gradients wells has been delayed, to allow for third party review as a measure of reducing the drilling risk. As such, more work to fill the identified gags has started in June-July 2015 done by GDC in collaboration with TGDC, this will continue to January 2016 with technical assistance from UNEP/ARGeo, aiming at defining of the conceptual model and location of drilling sites. This paper presents geothermal development in Tanzania covering the geology of geothermal potential sites, developments goals and strategies, institutional arrangements, new projects and future development plans for accelerating geothermal development and utilisation.