High-temperature batteries for geothermal and oil/gas borehole applications

A literature survey and technical evaluation was carried out of past and present battery technologies with the goal of identifying appropriate candidates for use in geothermal borehole and, to a lesser extent, oil/gas boreholes. The various constraints that are posed by such an environment are discussed. The promise as well as the limitations of various candidate technologies are presented. Data for limited testing of a number of candidate systems are presented and the areas for additional future work are detailed. The use of low-temperature molten salts shows the most promise for such applications and includes those that are liquid at room temperature. The greatest challenges are to develop an appropriate electrochemical couple that is kinetically stable with the most promising electrolytes-both organic as well as inorganic-over the wide operating window that spans both borehole environments.