Renewability of geothermal resources

In almost all geothermal projects worldwide, the rate of extraction of heat energy exceeds the pre-exploitation rate of heat flow from depth. For example, current production of geothermal heat from the Wairakei–Tauhara system exceeds the natural recharge of heat by a factor of 4.75. Thus, the current rate of heat extraction from Wairakei–Tauhara is not sustainable on a continuous basis, and the same statement applies to most other geothermal projects. Nevertheless, geothermal energy resources are renewable in the long-term because they would fully recover to their pre-exploitation state after an extended shut-down period. The present paper considers the general issue of the renewability of geothermal resources and uses computer modeling to investigate the renewability of the Wairakei–Tauhara system. In particular, modeling is used to simulate the recovery of Wairakei–Tauhara after it is shut down in 2053 after a hundred years of production.