Sustainable Utilization of Geothermal Resources for 100 – 300 Years

Geothermal resources have the potential of contributing significantly to sustainable development in many parts of the world. Sustainable management of a geothermal resource involves utilization at a rate, which may be maintained for a very long time (100300 years). The energy production potential of geothermal systems is primarily determined by the pressure decline caused by production. Overexploitation of geothermal systems mostly occurs because of poor understanding, due to inadequate monitoring, and when many users utilize the same resource without common management. Careful monitoring and modeling, as well as energy-efficient utilization, are essential ingredients in sustainable management. Reinjection is also essential for sustainable utilization of geothermal systems, which are virtually closed and with limited recharge. The Hamar low-temperature geothermal system in the volcanic lava-pile of Central N-Iceland and the low-temperature geothermal resources in the sedimentary basin below the city of Beijing, P.R. of China have been utilized for decades. They are examples of geothermal resources, of highly contrasting nature, which may each be managed in a sustainable manner. The sustainable potential of the Hamar system is estimated, through modeling, to be greater than 40 kg/s of 65°C water. Reinjection is essential for sustainable management of the Beijing resource. The Nesjavellir high-temperature geothermal field is located inside the volcanic zone in SW-Iceland. Production from the field is planned at 120 MWe, and 300 MWt, for the next decades. This production can’t be maintained in a sustainable manner for 100300 years, but the impact appears to be reversible and the field may likely be utilized at a reduced rate, in a sustainable manner following a 30-year period of excessive utilization.