According to statistics from the World Bank, thousands of tons of valuable minerals are imported to Germany from Chile every year, including raw materials for lithium-ion batteries. But their extraction causes ecological and social problems. “The use of the limited freshwater resources in northern Chile for mining regularly fuels conflicts with the local population,” says professor Thomas Kohl from the Institute of Applied Geosciences (AGW) at the Karlsruhe Institute of Technology (KIT; Germany; www.kit.edu). “Northern Chile is one of the driest regions on earth, but has extensive geothermal resources,” he says. “With a novel type of plant, it is not only possible to generate electricity in a climate-friendly way, but also to extract drinking water and even mineral resources at the same time.”
As part of BrineMine — a German-Chilean research project that began in 2019 with €1.5 million in funding from the Federal Ministry of Education and Research — the AGW team is developing the necessary strategies and technologies for extracting mineral resources, as well as drinking water, directly in geothermal power plants. One partner is the Fraunhofer Institute for Solar Energy Systems (ISE; Freiburg, Germany; www.ise.fraunhofer.de); which is developing the plant technology for later industrial use. In the process, heat from the geothermal brine is first used for energy recovery. The cooled liquid, which has a relatively low concentration, is then pre-concentrated by reverse osmosis, which also generates drinking water. The brine concentrate is then further concentrated by membrane distillation until it is saturated. “The thermal energy required for the entire process can be covered directly from the excess heat of the power plant process,” explains ISE project manager Joachim Koschikowski. A demonstration plant is now set up in a geothermal power plant in the Upper Rhine Graben and successfully integrates key components into ongoing power plant operations. The research is described in a recent issue of Geothermics.