ABOUT THE PROJECT
The use of renewable energy resource is usually directed to solar, wind or hydroelectric stations. However, there are other sources for getting the ‘green energy’. One of them is geo-energy, the energy stored in the Earth crust. The capacity of the geothermal installations in Poland reached 94 MW. Turkey, with a capacity of 397 MW, is one of the leading countries having electrical potential from geothermal resources. In the world, geothermal water is used mostly for heating purposes, greenhouses, agriculture, for generation of warm water, therapeutic and recreational purposes and to generate electricity in power stations. After extracting the thermal energy, the cooled water turns to problematic fluid due to its salinity and content of harmful components. Management of such fluids is a goal of our application.
If it is a need, geothermal water can be processed to get safe product water without such toxic elements as arsenic or boron. Reverse osmosis (RO) installations are commonly used for such task. When product water is used for irrigation, industry or household purposes, the concentrated brine remained is blended with untreated water and re-injected back to underground. That methodology causes accumulation of toxic components that can infiltrate into the underground aquifers. Reduction of this effect is the first goal of our project. The second goal is related to harvesting of energy from the salinity gradient. There is a possibility to get net-energy when two solutions of different salinity are mixed. When 1m3/s of fresh water is mixed with 1 m3/s of brine containing 30 g/L of salt, the energy to be obtained is around 1.4 MW at room temperature.
HOW DOES IT WORK ?
The project focused on integrated management of waste geothermal brine from the geo-stations. For this, the use of two innovative approaches will be considered. First, efficiency of hybrid systems for removal of toxic elements such as arsenic and boron from waste geothermal brine will be evaluated. Hybrid systems are based on the use of fine particles of selective sorbents that can bound the target components. Then, the sorbents are concentrated during the membrane filtration, regenerated and used again. The efficiency of the hybrid system is higher than fixed bed operation as it works with a high sorption rate to adsorb the target elements. The second innovative approach is related to energy harvesting from the salinity gradient. For this, two methods will be used: reverse electrodialysis (RED) and capacitive mixing (CAPMIX). Both of them are based on transportation of ions and can extract 50-85% of total energy from salinity gradient. The first process, based on RED, is now being commercialized for mixing seawater and river water, while the second one, based on the use of super- capacitors, is still under development. The aim of the project is to test applicability of both methods in energy harvesting from mixing of saline geothermal water/or its RO brine with water, before its re-injection to underground.
To achieve the goals, the partners (WUST, AGH and EGE) interact with each other. The scientific experiences of the participating teams allow them to share and to spread their knowledge among the partners. The team of Ege University focused on the use of sorption membrane system for removal of boron and arsenic from geothermal water and its RO brine. Additionally, the EGE team works on extraction of salinity gradient energy by the RED system. The team from Wroclaw University of Science and Technology works on extraction of salinity energy by means of the CAPMIX system. Team of AGH-University of Science and Technology recognizes the geothermal resources and make the economic, energetic and environmental analyses of the studied processes. The statistical description of the obtained data will be helpful in generalization of the obtained results.