| Abstract |
The amount of geothermal energy utilization of 1924.5 MW in Indonesia is still low compared to its 17,000 MW reserves. The development of the geothermal direct-use application for agriculture, farming, and space heating can be a catalyst to accelerate geothermal energy growth. The exploitation of manifestation water to be used as a working fluid for direct-use application can cut the excessive drilling expenditure. This study evaluates the geochemical properties of hot waters from geothermal manifestations in the Dieng region, Central Java, Indonesia, to be utilized for agriculture, aquaculture, and space heating. Published chemistry data of seven hot water samples in the region is analyzed based on solubility calculations and equilibrium modeling using PHREEQC to se1ect the most suitable hot water type and assess scaling potential. The results of solubility calculation show: i) undersaturation of sulfate minerals (anhydrite and gypsum) in all samples, ii) oversaturation of carbonate minerals (aragonite, calcite, dolomite, and magnesite) in most of the samples, and iii) varying saturation level of silica minerals (chalcedony, amorphous silica, and quartz). Equilibrium modeling shows that the pipeline pressure has a negligible effect on the saturation index value of possible scaling minerals, further emphasizing the possibility of carbonate and silica scaling to form in some of the waters. The risk of scaling formation may be reduced by mixing thermal water with fresh water by considering heat loss potential. |