Dr. Arna Pálsdóttir works for Reykjavik Energy in Research and Innovation as a chemical engineering specialist. The focus of her work is on integration of heat production from high temperature geothermal fields and low temperature fields, specifically relating to the chemical composition of the different fluids. Arna received her Ph.D. in chemical engineering from Cornell University in 2019. At Cornell she worked on the valorization of geothermal waters with lithium extraction under the guidance of Prof. Jefferson W. Tester. She received her M.S. in chemical engineering from Cornell University in 2017 and her undergraduate degree in chemical engineering from the University of Iceland in 2013.

Abstract:

Lessons learned in operational changes to a dually fed district heating system in the capital region of Iceland: A temporary switch between geothermal water and heated groundwater
Veitur operates a dually fed district heating system in the capital region of Iceland. About half of the district heating system is fed by low temperature boreholes inside the capital region while the other half is fed by heated up groundwater that comes from ON Power’s two geothermal power plants. Historically, the mixing of these two types of waters has been problematic, resulting in Veitur operating two parallel district heating systems in the capital region with waters that cannot be mixed. In the summer of 2019, an experiment where an area that is normally fed by low temperature borehole water was switched over to heated up groundwater for three weeks and then switched back to low temperature borehole water was performed. During this operation, the chemical content of the water in this part of the district heating system was carefully monitored. The most significant results of the chemical monitoring were changes to the concentration of magnesium and calcium throughout the system. The concentration of magnesium increased as was to be expected given that more magnesium rich water was being used, however, the concentration increased gradually. The calcium concentration in the system increased beyond the concentration of the input water for a short period of time and then settled at the expected value. This suggests an interaction of the water with the pipes in the district heating system, potentially scale formation or alternatively an ion exchange process. In this talk, the details of the chemical monitoring will be presented along with the results and the lessons learned for future water switches in Veitur’s district heating system.