Life-cycle economic impacts of geothermal district heating networks: a decision tree analysis

Authors
Pratiwi, Astu Sam; Trutnevyte, Evelina

Abstract
Geothermal district heating networks are one of the key options to decarbonize the heating sector in the State of Geneva. But the development of geothermal district heating requires high capital costs and involves risk of not finding sufficient resource, which make these systems less competitive. The wider contribution of these systems to the economy, domestically and overall, has rarely been evaluated too. Our study aims to analyze the competitiveness of geothermal district heating networks in the State of Geneva, Switzerland, and their wider economic impacts using four indicators: levelized costs of geothermal district heating and of district heating system as a whole, ratio of economic impacts to the total spending, and share of domestic economic impacts in Switzerland. We build a decision tree, incorporating multiple decision alternatives that decision makers encounter while setting up the strategies for geothermal district heating development: target of heat demand, share of geothermal coverage in the district heating system, choice of auxiliary heating sources, supply and return temperature, linear heat density, geothermal well depths, geothermal flowrate, and 3D seismic exploration program. We quantify the four indicators for each set of decision variables in a decision tree, including applying probability tree to account for geothermal resource risk. We then identify the most influential decision variables using a random forest regression and pinpoint the decision pathways that lead to lower levelized costs of heat and higher share of domestic economic impact. The results suggest that linear heat density and the geothermal coverage have the largest influence in determining the levelized costs of geothermal heat and of district heating system as a whole, respectively. Geothermal coverage has the largest influence in determining the ratio of economic impacts to total spending and the second largest in determining the share of economic impacts in Switzerland.