Sustainable energy supply system for consumers of city of Subotica based on geothermal energy of Pannonian geological basin

Abstract

According to the state energy balance, the total energy supply of Serbia in 2020 was 664,224 TJ and dominated by fossil fuels (coal, oil and gas) with a share of 84.2 %.Exactly electricity and heat producers with domination of carbon fossil fuels generate 68% of CO2 emission in Serbia. “Energy Sector Development Strategy of the Republic of Serbia for the period by 2025 with projections by 2030” fore sees available technical potential of renewable energy production in Serbia around 154,158 TJ perannum. The largest potential, approximately 100,232 TJ per year, belongs to biomass than geothermal energy potential is 7,327TJ per year and could be underestimatedas it is not included electricity production.The Serbia's total installed geothermal capacity is 82.8 MWth nowdays. Geothermal energy is used for agricultural, balneology, spa, district and individual heating. The share of district/space heating in total geothermal energy usage is 25%, what it is very small in comparison to its potential.The density of the geothermal heat flow in the significant part of the territory of Serbiais higher than its average value for the continental part of Europe, which is about 60mW/m2. The highest values, over 100 mW/m2, are in the Pannonian Basin, the centralpart of southern Serbia and in central Serbia. However, any geothermal energysystem design has high risks related to geological uncertainties and it successful development depends from proven and reliable geological data.Pannonian basin is located mostly in northern part of Serbia, Vojvodina province. This region is the center of oil and gas production of Serbia. That means that a lot of geological data were collected in a last 70 years of oil exploration activities in this area. In addition, is NIS (Naftna Industrija Srbije) Oil Company operates many oilfields in northern Serbia and available data and knowledge is reasonable to use.As the city of Subotica is an economical and cultural center of northern Vojvodina with high energetic heat demand, the goal of this Mater Thesis was research of potentialuse-case of geothermal direct heat usage in city of Subotica this topic required systematic analyses of followings: exist technologies and expiries in geothermal worldwide, in Europe and Serbia, geothermal potential in Panonian basin with a focus on the area near the city of Subotica and technical challenges of design of geothermal heat plant.As a result, doublet geothermal system power of 10 MWth and temperature regime 85/55oC was modeled and designed. Project evaluation took into account the anticipated reservoir performance in the context of heat generation strategies and well performance. As we have significant geological uncertainties, probabilistic approach was chosen for modeling and calculations as a common tool for such cases.Economical evaluation of the project showed that due to high investment costs related to subsurface part and high electricity price geothermal heat production is positive only in a case of CO2 trading that is not a common tool yet is Serbia as it is not a member of EU. Aiming to build sustainable business-case with a low carbon footprint additional scenario was set up - PV power plant and geothermal heat plant together,as one energy asset. This scenario proved its economic efficiency and feasibility as has a positive NPV and PI=1.02.The development of geothermal power and heat generation could be an important part of renewable energy agenda in Serbia. However, to harness its geothermal potential, Serbia will need to invest in research and development, provide financial incentives for geothermal projects, and establish a clear legal and regulatory framework for the sector.