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a b s t r a c tThe article presents the results of modelling geothermal conditions in the Lower Triassic sedimentary formations of the Polish Lowland area (central Poland) and an electricity production model for a prospective EGS (Enhanced Geothermal System) installation situated in that area. On the basis of comprehensive analyses, this area has been selected as optimal for EGS plants operating in sedimentary complexes in the Polish Lowland. Numerical modelling was conducted using TOUGH2 code and served to evaluate the energy performance of the prospective EGS plant operating in the area. Modelling results indicate that the energy performance of the EGS plant is strongly dependent on the volume and permeability of the artificially fractured zone and its net power is dependent on the power consumed by the circulating pumps that stimulate the flow. For the top layer of the Buntsandstein formation at a depth of ca. 5500 m and temperature of ca. 170 C, the modelled net power of an EGS plant operating in the area ranged from 2 to 3 MW for a circulation of 200 m 3 /h, and at 100 m 3 /h it ranged from 1.3 to 1.6 MW depending on the permeability and volume of the fractured zone used for the circulation in question.

The Chociwel region is part of the Szczecin Trough and constitutes the northeastern segment of the extended SzczecinGorzów Synclinorium . Lower Jurassic reservoirs of high permeability of up to 1145 mD can discharge geothermal waters with a rate exceeding 250 m 3 /h and temperatures reach over 90°C in the lowermost part of the reservoirs. These conditions provide an opportunity to generate electricity from heat accumulated in geothermal waters using binary ORC (Organic Rankine Cycle) systems. A numerical model of the natural state and exploitation conditions was created for the Chociwel area with the use of TOUGH2 geothermal simulator (i.e., integral finite-difference method). An analysis of geological and hydrogeothermal data indicates that the best conditions are found to the southeast of the town of Chociwel, where the bottom part of the reservoir reaches 3 km below ground . This would require drilling two new wells, namely one production and one injection. Simulated production with a flow rate of 275 m 3 /h, a temperature of 89°C at the wellhead, 30°C injection temperature and wells being 1.2 km separated from each other leads to a small temperature drop and moderate requirements for pumping power over a 50 years' time span. The ORC binary system can produce at maximum 592.5 kW gross power with the R227ea found as the most suitable working fluid. Geothermal brine leaving the ORC system with a temperature c. 53°C can be used for other purposes, namely mushroom growing, balneology, swimming pools, soil warming, de-icing, fish farming and for heat pumps.

The objective of this study is to assess the techno-economic potential of the proposed novel energy system, which allows for negative emissions of carbon dioxide (CO2). The analyzed system comprises four main subsystems: a biomass-fired combined heat and power plant integrated with a CO2 capture and compression unit, a CO2 transport pipeline, a CO2-enhanced geothermal system, and a supercritical CO2 Brayton power cycle. For the purpose of the comprehensive techno-economic assessment, the results for the reference biomass-fired combined heat and power plant without CO2 capture are also presented. Based on the proposed framework for energy and economic assessment, the energy efficiencies, the specific primary energy consumption of CO2 avoidance, the cost of CO2 avoidance, and negative CO2 emissions are evaluated based on the results of process simulations. In addition, an overview of the relevant elements of the whole system is provided, taking into account technological progress and technology readiness levels. The specific primary energy consumption per unit of CO2 avoided in the analyzed system is equal to 2.17 MJLHV/kg CO2 for biomass only (and 6.22 MJLHV/kg CO2 when geothermal energy is included) and 3.41 MJLHV/kg CO2 excluding the CO2 utilization in the enhanced geothermal system. Regarding the economic performance of the analyzed system, the levelized cost of electricity and heat are almost two times higher than those of the reference system (239.0 to 127.5 EUR/MWh and 9.4 to 5.0 EUR/GJ), which leads to negative values of the Net Present Value in all analyzed scenarios. The CO2 avoided cost and CO2 negative cost in the business as usual economic scenario are equal to 63.0 and 48.2 EUR/t CO2, respectively, and drop to 27.3 and 20 EUR/t CO2 in the technological development scenario. The analysis proves the economic feasibility of the proposed CO2 utilization and storage option in the enhanced geothermal system integrated with the sCO2 cycle when the cost of CO2 transport and storage is above 10 EUR/t CO2 (at a transport distance of 50 km). The technology readiness level of the proposed technology was assessed as TRL4 (technological development), mainly due to the early stage of the CO2-enhanced geothermal systems development.