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 MJ_LHV/kg CO₂ for biomass only (and 6.22 MJ_LHV/kg CO₂ when geothermal energy is included) and 3.41 MJ_LHV/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.

The beginnings of geothermal implementation research in Poland date back to 1989–1993 when the Mineral and Energy Economy Research Institute of the Polish Academy of Sciences (MEERI PAS) launched the first geothermal installation in the Podhale region, using the reconstructed Bańska IG-1 well. The knowledge acquired during these 30 years has highlighted the importance of geothermal energy—among other things, borehole reconstruction operations and the need for their further refinement. The technologies developed have been used in virtually all geothermal heating systems operating in Poland. Examples of successful reconstruction work include the Bańska IG-1 and Biały Dunajec PAN-1 wells operated by the PEC Geotermia Podhalańska S.A. geothermal company. The Mszczonów IG-1 well, which is operated by the Geotermia Mazowiecka S.A. heating company, has also undergone considerable work almost 24 years after its complete closure. Reconstruction processes can also be important in adapting existing wells for geothermal purposes. After World War II, more than 8000 boreholes deeper than 1000 m were drilled in Poland. They were primarily made for the purpose of geological surveys and hydrocarbon exploration. Some of these boreholes can be adapted for operation in geothermal systems. The paper presents selected methods of reconstructing abandoned, disused (not abandoned and not decommissioned) or damaged boreholes in order to use them in the geothermal water extraction process. Four examples of borehole reconstruction, designed and carried out with the participation of MEERI PAS in Kraków, are discussed in more detail.

The Chociwel region is part of the Szczecin Trough and constitutes the northeastern segment of the extended Szczecin-Gorzów Synclinorium. Lower Jurassic reservoirs of high permeability of up to 1145 mD can discharge geothermal waters with a rate exceeding 250 m3/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 m3/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 paper describes application of the cross-impact method in the process of selecting locations and technologies used in a geothermal system based on energy accumulated in a dry rock formation, where CO₂ is used as the working medium. The survey is based on the opinion of a group of 20 experts representing different fields of earth and technical sciences. They represent Norway and Poland, where the location of such a system is considered. Based on experts’ experience and opinions, all factors that seem to be significant were classified into the following groups: targets, key factors, results, determiners, motor and brakes, regulating factors, external factors, auxiliary factors, and autonomous factors. Direct influences between variables were indicated. Due to major differences in geological conditions in Poland and Norway, the factor of on- or offshore technology was pointed out as the primary determiner. Among key factors, the system operation’s long-term safety and level of technological readiness were indicated. As a target factor, an interest of local authority was pointed out. Among the variables that are important when selecting locations for this type of system, nine are essential: (1) Formal constraints related to local nature protection areas—this variable is essential in the case of an onshore system; (2) Availability of CO₂ sources; (3) Level of geological recognition; (4) The distance of the CO₂-EGS from a thermal energy user and electricity grid; (5) Existing wells and other infrastructure; (6) Depth of the EGS system; (7) Water depth if offshore, this variable is only important when offshore systems are involved; (8) Physical parameters of reservoir rocks; (9) Reservoir temperature.