Economic competitiveness of underground coal gasification combined with carbon capture and storage in the Bulgarian energy network

Abstract Underground coal gasification (UCG) allows for exploitation of deep-seated coal seams not economically exploitable by conventional coal mining. Aim of the present study is to examine UCG economics based on coal conversion into a synthesis gas to fuel a combined cycle gas turbine power plant (CCGT) with CO2 capture and storage (CCS). Thereto, a techno-economic model is developed for UCG-CCGT-CCS costs of electricity (COE) determination which, considering sitespecific data of a selected target area in Bulgaria, sum up to 72 e/MWh in total. To quantify the impact of model constraints on COE, sensitivity analyses are undertaken revealing that varying geological model constraints impact COE with 0.4 % to 4 %, chemical with 13 %, technical with 8 % to 17 % and market-dependent with 2 % to 25 %. Besides site-specific boundary conditions, UCG-CCGT-CCS economics depend on resources availability and infrastructural characteristics of the overall energy system. Assessing a model based implementation of UCG-CCGT-CCS and CCS power plants into the Bulgarian energy network revealed that both technologies provide essential and economically competitive options to achieve the EU environmental targets and a complete substitution of gas imports by UCG synthesis gas production.