The current work investigates the feasibility of a novel Carbon Capture and Utilization (CCU) approach—also known as Underground Sun Conversion (USC) or geo-methanation. The overall objective of the current work is a comprehensive assessment on the technical, economic and legal aspects as well as greenhouse gas impacts to be concerned for establishing USC technology concept. This is achieved by applying multidisciplinary research approach combining process simulation, techno-economic and greenhouse gas assessment as well as legal analysis allows answering questions about technical, economic feasibility and greenhouse gas performance as well as on legal constraints related to large scale CCU using geo-methanation in depleted hydrocarbon reservoirs. CO₂ from the industry and renewable H₂ from the electrolyser are converted to geomethane in an underground gas storage and used in industry again to close the carbon cycle. Process simulation results showed the conversion rates vary due to operation mode and gas cleaning is necessary in any case to achieve natural gas grid compliant feed in quality. The geomethane production costs are found to be similar or even lower than the costs for synthetic methane from Above Ground Methanation (AGM). The GHG-assessment shows a significant saving compared to fossil natural gas and conventional power-to-gas applications. From a legal perspective the major challenge arises from a regulative gap of CCU in the ETS regime. Accordingly, a far-reaching exemption from the obligation to surrender certificates would be fraught with many legal and technical problems and uncertainties.

This analysis estimates the technically available potentials of renewable gases from anaerobic conversion and biomass gasification of organic waste materials, as well as power-to-gas (H2 and synthetic natural gas based on renewable electricity) for Austria, as well as their approximate energy production costs. Furthermore, it outlines a theoretical expansion scenario for plant erection aimed at fully using all technical potentials by 2050. The overall result, illustrated as a theoretical merit order, is a ranking of technologies and resources by their potential and cost, starting with the least expensive and ending with the most expensive. The findings point to a renewable methane potential of about 58 TWh per year by 2050. The highest potential originates from biomass gasification (~49 TWh per year), while anaerobic digestion (~6 TWh per year) and the power-to-gas of green CO2 from biogas upgrading (~3 TWh per year) demonstrate a much lower technical potential. To fully use these potentials, 870 biomass gasification plants, 259 anaerobic digesters, and 163 power-to-gas plants to be built by 2050 in the full expansion scenario. From the cost perspective, all technologies are expected to experience decreasing specific energy costs in the expansion scenario. This cost decrease is not significant for biomass gasification, at only about 0.1 €-cent/kWh, resulting in a cost range between 10.7 and 9.0 €-cent/kWh depending on the year and fuel. However, for anaerobic digestion, the cost decrease is significant, with a reduction from 7.9 to 5.6 €-cent/kWh. It is even more significant for power-to-gas, with a reduction from 10.8 to 5.1 €-cent/kWh between 2030 and 2050.

Developing a Hybrid Energy Storage System (HESS) involves integrating technologies with complementary attributes. Coupling Redox Flow Batteries (RFBs) with Supercapacitors (SCs) emerges as one of the most promising options. For the first time at our knowledge, here we report about a study on the passive HESS VRFB-SC configuration that was investigated through experimental tests, modelling, life cycle and economic assessments. Indeed, we present a laboratory-sized HESS comprising a Vanadium Redox Flow Cell (VRFC) and a SC, directly connected in parallel without any power converter. Initially, individual tests were conducted on the standalone VRFB and SC using short discharge protocols (5 s). Subsequently, the two systems were interconnected in parallel and subjected to the same discharge protocol. An equivalent electrical model, resembling a parallel R-C circuit, was developed to elucidate the discharge mechanism of the direct parallel system. The tests revealed that the SC mitigates the VRFB's ohmic drop due to the transient behaviour of the R-C circuit. Furthermore, the hybrid system demonstrated enhanced energy delivery at higher currents compared to the standalone VRFB, a phenomenon elucidated by our proposed model. Additionally, the model facilitates the sizing of the SC relative to VRFB performance. In addition to technical findings, this article provides a comprehensive economic analysis and life cycle assessment (LCA) of the proposed system. These assessments highlight the potential cost-effectiveness and reduced global warming potential of the passively connected VRFB-SC HESS, underscoring its viability as a sustainable energy storage solution.

Starting in 2002, a continuous building of flood protection infrastructure aiming at preventing high monetary damages has been taking place in Upper Austria. As a result of investments in these flood protection measures between 2002 and 2015, significant positive effects on the gross regional product as well as on the employment level have been generated. However, the macroeconomic effects are found to depend substantially on the import quota for required materials.