Underground hydrogen storage: The techno-economic perspective.

The changes in the energy sector after the Paris agreement and the establishment of the Green Deal, pressed the governments to embrace new measures to reduce greenhouse gas emissions. Among them, is the replacement of fossil fuels by renewable energy sources or carbon-neutral alternative means, such as green hydrogen. As the European Commission approved green hydrogen as a clean fuel, the interest in investments and dedicated action plans related to its production and storage has significantly increased. Hydrogen storage is feasible in aboveground infrastructures as well as in underground constructions. Proper geological environments for underground hydrogen storage are porous media and rock cavities. Porous media are classified into depleted hydrocarbon reservoirs and aquifers, while rock cavities are subdivided into hard rock caverns, salt caverns, and abandoned mines. Depending on the storage option, various technological requirements are mandatory, influencing the required capital cost. Although the selection of the optimum storage technology is site depending, the techno-economical appraisal of the available underground storage options featured the porous media as the most economically attractive option. Depleted hydrocarbon reservoirs were of high interest as site characterisation and cavern mining are omitted due to pre-existing infrastructure, followed by aquifers, where hydrogen storage requires a much simpler construction. Research on data analytics and machine learning tools will open avenues for consolidated knowledge of geological storage technologies.

Progress for carbon dioxide geological storage in West Macedonia: A field and laboratory-based survey.

Background: It is widely acknowledged that carbon dioxide (CO 2), a greenhouse gas, is largely responsible for climatic changes that can lead to warming or cooling in various places. This disturbs natural processes, creating instability and fragility of natural and social ecosystems. To combat climate change, without compromising technology advancements and maintaining production costs at acceptable levels, carbon capture and storage (CCS) technologies can be deployed to advance a non-disruptive energy transition. Capturing CO 2 from industrial processes such as thermoelectric power stations, refineries, and cement factories and storing it in geological mediums is becoming a mature technology. Part of the Mesohellenic Basin, situated in Greek territory, is proposed as a potential area for CO 2 storage in saline aquifers. This follows work previously done in the StrategyCCUS project, funded by the EU. The work is progressing under the Pilot Strategy, funded by the EU. Methods: The current investigation includes geomechanical and petrophysical methods to characterise sedimentary formations for their potential to hold CO 2 underground. Results: Samples were found to have both low porosity and permeability while the corresponding uniaxial strength for the Tsotyli formation was 22 MPa, for Eptechori 35 MPa and Pentalofo 74 MPa. Conclusions: The samples investigated indicate the potential to act as cap-rocks due to low porosity and permeability, but fluid pressure within the rock should remain within specified limits; otherwise, the rock may easily fracture and result in CO 2 leakage or/and deform to allow the flow of CO 2. Further investigation is needed to identify reservoir rocks as well more sampling to allow for statistically significant results.

Indice de risco e etiologia bacteriana das infecçöes cirúrgicas: Hospital Regional de Taguatinga, 1993 a 1996 / Risk index and bacterial etiology of surgical site infections: Regional Hospital of Taguatinga, 1993 to 1996

Introduçäo: a ocorrência de infecçäo após cirurgia depende de uma série de fatores relacionados com as características do paciente, com a ferida operatória e com o microrganismo. O sistema tradicional de aferiçäo cirúrgica mostra-se incapaz de mensurar adequadamente o risco de infecçäo. Objetivo: avaliar a relaçäo entre a classificaçäo das cirurgias pelo índice de risco de infecçäo cirúrgica e a sua etiologia bacteriana. Local: Unidade de Cirurgia Geral do Hospital Regional de Taguatinga, com capacidade para 400 leitos e 1.000 cirurgias/ano. Material e métodos: estudo de corte prospectivo de 3.023 pacientes submetidos à cirurgia, no período de junho de 1993 a maio de 1996, com a utilizaçäo do componente de vigilância cirúrgico do National Nosocomial Infections Surveillance System e das definiçöes de infecçäo hospitalar dos Centers for Disease Control and Prevention. Um sistema de vigilância pós-alta, mantido em um ambulatório de egressos, permitiu avaliar, pelo menos uma vez, 2.510 pacientes operados (83 por cento). Quando suspeitou-se de infecçäo do sítio cirúrgico, amostra de material foi coletada, por meio de swab, após lavagem da ferida com soro fisiológico, e transportada em meio de Stuart (modificado). Resultados: a Escherichia coli e o Staphylococcus aureus foram os microrganismos mais frequentes (27,4 por cento e 25,4 por cento, respectivamente), seguindo-se o Staphylococcus coagulase-negativo (16,4 por cento) e o Enterobacter sp.(12,4 por cento). O índice de risco mostrou-se capaz de predizer o risco de infecçäo cirúrgica, na maioria dos pacientes, exceto naqueles cujas cirurgias apresentavam índice de risco 3. A incidência de infecçäo do sítio cirúrgico por bacilo Gram-negativo mostrou correlaçäo positiva com o índice de risco, o que näo ocorreu com a incidência de infecçöes do sítio cirúrgico por Staphylococcus sp. Conclusäo: o índice empregado foi útil para identificar o risco de infecçäo cirúrgica e capaz de predizer o risco dessas infecçöes por bacilo Gram-negativo; o índice näo demonstrou utilidade para predizer o risco para as infecçöes do sítio cirúrgico por Staphylococcus sp.