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AbstractThis paper presents the experimental plans and designs as well as examples of predictive modeling of a pilot-scale CO2 injection experiment at the Heletz site (Israel). The overall objective of the experiment is to find optimal ways to characterize CO2 -relevant in-situ medium properties, including field-scale residual and dissolution trapping, to explore ways of characterizing heterogeneity through joint analysis of different types of data, and to detect leakage. The experiment will involve two wells, an injection well and a monitoring well. Prior to the actual CO2 injection, hydraulic, thermal and tracer tests will be carried out for standard site characterization. The actual CO2 injection experiments will include (i) a single well injection-withdrawal experiment, with the main objective to estimate in-situ residual trapping and (ii) a two-well injection-withdrawal test with injection of CO2 in a dipole mode (injection of CO2 in one well with simultaneous withdrawal of water in the monitoring well), with the objective to understand the CO2 transport in heterogeneous geology as well as the associated dissolution and residual trapping. Tracers will be introduced in both experiments to further aid in detecting the development of the phase composition during CO2 transport. Geophysical monitoring will also be implemented. By means of modeling, different experimental sequences and injection/withdrawal patterns have been analyzed, as have parameter uncertainties. The objectives have been to (i) evaluate key aspects of the experimental design, (ii) to identify key parameters affecting the fate of the CO2 and (iii) to evaluate the relationships between measurable quantities and parameters of interest.

AbstractWe measured dissolved inorganic carbon (DIC) stable isotopes (813CDIC in ‰) of brine from an observation well within the first aquifer above the CO2 reservoir at the Ketzin pilot site, to test weather these can detect potential CO2 leakage. The monitoring revealed that DIC concentrations and 813CDIC values were masked by the used high alkaline drilling mud, even eight months after well development. However, subsequent changes in 813CDIC and DIC from of -27 ‰ and 165mg L−1 to -23.5 ‰ and 116mg L−1 reflect most likely a shift towards pristine values of the aquifer.

Abstract The complete cycle of specific processes related to the geological storage of CO 2 is investigated in detail at Ketzin since 2004. The scientific monitoring program targets different depths of the involved area and addresses the safety and reliability of the storage. The surface monitoring comprises long-term soil CO 2 flux measurements and soil gas analyses. Annual mean values of soil CO 2 fluxes ranged from 2.4 to 3.4 µmol m -2 s -1 before the injection started (2005-2008) and from 2.3 to 3.5 µmol m -2 s -1 during and after CO 2 injection (2009-2016) and thus do not indicate an upward migration of the injected CO 2 .

AbstractA high-pressure/high-temperature reactor has been used to lead PVT and H2-solubility experiments in saline solutions covering conditions for which no data are available in literature: salinity up to halite concentration, pressure up to 200bar and temperature up to 373K. The hereby presented preliminary results show significant deviations from theoretical models. Further analysis and more measurements are needed to assess precision and reproducibility of these measurements; however they pinpoint the importance of experimental work to reliably constrain predictive models.

Abstract In binary geothermal power plants based on the Organic Rankine Cycle (ORC) typically shell-and-tube heat exchangers are used as evaporators. In the shell-side, nucleate boiling of the working fluid takes place on the outer surface of the tubes. For the replacement of fluids with high global warming potential (GWP) or selection of efficient working fluids, a comprehensive evaluation has to be performed. Therefore, the knowledge about the nucleate boiling heat transfer coefficient (HTC) in combination with the electrical power output is necessary. In this study, the focus is led on the investigation of the replacement of R245fa by the low GWP fluid R1233zd(E) in geothermal applications. The nucleate boiling HTC on a horizontal tube and the electrical power of a 1 kW scroll expander are simultaneously measured with an ORC test rig for both fluids. The thermal input is provided by an electrically heated preheater and evaporator. Nucleate boiling takes place on a plain copper tube with an outer diameter of 32 mm and a heated length of 822 mm. The surface temperature of the copper tube is determined by thermocouples within the tube in consideration of thermal conduction. The obtained results, regarding power output as well as heat transfer characteristics, show that the working fluid R245fa performs better at equal saturation temperatures due to the higher density and pressure, and the lower viscosity. The HTC of R245fa is exemplarily up to 43.2 % increased in comparison to R1233zd(E).

AbstractDecreasing water resources and steadily rising water demand drive research towards new approaches for safe and reliable water supply for the municipal, agricultural and industrial sectors. One solution for fresh water provision is sea water desalination using solar thermal energy. This paper describes the coupling of a Multi Effect Distillation (MED) plant with a Clausius-Rankine cycle powered by a solar central receiver system. A steady state model of an MED plant is developed and a correlation for the Gained Output Ratio (GOR) as function of heating steam temperature, specific seawater massflow and specific heat transfer surface of the desalination plant is deduced. This correlation is integrated into a model of a central receiver plant, comprising the heliostat field, a molten salt receiver system, two-tank storage and the steam cycle. A showcase simulation for the location Al-Kosseir, Egypt is performed to show the trade-off between electricity and water production for a cogeneration situation.

AbstractCurrent world-wide scientific activities addressing geological CO2 storage highlight one question of utmost importance for the general feasibility of CO2 storage in saline aquifers: What is the risk for freshwater reservoirs by potential upward brine migration as a result of pressure elevation in the storage formations? A vertical 1D model from reservoir depth to the surface was applied of a prospective storage site in the North German Basin to study the sealing capacity of a multi barrier system. Results emphasize that saltwater does not reach into the groundwater resources through intact caprocks.

AbstractThis paper describes microbial metabolic processes that are considered to be relevant for the technical reliability of a geothermal heat store. The study reports on changes of the microbial community composition in geothermal well fluids of different temperatures and after plant downtimes monitored by genetic fingerprinting. Stagnant conditions favored the enrichment of bacteria, sulfate reducers (SRB), and sulfur oxidizers (SOB) in the well. Furthermore higher concentrations of DOC, SO42-, H2S, and H2 were detected in the first fluids produced after plant downtime. The increased abundance of SOB indicated oxygen ingress during plant downtime. The interaction of SRB and SOB might have further enhanced corrosion and scaling processes. A mobile bypass system installed at the site will help to understand the processes occurring in the well and to study biofilm formation and corrosion rates at different temperatures.