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This research proposes an innovative solar thermal plant able to generate mechanical power through an optimized system of heliostats with Scheffler-type solar receivers coupled with screw-type steam expanders. Scheffler receivers appear to perform better than parabolic trough collectors due to the high compactness of the focal receiver, which minimizes convective and radiative heat losses even at high vaporization temperatures. At the same time, steam screw expanders are volumetric machines that can be used to produce mechanical power with satisfactory efficiency also by admitting two-phase mixtures and with further advantages compared to steam turbines: low working fluid velocities, low operating pressures, and avoidance of overheating. This study establishes a mathematical model to assess the energetic advantages of the planned solar thermal power system by evaluating the solar-to-electricity efficiency for different off-design working conditions. For this purpose, a numerical model on the Scheffler receiver is initially investigated, thus assessing all the energy losses which affect the heat transfer phase. A thermodynamic model is then developed to evaluate the energy losses and performance of the screw expander under real working conditions. Finally, parametric optimization of the solar energy conversion is performed in a wide range of operating conditions by establishing thermodynamic formulations related to the whole solar electricity generation system. Water condensation pressure and vaporization temperature are so optimized with respect to global energy conversion efficiency which, under the best operating conditions achieved in this research, rises from 10.9% to 14.4% with increasing solar irradiation intensity. Hence, the combined use of screw expanders and Scheffler receivers for solar thermal power system application can be a promising technology with advantages over parabolic dish concentrators. Novelty statement: This research proposes an innovative direct steam solar power plant based on an SRC, with water utilized as both heat transfer and working fluid, equipped with Scheffler solar receivers as a thermal source and screw expanders as work-producing devices. Technical studies and energy assessments of this kind of SEGS at part-load operation do not exist in scientific literature; after reviewing the literature, it was determined that volumetric expanders have been rarely combined with Scheffler receivers for solar thermal power system application. In effect, combined use of screw expanders and Scheffler-type solar concentrator in a direct steam solar power system represents a completely new plant configuration; however, as a promising DSG solar system, at present numerical model of this new sort of SEGS is lacked in literature and the optimum operating conditions have yet to be defined. For this reason, the chief objective of this paper is to define a first parametric optimization of all thermodynamic variables involved to maximize global efficiency of the proposed solar thermal power generation system for ordinary working conditions.

Seasonal storage of hydrogen is a valuable option today increasingly considered in order to optimize cogeneration plants under continuous operation in an incentive framework where electricity sale to the national grids is becoming less economically profitable than in the past. The paper concerns the numerical study and optimization of a cogeneration plant installed in an industrial site having an availability of hydrogen over a continuous time scale, to meet the energy needs and mitigating the environmental impact of the plant operation by reducing the energy withdrawal from traditional sources. Two alternatives are analyzed into detail: the former regards energy production through an internal combustion engine, this last properly controlled to be fueled with blends of natural gas and increasing percentages of hydrogen, the latter concerning the addition of fuel cells to the proposed layout to further reduce the electricity integration by the grid. The dynamic response of the cogeneration system under examination is dynamically evaluated to efficiently fulfill the industrial loads to be fulfilled. First, optimization is performed by implementing a PID controller to better track the industrial demand of electric energy. The main results of this solution reveal a 81% reduction of excess electricity, a 7% reduction of natural gas consumed but a 47% raise of CO2 emissions due to the increase in thermal integration. Then, an additional energy generation from fuel cells is assumed. An economic analysis is carried out for each of the implemented configurations. The adoption of fuel cells, despite requiring a greater initial investment, allows obtaining a SPB of 1,4 years ( 16%), 1,17 Mln V of avoided costs ( 18,5%) and 1320 t/year of CO2 emissions avoided ( 95%) with respect to the initial layout.

The global energy shift towards the exploitation of renewable energy sources requires the development of proper energy storage and back-up technologies to deal with their intermittency and seasonality. Renewable energy chemical storage offers the possibility of efficiently storing large amounts of energy for long time. Ammonia is increasingly considered a feasible alternative to the use of hydrogen, due to the existence of already well assessed production technologies and transport infrastructures. However, it presents some challenges and the most relevant of these concern combustion stability and NO emissions when ammonia is burned in traditional conditions. A promising approach to ensure combustion stability while containing NO emissions relies on the shift from traditional to new combustion modes. MILD combustion has been proven as a reliable alternative to reach these targets. At the same time, water addition to reactants is a well-known strategy that promote DeNO routes in fossil fuel combustion. In this study, the influence of water addition to ammonia-air mixtures in a cyclonic flow burner was investigated to exploit the possible benefits of the simultaneous application of MILD combustion conditions and water addition. The experimental analyses were performed in premixed and non-premixed feeding conditions. Results indicated that water addition to the reactant mixture may represent a very simple and efficient solution in determining the reduction of NO emissions in ammonia combustion, especially in fuel-lean conditions. Moreover, the comparison between premixed and non-premixed configuration showed that it is possible to enhance the process performance through a simultaneous optimization of the burner internal flow-field and reactants injection strategies.

Increasing the share of renewable energies and reducing the emissions of carbon dioxide are two of the major challenges of this century. Effective use of solar energy can contribute to both targets. In this study, it is investigated an integrated process in which concentrated solar power is used to perform carbon dioxide capture from a combustion power plant through the calcium looping cycle in a dual interconnected fluidized bed system. Carbon dioxide is then reacted with hydrogen obtained from water electrolysis to produce methane (power-to-gas). Electrolytic cells may be powered by photovoltaics or excess renewable energies, thus reducing their curtailment. The integrated process was studied by means of model computations. Steady state operation of the different units was considered. Intrinsic variability of the solar energy was managed with implementation of a seasonal and/or daily thermochemical energy storage strategy. Design and operational conditions assumed as a reference were those of a combustion plant of municipal solid waste located in Manfredonia (Italy). Parameters were chosen so as to reproduce realistic conditions. Model results suggest that carbon dioxide capture can range from 30% to 85%. Input thermal power of the concentrated solar power must range between 50 and 175 MW, for 12 h of operation. A share of this energy can be integrated in the power cycle for electricity generation, upgrading the potentiality of the original combustion plant. Size of cubic storage vessels required for continuous operation of the system ranges from 10 to 70 m according to the implemented strategy. Methane yield ranges within 3-12 × 10 tons per year, and production of H needs a photovoltaic field of 4-5 km if built in Manfredonia. Altogether, the integrated plant has an overall efficiency of 20-22% and allows, simultaneously, for carbon dioxide capture, continuous integration of solar energy in the energy production cycle and carbon dioxide utilization for methane production.

------------------------------------------------------------------------------------------------------------------------------------------- This version has been superseded. The latest version is at https://doi.org/10.5281/zenodo.5517550 ------------------------------------------------------------------------------------------------------------------------------------------- Eddy covariance flux tower datasets of all Urban-PLUMBER sites, associated with the manuscript: "Harmonized, gap-filled dataset from 20 urban flux tower sites" Use of any data must give credit through citation of the above manuscript and other sources as appropriate. We recommend data users consult with site contributing authors and/or the coordination team in the project planning stage. Relevant contacts are included in timeseries metadata. For site information and timeseries plots see https://urban-plumber.github.io/sites. For processing code see https://github.com/matlipson/urban-plumber_pipeline. Within each site folder: - `index.html`: A summary page with site characteristics and timeseries plots. - `SITENAME_sitedata_vX.csv`: comma seperated file for numerical site characteristics e.g. location, surface cover fraction etc. - `timeseries/` (following files available as netCDF and txt) - `SITENAME_raw_observations_vX`: site observed timeseries before project-wide quality control. - `SITENAME_clean_observations_vX`: site observed timeseries after project-wide quality control. - `SITENAME_metforcing_vX`: site observed timeseries after project-wide quality control and gap filling. - `SITENAME_era5_corrected_vX`: site ERA5 surface data (1990-2020) with bias corrections as applied in the final dataset. - `log_processing_SITENAME_vX.txt`: a log of the print statements through running the create_dataset_SITENAME scripts. Authors Mathew Lipson, Sue Grimmond, Martin Best, Andreas Christen, Andrew Coutts, Ben Crawford, Bert Heusinkveld, Erik Velasco, Helen Claire Ward, Hirofumi Sugawara, Je-Woo Hong, Jinkyu Hong, Jonathan Evans, Joseph McFadden, Keunmin Lee, Krzysztof Fortuniak, Leena Järvi, Matthias Roth, Nektarios Chrysoulakis, Nigel Tapper, Oliver Michels, Simone Kotthaus, Stevan Earl, Sungsoo Jo, Valéry Masson, Winston Chow, Wlodzimierz Pawlak, Yeon-Hee Kim. Corresponding author: Mathew Lipson <m.lipson@unsw.edu.au>

The main target of this paper is to numerically study a multi-source (air/sun/ground) heat pump with the implementation of a thermal energy storage, using either water or PCM, for residential space heating. The system was modelled considering several sub-models for each of the components (compressor, solar panels, storage tank, heat exchangers etc.). A control strategy has been established to decide which operating mode of the system provides the highest coefficient of performance (COP). A multi-objective optimization through genetic algorithm of several decisional variables of the system was carried out, in different configurations and climate conditions, by considering different scenarios in terms of total investment and energy consumption costs, to optimize seasonal performances and investment cost of the entire system. Results show that solar thermal and solar photovoltaic collectors coupled with water storage tank give higher seasonal energy performance, especially in warmer climates, whereas the exploitation of the ground source can be more advantageous for colder climates. From the optimization analysis, it results that optimal non-dominated solutions characterized by a SCOP increase between 50% and 250% are characterized by higher investment costs between 215% and 730%, depending on the climate conditions. None of the solutions employing a PCM storage tank results economically feasible, due to a slight effect on system performance, and a much higher effect on investment costs. Finally, several cost scenarios in terms of incentives on investment costs and increased energy prices were analysed, for which the employment of scenarios with higher capital investment can be more advantageous in terms of lower total costs. This work was partially funded by Ministerio de Ciencia, Innovación y Universidades - Agencia Estatal de Investigación (AEI) (PID2021-123511OB-C31 - MCIN/AEI/10.13039/501100011033/FEDER, UE and RED2018-102431-T - MCIU/AEI). This work is partially supported by ICREA under the ICREA Academia programme. The authors form University of Lleida would like to thank the Catalan Government for the quality accreditation given to their research group (2017 SGR 1537). GREiA is certified agent TECNIO in the category of technology developers from the Government of Catalonia.

The interplay of biomechanical and neuromuscular aspects aids in the conversion of power production in running performance, and when combined with metabolic factors, these aspects may lead to improved running economy (RE). Therefore, the purpose of this study is to determine the association between the Stryd Power Meter foot pod metrics with RE and performance. Fifteen high-caliber male athletes completed two treadmill running sessions. First, RE was determined at 10 and 12 km/h. Second, two all-out efforts of nine and three minute duration were completed. At 10 km/h, the simple and stepwise multiple linear regression analysis revealed that form power (FP) was the best RE predictor (adjusted R2 = 0.464; p = 0.005) followed by vertical oscillation (VO) ( R2 = 0.424; p = 0.005) and ground contact time (GCT) ( R2 = 0.363; p = 0.010). At 12 km/h, such regressions confirmed that GCT was the best RE indicator (adjusted R2 = 0.222; p = 0.043) followed by FP (adjusted R2 = 0.213; p = 0.047). During the nine and three minute all-out effort sessions, GCT was the best performance predictor ( R2 = 0.491; p = 0.002 and R2 = 0.380; p = 0.014, respectively). The biomechanical factors of GCT and FP are good indicators of RE and running performance.

Thermochemical energy storage is gaining widespread consideration to increase energy dispatchability in concentrating solar thermal power plants. Accordingly, excess solar energy input drives an endothermic reaction, accomplishing high energy densities and virtually unlimited storage times. As gas-solid reactions are usually involved, multiphase reactor design is essential for the success of this technology. A novel concept of directly-irradiated fluidized bed autothermal reactor is investigated for applications in concentrated solar thermal technologies. The device can be operated as a rechargeable battery, alternating a charge phase, during which solar energy is collected and stored by an endothermal gas-solid reaction, and a discharge phase, during which the stored chemical energy is released by the reverse exothermic reaction. The autothermal operation, during the charge process, consists in the recovery of the sensible heat of the reaction products to preheat the reactants by means of an internal double-pipe countercurrent heat exchanger. This operation allows to increase the overall efficiency, reducing the required solar energy input. A compartmental model to simulate the operation of the thermochemical battery is developed and closed with constitutive equations and parameters obtained by previous experimental studies on lab-scale test facilities. Limestone calcination/carbonation has been considered as model reversible reaction. Both the charge and the discharge steps were assessed investigating the effect of the design and operational variables. For the charge operation, an optimal temperature was found around 900 °C with thermal efficiencies close to 90%. For the discharge operation, thermal efficiency was found to depend almost solely on the reactor temperature, reaching values as high as 80%, whereas the gas flowrate can be set independently. The upper limit for reaction temperature is set to the reaction equilibrium condition corresponding to the inlet concentration of carbon dioxide. The obtained results represent the basis for the realization of a new prototype, that will serve for the complete proof-of-concept of the directly-irradiated fluidized bed autothermal reactor.

Concentrating solar thermal (CST) technologies for power production can play a major role in the future portfolio of renewable energies. Limestone calcination/carbonation (Calcium Looping (CaL)), is an appealing reaction whose integration with CST is widely investigated for thermochemical energy storage (TCES) and carbon capture and storage/utilization (CCSU). Experimental data under realistic CST conditions/reactors currently lacks, since most of the experimental activities have been performed in thermogravimetric analyzers. In this study, CaL-CST integration was investigated in a lab-scale directly irradiated fluidized bed reactor, able to mimic the operating conditions required for industrial implementation of the technology. Three different techniques to improve the performance of CaL-CST for TCES and CCSU were investigated: i) lowering of calcination temperature; ii) precalcination; iii) use of dolomite instead of limestone. Experimental results revealed that all the strategies moderately improve system performance. After 20 cycles, depending on the technique applied, the mean carbonation degree ranges within 28.1-37.1% (TCES) and 15.3-18.7% (CCSU) with limestone, and values 61.5% (TCES) and 36.7% (CCSU) with dolomite. Figures of energy storage density are less sensitive to the different techniques, as pay for the lower calcination temperature (limestone), or for the presence of an inert MgO fraction (dolomite). Corresponding values range within 941-1065 MJ m (TCES) and 777-872 MJ m (CCSU), for loose-packed conditions. N-physisorption analyses revealed that the increased reactivity arises from better microstructural properties in terms of specific surface. Optimal choice among the different strategies should consider the intrinsic peculiarities of each investigated technique.