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To enable the widespread exploitation of intermittent, low-cost, and non-dispatchable renewable energy technologies, energy storage plays a key role in providing the required flexibility. This study introduces maps of optimal combination of Thermal Energy Storage (TES) and power cycles, supporting decision-making in power-to-heat-to-power applications. These maps span a wide temperature range from 200 to 1200 °C and are proposed for different charging costs, installed capacities, and storage durations. For thermal-to-electricity reconversion, this study explores power blocks including steam Rankine cycle, supercritical CO2 (sCO2) Brayton cycle, Organic Rankine Cycle (ORC), and combined gas turbine with Rankine and sCO2. Results highlight that, in a grid-based plant with a 50 EUR/MWh charging cost, the most cost-effective pairing involves sCO2 cycles with recompression and intercooling, with particle TES at 600–800 °C. Air packed-bed suits scenarios where TES contributes significantly to capital costs or involves low charging costs. Molten salt TES is the optimal choice when the design temperatures align with salt temperature limitations. Particle TES proves cost-effective across a broad temperature range and scales (10–200 MW). For solar-based systems, the integration of molten salt TES with simple sCO2 recuperated cycles demonstrates market potential for southern European locations., QC 20241108

In this article we present the results of six experiments identified as HP5 series, performed in the large-scale PANDA (Passive Nachzerfallswärmeabfuhr und Druck-Abbau Testanlage) thermal-hydraulics facility within the OECD/NEA HYMERES (Hydrogen Mitigation Experiments for Reactor Safety) project. These experiments focus on thermal stratification and mixing induced by steam injection in a water pool through a vertical sparger with horizontal holes. The pool stratification was created at low steam flow rate and mixing was achieved by either: steam injection at higher flow rate or a combined effect of injection low steam flow rate and horizontal water jet. The phenomena investigated are relevant for the safety of light water reactor, normal operation and accident scenarios during which steam is directly vented and condensed in a large water pool. We find that the initial pool temperature plays an important role in the thermocline formation. Higher initial pool temperature leads to the formation of a thermocline at lower elevations farther away from the sparger and with a larger density difference across the thermocline. The flow field in the pool is affected by initial pool temperature as indicated by Particle Image Velocimetry (PIV). Higher steam flow rate during the second phase showed the effect of steam momentum on mixing. It was found that for the range of parameters considered in the experiments with water injection the density difference between the pool water and the water injected by the nozzle has a greater influence on the mixing time compared with the momentum of the water jet., QC 20240326

Design of a sustainable and economical composite structure is challenging due to the often contradicting design drivers such as energy consumption and cost. Therefore, predicting the environmental and economic impact in the early stages of product design results in the significant reduction of energy consumption and cost. Consequently, the impact of contrasting objectives on an optimized carbon fibre reinforced polymer (CFRP) demonstrator is evaluated in this study. This evaluation is performed by integrating a predictive life-cycle assessment and costing framework in a multi-objective optimization methodology. The varying design configurations include designs with and without stiffeners. Furthermore, the impact of end-of-life allocation on the optimized design is also evaluated in this study. The results show a marked difference between the energy consumption of the various optimized designs with energy optimization producing the most efficient solution. However, the mass of the demonstrator increases by 7–9 kg across the different design configurations when the closed loop allocation model is implemented. Consequently, the results show the importance of selecting an appropriate EOL allocation methodology in evaluating the energy consumption of a product. The results also show that the parameters driving the energy consumption (mass and material configuration) and cost (complexity and manufacturability) are varied and often contrasting. The differences in mass, cost, and energy optimized designs further reinforces the importance of coupling cost and energy evaluation in design of sustainable products. Finally, the study demonstrates the need for a holistic life-cycle based assessment in early stage sustainable product design., QC 20240130

The process temperatures in the friction stir welding of thick polymer plates play a significant role in the joint's quality since the process is characterized by mixed solid and viscous flow states. The heat generation mechanism in each state is fundamentally different, with heat being generated by friction in the solid-state and by viscous shear flow in the viscous state. In this study, the heat generation and dissipation in the friction stir welding of 14 mm thick high-density polyethylene plates were studied numerically through solving the direct heat conduction problem. Two models of heat generation were used in the numerical solution and the effect of the pin rotational speed on the process temperatures was investigated. It was shown that the utilization of a mixed heat generation model consisting of both the solid state and the viscous shear flow considerably improves the numerical model predictions. The temperature predictions were validated through welding experiments and showed a temperature difference of 3 %. Furthermore, it was found that the welding process stabilizes at rotational speeds higher than 800 rpm, where no considerable change occurs in the volume of the viscous flow region and the welding power requirement. The numerical results based on the combined solid-viscous heat model were in good agreement with the experimental thermal histories., QC 20240209

Dynamic rating of the transformer is a promising technology, which is suitable for various applications. Using dynamic rating for connecting renewable energy is believed to be beneficial for the economy and flexibility of the power system. However, to safely deploy such operation strategies, it is important to have more precise estimates for the total costs of owning such units and determine how effective such operation method is for a solar power plant. This study proposes a method for calculating total ownership costs (TOC) of dynamically rated transformers used for the connection of the solar power plant to the grid as well as analyzes its efficiency. The sensitivity analysis looks into the change in TOC and peak efficiency index (PEI) after considering reactive power dispatch. Results of this study also show how TOC, PEI, and load and no-load losses change depending on the transformer size., QC 20240125

Dynamic thermal rating allows transformers to operate beyond the nameplate rating according to the actual weather and loading conditions. This paper proposes a methodology to improve the application of this technology in the design of new transformers or in the operation of existing transformers connected to wind farms by accurately predicting their load profiles, accounting for the influence of wake effect and turbine availability. Specifically, the variation of turbine availability due to the intermittent wind is considered in the load profile estimation. Additionally, a correction method, which can be incorporated into any wake model, is proposed to improve the accuracy of wake loss computation. A case study shows that the wake effect and the changing turbine availability shorten the time that the transformers maintain at full load, thereby reducing the aging rate of the wind farm export transformers. The findings suggest that considering these two factors in the DTR application can benefit the longevity and efficiency of wind farm exported transformers., QC 20240201

Ground source heat pump (GSHP) systems offer a low carbon heating and cooling solution for the decarbonization of buildings. As global temperatures rise, the cooling requirements of buildings will grow, even in regions where cooling systems have been historically uncommon due to their colder climate, such as Sweden. The combination of free cooling (FC) with GSHPs seems like a natural way to meet the increasing cooling needs, since the heat extracted from the building during the summer months can be injected into the ground to potentially regenerate the borehole field and enhance heat pump performance. However, a technology that is generally integrated with GSHP systems for borehole regeneration are photovoltaic/thermal collectors. This study investigates the performance of a ground source heat pump system with free cooling for a multi-family building in Stockholm, Sweden, and the interference on the free cooling capabilities of the system when photovoltaic/thermal collectors are present. The results demonstrate that the integration of PVT and FC not only maintains the cooling supply but also enhances heat pump performance, all the while reducing borehole length and land area requirements., QC 20240209

Using solar energy and waste heat for medium-temperature thermal applications depends on efficient and economical heat storage development. Developing a compact thermal energy storage system is essential to use excess thermal energy from a source in a process or to shift the utilisation time of solar thermal energy or recovered waste heat. Phase change materials are commonly used for energy storage applications globally. In this work, a latent heat thermal energy storage (LHTES) system with 2.37 kg of Erythritol as the phase change material (PCM) has been studied. A shell and tube heat storage system is selected due to its effectiveness in heat transfer. Synthetic silicone oil Hi-Tech Therm-60 was used as heat transfer fluid. Thermal stability tests in a differential scanning calorimeter (DSC) for a small sample mass and a specifically designed experiment for a larger sample mass were performed to assess the stability of the PCM. The time-dependent temperature distribution inside the storage system and the effect of heat transfer fluid (HTF) inlet temperature on the charging behaviour were studied during the charging process. Charging time and melt fraction have been calculated. No significant change in melting temperature and a 10% reduction in latent heat of PCM was observed in the thermal stability test for a small sample mass in DSC. The charging time of the storage device was observed to be 91–97 min and 195 min for 140 °C and 130 °C HTF inlet temperatures, respectively. The total stored energy in the system was 922 kJ with a Stefan number of 0.59. Temperature variation during the charging process inside the storage also suggests a buoyancy effect, leading to increased natural convection during the melting process., QC 20240102

Due to the growth in the share of renewable energy sources (RES) in the power generation sector worldwide and their intermittency, storage of surplus electricity is needed. The technology known as Power to X (PtX) facilitates the extended storage of excess electricity by converting it into gaseous or liquid fuels such as hydrogen, methane, ammonia, or methanol. This study examines the potential of synthetic natural gas (SNG) technology as a viable energy storage solution. The paper introduces three distinct SNG production systems, all of which are based on the processes of biomass gasification and methanation. Case 1 assumes further CO2 capture from generated SNG, and Cases 2 and 3 additionally assume hydrogen production and almost complete CO2 utilization by syngas hydrogenation via the methanation process. The methanation process converts syngas and hydrogen into SNG with a high methane content (>90 vol% dry), that can be injected into the natural gas grid. The thermodynamic and economic potential of SNG production systems is presented in this work. The simulations were conducted using the AspenONE software. The methanation process was analyzed for various design conditions such as methanation temperature and pressure, and different H2:CO, and H2:CO2 ratios. The estimated cold gas efficiency of proposed SNG production systems varies from 63.27% to 77.10% and can be increased up to about 69.10–75.58% when the recovery of heat from methanation is considered. A sensitivity analysis was conducted to determine the break-even price of SNG, considering different scenarios for the costs of feedstock, specifically biomass and electricity. The results indicate that under the most optimistic conditions, the break-even price of SNG is estimated to be 115 €/MWhSNG, 58 €/MWhSNG and 67 €/MWhSNG for Cases 1, 2, and 3, respectively., QC 20240110

Internally heated (IH) natural convection can be found in nature, industrial processes, or during a severe accident in a light water reactor. In this accident scenario, the nuclear reactor core and some internal structures can melt down and relocate to the lower head of the reactor pressure vessel (RPV) and interact with the remaining coolant. Subsequent re-heating and re-melting under decay and oxidation heat creates a transition from a debris bed to a molten pool. The molten pool, which can involve more than hundred tons of dangerously superheated oxidic and metallic liquids, imposes thermo-mechanical loads on the vessel wall that can lead to a thermal and/or structural failure of the vessel and subsequent release of radioactive materials to the reactor pit, and can possibly make its way to the environment. This study uses Direct Numerical Simulation (DNS) to investigate homogeneous IH molten pool convection in a hemispherical domain using Nek5000, an open-source spectral element code. With a Rayleigh number of 1.6 × 1011, the highest reached through DNS in this confined hemispherical geometry, and a Prandtl number of 0.5, which corresponds to a prototypic corium, the study provides detailed information on the thermo-fluid behavior. The results show a turbulent flow with three distinct regions, consistent with the general flow observations from the BALI experiments. The study also presents detailed information on turbulence, such as turbulent kinetic energy (TKE), turbulent heat flux (THF), and temperature variance. Additionally, the study provides 3D heat flux distributions along the boundaries. The heat fluxes along the top boundary fluctuate due to the turbulent eddies in the vicinity, while along the curved boundary the heat fluxes increase nonlinearly from the bottom to the top., QC 20240108

During a severe accident of light water reactors (LWR), melt penetration in a debris bed (also called infiltration) may occur due to the failure of a crust which accommodates a molten pool over the debris bed, or due to earlier re-melting of metallic components (i.e., Zr and Fe) which has lower melting points than oxidic ones (i.e., UO2 and ZrO2) of corium debris. Although understanding and modeling of melt infiltration plays a significant role in the prediction of severe accident progression, little work has been done in this respect due to its complexity. To fill this knowledge gap, the present study develops a Moving Particle Semi-implicit (MPS) code with various models representing key physics in melt infiltration. REMCOD experiment, recently carried out at KTH, has been simulated to validate the updated MPS code. The comparative results show that the melt infiltration in the tests can be reproduced by the MPS code. For a debris bed of cylindrical particles, the melt infiltration process in the experiment can be predicted by using Sauter mean diameter of the particles in the simulation. The code is also applied to investigate the influences of important parameters on the melt infiltration, and it is found that contact angle has little impact on melt penetration process in the case of debris beds with large pore sizes., QC 20231218

This paper presents the development of accurate map-based models for characterizing a new Dual Source Heat Pump prototype. This unit includes three braze plate heat exchangers and a round tube fin heat exchanger, allowing the unit to select different operating modes such as heat pump, chiller, and domestic hot water production using as source the ground or air. Therefore, due to the hybrid typology of this unit and the possibility of reversing the cycle, this work covers the main heat pump and refrigeration equipment technologies currently available on the market (air source and ground source units). The modeling strategy selected has been to provide several polynomial expressions to predict the performance of these units, i.e., compressor energy consumption and condenser and evaporator capacities. This approach allows obtaining accurate, compact, and easy-to-implement models for developing dynamic models of more complex systems where this type of unit – the heat pump – is an integrated part of the system. Currently, a clear example of this modeling strategy can be found in characterizing one of the main components installed in these machines, the compressor. The AHRI-540 standard specifies a polynomial model as a function of evaporating and condensing temperatures. In this sense, for the characterization of heat pumps, the polynomials developed depend only on the unit's external variables, so they can be useful in many scenarios, obtaining direct feedback on the heat pump performance when developing a dynamic model to optimize system control strategies or to develop techno-economic studies. In this case, the hybrid typology of this unit makes it particularly relevant to optimize the control to manage the type of source to be used (air or ground), allowing the development of a more efficient and sustainable technology by selecting the most adequate source in terms of performance. This study focuses on obtaining the polynomial expressions that minimize the number of, QC 20231031

To compute few-group nodal cross sections, lattice codes must first generate multi-group cross sections using continuous energy cross-section libraries for each material in each fuel cell. Since the processing cost is significant, we propose representing the multi-group cross sections during lattice calculations using a pre-trained deep-learning-based model. The model utilizes a combination of Principal Component Analysis (PCA) and fully connected Neural Networks (NN). The model is specifically designed to manage extensive multi-group cross-section data sets, which contain data for several dozen nuclides and encompass more than 50 energy groups. Our testing of the trained model on a PWR assembly with a realistic boron letdown curve revealed an average relative error of around 0.1% for both fission and total macroscopic cross sections. The average time required for the model to generate the cross sections was approximately 0.01% of the time needed to execute the cross-section processing module., QC 20231013

In this study time-resolved char conversion and alkali release under steam gasification conditions were investigated using a fixed bed reactor. The behaviour of an industrial char and chars produced from straw and furniture waste was investigated. For woody chars, an increase in gasification reactivity is observed together with a notable alkali release as the gasification approaches completion (degree of conversion > 0.8). In contrast, straw char exhibited a decrease in conversion rate and alkali release throughout the gasification process, attributed to the formation of catalytically inactive potassium silicates inhibiting the catalytic role of alkali. Aerosol particles in the 0.01–22 µm size range are emitted during the char conversion. A fraction is formed by nucleation of alkali compounds and other condensable gases. A wide particle distribution that extends over the whole size range is also observed, and the particles are likely to consist of solid char fragments. The study concludes on the importance of alkali release, illustrating the difference in alkali release pattern for high and low ash char., QC 20231003

The efficiency of the gasification process and product quality largely depend on the degree of fuel conversion. We present the real-time in-situ tunable diode laser measurements of main carbon and oxygen-containing species in the hot reactor core of a pilot-scale entrained flow biomass gasifier (EFG). The concentrations of CO, CO2, CH4, C2H2, H2O, soot, and gas temperature were measured during the air and oxygen-enriched gasification of stem wood at varying equivalence ratios. The experiments were made at the upper and lower optical ports inside a 4 m long, ceramic-lined, atmospheric EFG, allowing to access the degree of the fuel conversion inside the reactor. The exhaust composition was measured by micro-GC, FTIR, and low-pressure impactor. There was a good agreement between the data measured inside the reactor and at the exhaust for oxygen-enriched gasification implying that the chemical reactions are practically frozen downstream the optical ports. For air, the data indicated that the gasification reactions are still active at the measurement locations. Significant concentrations of C2H2, up to 5000 ppm, were found inside the reactor., We gratefully acknowledge financial support from the Swedish Energy Agency through 50470-1 project.

A new experimental study (aka SPAYCOR-S2) on multi-nozzle spray cooling of a downward-facing heater surface is conducted on the SPAYCOR facility at KTH, to provide data assessing the feasibility of spray cooling for in- vessel melt retention (IVR) in light water reactors. It is intended to investigate the potential for reducing the number of nozzles for spray cooling of an 80 mm x 120 mm surface, from the 2 x 3 nozzle array in the previous study (Bandaru, 2021) to a 2 x 2 nozzle array in the present study. Given the same heater surface, the pitch-to- diameter ratio is enlarged in a 2 x 2 nozzle array, resulting a partial coverage of the spray cones of four nozzles, in contrast with the 2 x 3 nozzle array where the heater surface was fully covered by six-nozzle spray. The tests focus on the cooling performance of such partial coverage of multi-nozzle spray and the effects of heater surface's inclination angle. The experimental results reveal that the inclination angle of the heat surface has a negligible impact on cooling capacity, although it is slightly higher on the surface inclined at 90 degrees degrees than on the surfaces inclined at 45 degrees degrees or 60 degrees. degrees . The maximum steady heat flux of the 2 x 2 nozzle array at its minimum spray flowrate is determined as 1.96 MW/m2. 2 . A numerical study on the spray cooling of the 2 x 2 nozzle array is also performed with models in OpenFOAM, which are extended from our previous development (Fang, 2023) by adding models for thin-film boiling and conjugate heat transfer in solid. For validation of the numerical study, the spray cooling of the heater surface inclined at various degrees is simulated, and the results are compared with those of experiment. The simulation generally shows good correspondence with experiments., QC 20240910

This article presents and thoroughly examines an innovative, practical, cost-effective, and energy-efficient smart heating, ventilation, and air conditioning (HVAC) system. The fundamental component of this concept is a stateof-the-art method called Deep Green Cooling technology, which uses deep drilling to utilize the ground's heating and cooling potential directly without the need for machinery or heat pumps. This method satisfies demands with the least energy use, environmental impact, and operational costs. In order to effectively oversee and regulate energy production, storage, and utilization, the system consists of an intelligent control unit with many smart controllers and valves. Renewable energy deployment is made easier, and the intelligent automation unit is more compatible with the help of a high-temperature cooling resource with a high supply temperature of 16 degrees C. The technical, environmental, and financial aspects of the suggested smart office building system in the southern region of Uppsala, Sweden, are evaluated using TRNSYS software. According to the results, boreholes provide more than 28.5 % of the building's energy requirements by utilizing the ground's ability to generate affordable, dependable seasonal thermal energy. The district heating network satisfies the remaining demand, amounting to 787.2 MWh, highlighting the benefits of combining conventional and renewable energy sources for increased supply security and dependability. The borehole thermal energy storage system meets the building's entire cooling need, underscoring the importance of high-temperature cooling systems. The most expensive part of the system is the borehole thermal energy storage, which accounts for over half of the total investment. The system has an appropriate payback period of ten years, proving its long-term profitability and cost-effectiveness, thanks to removing the machinery and heat pump. With 3138 MWh of ground-source heating and cooling, the system save, QC 20240910

In practice, film cooling on gas turbine blade inevitably works in an unsteady environment, which is introduced by periodical rotor/stator interaction and unsteady combustion. Previous studies have introduced two methods to simulate the realistic unsteady condition: 1) the pulsation of mainstream velocity; and 2) the pulsation of coolant injection. However, up to this point, the differences in instantaneous film cooling behaviors between these two methods remain unclear. This work presents a series of large eddy simulations to exhibit the unsteady flow and film cooling behaviors under steady and the two unsteady flow conditions. The numerical strategy is validated against our time-resolved experimental data. Time-averaged results show that the difference between the two pulsations is not significant if the averaged blowing ratio remains the same. However, the pulsation type plays a dominant role on the transient mode of film coverage. Under the steady condition, film coverage instability is induced by the unsteady trajectory of near-wall vortex structure; but with pulsed environments, the unsteadiness magnitude increases, and the area with high unsteadiness level enlarges. The pulsation of the mainstream velocity induces a more severe film coverage instability compared to the pulsation of the cooling air injection, because of the higher fluctuation energy of the mainstream bulk. Under mainstream pulsation, the probability distribution of instantaneous cooling effectiveness is the most scattered, and the corresponding fluctuation range is the largest., QC 20240912

Hydrogen is envisioned to become a fundamental energy vector for the decarbonization of energy systems. Two key factors that will define the success of hydrogen are its sustainability and competitiveness with alternative solutions. One of the many challenges for the proliferation of hydrogen is the creation of a sustainable supply chain. In this study, a methodology aimed at assessing the economic feasibility of holistic hydrogen supply chains is developed. Based on the designed methodology, a tool which calculates the levelized cost of hydrogen for the different stages of its supply chain: production, transmission & distribution, storage and conversion is proposed. Each stage is evaluated individually, combining relevant technical and economic notions such as learning curves and scaling factors. Subsequently, the findings from each stage are combined to assess the entire supply chain as a whole. The tool is then applied to evaluate case studies of various supply chains, including large-scale remote and small-scale distributed green hydrogen supply chains, as well as conventional steam methane reforming coupled with carbon capture and storage technologies. The results show that both green hydrogen supply chains and conventional methods can achieve a competitive LCOH of around €4/kg in 2030. However, the key contribution of this study is the development of the tool, which provides a foundation for a comprehensive evaluation of hydrogen supply chains that can be continuously improved through the inputs of additional users and further research on one or more of the interconnected stages., QC 20240531

Recently, several countries, including Sweden, have begun investigating the deployment of Small Modular Reactors. Licensing documentation for new reactors must include (preliminary) waste management and decommissioning plans. For light water reactors, the majority of the long-lived radioactive waste from their decommissioning consists of neutron-activated metallic components in the core region, the reactor internals and the reactor pressure vessel. Usually, this waste is planned to be disposed of in geological repositories, and the long-term safety after closure of Sweden's operating and planned repositories is mainly determined by their inventory of the long-lived radioisotopes C-14, Ni-59, and Ni-63. In this study, a three-dimensional model of NuScale's Power ModuleTM, a light-water small modular reactor, was created using Serpent 2, a multi-purpose three-dimensional continuous-energy neutron and photon transport code. The model consists of the nuclear core and surrounding metallic components. Based on burn-up calculations, the neutron flux in the equilibrium core was obtained. From the neutron flux, the cumulative concentrations for a range of relevant short- and long-lived radioisotopes were calculated in the metallic structures in the core region after 60 years of operation. The average specific activity of the selected radionuclides in the different components of the NuScale Power Module was calculated and compared to the activities in existing or anticipated decommissioning waste from Swedish reactors to evaluate the suitability of the Power Module's decommissioning waste for the Swedish waste management system. This study indicates that a single NuScale Power ModuleTM could generate between 1.08 and 2.13 m3 metallic LL-ILW/ GWel-year, i.e., radiologically suitable for disposal in the planned Swedish geological repository for long-lived, intermediated-level radioactive waste. These energy-equivalent volumes are estimated to be somewhat larger than those antic, QC 20240912

This study addresses the measurement of thermophysical properties in molten core materials (corium), which is crucial for modeling severe accidents in light water reactors. Due to the measurement challenges at temperatures above 3000 K, there is a significant lack of experimental data for corium. Focusing on a UO2-ZrO2 melt (atomic ratio U/Zr=0.456), density and viscosity measurements were conducted using aerodynamic levitation, a non-contact method chosen to avoid interactions between the samples and container walls. Samples were prepared using the pressing sintering method and levitated by argon gas above a conical converging-diverging nozzle. Density was measured using the cooling traces method under the axisymmetric ellipsoid hypothesis, while viscosity was measured by inducing damped oscillations which occurred when the levitated droplet was forced to oscillate around its resonant frequency through acoustic excitation, followed by the cessation of the acoustic excitation. The provided data and derived equations for the density and viscosity of the UO2-ZrO2 melt contribute to enriching the thermophysical property database for materials in nuclear reactors., QC 20240912

Biomass has enormous potential globally, but it requires sustainable management and conversion into modern bioenergy that aligns with the Sustainable Development Goals (SDGs). This study assesses sustainable biomass potential for energy generation in South America, considering forestry, agriculture, agro-industrial, and municipal solid waste biomass. The Autoregressive Integrated Moving Average (ARIMA) time series forecasting model with data from the Food and Agriculture Organization Corporate Statistical Database (FAOSTAT) and the World Bank up to 2050 is used. In 2021, the total biomass theoretical potential amounts to 1214 million tonnes (Mt), projected to increase to 1371 Mt by 2050. The available technical potential for energy purposes ranges from 796 Mt in 2021 to 916 Mt by 2050, with approximately 66 % attributed to agricultural biomass, 10 % to agro-industrial biomass, 17 % to forestry biomass, and 7 % to municipal waste biomass. Notably, not all countries experience growth in bioenergy potential from 2021 to 2050. Increasing forestry biomass recoverability from 25 % to 75 % enhances the total technical potential by 7 % for 2050. Primary bioenergy potential, utilizing available biomass, ranges from 13,831–15,892 PJ between 2021 and 2050, equivalent to 1278 to 1444 Terawatt hour (TWhe) when considering biomass conversion to electric energy. The share of bioelectricity could be 24 % of the total electricity generation in 2021. Additionally, modern bioenergy could help achieve sustainable development goals and decarbonize the energy sector in the region. This assessment of modern bioenergy potential in South America is relevant for subsequent techno-economic and environmental evaluations towards global energy decarbonization by 2050., QC 20240830

The present article proposes a novel smart building energy system utilizing deep geothermal resources through naturally-driven borehole thermal energy storage interacting with the district heating network. It includes an intelligent control strategy for lowering operational costs, making better use of renewables, and avoiding CO2 emissions by eliminating heat pumps and cooling machines to address the heating and cooling demands of a commercial building in Uppsala, a city near Stockholm, Sweden. After comprehensively conducting techno-environmental and economic assessments, the system is fine-tuned using artificial neural networks (ANN) for optimization. The study aims to determine which ANN design and training procedure is the most efficient in terms of accuracy and computing speed. It also assesses well-known optimization algorithms using the TOPSIS decision-making technique to find the best trade-off among various indicators. According to the parametric results, deeper boreholes can collect more geothermal energy and reduce CO2 emissions. However, deep drilling becomes more expensive overall, suggesting the need for multi-objective optimization to balance costs and techno-environmental benefits. The results indicate that Levenberg-Marquardt algorithms offer the optimum trade-off between computation time and error minimization. From a TOPSIS perspective, while the dragonfly algorithm is not ideal for optimizing the suggested system, the non-dominated sorting genetic algorithm is the most efficient since it yields more ideal points rated below 100. The optimization yields a higher energy production of 120 kWh/m2, as well as a decreased levelized cost of energy of 57 $/MWh, a shorter payback period of two years, and a reduced CO2 index of 1.90 kg/MWh. The analysis reveals that despite the high investment costs of 382.50 USD/m2, the system is financially beneficial in the long run due to a short payback period of around eight years, which aligns with the goals of futu, QC 20240829

This paper presents a numerical study investigating the effect of ribbed pinfins on the thermal–hydraulic performance of a microchannel heat sink. A three-dimensional numerical model of a single rectangular microchannel with rectangular pinfins having ribs on them is developed, and simulations are performed for different rib configurations under laminar flow conditions with deionized water as the coolant. The study is conducted in two parts. The first part examines the influence of varying numbers of ribs on the pinfins while maintaining a constant rib width. The results show that increasing the number of ribs initially enhances heat transfer, with the case having two ribs (R2) exhibiting the highest Nusselt number ratio and lowest thermal resistance, up to 16 % lower than the nonribbed case (R0). However, a further increase in the number of ribs leads to a decrease in heat transfer performance due to the reduced cross-sectional area for heat conduction through the ribs. Moreover, the highest performance factor is exhibited by the case consisting of seven ribs (R7). The second part explores the impact of varying rib width, using the optimal R7 configuration based on the performance factor from the first part. The results indicate that increasing the rib width significantly improves heat transfer, with the widest rib case (W7) achieving up to a 25 % increase in Nusselt number compared to a plain microchannel. The study provides insights into the design of efficient microchannel heat sinks with ribbed pinfins for effective cooling of high-heat-flux electronic devices., QC 20240829

The transition towards sustainability necessitates robust growth of renewable energy, especially solar power. However, increasing the shares of solar power may lead to mismatch of electricity supply and demand, thus worse solar power performance could be received due to lower self-consumption and self-sufficiency. This issue has attracted more attention recently as it also requires additional costs for controlling and battery integration. This study combines several load profiles from consumers having different behaviors with different proportions to find out the optimal shares with higher level of PV penetration and self-sufficiency. A visualizing matching layout is proposed to present the PV-load matching level of all the possibilities at different seasons based on a Swedish context. It is found an 8% improvement of self-sufficiency reaching 70% in summer without additional equipment and scarification of self-consumption. The results could assist in the design and planning of the future power sector. Regarding specific targets, various optimal solutions could be found based on the layout., QC 20240919

At a time when European countries try to cope with escalating energy prices while decarbonizing their economies, waste heat recovery and reuse arises as part of the solution for sustainable energy transitions. The lack of appropriate assessment tools has been pointed out as one of the main barriers to the wider deployment of waste heat recovery projects and as a reason why its potential remains largely untapped. The EMB3Rs platform emerges as an online, open-source, comprehensive and novel tool that provides an integrated assessment of different types of waste heat recovery solutions, (e.g. internal or external) and comprises several analysis dimensions (e.g. physical, geographical, technical, market, and business models). It has been developed together with stakeholders, and tested in a number of representative contexts, covering both industrial and heat network applications. This has demonstrated the enormous potential of the tool in dealing with complex simulations, while delivering accurate results within a significantly lower time-frame than traditional analysis. The EMB3Rs tool removes important barriers such as analysis costs, time and complexity for the user, and aims at supporting a wider investment in waste heat recovery and reuse by providing an integrated estimation of the costs and benefits of such projects. This paper describes the tool and illustrates how it can be applied to help unlock the potential of waste heat recovery across European countries., QC 20240506

The occurrence of porous deposits on the core surface during the operation of a pressurized water reactor can seriously affect its heat transfer characteristics and increase the surface temperature of the cladding. Continued heat transfer deterioration causes subcooled boiling and boron enrichment within porous deposits, leading to axial power anomalies in the core, and the study of porous deposits is beneficial to improving the economics and safety of reactor operation. In this paper, a two-dimensional boiling unit model of a porous deposits was established using COMSOL software to couple heat conduction, darcy flow, solute transport and chemical reactions in a multiphysics field to reasonably predict the temperature field, velocity field, boric acid concentration distribution, and PH distribution within the porous deposits. On this basis, the influence of different parameters (porosity, boiling unit radius of porous deposits, heat flow density) on the maximum effective thermal conductivity, the pattern of thermal parameters (temperature, superheat, percentage of subcooled boiling, and saturation temperature) on the chimney boundary are analyzed. The results show that localized superheating, maximum boric acid concentration and subcooled boiling occur at the bottom of the porous deposits. There is a negative correlation between the porosity and the percentage of subcooled boiling area, and a positive correlation between the radius of the porous deposits and the heat flow density and the percentage of subcooled boiling area., QC 20240912

Carbon capture technology is a prospective strategy to address the increasing concentration of CO2 in the atmosphere, with the core challenge of developing new cost-effective processes. In this work, the energy analysis and economic evaluation were conducted based on rigorous thermodynamic models and the process simulation results of a novel chemical absorption-dominated hybrid solvent which consists of functional ionic liquid of choline triazole ([Cho][Triz]) and sulfolane (TMS) to separate CO2 from shale gas. The solubility of CO2 and CH4 in different solvents were calculated using phase equilibrium model including the NRTL activity coefficient equation, the RK equation of state, chemical reaction equilibrium equations, and the mass balance equation. The physical properties of the ionic liquid-based solvent systems were calculated with empirical equations which was corrected using experimental data. The results obtained from the thermodynamic models exhibited good agreement with experimental data. Subsequently, the established models and the parameters obtained were embedded into Aspen Plus for further analysis. The total CO2 capture energy consumption of 1.65 GJ·t−1 CO2 and the cost of 48.07 $·t−1 CO2 were achieved using the new solvent when the mass fraction of IL was 60 wt%. Compared with the commercial 30 wt% MDEA carbon capture process, it reduced the energy consumption and economic cost of 64.16 % and 45.59 %, respectively., QC 20240719

There are a large number of airplanes currently being operated, in which the ventilation system needs to be improved to more effectively remove air contaminants. A potential approach is to adjust the supply air directions with the use of simple airflow deflectors. This study proposed a method for optimizing the supply air direction of ventilation in aircraft cabins based on the Re-field synergy index and Bayesian optimization. A validated numerical model was used to calculate the air distribution and air contaminant transport in a single-row single-aisle aircraft cabin to obtain the Re-field synergy values. The Bayesian optimization approach was used to identify the supply air direction which maximizes the Re-field synergy, namely, maximizes the mass transfer effectiveness. Finally, the air contaminant transport in a 7-row single-aisle aircraft cabin with the optimized supply air direction was evaluated to demonstrate the enhancement of ventilation performance. The results show that the proposed method based on the Re-field synergy index and Bayesian optimization can efficiently optimize the supply air direction in order to enhance the air contaminant removal in aircraft cabins. In the 7-row single-aisle aircraft cabin, the optimized supply air direction can reduce the average air contaminant concentration in the breathing zone of the passengers by up to 23 %., QC 20240828

Thermo-mechanical coupled systems are typically complex, however, the demand for analyses of this kind of multi-physics system is increasing, for example, accurately predicting the temperature and thermal stress of the railway disc brakes. However, many models ignore the phenomenon of thermal expansion and wear on brake pads. Therefore, their influence on the result is unclear. This research aims to investigate the effect of these two phenomena on the temperatures and stresses. These influences represent different heat flux input methods. Based on the finite element method (FEM), a three-dimensional (3D) transient thermo-mechanical model is built up. Three cases with or without thermal expansion and wear are conducted. The model is validated against measurement data. Simulation results show that thermal expansion and wear on the brake pads cause a 10% difference in the average temperatures of the brake discs, while a 257% difference in the maximum temperatures. As for the equivalent stresses (Von Mises stress), the difference can reach 3500%. Overall, this research builds a thermo-mechanical model and quantifies the effects of thermal expansion and wear on the temperatures and stresses of railway brake discs. The model can be transferred to other thermo-mechanical coupled multi-physics systems., QC 20240815

Boiling Water Reactors (BWR) and Advanced Pressurized Water Reactors (APWR) often use spargers to release steam from the primary coolant system into a pool with subcooled water to prevent containment overpressure. Direct contact Condensation (DCC) creates sources of mass, heat, and momentum determined by the condensation regimes in a subcooled pool. Thermal stratification can develop in the pool if buoyancy forces created by the heat source dominate the momentum source. Only part of the stratified pool volume can be used as the heat sink which is a safety concern. Modeling of steam injection and its effect on a large pool is computationally expensive due to the considerable spatial and temporal scale differences between the steam-water interface dynamics and global pool circulation. To enable the prediction of realistic plant transients, Effective Heat Source (EHS) and Effective Momentum Source (EMS) models were proposed. These models aim to calculate the timeaveraged integral effects of the steam injection on the pool without resolving the dynamics of the interface and DCC phenomena. This work aims to develop the empirical correlations that predict the time-averaged effective momentum induced by steam injection into a subcooled pool. The experimental data were collected in a Separate Effect Facility (SEF-POOL) at LUT, Finland. The force acting on the injection pipe was measured in SEF-POOL to estimate the effective momentum rate created by steam injection. The condensation regime coefficient C, defined as the ratio of effective momentum rate to the theoretical momentum rate of injected steam, is presented as a function of Jakob and Mach numbers. We found that the pitch-to-diameter ratios (P/D) had a significant effect on both the effective (time averaged) momentum rate and instantaneous forces measured in the low Jakob number region, which might be attributed to the interactions between neighboring nozzles., QC 20240813

Ensuring access to essential services, such as clean water and electricity, is a key challenge for achieving sustainable development goals in rural areas. This study proposes a novel Brayton-Stirling combined cycle-based cogeneration system for utilizing locally available biomass waste to generate both electricity and clean water. The system employs an externally fired gas turbine, a Stirling engine, and an air–gap membrane distiller. Four operation modes—parallel-powered, fully-fired, straightforward, and by-pass—were modeled for their efficiency and output. Four operation modes can be switched by two three-way valves. Sunflower husk, identified as the most effective biomass source, enabled the system to achieve up to 160 kW of electricity and 0.7 m3/h of freshwater. The electrical and exergy efficiencies of the system peaked in the parallel-power mode, offering a practical solution for enhancing rural sustainability. Moreover, the by-pass mode maximized water production, highlighting its effectiveness in addressing water scarcity along with energy generation. Through a case study, the cogeneration system has demonstrated its capability in satisfying both rural electricity and water demands throughout the day by controlling the combination of different operation modes and parameters. Therefore, it provides a promising solution for advancing rural electrification and water purification in rural areas., QC 20240719

In the context of severe accidents, one mitigation strategy that has been shown to work for low-to-intermediate power reactors is the In-Vessel Melt Retention (IVMR) of molten corium. For this reason, several efforts have been put forward to make this strategy feasible for high power reactors. In particular, the aim of the European H2020 IVMR project was to evaluate and improve current modeling strategies, such as the use of Computational Fluid Dynamics (CFD) codes for the prediction of flow and heat transfer in a homogeneous corium pool. Due to evident limitations, the validation was mainly performed against an available water-based experimental data, rather than a corium mixture. In order to overcome this limitation, complementary high fidelity numerical simulations, in the form of Direct Numerical Simulation (DNS), have been performed recently and are used in the current work as a reference for the validation purposes of the Reynolds Averaged Navier–Stokes (RANS) approach. More specifically, RANS numerical simulations of a three-dimensional hemispherical configuration are performed using the STAR-CCM+ software. Consistent with the DNS approach, the Boussinesq assumption is used to characterize the internally heated (IH) natural convection problem. The flow conditions correspond to a Rayleigh number of 1.6⋅1011 and a Prandtl number of 0.5. Several turbulence models available in STAR-CCM+, which are generally used for buoyancy driven flows, are compared and evaluated against the DNS results, in terms of velocity, temperature, buoyancy production of the turbulent kinetic energy and heat flux. Reasonable results are obtained by the RANS models, especially in predicting the main qualitative features of the flow configuration, such as thermal stratification, fast descending flow on the curved walls and high turbulence at the top of the domain. The main divergence between RANS and DNS is observed in the bulk region, where all the RANS computations present strong recircu, QC 20240815

This paper presents a new methodology to adjust map-based models to experimental data and reports the main results of a comprehensive experimental campaign of a Dual Source Heat Pump (DSHP) prototype. The prototype tested incorporates variable speed components (compressor, circulation pumps, and fan). The novelty of this prototype lies in its ability to select two possible heat sources: air or ground. Thus, it can operate as a geothermal or aerothermal heat pump, as well as a chiller, thanks to the additional capacity to reverse the cycle. Thanks to this hybrid approach, several advantages can be obtained compared to conventional equipment, such as higher efficiency, the requirement of smaller borehole heat exchangers, or the absence of defrost cycles. In a prior study, polynomial models were developed to accurately characterize the DSHP's performance (i.e., condenser and evaporator capacities and electrical energy consumption). These models were obtained considering the external variables to the unit as independent variables to facilitate their applicability using variables commonly measured in real installations. Due to the complexity of heat pump performance, which in current equipment can be influenced by up to 5 or 6 independent variables, the search for suitable polynomial models required the availability of a complete working map including more than 3000 working points. Thus, this previous work developed these models based only on simulation results. In this sense, this paper concludes the development of these models by focusing on two critical issues concerning empirical model development. The first aspect involves determining the minimum number and location of testing points needed to define the experimental sample for the model adjustment. The reported experimental data were obtained by analyzing the most suitable experimental design methodology to create the experimental matrices in each operating mode of the DSHP. The second aspect focuses on the final a, QC 20240719

In traditional wind farm planning, the design of wind turbine locations and cable layouts is usually undertaken sequentially. However, this approach may potentially result in suboptimal solutions. While the increased spacing between wind turbines enhances power output by reducing wake losses, it also imposes a negative impact by raising cable costs. Addressing this challenge, we propose a novel multi-objective optimization model that simultaneously considers the micrositing of wind turbines and cable routing. A joint framework of the Non-dominated Sorting Genetic Algorithm II (NSGA-II) and the Mixed-Integer Linear Programming (MILP) is established to optimize the layout of wind turbine locations, points of connection, and cable paths. The results indicate that, compared to the traditional sequential optimization, our integrated optimization exhibits significant economic advantages since improved the balance between micro siting and cable routing. By strategically sacrificing a portion of power generation to reduce cable costs, the overall investment profitability can be remarkably improved, with a maximum gain equivalent to 10.02 % of the cable costs., QC 20240823

This study reports a comprehensive techno-economic and environmental assessment of a realistic pathway for decarbonizing the urea industry. The proposed green urea synthesis plant utilizes hydroelectricity-powered electrolysis process and carbon capture from cement flue gas to create sustainable and environmentally friendly production process. Utilizing Aspen Plus and MATLAB, this study first, models the electrolysis, air separation, ammonia synthesis, carbon capture and urea synthesis units, and then evaluates the economic and environmental parameters of the synthesis process. Furthermore, the study highlights the transformative impacts of carbon credit and the renewable energy prices on the profitability metrics of the green urea plant. For the proposed 220 kt/year urea plant, the total energy consumption is 8.18 × 106 GJ/year with the electrolysis unit accounting for half of the energy demand. The estimated total capital investment for the urea plant is 510.79 million USD, with an annual operating expenditure of 156.02 million USD. The urea synthesis unit accounted for half of the total capital expenditure, while electricity contributed to the largest proportion (73%) of the operating expenses. The levelized cost for urea (LCOU) is estimated to be 570.96 USD/t which is approximately 62.2% higher than the urea obtained from conventional process. The electrolyzer unit contributed to 34.4% of the total LCOU. Sensitivity analysis showed that 30% decrease in the electricity price from the base case could lower the LCOU by 27%. The global warming potential of the proposed green urea process is 326.11 kg CO2/t of urea. Lower hydroelectricity prices and carbon credit opportunities significantly improve the economic viability of the green urea production process., QC 20240719

The trend toward thinner and lighter electronic devices necessitates developing advanced thermal management solutions to address modern microprocessors’ escalating heat dissipation demands. This study introduces an advanced thermal solution incorporating a gyroid TPMS structure with remarkable physical properties for microprocessor cooling. Detailed investigations were conducted using a full-scale heat sink model to understand the inner geometric structure, flow, and heat transfer characteristics within a gyroid heat sink (GHS). The thermo-hydraulic performance of the GHS design was systematically assessed against that of a pinfin heat sink (PHS) across different porosities and flow rates. Both heat sinks were evaluated under non-uniform heating conditions, considering three heating schemes, each with eleven randomly distributed hotspots. The thermohydraulic performance was assessed by calculating temperature non-uniformity, thermal resistance, and pumping power. A correlation was established using the cell size and cell wall thickness of a unit cell of gyroid TPMS to calculate its hydraulic diameter. The analysis revealed that the enhanced thermal performance of the GHS design can be attributed to its intricate and convoluted flow structure, along with a significantly large heat transfer surface area. However, these same factors contribute to a notably high-pressure drop. Compared to the PHS design, the GHS design showed better thermal performance at all the selected porosities and flow rates, albeit with higher pumping powers. The GHS design showed improvement in the thermal performance as the porosity decreased. Investigation under heterogeneous heating conditions showed substantially lower temperatures at the hotspots in the GHS design, along with reduced temperature variation among them. The study's findings provide valuable insight into the advantages and drawbacks of gyroid TPMS structure for their application in electronic cooling., QC 20240829

Demand response (DR) and Energy Communities are highlighted as two key means to facilitate the energy transition in Europe by providing flexibility to the grid in a decentralized way. This paper uses a theoretical framework, the balanced readiness level assessment, to review five social and techno-economic dimensions regarding the status of demand response technology, emphasizing key challenges and opportunities. Focusing specifically on Energy Communities in Spain, issues such as the split-incentive problem in technology investments, market rules favouring large generators, and the imperative for improved coordination in the electricity market and network operations are identified as significant hurdles to further DR development. A balanced readiness level score of 7.25 is assessed for Spanish energy communities, composed of a 9 for the technological, a 7 for the regulatory and the acceptance, and a 5 for explicit and 7 for implicit market readiness level. The application of the balanced readiness level assessment methodology is novel to the energy industry and does not only prove the value it can create in this sector, but also provides insights for policymakers and stakeholders navigating the dynamic landscape of Demand Response for Spanish Energy Communities., QC 20240722

The pressure fluctuations caused by the rapid volume changes during the initial growth stage for a single bubble are crucial excitations of boiling induced vibration. Therefore, it is necessary to accurately model the dynamic behavior of bubbles during this stage to obtain reasonable excitation forces, which can be used to estimate the vibration response of structures. The present study develops a dynamics model, which is verified and validated to be applicable to the growth of spherical bubbles in infinite superheated liquid and hemispherical bubbles growing on a vertical heated surface. The effects of mass transfer are considered for the vapor-liquid interface motion, and the temperature variations at the liquid side are determined by the finite difference method. The numerical data match well with the theoretical and experimental results, and the characteristics of the excitation forces caused by a single boiling bubble are obtained and analyzed. In addition, the influences of superheat, accommodation coefficient for phase change, and the temperature gradient at the liquid side on excitation forces caused by bubble growth are studied. The results show that the temperature distributions near the heated surface strongly affect the frequency domain characteristics of the excitation forces., QC 20240725

While fundamental mechanisms of non-reactive jet impingement have been extensively researched, the reactive jet impingement is yet unexplored although it offers the potential to increase further the heat transfer. The present work fills this knowledge gap via high-fidelity numerical simulation of reactive jet impingement invoking the finite rate one-step chemistry. Endo-/exothermic reactions are found to have very limited influence on time-averaged fluid flow, while they induce substantial modifications in heat transfer characteristics. This influence is manifested as discernible changes in the momentary or instantaneous fluid dynamics. Specifically, the primary vortices are responsible for downwashing cold fluid (mostly N2O4) towards the hot plate, posing low local convective heat transfer. The secondary vortices are responsible for extracting heat from the hot plate via the dissociation reaction N2O4→2NO2, followed by transporting NO2 away from the hot plate and towards the upwashing side of the primary vortex. At the upside of the primary vortex, hot NO2 is cooled by the environment, therefore reforming N2O4 to give out energy. This intense and long-lasting heat absorption and heat release process explains the outstanding performance of reactive jet impingement., QC 20240704

The adoption of electric boats faces challenges due to range anxiety. This study addresses this challenge by optimizing the allocation of slow and fast chargers for public electric boat charging stations. A mixed-integer linear programming model was developed to minimize charging infrastructure and electricity costs while meeting the demand of each participating marina in Stockholm, Sweden. The model identified three distinct categories of stations based on the optimal charger allocation: stations prioritizing fast chargers (e.g., Sickla station with 13 fast and 8 slow chargers for 208 boats), stations prioritizing slow chargers (e.g., Kungsholmen station with 2 slow and 3 fast chargers for 50 boats), and stations with an equal number of both charger types (Äppelviken station with 2 each for 25 boats). This study found out that all stations will achieve financial viability within seven years, indicating a promising return on investment. This study also proposes a novel way for optimizing charger allocation in electric boat charging infrastructure, promoting wider electric boat adoption., QC 20240719

This report examines the long-term usage and satisfaction levels of a biochar-producing gasifier stove among rural households in Kenya. The primary objective was to investigate the factors that influence stove satisfaction and dissatisfaction among participants, with the aim of assessing the gasifier stove's viability as an alternative for rural households. Data for this study was collected from representatives from 30 households through surveybased interviews covering cooking practices, fuel collection, and user experiences with the gasifier stove six years after receiving it. The findings indicate that households typically use multiple stoves. Almost all participants used the three stone stove on a daily basis, while the gasifier stove had a lower use frequency. Although households acknowledged the benefits of the gasifier stove, they expressed difficulties in relying on it as their primary cooking appliance due to its lack of convenience. The main contributing factors were the additional workload required for fuel preparation and the extended cooking time. Participants prepared various dishes using the gasifier stove, and the char produced by the stove was utilized for cooking, farming, and other purposes. The differences between users and non -users in terms of perception of stove benefits were small, though users appreciated the biochar production more than non -users. The study offers insights into the long-term usage of the gasifier stove and its dual potential as a clean cooking solution, and a biochar-producing technology, for rural households across the world., QC 20240722

During a severe accident in light water reactors, the molten reactor core (corium) falls into a water pool in the form of a jet. Complex interactions may occur between the melt and coolant known as molten fuel-coolant interactions (FCI), including energetic coolant evaporation and metallic melt (e.g., Zr and Fe) oxidation. This may further lead to steam and hydrogen explosions, which are both substantial safety risks for nuclear power plants. The heat of reaction and hydrogen production during oxidation can influence the progress and severity of the accidents. For example, the reaction heat may prolong the liquid state of corium, potentially leading to highintensity explosions, whereas the generated hydrogen can create a combustible atmosphere, increasing the risk of hydrogen explosion. Therefore, this study evaluates the hydrogen production and oxidation degree of molten metallic droplets falling into a water pool to improve the FCI models for the risk evaluation of severe accident safety. The MISTEE-OX facility at KTH, which has been primarily built to study steam explosions is modified to investigate oxidation during FCI and provide experimental data on the oxidation behaviour of metallic droplets (Zr/Fe) quenched in a subcooled water pool. The dynamics of the falling droplets and generated bubbles are recorded using a high-speed camera, and the total volume of the bubbles is measured using a graduated cylinder. This study presents preliminary experimental results of the oxidation between Zr/Fe droplets and water, as well as recent improvements in measurement methods and facility upgrades. Our research findings are useful to enhance the knowledge of the oxidation process in FCI phenomena and validate the related mechanistic models in FCI codes., QC 20240722

The study investigated the characteristics of different natural refrigerants and their mixtures in a residential heat pump with low refrigerant charge. Three main evaluation criteria were utilized for comparing different mixtures: Coefficient of Performance (COP), Volumetric Heating Capacity (VHC), and a newly proposed indicator, the heating capacity at charge limit. Propane was used as a reference refrigerant. It was found that some mixtures significantly improved both COP and the heating capacity at charge limit while maintaining similar volumetric heating capacity and operating conditions. Alternative multi-criteria decision-making techniques were adopted to rank the best refrigerant mixtures. Mixtures rich in Dimethyl Ether (DME), such as DME-CO2 [0.96-0.04] and DME-Propylene [0.75-0.25] were found consistently among the best options. Those were followed by Propylene-rich mixtures such as Propylene-CO2, Propylene-Isobutane and Propylene-Butane. The levelized cost of heat (LCOH) could be improved by up to 12 %. To accelerate the transition to natural refrigerants, without compromises on efficiency and costs, further research and certification activities on non-fluorinated refrigerants based on Dimethyl Ether (R-E170), CO2 (R-744) and Propylene (R-1270) are recommended., QC 20240620

Melt infiltration into porous media is an intriguing phenomenon that holds immense significance across various sciences and technologies. In this work, the problem of metallic melt infiltration in particulate beds is investigated for understanding and prediction of severe accident progression associated with a molten pool penetrating through an underlying debris bed which may form in the reactor core or in the lower head of a light water reactor. The present study aims to quantify the effect of particle surface's wettability on melt infiltration kinetics. For this purpose, two categories of experiment are conceived and carried out to measure the wettability of different material surfaces by melt and to characterize melt infiltration kinetics in one-dimensional particulate beds, respectively. The melt material is tin–bismuth eutectic alloy with a melting point of 139 °C. Copper (Cu), stainless steel (SS), Tin (Sn) and tin-coated stainless steel (Sn-coated SS) are chosen as materials of substrates and particles in wettability measurement and melt infiltration study. The particulate beds, packed with 1.5 mm spheres, are preheated to 200 °C before the melt infiltration begins. The experimental data of wettability measurement shows that the contact angles of liquid Sn-Bi eutectic on the above-mentioned material surfaces range from 79° to 135°. The results of melt infiltration tests confirm the significant effect of wettability on melt penetration kinetics. The capillary force plays a significant role in the initial infiltration of particulate beds. Specifically, a wettable particulate bed enhances the initial melt infiltration, whereas non-wettable beds hinder it., QC 20240702

Latent heat thermal energy storage (LHTES) implemented in residential heating systems has attracted attention for its role in peak/load shifting. A novel layout integrating LHTES with a heat pump is proposed to store low grade heat during off-peak demand period, later used as heat source for the heat pump during on-peak demand period. This novel layout is assessed according to different seasons, LHTES height-to-diameter (H/D) ratios, mass ratios of inflow water to radiator return water, and levelized cost of energy (LCOE). The results show that an overall increased amount of power input is required when utilizing LHTES, while it can shift 2.8–3.6 kW electricity from on-peak to off-peak. The case with an H/D ratio of 1.7 shows slight reductions in heating costs and LCOE as compared to a H/D ratio of 0.6. Considering heating costs, a mass ratio of 50 % performs better in December 2022 and a mass ratio of 10 % performs better in January 2023 due to different operating conditions. The heating costs of the integrated system are 1.0 %–2.1 % higher than those of the typical system due to limitations in the rated capacity of the heat pump and lower effectiveness of the shell-and-tube heat exchanger., QC 20240506

This study empirically investigates the optimal design features of photovoltaic-thermal (PVT) collectors for integration with ground source heat pump (GSHP) systems, considering technical and economic factors. Outdoor experiments are conducted in Stockholm, Sweden, comparing five unglazed and uninsulated PVT collector designs a) Reference Sheet & Tube b) Sheet & Tube with a narrow air gap between PV and absorber plate c) Box-channel polypropylene d) Finned tube and e) Box-channel aluminum with fins at operating temperatures below ambient. The findings indicate that the box-channel aluminum design with fins, characterized by a superior combination of high zero-loss efficiency and a high U-value, emerges as the ideal PVT design for integration with ground source heat pumps, taking into account both technical and economic considerations. Despite having a relative specific thermal cost 9% higher than the reference collector, this design demonstrates the capability to generate 2,096 kWh/(m2a) of thermal energy, marking an 83.3% increase compared to the reference, with a 136% higher energy-to-mass ratio., QC 20240617

Blending of partially cracked ammonia with biosyngas is an attractive strategy for improving NH3 combustion. In practice, products of biomass gasification and those of thermo-catalytic cracking of NH3 are subject to some compositional uncertainties. Despite their practical importance, so far, the effects of such uncertainties on combustion systems remained largely unexplored. Hence, this paper quantifies the effects of small compositional uncertainties of reactants upon combustion of partially cracked NH3/syngas/air mixtures. An uncertainty quantification method, based on polynomial chaos expansion and a data-driven model, is utilised to investigate the effects of uncertainty in fuel composition on the laminar flame speed (SL) and adiabatic flame temperature (Tad) at different inlet pressures (Pi). The analysis is then extended to the power output of a combined-cycle gas turbine fuelled by the reactants. It is found that 1.5% fuel compositional uncertainty can cause 12–21% of SL uncertainty depending on the inlet pressure. Furthermore, the effect of compositional uncertainty on Tad increases at higher ratios of H2 to NH3. Sensitivity analysis reveals that the uncertainty of CO contribution to SL uncertainty is higher than that of NH3, while the trend is reversed for the Tad uncertainty. In addition, the power output from the combined-cycle gas turbine system varies between 4 and 6% with 1.5% of fuel compositional uncertainty. This become more noticeable at elevated Pi [5–10 atm], particularly when the fuel mixture contains high H2 which is the main contributor to Tad variability., QC 20240520

Realization of multi-source energy harvesting with one single device would maximize power output. Thus, it is emerging as a promising strategy towards renewable energy generation and has attracted worldwide attention in the past decades. Capable of capturing mechanical energy that is ubiquitous in the ambient environment, triboelectric nanogenerator (TENG) has been considered a novel yet effective source towards next-generation energy harvesting. In this work, a flexible hybrid energy harvester (HEH) is developed via the rational integration of autonomous self-healing TENG and high bending-stable lead sulfide quantum dot (PbS QD) solar cell, enabling independent electricity generation by two different mechanisms. The single-electrode mode TENG component with self-healing is realized by a polydimethylsiloxane/Triton X-100 (PDMS/TX100) mixture as the dielectric layer and the shared gold (Au) electrode, which generates 0.39 µA of output current (Iout), 24.6 V of output voltages (Vout), 15.4 nC of transfer charges (Qsc), and 7.80 mW m−2 of output power peak density. The thin-film solar cell component is based on a PbS QD layer as the light absorber with a planar structure fabricated under low-cost and compatible conditions, achieving 22.8 mA cm−2 of short-circuit current density (Jsc) and 4.92% of power conversion efficiency (PCE). As a proof of concept, an electronic watch is successfully powered by harnessing ambient mechanical and solar energy with a hybridized energy cell. This approach will offer more opportunities to construct a versatile platform towards remote monitoring and smart home systems., QC 20240424

Advanced Pressurized Water Reactors (APWRs) and Boiling Water Reactors (BWRs) employ a suppression pool as a heat sink to prevent containment overpressure. Steam can be discharged into the pool through multi-hole spargers or blowdown pipes in both normal and accident conditions. Direct Contact Condensation (DCC) creates sources of momentum and heat. The competition between these two sources determines the development of thermal stratification or mixing of the pool. Thermal stratification is of safety concern as it reduces the cooling capability compared to a completely mixed pool condition. In this work we develop a scaling approach to prediction of the thermal stratification in a water pool induced by steam injection through spargers. Experimental data obtained from large-scale pool tests conducted in the PPOOLEX and PANDA facilities, as well as simulation results obtained using validated codes are used to develop the scaling. Two injection orientations, namely radial injection through multi-hole Sparger Head (SH) and vertical injection through Load Reduction Ring (LRR), are considered. We show that the erosion rate of the cold layer can be estimated using the Richardson number. In this work, scaling laws are proposed to estimate both the (i) transient erosion velocity and (ii) the stable position of the thermocline. These scaling laws are then implemented into a 1D model to simulate the thermal behavior of the pool during steam injection through the sparger., QC 20240430