Cogeneration Of Heat Research Articles

Analysis of the ecological footprint of mining machines in the phase of material extraction and processing in LCA

Sustainability in the mining industry continues to be a challenge. Although there is research in this area, there are still no solutions supporting the assessment of environmental impact in this sector. Therefore, it is important to look for and conduct various types of analyses that will be useful in this area. Therefore, the objective of the research was to analyse the ecological footprint of mining machines in the first phase of the LCA life cycle (obtaining and extracting materials). The analysis was based on the example of a hydraulic actuator, which is considered crucial to control machines in the mining industry. The ecological footprint burdens analysed included direct and indirect land take, sequestration of carbon dioxide (CO2) emissions, and the use of nuclear energy. Life cycle assessment was carried out using the OpenLCA software with the ecoinvent v3.10 database. It has been shown that the largest amount of emissions occurs during off-site treatment of nonsulphide waste, cogeneration of heat and energy (hard coal), production of ferrochrome, high carbon, 68% Cr, and heat production in an industrial furnace using hard coal. It is proposed to carry out improvement activities that will first contribute to reducing the main environmental burdens. Then, it will be possible to significantly reduce the negative environmental impact of the hydraulic actuator's extraction and processing of materials. The results from the analysis may be useful not only for products from the mining industry but also in other areas of activity using this type of machine.

Performances, energy, and exergy analysis on co-disposal of municipal solid waste and coal for co-generation of heat, power, and syngas from gasification-based route

Performances, energy, and exergy analysis on co-disposal of municipal solid waste and coal for co-generation of heat, power, and syngas from gasification-based route

Performance and Stability of Pt-Based Alloy Catalysts for High-Temperature PEM Fuel Cell Application

Ever increasing energy demands and push for low-carbon imprint technologies require at least partial replacement of internal combustion engines. For many stationary and heavy-duty applications, high-temperature fuel cells with proton-exchange membrane (HTPEMFC) represent a feasible solution for electric energy and heat co-generation. HTPEMFC operates with hydrogen as a fuel and atmospheric oxygen as an oxidant. The core of the technology is membrane (PEM), based on polymer doped with phosphoric acid, enabling operating temperature between 120 and 200 °C. Elevated temperature is necessary for heat cogeneration and enables use of hydrogen produced from fossil fuels and other sources without additional demanding purification. On the other hand, in synergy with phosphoric acid, it also accelerates degradation processes in HTPEMFC, making relatively high loadings of Pt on the electrodes necessary.The basic catalyst used in HTPEMFC comprises Pt nanoparticles on carbon black graphitized support, exhibiting reasonable activity and stability. Phosphoric acid is an adsorbing electrolyte, decreasing Pt catalyst activity by blocking the active Pt surface with phosphate anions and products of phosphoric acid reduction on the anode. Additionally, dissolution of Pt in phosphoric acid at elevated temperature is relatively high, leading to pronounced Ostwald ripening process on the cathode resulting in the progressive loss of Pt surface area. Both these effects can be, to a certain degree, mitigated by the introduction of highly active, Pt-based alloy catalysts on stable, carbon-based supports. Nanoparticles with Pt-rich shell and intermetallic Pt-X core can have activity superior to Pt, lower susceptibility to phosphate adsorption and, possibly, different kinetics of degradation. Introduction of novel, oxidation-resistant supports can further improve catalyst durability by nanoparticle-support interaction and minimize nanoparticle sintering due to support corrosion.Accordingly, this study investigates possibility of introduction of Pt-Co and Pt-Ni nanoparticular catalysts on supports including Ketjenblack and reduced graphene oxide to HTPEMFC. The study is divided to stages, including the investigation of alloying metal dissolution in phosphoric acid at elevated temperatures, determination of catalyst activity at conditions relevant to HTPEMFC operation using thin film-modified rotating rod disc electrode and finally, single cell testing. Leaching of Pt alloy catalysts proved that during relatively short time, majority of alloying metal is lost in case of Ketjenblack support. However, supporting of Pt alloys on reduced graphene oxide significantly improved alloy stability. The activity towards oxygen reduction reaction of Pt alloy catalysts was in majority of cases superior to commercial Pt catalyst, underlining the positive effect of alloying metal presence. Single cell experiments with Pt-Co and commercial Pt catalyst proved feasibility of alloy catalyst application. When used on the cathode and commercial Pt catalyst on the anode, Pt-Co catalysts led to superior cell performance in comparison with cell utilizing commercial Pt catalyst on both electrodes. Moreover, the performance of cells with Pt-Co on the cathode progressively improved during 300 hours of operation, pointing out to the combination of dealloying and restructuring of nanoparticle. In line with these results, it is evident that Pt alloy catalysts are an interesting alternative to Pt catalysts and, after optimization of alloy nanoparticle-support combination, can lead to improved performance and stability of HTPEMFC, making the technology even more attractive for market.The study was funded by the Czech Science Foundation (GAČR), project No. 22-23668K.This work was supported by the project "The Energy Conversion and Storage", funded as project No. CZ.02.01.01/00/22_008/0004617 by Programme Johannes Amos Commenius, call Excellent Research.

The biofactories: Quantifying environmental benefits of the wastewater circular economy in Chile using life cycle assessment

The wastewater circular economy promises improved environmental impacts within the food-water-energy nexus. This requires verification as the global sanitation sectors seek to improve environmental impacts and achieve integrated water management. Life cycle assessment (LCA) has been used to compare novel technologies for wastewater treatment and recovery, but research addressing plant-wide improvements of co-product resource recovery using real data from full-scale plants is still needed, particularly in a Latin American context. In Chile, two wastewater treatment plants (WWTPs) have embraced the circular economy configuration, recovering treated effluent, biosolids, and biogas, in addition to implementing advanced nitrogen removal using different technologies. The LCA of these two WWTPs demonstrated that Plant A improved 8 out of 10 impact categories compared to the baseline conventional scenario, while Plant B improved 5 categories out of 10. The analysis of the two plants showed the influence of influent quality on environmental impacts and the trade-off that occurs between the different technologies implemented. Plant B generated larger environmental credits through increased biogas and biosolids recovery due to thermal hydrolysis pre-treatment and anaerobic digestion, combined with cogeneration of heat and power. Plant A implemented water recovery, which provided benefits on a smaller magnitude but to more impact categories. Therefore, both plants improved environmental impacts through the wastewater circular economy, but further improvements in system configurations are recommended in each.

Analysis and Optimization of Operating Modes of Mini-CHP on Local Fuels in Conditions of Surplus Electric Power Capacities in the Unified Energy System of Belarus. Part 1

The paper presents the results of a study to determine the rational structure of mini-CHP (Cogeneration Heat and Power Plant) using local fuels types (LFT) for operation as part of the United Energy System (UES) of Belarus with a surplus of electricity generating capacity and dominance of imported types of energy resources (natural gas and nuclear fuel) in the fuel balance. When optimizing the operating modes of mini-CHPs using LFT and operating in parallel with the UES, which has a significant surplus of electricity generating capacity, it is necessary to separate options for existing stations and options for newly built ones. In the first case, due to the fact that the power of the equipment is known, it is advisable to consider two extreme options, i.e., the operation of the heating unit according to an electrical or thermal load schedule. In this case, in order to maintain the daily consumption traffic it is necessary to provide for the accumulation of thermal or electrical energy, respectively. In the case of new construction, the optimized parameter is the power of the generating equipment, so it is advisable to give preference to the option with the maximum number of hours of use of the rated power. In order to increase the economic attractiveness of mini-CHP, options for developing the structure of mini-CHP using LFT with the transition to multi-generation technologies and adaptation to the existing operating conditions of the UES of Belarus have been considered. The results of an analysis of commercially available technologies for storing excess electrical energy are presented in accordance with current and projected (until 2030) cost and operational indicators. For adapting mini-CHP to operate in the UES in conditions of a surplus of electrical power capacity, an electrical energy storage system using hydrogen as an intermediate energy carrier is of greatest interest. To utilize the excess electrical energy consumption from a mini-CHP with a heating ORC unit during the daily dips, a structural diagram configuration using an alkaline electrolysis module for hydrogen production is proposed. The efficiency of energy storage and use technology is considered depending on the specific energy intensity for various electrical energy storage technologies. The use of the two most energy-intensive energy storage technologies is proposed: accumulation based on electrochemical batte-ries and the “electricity-hydrogen” type. During the study, an analysis of the functioning of the ORC-installation Turboden 14 CHP ORC-installation operating as part of a mini-CHP using LFT was carried out. It was revealed that today the installation operates in a wide range of load changes (from 17 to 87 % of the rated electrical power), while the generation of electrical energy from thermal consumption varied in the range from 0.20 to 0.026 MW/MW. Due to the fact that the ORC installation under study is a component of the energy source with a high installed peak thermal power, in the current state there is no direct correlation between the outside air temperature and the generation power of the ORC installation. This circumstance indicates the need to continue the study of heat load trends to build functional models for short- and medium-term forecasting of heat load depending on the time of day and average hourly outside air temperature, which was implemented in the second part of the work.

A novel green methanol – heat cogeneration system based on municipal solid waste plasma gasification and coke oven gas: Energy, exergy, economic, and environmental assessment

Burning municipal solid waste for disposal contributes significantly to atmospheric pollution. Utilizing municipal solid waste for green methanol production can alleviate environmental burdens. This study proposes a novel approach based on municipal solid waste plasma gasification, integrating coke oven gas catalytic reforming for green methanol synthesis. A comparative analysis is conducted against a conventional scheme involving water gas shift for syngas production. Simulation models of both approaches are constructed, revealing that the newly proposed system achieves higher methanol synthesis yield and energy utilization efficiency at 90.57 % and 61.28 %, respectively, with an exergy efficiency of 63.74 %. The project incurs an investment cost of 11,448.70 k$, with a dynamic payback period of 4.18 years after a 1-year construction cycle. The net present value over a 25-year operational span is 21,899.16 k$. Additionally, the proposed system emits less than 0.06 tons of carbon dioxide per ton of green methanol, significantly lower than the 0.72 tons emitted by the water gas shift-adjusted syngas synthesis scheme. It makes the proposed approach a potential negative carbon emitter compared to municipal solid waste incineration. Therefore, the system demonstrates favorable thermodynamic performance, coupling with substantial economic and environmental benefits.

Harnessing Geothermal Energy Potential from High-Level Nuclear Waste Repositories

The disposal of high-level nuclear waste (HLW) has been one of the most challenging issues for nuclear energy utilization. In this study, we have explored the potential of extracting decay heat from HLW, taking advantage of recent advances in the technologies to utilize low-temperature geothermal resources for the co-generation of electricity and heat. Given that geothermal energy entails extracting heat from natural radioactivity within the Earth, we may consider that our approach is to augment it with an anthropogenic geothermal source. Our study—for the first time—introduces a conceptual model of a binary-cycle geothermal system powered by the heat produced by HLW. TOUGHREACT V3.32 software was used to model the heat transfer resulting from radioactive decay to the surrounding geological media. Our results demonstrate the feasibility of employing the organic Rankine cycle (ORC) to generate approximately 108 kWe per HLW canister 30 years after emplacement and a heat pump system to produce 81 kWth of high-potential heat per canister for HVAC purposes within the same timeframe. The proposed facility has the potential to produce carbon-free power while ensuring the safe disposal of radioactive waste and removing the bottleneck in the sustainable use of nuclear energy.

Thermal-integration in photoelectrochemistry for fuel and heat co-generation

Numerous photoelectrochemical systems designs are compared on an energy and exergy basis for their capacity to produce hydrogen and heat. Systems include both liquid and vapor-phase reactants, solar concentration, and spectrum splitting optics.

Thermodynamics and flexibility assessment on integrated high-temperature PEMFC and double-effect absorption heating/cooling cogeneration cycle

High-temperature proton exchange membrane fuel cell (HT-PEMFC) is promising in the next-generation integrated energy systems, because of its reliability, controllability and high-grade exhaust heat which enables the operation of combined heating, cooling and power generation (CCHP). However, the conventional HT-PEMFC based CCHPs suffers from the electric-thermal coupling, which is incompatible with the varying electricity and heating/cooling loads. To this end, a double-effect absorption heating/cooling cogeneration cycle (DACC) is proposed to decouple the production of electricity and heating/cooling, by flexibly adjusting the ratio of the vapor distributed to the branches of turbine and evaporator. The mathematical model is developed and validated, based on which the parametric analysis is characterized under different conditions. Under the heating cogeneration mode, the overall efficiency of the system is improved by 5.9–26.2% compared with the single HT-PEMFC. The maximum overall efficiency is 0.4797, corresponding the current density of 0.23 A/cm2. Under the cooling cogeneration mode, the system cooling capacity, net power, and cooling/power ratio can be adjusted in the range of 17.78–137.55 kW, 77.46–156.3 kW and 0.19–1.21, respectively. Owing to the flexible adjustment ability, the HT-PEMFC-DACC system can serve as an effective solution in future zero-carbon distributed energy systems.

Comprehensive analysis of energy, exergy, economic, and environmental aspects in implementing the Kalina cycle for waste heat recovery from a gas turbine cycle coupled with a steam generator

This study introduces a transformative approach by integrating the Kalina Cycle System (KCS) within a cogeneration of heat and power (CHP) framework alongside a gas turbine (GT) cycle and a single-pressure heat recovery steam generator (HRSG). Through development of thermodynamic and thermo-economic models, a comprehensive assessment of the system's performance is conducted, emphasizing energy, exergy, and exergoeconomic considerations. The outcomes reveal a remarkable enhancement in both 1st and 2nd law efficiencies for the GT-HRSG/KCS-11 system compared to its conventional counterpart. Witnessing an ascent from 53.60 % to 54.31 % in efficiency and an increase from 50.59 % to 51.27 % in 2nd law efficiency underscores the profound impact of the proposed system. Furthermore, a parametric study scrutinizes the influence of diverse design parameters on critical objective functions, encompassing second law efficiencies and the total system cost rate. Findings spotlight the combustion chamber, heat recovery steam generator, and gas turbine as focal points of exergy destruction, revealing crucial insights for system optimization. The combustion chamber, heat recovery steam generator, and gas turbine emerge as pivotal contributors to the total cost rate, highlighting key areas for economic consideration. According to the results, the share of the environmental cost rates in the system cost rate is insignificant.

Fuel cell preventive maintenance in an electricity market with Hydrogen storage and Scenario-Based risk management

The application of the fuel cell (FC) in improving the clean and energy-efficient cogeneration of heat and power has been broadly justified by researchers. However, the reliable operation of FC units requires periodic maintenance services. In this regard, preventive generation maintenance scheduling (GMS) notably preserves the units’ lifespan, prevents unexpected failures, and restricts imposed repair costs caused by failures. The present work models the GMS problem for FC and highlights its challenges compared to the GMS of conventional generation units. The main challenges, including simultaneous satisfaction of the power-heat dual dependency in FC, the power and heat demand balances, and maintenance considerations, including duration, continuity, and coordination of maintenance, are addressed in this research. The maintenance program is first planned for a year to optimize the maintenance timetable. Afterward, daily generation scheduling is optimized subject to the GMS program obtained for the studied year. Moreover, by using risk management, the economic risk associated with the problem (due to uncertainty in the electricity price) is handled. The obtained results for the impacts of risk management on FC’s maintenance schedule depict an 11.5% improvement in the cost of the worst-case scenarios, namely a cost reduction from M$111.4 to M$98.6.

Comparative life cycle analysis of PHA-based consumer items for daily use

USABLE Packaging project has developed an innovative value chain based on mixed microbial cultures using organic wastes as feedstock to produce prototypes of PHA-based items that were compared to their commercial counterparts, so the expected better environmental performance can be checked. To do so, a cradle-to-grave life cycle assessment was carried out. The system was modeled integrating all available knowledge, from pilot-scale data to process simulators, and following upscaling frameworks. PHA-based items outperform their commercial counterparts since they show environmental benefits thanks to the avoided electricity obtained in the cogeneration heat and power unit within the PHA production; however, these environmental benefits are very sensitive to the substituted electricity environmental burdens. The different levels of development and market implementation are seen as critical and therefore attention should be paid on how upscaling affects the results and interpretation of the LCA while serving as a guide for process and product development.

Performance investigation on a concentrating photovoltaic thermal system integrated with spectral splitter and absorption heat pump

To alleviate the energy consumption crisis and environmental pollutant problems, a concentrating photovoltaic thermal system integrated with spectral splitter and absorption heat pump is proposed. Through solar spectral splitting, the photo-electric and photo-thermal processes are decoupled, which facilitates the cogeneration of electricity and high-temperature heat. Through absorption heat pump, the temperature of geothermal energy is improved by high-temperature solar heat for subsequent utilization. Thus, the efficient utilization of full spectrum solar energy is achieved. To further evaluate the performances, an electric-thermal coupled model is developed and the comprehensive analysis is carried out from energy, exergy and exergoeconomic viewpoints. Results indicate that for an optical window of 400–1300 nm, strong LiBr/H2O solution concentration of 64 %, concentration difference of 5 % and thermal receiver temperature of 438.15 K, the overall energy and exergy efficiency is obtained about 102.14 % and 37.49 %, respectively. Among all components, parabolic trough concentrator is the most inefficient component with energy losses of 123.86 MWh. Highest exergy destruction is observed in the solar cell, accounting for 67.51 % of the total destruction. Moreover, a total exergoeconomic factor of 79.94 % is obtained for the entire system indicating that 20.06 % of the total costs are related to exergy destruction.

Characteristics Analysis of Integrated CAES and CFPP Trigeneration System Considering Working Conditions and Application Scenarios

To meet the goal of worldwide decarbonization, the transformation process toward clean and green energy structures has accelerated. In this context, coal-fired power plant (CFPP) and large-scale energy storage represented by compressed air energy storage (CAES) technology, are tasked with increasing renewable resource accommodation and maintaining the power system security. To achieve this, this paper proposes the concept of a CFPP–CAES combined cycle and a trigenerative system based on that. Considering the working conditions of the CFPP, thermal characteristics of three typical operation modes were studied and some general regularities were identified. The results of various potential integration schemes discussion indicated that extracting water from low-temperature points in the feedwater system to cool pressurized air and simultaneously increase the backwater temperature is beneficial for improving performance. In addition, preheating the pressurized air before the air expanders via low-grade water in the feedwater system as much as possible and reducing extracted steam contribute to increasing the efficiency. With the optimal integration scheme, 2.85 tonnes of coal can be saved per cycle and the round-trip efficiency can be increased by 2.24%. Through the cogeneration of heat and power, the system efficiency can reach 77.5%. In addition, the contribution degree of the three compression heat utilization methods to the performance improvement ranked from high to low, is preheating the feedwater before the boiler, supplying heat, and flowing into the CFPP feedwater system. In the cooling energy generation mode, the system efficiency can be increased to over 69%. Regardless of the operation mode, the benefit produced by integration is further enhanced when the CFPP operates at higher operating conditions because the coupling points parameters are changed. In addition, the dynamic payback period can be shortened by 11.33 years and the internal rate of return increases by 5.20% under a typical application scenario. Regarding the effect of different application scenarios in terms of economics, investing in the proposed system is more appropriate in regions with multiple energy demands, especially heating demand. These results demonstrate the technical advantages of the proposed system and provide guiding principles for its design, operation, and project investment.

Система совместного использования обедненного метана угольных пластов и биогаза для выработки электроэнергии в угольных шахтах

Purpose: Justification and development of new resource-saving technologies aimed at utilization of coal bed methane. The problem of low efficiency of utilization of lean methane-air mixtures is primarily due to the low content of methane itself, which varies significantly depending on the type of coal or concentration. This paper discusses the concept of a co-production system that mixes low-methane methane-air mixtures and biogas to generate power. Methods: Analysis of the possible volumes of utilized methane, biogas requirements and the suitability of the primary feedstock for co-generation of heat and electricity. Selection of appropriate parameters for the processes of utilization of mine methane. Analysis of the merits of the proposed method of utilization of lean coal mine methane. Results: It is recommended that biogas produced by agriculture and forestry in the vicinity of the mines be added to the dry methane stream to obtain the necessary gas concentration for electricity generation. Potential electricity production and greenhouse gas emission reductions have also been evaluated. The result shows that the co-production system can significantly improve the efficiency of poor methane-air mixtures in coal mines. Practical significance: The joint use of lean methane and biogas from straw offers practical advantages both economically, ensuring sufficient energy supply in mines, and as a foundation for broad future prospects. It allows for energy cost reduction and environmental pollution reduction, such as decreasing carbon dioxide emissions.

A solar spectral splitting-based PVT collector with packed transparent tube receiver for co-generation of heat and electricity

Combined heating and power (CHP) systems co-generating electrical energy as well as thermal energy is indispensable for modern-day distributed applications. Photovoltaic thermal (PVT) systems are such hybrid co-generation systems. However, in a conventional PVT system, the PV module/cell temperature restricts the thermal output, making these systems unsuitable for various applications. This study offers a novel and resilient design for a spectral beam splitting-powered compound parabolic collector-based PVT system that employs a nanofluid optical filter within borosilicate glass tubes for volumetric absorption. By maximizing the “splitting effect”, the goal of this work is to disrupt the long-standing relationship between the thermal and electrical yield from a PVT collector, i.e., obtaining a higher heat transfer fluid temperature than the PV cell temperature. Several configurations with varying array width-to-receiver tube diameter ratios, i.e. bdo ratios (ranging from 3 to 8) and one, two, and three rows/layers of receiver tubes were evaluated and compared. The optical and thermal performance of the collector designs are compared using metrics such as heat flux distribution, optical efficiency, temperature distribution, receiver efficiency, and splitting ratio. This work determines how the splitting effect dictates the performances of the collector. Through the ray-tracing routine and thermal analysis, it is demonstrated that for certain bdo ratios, the developed collector attained a maximum cumulative temperature rise of >100∘ C using ZnO–water–ethylene glycol nanofluid as the optical filter. Also, the receiver and electrical efficiency of 51.81% and 18.77%, respectively, are achieved. Moreover, the packed borosilicate glass receiver tubes with a bdo ratio of 8 and two receiver rows/layers achieved the so-called “splitting ratio” (ratio of filter fluid temperature to cell temperature; THTFTcell) of >1.6. The studied configurations find their application depending on the extent of the achieved splitting ratio. Based on these findings, it is concluded that the analyzed packed glass tube receiver designs provide a viable new route towards cost-effective and dependable robust PVT collectors for distributed and other applications.

Comprehensive Evaluation of Different Heating Modes in Northeast China

Given the freezing temperatures and extended winters, heating is essential for residents living in Northeast China. When selecting the optimum heating mode for the region, various factors are taken into consideration, such as the impact on the environment, financial cost and energy consumption. However, it is uncertain which heating mode can fulfill all conditions and requirements. In this study, seven heating modes were selected from the national and northeastern heating strategies. A comprehensive index system based on the life cycle theory was developed from the perspectives of energy, the environment, the economy, technology and society. Additionally, a comprehensive evaluation of the seven heating modes was performed using the analytical hierarchy process (AHP) and gray relation analysis. The results of this research showed that, from a complete standpoint, the ground-source heat pump heating mode (HMg) had the best comprehensive benefit, with a correlation of 0.8173, followed by the coal-fired cogeneration heating mode (HMcc), which had the highest correlation degree among the centralized heating modes at 0.6111. Based on the findings of our thorough examination, a recommended scheme made up of HMg, HMcc, the electro-thermal membrane heating mode (HMef), the natural gas boiler room regional central heating mode (HMgrc) and the natural gas boiler room decentralized heating mode (HMgrd) was established. The recommended scheme can provide a theoretical basis for the implementation of clean heating policies in Northeast China.

Impact of the Catalyst Type and Dopant Composition on the Performance of High-Temperature PEM Fuel Cell

Increasing interest in hydrogen-powered fuel cells for electric energy generation led to the identification of serious limitations of state-of-the-art technologies. In particular, low-temperature fuel cell with a proton-exchange membrane (LT-PEM FC), which is widely considered as an optimal type for mobility, is reaching its technological limits. This is due to its operating temperature up to 90 °C, defined by properties of perfluorinated, sulfonated membranes used as PEM, requiring liquid water for ensuring their ionic conductivity. In the case of heavy duty applications, high-power LT-PEMFC stacks suffer from local overheating, which is currently solved by intensive cooling. Ineffective heat-exchange and necessity of water regime control lead to limitations in total energy utilization. Such problem can be solved by increasing operating temperature up to 180 °C, which is suitable for heat cogeneration. This requires application of appropriate PEM conducting even at an elevated temperature.Current state-of-the-art high-temperature PEM fuel cells (HT-PEM FCs) utilize PEMs based on polymer doped with phosphoric acid. Polymers, such as polybenzimidazole or pyridine aromatic polyether, act as a matrix and a bonding agent for the phosphoric acid dopant. Such PEMs can operate within the temperature range of 120 to 180 °C. In terms of the catalyst, HT-PEM FCs use Pt-based, nanoparticle catalysts on carbon support as in LT-PEM FCs. However, due to the mobile nature of phosphoric acid, which is responsible for pronounced catalyst degradation, poisoning as well as local catalytic layer flooding, Pt loading used in HT-PEM FCs is within an order of magnitude higher than in LT-PEM FCs.Due to its high operating temperature, HT-PEM FC technology offers numerous advantages, such as heat and electric energy cogeneration, simple water regime and, due to improved tolerance to catalyst poisons like CO, the possibility of utilization of contaminated H2 produced from fossil fuels and biomass. However, degradation of components, in particular the catalyst and the membrane, remain the main bottlenecks for wide HT-PEM FC commercialization. With respect to the latest advances in technology, two critical aspects were identified. Firstly, the necessity of new catalysts immobilized on durable supports, with improved stability, activity and resistance against poisoning by phosphate anions. Secondly, membrane with improved fixation of phosphoric acid and greater durability. A special case of the membrane degradation is the reduction of phosphoric acid, by hydrogen or at low potentials on the anode, to phosphorous acid. This compound can poison the anode catalyst, incorporate into the membrane as well as oxidize on the cathode to phosphoric acid, completing dopant lifecycle. Nevertheless, the exact impact of phosphorous acid on HT-PEM FC performance is still not fully understood.Accordingly, the study had two major goals. A first one was to investigate the performance and degradation of Pt-based alloy catalyst on graphene-type support using thin-film modified rotating disc electrode, half-cell and single cell setups. All experiments have been performed at HT-PEM FC relevant conditions, i.e. in concentrated phosphoric acid electrolyte within temperature range of 120 to 180 °C. On the other hand, the second one goal investigated the influence of the dopant composition in terms of phosphorous acid addition to phosphoric acid electrolyte on the activity of the catalyst.Performance of experimental catalysts based on Pt-Co on various supports, including carbon black and graphene was compared to commercial Pt/C catalyst. Experimental catalysts exhibited superior activity for oxygen reduction. The overall performance of single cells with experimental catalyst on the cathode was better than the one with the commercial catalyst, with best results obtained for the graphene supported Pt-Co. The impact of phosphorous acid on oxygen reduction on commercial Pt/C catalyst was significant, due to simultaneous oxidation of acid and reduction of oxygen, as confirmed using rotating disc electrode and half-cell setups. Using the addition of phosphorous acid after single cell break-in on the cathode, the anode or both electrodes at once, it was determined that after stabilization the performance improved. Electrochemical impedance spectroscopy showed that addition of phosphorous acid decreases cell Ohmic resistance, but the comparative I-U curves and CO stripping analysis performed on cathode indicated significant decrease of available Pt surface. This reflects the ambivalent influence of phosphorous acid on HT-PEM FC.This study was supported by the Grant Agency of the Czech Republic under project No. 22-23668K.

Experiment study on heat transfer enhancement of micro heat pipe PV/T by Reynolds number improvement

The rapid performance improvement of photovoltaic/thermal (PV/T) implies great potential application to various aspects of society. The previously developed micro heat pipe PV/T by our team has shown favorable cogeneration of electricity and heat in cold regions, while it is badly needed to improve its comprehensive performance by enhancement of heat transfer. For same working fluid as HCFC141b in micro heat pipe, higher Reynolds Number (Re) theoretically means better heat transfer. Therefore, two available micro heat pipes were developed with trapezoidal cross section and rectangular cross section respectively while with same cross section area and applied in two micro heat pipe PV/T systems. Subsequent experiment study testifies that the rectangular micro heat pipe PV/T of higher theoretical Re verily shows more favorable performance than the trapezoidal micro heat pipe PV/T when they are at 45° inclination angle. Deducting power consumption of circulating pump, the average electrical efficiency of rectangular micro heat pipe PV/T system is 12.4%, while that of trapezoidal micro heat pipe PV/T system is 11.9%. Moreover, the thermal efficiency, total energy power, and total energy efficiency of rectangular micro heat pipe PV/T system are respectively 28.1%, 472.3 W, and 40.5%, which are 10.1%, 119.8 W, and 10.8% higher than those of trapezoidal micro heat pipe PV/T system. The results are significant and valuable for the application of micro heat pipe PV/T in cold regions.

A licensing plan for coupling nuclear–renewable hybrid energy systems

South Africa committed to reducing greenhouse gas emissions by 34% below "Business As Usual" levels by 2020 and 42% by 2025 at the Copenhagen climate change conference. However, global energy demand was projected to rise due to population and industrial growth, with energy usage expected to increase by 13% through 2040. In South Africa, a steady increase in electricity demand prompted the government to implement a new growth path (NGP), which prioritized job creation in all economic policies, including energy. To address the growing energy demand, an alternative energy source for combined heat and power was necessary, particularly for synthetic fuel production. The coupling of a high temperature reactor (HTR) with a chemical process plant could improve carbon and thermal efficiency, as seen in international organizations like the ARCHER (Advanced High-Temperature Reactors for Cogeneration of Heat and Electricity R&D) project. HTRs are still in their conceptual stages andaresuitable candidate forcouplingto an energy-intensiveindustrythat require process heat with sufficiently hightemperatures,with potential uses for NRHES (Nuclear-Renewable Hybrid Energy Systems). The South African team aimed to model the SASOL process, assess its financial viability, and develop a licensing plan.