Effect of operating parameters on the performance of thermally regenerative ammonia-based battery for low-temperature waste heat recovery

This study investigated the important factors that affect the operating parameters of thermally regenerative ammoniabased batteries(TRABs),including the metal electrode type,membrane type,electrode surface area,electrode distance,electrolyte concentration,and ammonia concentration.The experimental results showed that the maximum power density of TRABs with a Cu electrode was 40.0 W·m^(2),which was considerably higher than that with Ni(0.34 W·m^(2))and Co(0.14 W·m^(2))electrodes.TRABs with an anion exchange membrane had a 28.6%higher maximum power density than those with a cation exchange membrane.An increased electrode surface resulted in an increased maximum power but a decreased maximum power density.Within a certain range,TRAB performance was enhanced with decreased electrode distance and increased electrolyte concentration.An increased ammonia concentration resulted in enhanced ammonia transfer and improved the TRAB performance.

Innovative Design and Additive Manufacturing of Regenerative Cooling Thermal Protection System Based on the Triply Periodic Minimal Surface Porous Structure

The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of hypersonic vehicles.Triply periodic minimal surface(TPMS)is especially suitable for the structural design of the internal cavity of regenerative cooling structures owing to its excellent structural characteristics.In this study,test pieces were manufactured using Ti6Al4V lightweight material.We designed three types of porous test pieces,and the interior was filled with a TPMS lattice(Gyroid,Primitive,I-WP)with a porosity of 30%.All porous test pieces were manufactured via selective laser melting technology.A combination of experiments and finite element simulations were performed to study the selection of the internal cavity structure of the regenerative cooling thermal protection system.Hence,the relationship between the geometry and mechanical properties of a unit cell is established,and the deformation mechanism of the porous unit cell is clarified.Among the three types of porous test pieces,the weight of the test piece filled with the Gyroid unit cell was reduced by 8.21%,the average tensile strength was reduced by 17.7%compared to the solid test piece,while the average tensile strength of the Primitive and I-WP porous test pieces were decreased by 30.5%and 33.3%,respectively.Compared with the other two types of unit cells,Gyroid exhibited better mechanical conductivity characteristics.Its deformation process was characterised by stretching,shearing,and twisting,while the Primitive and I-WP unit cells underwent tensile deformation and tensile and shear deformation,respectively.The finite element predictions in the study agree well with the experimental results.The results can provide a basis for the design of regenerative cooling thermal protection system.

Performance Evaluation of a Molten Carbonate Fuel Cell-Graphene Thermionic Converter-Thermally Regenerative Electrochemical Cycles Hybrid System

A combined system model is proposed including a molten carbonate fuel cell(MCFC),a graphene thermionic converter(GTIC)and thermally regenerative electrochemical cycles(TRECs).The expressions for power output,energy efficiency of the subsystems and the couple system are formulated by considering several irreversible losses.Energy conservation equations between the subsystems are achieved leaned on the first law of thermodynamics.The optimum operating ranges for the combined system are determined compared with the MCFC system.Results reveal that the peak power output density(POD)and the corresponding energy efficiency are 28.22%and 10.76%higher than that of the single MCFC system,respectively.The effects of five designing parameters on the power density and energy efficiency of the MCFC/GTIC/TRECs model are also investigated and discussed.

Graphene oxide modified membrane for alleviated ammonia crossover and improved electricity generation in thermally regenerative batteries

Thermally regenerative batteries(TRBs) are promising for harvesting low-grade waste heat into electrical power. However, the ammonia crossover from anode to cathode causes self-discharge and then leads to the decay of capacity. To alleviate the ammonia crossover and improve electricity generation, a stable graphene oxide(GO) modified anion exchange membrane(AEM) was proposed. Compared with the original AEM, the GO modified AEM with a 39.5% lower ammonia permeability induces a 24.3% higher maximal power output and 20.2% higher energy density in TRBs. Together with the visualization result,it was demonstrated the ammonia crossover was effectively alleviated by GO modifying the AEM not at a cost of the reduced battery performance, indicating the promising application in future TRBs.

Performance of a thermally regenerative ammonia-based battery using gradient-porous copper foam electrodes

Gradient-porous copper foam electrodes were applied to alleviate the adverse effects of the uneven current distribution of electrodes along the electrolyte flow direction in thermally regenerative ammonia-based batteries(TRABs).The results indicated that gradient-porous copper foam with a decreasing pore size(TRAB-LMS)provided the most uniform current distribution and generated the highest power density(15.5 W/m^(2)),total charge(1800 C)and energy density(1224 W h/m^(3)).With the increase in flow rate,the power density of the TRAB-LMS increased considerably within a certain range and then decreased slightly,with the optimal flowrate at 15 mL/min.Under the optimal flow rate,the performance of TRAB-LMS increased when the ammonia concentration rose from 0.5 to 2 M(1 M=1 mol L^(-1));however,it decreased slightly when the ammonia concentration further increased to 3 M.The slight decrease in the cathode potential suggested that the flow and ammonia concentration beyond the optional values facilitated not only the transfer of ammonia into the porous anode,but also the crossover of ammonia from the anode to the cathode.

Development of non-premixed porous inserted regenerative thermal oxidizer

In this study, a porous inserted regenerative thermal oxidizer （PRTO） system was developed for a 125 kW industrial copper-melting furnace, due to its advantages of low NOr emissions and high radiant efficiency. Zirconium dioxide （ZrOz） ce- ramic foams were placed into the combustion zone of a regenerative thermal oxidizer （RTO）. Different performance characteris- tics of the RTO and PRTO systems, including pressure drop, temperature distribution, emissions, and energy efficiency, were evaluated to study the effects of the porous inserts on non-premixed CH4 combustion. It was found that the PRTO system achieved a significant reduction in the NOx emission level and a fuel saving of approximately 30% compared to the RTO system. It is most suitable for a lean combustion process at an equivalence ratio 〈0.4 with NOx and CO emission levels within 0.002%~）.003% and 0.001%q3.002%, respectively.

Exploitation of Waste Heat from a Solid Oxide Fuel Cell via an Alkali Metal Thermoelectric Converter and Electrochemical Cycles

In order to employ the waste heat effectively,a novel three-stage integrated system based upon a solid oxide fuel cell(SOFC),an alkali metal thermoelectric converter(AMTEC)and thermally regenerative electrochemical cycles(TRECs)is put forward.Considering the main electrochemically and thermodynamically irreversible losses,the power output and the efficiency of the subsystems and the integrated system are compared,and optimally operating regions for the current density,the power output,and the efficiency of the integrated system are explored.Calculations demonstrate that the maximum power density of the considered system is up to 7466 W/m2,which allows 18%and 74%higher than that of the conventional SOFC-AMTEC device and the stand-alone fuel cell model,respectively.It is proved that the considered system is an efficient approach to boost energy efficiency.Moreover,the influence of several significant parameters on the comprehensive performance of the integrated system is expounded in detail,including the electrolyte thickness of the SOFC,the leakage resistance of the SOFC,and the area ratio between the SOFC electrode and the AMTEC subsystem.

Charging-free thermally regenerative electrochemical cycle for electricity generation from daytime solar heat and nighttime darkness

The extensive exploration of energy conversion harvested from the environment into electricity is recently driven by the significant demand to power off-grid electronics,particularly Internet-of-Things(IoT)sensors.This highlight previews the latest advance of a charging-free thermally regenerative electrochemical cycle(TREC)for continuous electricity generation from solar heat and darkness with the aid of dual-mode thermal regulations.Such a spontaneous all-day electricity generation with high power and efficiency shows great potential for powering a wide range of distributed electronics for IoT and other applications.