Day-ahead seasonal solar radiation prediction,combining VMD and STACK algorithms

This article proposes a method for accurately predicting solar irradiance over a 24-hour horizon to forecast photovoltaic energy generation in a positive-energy building.In order to make this prediction,the input data are divided into seasons and preprocessed using the variational mode decomposition(seasonal-VMD)method.The VMD method is used for extracting high-bandwidth features from the input data,decomposing them into a finite number of smooth modes and focusing on specific frequency ranges.Hence,the accuracy of signal extraction using the VMD method can be improved by selecting particular parameters judiciously,which impacts the smoothing and frequency concentration of the extracted signal.In this regard,the salp swarm algorithm(SSA)is employed to identify the optimal VMD parameters that can be used to enhance extraction accuracy.In addition,the obtained residual between the observed solar irradiation data and their decomposed modes is treated to enhance the prediction process.A stacking algorithm(STACK)is used to predict the following 24-hour solar irradiance modes and the residual,which are finally summed to reconstruct the desired signal.The performances of the proposed prediction method are evaluated using two quantitative evaluation indices:the normalized root mean square percentage error(NRMSPE)and normalized mean absolute percentage error(NMAPE).The proposed model is trained on data collected for three years in Rabat(2019–22).The performance of the proposed model is evaluated by predicting the 24-hour solar irradiance for a different season.The proposed approach seasonal-VMD-STACK is compared with two other methods in the case of using VMD-based STACK without season partition and STACK method only.Moreover,the proposed method has exhibited stability and proven good results with an NRMSPE of 3.87%and an NMAPE of 1.58%for cloudy days during the test phase.The results demonstrate that residual preprocessing,seasonal input data partition and appropriate selection of VMD parameters improve the performance and accuracy of the prediction.

An efficient energy-management strategy for a DC microgrid powered by a photovoltaic/fuel cell/battery/supercapacitor

The outcome of this paper is to suggest an efficient energy-management strategy(EMS)for a direct-current(DC)microgrid(MG).The typical MG is composed of two renewable energy sources[photovoltaic(PV)systems and fuel cells(FCs)]and two energy-storage elements(lithium-ion battery and supercapacitor).An EMS was proposed to ensure optimal bus voltage with a power-sharing arrangement between the load and the sources.As a result,in the suggested DC MG,non-linear flatness control theory was used instead of the traditional proportional-integral control approach.The suggested EMS is intended to supply high power quality to the load under varying load conditions with fluctuating solar irradiation while considering the FC status.To validate and prove the effectiveness of the proposed EMS,a MATLAB®environment was used.In addition,the output power of the PV system was maximized using the particle swarm optimization algorithm as a maximum power point tracking(MPPT)technique to track the MPP of the 3000-W PV system under different irradiance conditions.The results show that the suggested EMS delivers a stable and smooth DC bus voltage with minimum overshoot value(0.1%)and improved ripple content(0.1%).As a result,the performance of the DC MG was enhanced by employing the flatness control theory,which provides higher power quality by stabilizing the bus voltage.

Carbon footprinting of carbon capture and -utilization technologies: discussion of the analysis of Carbon XPRIZE competition team finalists

Life cycle assessments(LCAs)of early-stage technologies can provide valuable insights about key drivers of emissions and aid in prioritizing research into further emissions-reduction opportunities.Despite this potential value,further development of LCA methods is required to handle the increased uncertainty,data gaps,and confidentially of early-stage data.This study presents a discussion of the life cycle carbon footprinting of technologies competing in the final round of the NRG COSIA Carbon XPRIZE competition-a US$20 million competition for teams to demonstrate the conversion of CO_(2) into valuable products at the scale of a small industrial pilot using consistent deployment conditions,boundaries,and methodological assumptions.This competition allowed the exploration of how LCA can be used and further improved when assessing disparate and early-stage technologies.Carbon intensity estimates are presented for two conversion pathways:(i)CO_(2) mineralization and(ii)catalytic conversion(including thermochemical,electrochemical,photocatalytic and hybrid process)of CO_(2),aggregated across teams to highlight the range of emissions intensities demonstrated at the pilot for individual life cycle stages.A future scenario is also presented,demonstrating the incremental technology and deployment conditions that would enable a team to become carbon-avoiding relative to an incumbent process(i.e.reducing emissions relative to a reference pathway producing a comparable product).By considering the assessment process across a diverse set of teams,conversion pathways and products,the study presents generalized insights about opportunities and challenges facing carbon capture and-utilization technologies in their next phases of deployment from a life cycle perspective.

Institute of Energy Process Engineering and Chemical Engineering (IEC), TU Bergakademie Freiberg: Towards a Circular Carbon Economy

1 History of the Institute of Energy Process Engineering and Chemical Engineering(IEC)The history of IEC dates back to 1918,when the Lignite Foundation of the State of Saxony was founded to develop pro-cesses and technologies for lignite utilization in Saxony.In 1919,the precursor department of IEC with a focus on the thermochemical conversion of lignite was established.

Effect of hydrogen impurities on hydrogen oxidation activity of Pt/C catalyst in proton exchange membrane fuel cells

High-purity of hydrogen is vital to the guarantee of end usage in proton exchange membrane fuel cell(PEMFC)electric vehicles(EVs)with superior durability and low expense.However,the currently employed hydrogen,primarily from fossil fuel,still contains some poisoning impurities that significantly affect the durability of PEMFCs.Here,we investigate the poisoning effect of several typical hydrogen impurities(S^(2-),Cl^(-),HCOO^(-)and CO_(3)^(2-))on the hydrogen oxidation reaction(HOR)of the state-of-the-art carbon-supported platinum(Pt/C)catalyst used in the PEMFC anode.Electrochemical results indicate that the electrochemically active surface area of Pt/C is hampered by these hydrogen impurities with reduced effective Pt reactive sites due to the competitive adsorption against hydrogen at Pt sites showing the extent of the poisoning on Pt sites in the order:S^(2-)>Cl^(-)>HCOO^(-)>CO_(3)^(2-).Density functional theory calculations reveal that the adsorption energy of S2-on Pt(111)is greater than that of Cl^(-),HCOO^(-)and CO_(2),and the electronic structure of Pt is found to be changed due to the adsorption of impurities showing the downshift of the d-band centre of Pt that weakens the adsorption of hydrogen on the Pt sites.This work provides valuable guidance for future optimization of hydrogen quality and also emphasizes the importance of anti-poisoning anode catalyst development,especially towards H_(2)S impurities that seriously affect the durability of PEMFCs.

Effect of various ratios of poly(3-hexylthiophene)with polyvinyl alcohol gel-polymer electrolytes in flexible sodium-ion batteries using Samanea saman tree-leaf-derived carbon quantum dots decorated with SnO_(2)and NaVO_(3)

Gel-polymer electrolytes with high thermal stability and mechanical properties were considered suitable in rechargeable batteries so as to overcome the problems encountered in liquid electrolytes.In a previous study,flexible sodium-ion batteries(FSIBs)were fabri-cated using electrodes made of carbon quantum dots(CQDs)decorated with SnO_(2) and NaVO_(3) utilizing a polyvinyl alcohol(PVA)/P3HT gel-polymer electrolyte at a ratio of 1:0.05.In addition,various separators such as indium-doped tin oxide/polyoxyethylene tridecyl ether(ITO/PTE),rice paper(RP),silicone with three big holes(SIL BH),silicone with many small holes(SIL SH)and cellulose paper(CP)were tested in flexible Na-ion batteries.The SIL SH delivered a high specific discharge capacity of 4246 mAh g^(-1) in the initial cycle at 2 V and maintained a value of 71 mAh g^(-1) in the 50th cycle.With the aim of improving the cyclic ability of FSIBs,different weight ratios of PVA/P3HT(1:0.025,1:0.05,1:0.1,1:0.15,1:0.2)were tried in this work using the electrodes CQDs@SnO_(2) and CQDs@NaVO_(3).The above ratios were referred to as B25,B50,B100,B150 and B200,respectively.SIL SH was used as a separator.Cyclic voltammetry studies indicated that B150 had a high specific capacitance of 13062 F g^(-1).B25 and B100 exhibited high discharge capacities(171 mAh g^(-1))and(151 mAh g^(-1))compared to that of other ratios B50(75 mAh g^(-1)),B150(88 mAh g^(-1))and B200(54 mAh g^(-1))in the 50th cycle at 2.0 V.This study reveals the scope of developing FSIBs of high capacity and cyclability at different voltages using carbonaceous electrodes and gel-polymer electrolytes with different ratios of PVA/P3HT.The focus of the present study is to bring out the optimum ratio of PVA/P3HT for maximizing the cyclic ability of FSIBs.

Performance analysis of a novel integrated photovoltaic-thermal system by top-surface forced circulation of water

Almost 80-90%of energy is wasted as heat(provides no value)in a photovoltaic(PV)panel.An integrated photovoltaic-thermal(PVT)system can utilize this energy and produce electricity simultaneously.In this research,through energy and exergy analysis,a novel design and methodology of a PVT system are studied and validated.Unlike the common methods,here the collector is located outside the PV panel and connected with pipes.Water passes over the top of the panel and then is forced to the collector by a pump.The effects of different water-mass flow rates on the PV panel and collector,individual and overall efficiency,mass loss,exergetic efficiency are examined experimentally.Results show that the overall efficiency of the system is around five times higher than the individual PV-panel efficiency.The forced circulation of water dropped the panel temperature and increased the panel efficiency by 0.8-1%and exergy by 0.6-1%,where the overall energy efficiency was~81%.

4E analysis and optimization of cold thermal-energy storage under partial operating mode and demand-limiting mode for air-conditioning systems

Cold thermal energy storage is an active method for reducing the peak electrical demand and electricity consumption of air con-ditioners.This paper investigates two different cases:partial operating mode-load levelling(POM-LL)and demand-limiting mode(DLM).4E(energy,exergy,economic,environment)analyses along with a multi-objective optimization process based on a genetic algorithm is applied to determine optimal design values.Exergy efficiency,total annual cost and payback-period time are considered as objective functions in this study.The results have shown that POM and DLM decreased the electricity consumption by 10.36%and 11.29%,respectively,resulting in raising the annual costs by 11.08%and 11.42%.Also,their annual payback periods were 4.36 and 4.18 years each.In addition,using off-peak hours instead of on-peak hours for electricity consumption and reducing electricity consump-tion are the two main ways of decreasing CO_(2) emissions during electricity generation.Therefore,the CO_(2) emissions through POM and DLM are 13.31%and 13.72%less than those of conventional systems,respectively.

Short-term wind power prediction using an improved grey wolf optimization algorithm with back-propagation neural network

A short-term wind power prediction method is proposed in this paper with experimental results obtained from a wind farm located in Northeast China.In order to improve the accuracy of the prediction method using a traditional back-propagation(BP)neural network algorithm,the improved grey wolf optimization(IGWO)algorithm has been adopted to optimize its parameters.The performance of the proposed method has been evaluated by experiments.First,the features of the wind farm are described to show the fundamental information of the experiments.A single turbine with rated power of 1500 kW and power generation coefficient of 2.74 in the wind farm was introduced to show the technical details of the turbines.Original wind power data of the whole farm were preprocessed by using the quartile method to remove the abnormal data points.Then,the retained wind power data were predicted and analysed by using the proposed IGWO-BP algorithm.Analysis of the results proves the practicability and efficiency of the prediction model.Results show that the average accuracy of prediction is~11%greater than the traditional BP method.In this way,the proposed wind power prediction method can be adopted to improve the accuracy of prediction and to ensure the effective utilization of wind energy.

Structural optimization of baffle internals for fast particle pyrolysis in a downer reactor using the discrete element method

The structural optimization of baffle internals for fast pyrolysis of coal with particulate mixing and heat transfer in a downer reactor using the discrete element method(DEM)has been investigated in this research.The pyrolysis terminal temperature at the exit of the downer reactor is not only decided by the volume-feeding-rate ratio of the coal to the sand,but also is affected by the inner structural design of the baffle internals in the downer reactor.As presented in the previous publication of the author,the inhibition from the baffle internals in a downer reactor can improve the particulate-mixing degree and heat carrier,and increase the mean residence time of the coal and heat-carrier particles in the downer reactor.The structure of the baffle internals in the downer reactor mentioned in this research can be optimized by the independently developed 3D soft-sphere model of the DEM programme of a 40-mm baffle length,a 30°baffle-slope angle and at least four baffles designed in the downer reactor,which is beneficial for the process design of coal pyrolysis with a heat carrier in the downer reactor.

A polyoxometalate redox flow battery: functionality and upscale

While redox flow batteries carry a large potential for electricity storage,specifically for regenerative energies,the current technology-prone system-the all-vanadium redox flow battery-exhibits two major disadvantages:low energy and low power densities.Polyoxometalates have the potential to mitigate both effects.In this publication,the operation of a polyoxometalate redox flow battery was demonstrated for the polyoxoanions[SiW_(12)O_(40)]^(4-)(SiW_(12))in the anolyte and[PV_(14)O_(42)]^(9-)(PV14)in the catholyte.Emphasis was laid on comparing to which extent an upscale from 25 to 1400 cm^(2) membrane area may impede efficiency and operational parameters.Results demonstrated that the operation of the large cell for close to 3 months did not diminish operation and the stability of polyoxometalates was unaltered.

Experimental investigation of photovoltaic systems for performance improvement using water cooling

This research aims to analyse the comparative performance of two identical photovoltaic(PV)panels with load variations and integrating an automated water-cooling process under the climatic conditions of the United Arab Emirates.The work also presents the steps of system design,implementation and performance evaluation of the proposed PV system,and all electrical,control and mechanical components along with how they were integrated within a 100-W PV system.MATLAB/Simulink?was used only to simulate the behaviours of the PV panel under wide ranges of incident sunlight and ambient temperature.The tests were performed for a day-long operation during a clear summer day.The experimental results demonstrate an improvement in the PV system performance compared with the uncooled system by~1.6%in terms of total harvested energy using the proposed water-cooling process with a frequency of 2 minutes of cooling operation every 30 minutes during day hours.

Emission characteristics of flue gas during the chemical-looping combustion process for multi-component solid waste

Solid waste has interactions with its flue-gas products during combustion,which offers the possibility of regulating its pollutant emissions.Especially,these interaction pathways would be clearer under anaerobic conditions when the chemical-looping combus-tion(CLC)process is used.The CLC experiments of multi-component solid waste were conducted on a homemade twin-bed reactor and the characteristics of flue gas were investigated for the effect of the mixing ratio of sewage sludge and polyvinyl chloride(PVC).The results indicated that the combustion efficiency was>99.9%for these CLC processes;the highest carbon-conversion rate was obtained at 96.3%for PVC with 60%sludge.The highest NO and SO_(2)emissions were 26%and 19%,respectively,when the sludge was mixed with 20%PVC.As the proportion of PVC blended into the sludge increased,the time when the concentration of NO in the flue-gas peaks moved backwards,while peak SO_(2)concentration moved forward.The general trend was to increase first and then de-crease.In addition,there were multiple peaks in carbon emissions,corresponding to~10%,30%and~70%of the carbon-conversion rate;nitrogen emissions reached 90%of total emissions before the carbon-conversion rate was 40%;sulphur emissions had a longer cycle and were mainly emitted between 10%and 60%of the carbon-conversion rate.The results are expected to provide a reference for solid-waste source suppressing to inhibit the generation of pollutants.

Techno-economic analysis of the Li-ion batteries and reversible fuel cells as energy-storage systems used in green and energy-efficient buildings

Green buildings have become broadly adopted in commercial and residential sectors with the objective of minimizing environmental impacts through reductions in energy usage and water usage and,to a lesser extent,minimizing environmental disturbances from the building site.In this paper,we develop and discuss a techno-economic model for a green commercial building that is 100%powered by a photovoltaic(PV)system in stand-alone configuration.A medium-sized office building in El Paso,TX was modelled to rely on a photovoltaic system to supply all of its electricity needs either directly from the PV system or through an energy-storage system(ESS)using Li-ion batteries(LIBs)or reversible fuel cells(RFCs).Cost results show that a 400-kW PV system can generate electricity at a cost of 2.21 cents/kWh in El Paso,TX and the average levelized cost of energy storage(LCOS)using 450-kW RFC is~31.3 cents/kWh,while this could reach as low as 25.5 cents/kWh using a small LIB ESS.While the RFC provides the flexibility required to meet building-energy demand,LIBs may not be able to meet building needs unless the storage size is increased substantially,which in turn incurs more energy-storage cost,making LIBs less favourable from an economic perspective.Sensitivity analysis revealed that capital cost,discount rate and expected system lifetime play key roles in shaping the LCOS in both systems.

Experimental study on dense-phase pneumatic conveying of coal powder at high pressures

Clean utilization and conversion of coal resources is significant to China’s energy sustainable development.Entrained-flow coal gasification technology is an important method used for clean and efficient conversion of coal.The characteristics and stability of high-pressure dense-phase pneumatic conveying of pulverized coal is crucial to the safe and stable operation of dry-feed entrained-flow coal gasifiers.Dense-phase pneumatic conveying experiments were carried out using a high-volatile bituminous coal in pipes with diameters of 25,15 and 10 mm,respectively,and at back pressures of 1.0-4.0 MPag.The conveying characteristics and effects of operating and structure parameters were studied.Pressure drop models were established for horizontal and vertical upward conveying.The prediction uncertainty was within±30%for the horizontal conveying and±20%for the vertical upward conveying.The relative standard deviation of solid flow rate was proposed to explain conveying stability.The effect of operating parameters on conveying stability was systematically analyzed.The gas velocity-related criterion was proposed for stable conveying.

Economic analysis of hydrogen production from China’s province-level power grid considering carbon emissions

Hydrogen energy contributes to China’s carbon peaking and carbon neutralization by serving as an important energy carrier.However,the calculation of the cost of hydrogen production by the power grid ignores the current cost of carbon emissions.To measure the cost of hydrogen-production projects in various provinces more comprehensively and accurately,this study incorporates the carbon-emission cost into the traditional levelized cost of hydrogen model.An analysis of the energy structure of the power supply is conducted in each province of China to calculate carbon-emission costs,which are then subjected to a sensitivity test.Based on the results,the carbon-emission costs for hydrogen in each province are between 0.198 and 1.307 CNY/kg,and the levelized cost of hydrogen based on carbon-emission costs varies from 24.813 to 48.020 CNY/kg;in addition,carbon-emission costs range from 0.61%to 3.4%of the total costs.The results also show that the levelized cost of hydrogen considering carbon-emission costs in the Shanghai municipality specifically is most sensitive to the carbon-emission price,changing by 0.131 CNY/kg for every 10%fluctuation in the carbon-emission price.

Use of solar PV inverters during night-time for voltage regulation and stability of the utility grid

Photovoltaic(PV)inverters are vital components for future smart grids.Although the popularity of PV-generator installations is high,their effective performance remains low.Certain inverters are designed to operate in volt-ampere reactive(VAR)mode during the night.Yet,this approach is ineffective due to the consumption of active power from the grid(as internal losses)and the regulation necessity of the direct-current(DC)bus.This paper will demonstrate the operation of a PV inverter in reactive power-injection mode when solar energy is unavailable.The primary focus is on the design of the inverter controller with respect to the synchronous rotating frame control method.The proposed novel method enables an inverter to inject the required level of reactive power to regulate the voltage levels of the utility grid within specified limits.In the process,the inverter does not absorb active power from the grid for its internal operation.The presented model has the ability to inject≤2 kVAR of reactive power at zero power factor without absorbing active power from the grid.Simulation and hardware models of the inverter were developed and tested for different reactive loads in which the hardware model represented the real-world application.The reactive power injection of the two models ran at zero power factor and produced the expected outcomes for their corresponding independent reactive loads.Henceforth,it was evident that the proposed method can enhance the efficiency of an inverter and ensure the stability of the utility grid to which it is connected.

Control of hybrid DC/AC microgrid system employing fuel cell and solar photovoltaic sources using grey wolf optimization

The outcome of this study is to improve and enhance the power quality of the hybrid DC/AC microgrid(MG).The photovoltaic(PV)system and the proton exchange membrane fuel cell(PEMFC)are used as renewable energy sources to deliver the optimum active power to the utility grid.The MG system based on the PV system,PEMFC and voltage source inverter is modelled mathematically.Also,the maximum power point tracking(MPPT)-based grey wolf optimization(GWO)is used to increase the PV module efficiency and enhance performance.Also,to improve the PEMFC performance,a digital proportional-integral controller is used to control the PEMFC circuit.The proposed inverter is controlled using synchronous reference frame theory,called the direct-quadrature(dq)control method.Hence,the performance of the proposed MG system is tested using MATLAB®for various weather and loading conditions.From the simulation results,the proposed MG system can deliver and absorb an active power based on the PV and fuel cell characteristics.As a result,the hybrid DC/AC MG is enhanced in terms of stabilization of the DC-bus voltage.Also,the power quality of the MG is improved using GWO optimization based on MPPT.Finally,good results are achieved using GWO in terms of the total harmonic distortion of the output current of 2.3%and higher efficiency of 98.9%.

A software-based approach in designing a rooftop bifacial PV system for the North Hall of Residence, IUT

Bifacial rooftop photovoltaic panels appear to be an excellent means of power generation in this era of urbanization,especially for land-limited countries like Bangladesh.This paper presents a software-based approach to design and simulate a bifacial solar-panel-based energy model on the rooftop of the North Hall of Residence of the Islamic University of Technology,Gazipur.This vertically mounted model investigates the feasibility and applicability of such an energy model in a university residence,situated in a load-shedding-prone area.Hence,three prominent software platforms,namely PVSOL,PVsyst and System Advisor Model(SAM),are brought into action and rigorous simulations are performed for three different orientations;promising outcomes are observed in terms of annual energy yield,bifacial gain(BG)and consumption coverage of the grid and PV model.The annual energy demand of the North Hall is~444733.5 kWh.The three orientations can generate annually 92508.62,94643.48 and 86758.94 kWh,respectively.Hence,it is evident that the proposed orientations can supply almost 19-21%of the site’s annual demand.Monthly BG analysis shows an overall increase in energy gain of 13%,15.6%and 6%for Orientation-1,Orientation-2 and Orientation-3,respectively.A rigorous comparative analysis and deviation analysis among the software results has been accomplished to gain more insight into the feasibility of the proposed system.Thus,we have focused on a detailed software-based estimation of energy production for different orientations of the PV panels,considering several factors,which will provide prior knowledge and assessment before going for hardware implementation in the future.

Design of a new static solar concentrator with a high concentration ratio and a large acceptance angle based on bifacial solar cells

Solar concentrators are used in solar photovoltaic systems to lower the cost of producing electricity.In this situation,fewer solar cells can be used,lowering the overall cost of the system.The purpose of this article is to design,construct,install and test a stationary(non-tracking)concentrating system in Irbid,Jordan.Bifacial solar cells are used in the design.Two concentrator designs(with the same concentration ratio)are experimentally tested.Conc-A has a parabolic shape in the lower part but flat reflecting walls,whereas Conc-B has a standard compound parabolic shape in all parts.The receiving solar cells are arranged in three distinct positions in each concentrator.The results reveal that the output power from both concentrators is affected by the placement of the receiving solar cells within the concentrator.It has also been found that concentrators with flat reflecting walls perform better than those with parabolic reflecting walls.Conc-A’s power collection is~198%greater than that of a non-concentrating device.When Conc-B is used,the increase in power is~181%.