Real Solar Radiation Research Articles

Thermal energy storage behaviour of 3D ceramic/molten salt structures under real concentrated solar radiation

Molten salts, phase change materials commonly employed in thermal energy storage (TES) systems, are widely known to enhance the efficient use and storage of solar energy in concentrated solar power (CSP) plants. Here, three-dimensional TES (3DTES) have been manufactured from highly porous (up to ∼90 %) 3D printed patterned vermiculite (V) and alumina (Al2O3) supports, which have been infiltrated with molten sodium nitrate salt (nn) and solar salt (ss). These 3DTES have been validated under real concentrated solar radiation in a parabolic solar furnace. Among the different 3DTES, those based on V-nn exhibits the best efficiency for the conversion of the incident solar radiation into heat; whereas Al2O3-nn transfers the heat more efficiently and allows a faster charging-discharging cyclability due to its higher thermal conductivity. This study confirms the benefits of additive manufacturing to develop a new class of innovative TES for CSP applications.

Experiment and dynamic simulation of micro gas turbine combined with concentrated solar power system

The solar micro gas turbine (SMGT) system is a promising solution to address the instability and intermittency of renewable energy sources. Its dynamic characteristics under unstable input conditions and uncertain output load demands are crucial for peak shaving. This paper constructs an SMGT system based on experiments with micro gas turbine (MGT) and concentrated solar power (CSP), analyzing the impact of integrating CSP system on the MGT. Then the performance of the SMGT under varying ambient conditions and load demands is studied. Results show that in grid-connected mode, the turbine speed of MGT and SMGT is determined by ambient temperature and set power, with electrical efficiency decreasing as temperature and DNI increase. The solar receiver in the SMGT should maximize temperature increase while maintaining pressure loss below 55 kPa. Additionally, a higher heat capacity can reduce sensitivity to ambient changes but also extends stabilization time. Under real solar radiation, the SMGT system can keep constant power within 0.6% fluctuation, with a solar share of 36.5%. When combined with photovoltaic, the hybrid system’s maximum power fluctuation does not exceed 2.6%, with a solar share of 48.8%. This study provides guidance for optimizing SMGT systems and their application in peak shaving scenarios.

Radiometric characterization of daytime luminescent materials directly under the solar illumination

The materials efficiently emitting photoluminescence (PL) under solar irradiation could find broad applications in passive radiative cooling of buildings, urban heat mitigation, and solar energy harvesting. In this work, we discuss the limitations of common laboratory characterization of such materials (using tunable light sources or solar simulators) and propose a methodology for direct outdoor characterization of PL efficiency under full solar irradiation. A simple, portable radiometry setup with an integrating sphere is described, and its capability of rapid determination of the spectral distribution of the absorbed and emitted power, as well as the overall PL power efficiency and quantum yield, is demonstrated. By characterization of three materials developed for daytime radiative cooling applications, we reveal deviations of obtained parameters caused by the replacement of the real solar irradiation by that of solar simulators. The described method is suitable for studies of long-term stability, photo-induced degradation, or thermal effects.

Optimal Design of a Hybrid Solar–Battery–Diesel System: A Case Study of Galapagos Islands

In this study, the sizing problem of hybrid diesel–photovoltaic–battery systems was determined using a particle swarm optimization approach. The goal was to optimize the number of solar panels and batteries that could be installed to reduce the overall cost of an isolated grid system, originally powered by diesel generators, located on Isabela Island in the Galapagos, Ecuador. In this study, real solar radiation and temperature profiles were used, as well as the load demand and electrical distribution system relative to this island. The results reveal that the total cost for the proposed approach is lower as it reaches the global optimal solution. It also highlights the advantage of a hybrid diesel–photovoltaic–battery (DG-PV-BAT) system compared to conventional systems operated exclusively by diesel generators (DGs) and systems made up of DGs and PV panels; compared to them, a reduction in diesel consumption and total cost (71% and 56%, respectively) is achieved. The DG-PV-BAT system also considerably improves environmental factors and the quality of the power line. This study demonstrates the advantages of hybridizing systems isolated from the network through the proposed approach.

A cascaded thermochemical energy storage system enabling performance enhancement of concentrated solar power plants

Calcium looping (CaL) thermochemical energy storage (TCES) exhibits promising potential for application in concentrated solar power (CSP) plants. However, the CSP-CaL integrating system encounters challenges related to elevated heat loss and diminished power generation efficiency. Herein, for the sake of a more rational heat management and enhanced energy utilization, we propose a cascaded energy storage and utilization strategy. Accordingly, a cascaded TCES system model consisting of Calcium looping and Magnesium looping (MgL)-MgCO3/MgO thermochemical cycle subsystem is developed. The energy analysis and exergy analysis results show that the solar power efficiency and exergy efficiency of the considered system are 41.7% of 44.7%, which are 2.6% and 2.8% higher than the single CaL energy storage CSP system, respectively, demonstrating the superiority of the proposed strategy and system for CSP application. Furthermore, the operation strategy of the system under off-design conditions is proposed by considering the real solar irradiation, and the yearly overall solar power efficiency is 39.2%. The economic analysis of the proposed system indicates that the levelized cost of electricity ranges from 179–156 $/MWh for different plant sizes and is superior in large-scale CSP plants. The cascaded energy storage and utilization strategy of thermochemical cycles with different working temperatures provides better dispatchability to meet the different thermal energy demands.

Research on the generation method of missing hourly solar radiation data based on multiple neural network algorithm

Solar radiation is an essential meteorological parameter for building energy efficiency analysis, and the quality of the data directly affects the analysis results. This paper investigates the estimation of hourly solar radiation based on the generation of the typical meteorological year(TMY) using various real meteorological parameters and limited solar radiation data. The focus of this paper is to use two types of neural network algorithms to improve the estimation accuracy and applicability, and to solve the problem of hourly solar radiation data acquisition in non-radiation areas. First, select two city station data and use three methods to generate TMY. Then, two neural network models, BP Neural Network (BP)，Convolutional Neural Network (CNN) are used to estimate the hourly solar radiation data and verify the results. Finally, by constructing a photovoltaic-integrated office building model, the accuracy of the hourly solar radiation estimation model is verified using energy consumption simulation and photovoltaic (PV) power generation simulation. The results show that this paper can well solve the problem of limited radiation data, which provides a new idea for the study of building energy efficiency in areas where radiation data is missing.

Anlık Güneş Işınımı ve Meteorolojik Parametrelere Bağlı Olarak Fotovoltaik Panel Güç Üretiminin Değerlendirilmesi

The solar radiation incident on the surface of photovoltaic (PV) panels, dependent on the inclination 
 angle, and the temperature of the panels are the most significant parameters affecting power 
 generation. These two parameters are necessary to accurately evaluate the electrical performance by 
 enabling the calculation of cell and module temperatures. In this study, the efficiencies and electrical 
 power behaviors of PV panels positioned towards the sun at a 37° inclination angle in Hakkari province 
 were examined under real solar radiation and ambient temperature values. In addition, the effect of 
 wind speed parameters was also considered, and the impact on panel efficiency and PV panel output 
 power was evaluated. When the results were evaluated, it was confirmed that the effect of wind 
 increases the efficiency of PV panels, resulting in an increasing in PV output power.

Estimation of renewable energy systems for mobile network based on real measurements using HOMER software in Egypt

With the increasing of global awareness of the importance of reducing polluting emissions and maintaining a clean and healthy environment. So, the tendency to generate electric energy from new and renewable sources has become an urgent need to achieve this goal. In this paper an optimal economic cost analysis using hybrid renewable energy sources to generate the electricity needed for long-term evolution mobile phone systems was estimated. The proposed electric system accounts for the reduction of polluting emissions to the environment. The electrical profile of the optimal approaches or the hybrid technology and traditional methods which contain solar photovoltaic’, batteries, wind turbines, diesel generator were estimated and provides the electrical power for a Long-Term Evolution mobile network (LTE) as the load at a remote located area. A real time optimal cost analysis of each proposed network is done based on the real load profile, wind speed and solar radiation was placid on from 6 October city in Egypt. Statistical analysis was performed by varying the systems through comparison to determine the optimal approaches based on the Hybrid Optimization Model for Electrical Renewables software (HOMER).

Improving solar fuel production performance from H2O and CO2 thermochemical dissociation using custom-made reticulated porous ceria

Thermochemical CO2- and H2O-splitting cycles for sustainable fuel generation were investigated by using custom-made reticulated ceria foams integrated in a solar-heated cavity reactor. A parametric study revealed the suitable conditions to produce H2/CO with maximum fuel rates and yields per unit mass of redox material. Various operating parameters such as the total pressure during the reduction step, the gas inlet flowrates, the temperature, or the reactive gas content during the oxidation step were studied in detail. A series of on-sun experiments including more than 20 cycles under different cycling conditions were carried out with relevant performance repeatability and stability. With a ceria foam reduction temperature in the range 1400–1470 °C and a reduction pressure of 103 mbar, the ceria foams produced 281 μmol of H2 and 332 μmol of CO per gram of material during oxidation below 1000 °C under cooling with a maximum production rate of 3.0 mL/min.g and 10.2 mL/min.g, respectively. Direct syngas production was also evidenced during on-sun experiments with simultaneous H2O- and CO2-splitting, which yielded a H2:CO ratio ranging from 0.7 to 1.14. The dual-scale porous ceria structures were characterized using X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis to confirm material thermal stability during cycling. Finally, optimization of fuel production capacity was achieved by maximizing the total amount of ceria foam loaded into the reactor, yielding 667 mL of CO (409 μmol/g) and 513 mL of H2 (314 μmol/g) per cycle. A maximum solar-to-fuel efficiency of 10.1% was calculated for CO2-splitting vs. 4.9% for H2O-splitting cycle. This study thus demonstrated noteworthy fuel production performance in an efficient monolithic reactor under real concentrated solar radiation, from highly reactive customized ceria foams.

Optimal Capacity of a Battery Energy Storage System Based on Solar Variability Index to Smooth out Power Fluctuations in PV-Diesel Microgrids

Battery energy storage systems can be integrated with photovoltaic (PV)-diesel microgrids as an enabling technology to increase the penetration of PV systems and aid microgrid stability by smoothing out the power fluctuations of the PV systems. This paper focuses on this topic and aims to derive correlations between the optimal capacity of the smoothing batteries and variabilities in the daily solar irradiance. To this end, the two most commonly used moving average and ramp rate control techniques are employed on a real solar irradiance dataset with a 1-min resolution for a full calendar year across 11 sites in Australia. The paper then presents the developed empirical model, based on linear regressions, to estimate the batteries’ optimal capacity without requiring detailed simulation studies, which are useful for practitioners at the early stages of a project’s feasibility evaluation. The performance of the developed technique is validated through numerical simulation studies in MATLAB®. The study demonstrates that the empirical model provided reasonably accurate estimates when using the moving average smoothing technique but had limited accuracy under the ramp rate control technique.

Integration of a lithium-ion battery in a micro-photovoltaic system: Passive versus active coupling architectures

A balcony photovoltaic (PV) system, also known as a micro-PV system, is a small PV system consisting of one or two solar modules with an output of 100–600 Wp and a corresponding inverter that uses standard plugs to feed the renewable energy into the house grid. In the present study we demonstrate the integration of a commercial lithium-ion battery into a commercial micro-PV system. We firstly show simulations over one year with one second time resolution which we use to assess the influence of battery and PV size on self-consumption, self-sufficiency and the annual cost savings. We then develop and operate experimental setups using two different architectures for integrating the battery into the micro-PV system. In the passive hybrid architecture, the battery is in parallel electrical connection to the PV module. In the active hybrid architecture, an additional DC-DC converter is used. Both architectures include measures to avoid maximum power point tracking of the battery by the module inverter. Resulting PV/battery/inverter systems with 300 Wp PV and 555 Wh battery were tested in continuous operation over three days under real solar irradiance conditions. Both architectures were able to maintain stable operation and demonstrate the shift of PV energy from the day into the night. System efficiencies were observed comparable to a reference system without battery. This study therefore demonstrates the feasibility of both active and passive coupling architectures.

Modeling and control of islanded DC microgrid fed by intermittent generating resources

In this paper an islanded microgrid fed through the wind and solar energy resources is presented. The power flow within the microgrid is controlled using a Neutral Point Clamped Dual Active Bridge (NPC-DAB) converter. In the proposed dc microgrid, the solar energy source is associated at the low voltage (LV) bus and the wind energy source is connected at the high voltage (HV) bus. A permanent magnet synchronous generator (PMSG) machine is used in wind energy conversion system. The real time solar radiation and wind speed data of Rupangarh, Rajasthan, India is used as an input for renewable energy resource. The NPC-DAB will work as a power electronics juncture for expediting the energy exchange in the islanded DC Microgrid. The proposed closed loop controller based on the capacitor voltage and load voltage will expedite a complete automatic operation of the islanded DC-microgrid considering various load changes. The system is studied without storage element as the automatic control of energy generation and load feeding is carried out by the NPC-DAB, also this makes the scheme cost effective. The optimum duty ratios for NPC-DAB operation are obtained and thus the increased load demand is met. The modeling of PMSG, NPC-DAB and wind energy system is discussed in details in this work. The proposed system is studied in MATLAB/Simulink environment and results are obtained for different load variations. All the wind control parameters, NPC-DAB waveforms, load waveforms are also plotted using MATLAB.

Solar photocatalytic performance of glass substrates coated with Ag3PO4 thin films

Silver-orthophosphate (Ag3PO4) photocatalysts exhibit excellent photo-oxidative capabilities under visible light irradiation, especially in their powders form. However, Ag3PO4 in the form of thin films has not been explored that much and very little is known about their performance under solar irradiation. In the present study, glass substrates were coated with Cu-doped Ag3PO4 (Cu-Ag3PO4) and Ag3PO4 thin films using successive ionic layer adsorption and reaction (SILAR) due to its simplicity, relatively low-cost and ability to be performed at low temperatures with low time requirements. The as-deposited thin films were characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and UV–Visible spectrophotometry, while their photocatalytic performances were evaluated on Rhodamine-B (Rh-B) dye degradation under real solar light irradiation. The adopted coating protocol resulted in regular thin films that crystallize in the desired P4̅3n cubic phase, where doping with Cu was shown to be responsible of a crystallite size reduction within the film. From the optical point of view, a broad absorbance in the entire visible range was obtained with bandgap energies of about 2.2 eV in the case of Ag3PO4 thin films, and around 1.65 eV in the case of Cu-Ag3PO4 thin films. Such optical features were exploited to test the photocatalytic performance in the degradation of Rh-B dye. After 4 h of solar irradiation, the variation of the relative concentration of Rh-B solution relative to the degradation efficiency of the photocatalysts was of 54% in the case of Cu-Ag3PO4 thin films and of 89% in the case of Ag3PO4 thin films. So, exploration of a wide area of the solar visible spectrum is made possible under doping, a finding that would improve the overall photocatalytic activity which is very promising for the degradation of other organic pollutants under solar irradiation.

Optimal model predictive control of energy storage devices for frequency stability of modern power systems

Load Frequency Control (LFC) has become a more challenging issue, especially with the increases in generation's unpredictability, inconsistency, and load variations leading to reduced system stability and reliability. This paper presents a novel application of the transient search optimization (TSO) upon Model Predictive Control (MPC) based regulators to solve the LFC problem for multiple zones power networks with hybrid renewable generators and storage devices. An exact model with a governor's dead band, generator's rate constraint, and measurement communication delay are employed. Renewable energy sources (RESs), such as wind and solar systems, in addition to fuel cell generators with different storage elements, such as superconducting magnetic energy storage (SMES) and battery energy storage (BES), are incorporated into the power system investigated in this study. To assess the effectiveness of the TSO-MPC controllers in nonlinear conditions due to renewable energy generation and storage ambiguities, actual wind speed measurements are incorporated into the wind generation model and real solar irradiance and temperature data for the photovoltaic system to achieve an extra credible analysis. Furthermore, the performance of the TSO-MPC regulator is compared with the performance of other optimization techniques based on proportional-integral-derivative (PID) controllers under different conditions, and the results of the proposed controller outperform other controllers by >10 % of the transient specifications. The transient response of the power system is significantly enhanced with the controller proposed in this study.

Experimental and thermodynamic analysis of solar air dryer equipped with V-groove double pass collector: Techno-economic and exergetic measures

• Thermodynamic model and experimental validation of v-groove solar dryer. • Optimum flow rate of air within the collector was obtained for maximum efficiency. • SEC was 3.01 kWh/kg at 0.041 kg/s with 59% energy saving for apple drying compared with electricity driven heating. • Sustainability indices of the solar air collector and dryer are 1.50 and 1.047 respectively. • Energy payback period for the system is less than 1 year. Optimised solar air dryers, in terms of efficiency and performance, can solve some major concerns in the agro-industrial processing sector. Solar air dryers can reduce the large share of energy costs of a final product and can provide sustainable energy in rural areas where access to energy is often limited. In this study, a pilot scale v-groove double pass solar air collector has been analysed thermodynamically with real time solar radiation and mass flow rate (0.021-0.061 kg/s) inputs and validated experimentally in terms of first and second law efficiencies. Performance of the process was assessed using experimental drying measures including final moisture content, drying rate and exergy efficiency for drying of Pink Lady apples. Energy payback time and specific energy consumption were calculated to reveal the techno-economic value of the system. The maximum thermal efficiency of the collector was observed to be 88.8% at 0.061 kg/s having exergy efficiency of 6.6% which shows an efficient sourcing for the operation. In terms of the performance of the dryer, mass flow rate of 0.041 kg/s offers a higher moisture removal. Specific energy consumption (SEC) was 3.096 kWh/kg. Thermodynamic model was validated with matching experimentation with acceptable RMSE for the range of investigated measures. Energy payback period time calculated by the embodied energy of the system was obtained to be 0.78 years which implies that the system is capable of addressing a large capacity drying if it is to be scaled-up.

Photocatalytic Cr(VI) reduction over MIL-88A(Fe) on polyurethane sponge: From batch to continuous-flow operation

MIL-88A(Fe)@sponge (MS) was synthesized by a dip-coating method, which displayed efficient photocatalytic Cr(VI) reduction efficiency under both low power LED UV light and real solar light irradiation. It was observed that MS (0.2 g/L) could remove 100% Cr(VI) (10 mg/L) by adding 0.4 mmol/L tartaric acid (TA) without adjusting pH (pH 5.05) within 6.0 min and 3.0 min under UV light and real solar light irradiation, respectively. Besides, the photo-induced e− and radicals (O2•− and CO2•−) were found to play the momentous roles in the MS/TA/UVL/Cr(VI) system by the scavenger experiments and electron spin resonance (ESR) tests. MS was also filled into a fixed-bed reactor to test the possibility of long-term Cr(VI) reduction operation in TA/UVL system. As expected, the results revealed that MS could still maintain 100% activity up to 60 h. These results demonstrated that MIL-88A(Fe) might be the potentially efficient catalyst for large-scale wastewater treatment in the near future.

Grid connected hybrid renewable energy systems for urban households in Djibouti: An economic evaluation

The cost of electricity produced by thermal power plants in Republic of Djibouti is relatively high at about $0.32/kWh. This is due to its dependence on imported oil coupled with fluctuating oil prices. Consequently, the customer pays a high electricity bill. However, Djibouti is endowed with indigenous renewable energy resources such as a good solar irradiance of 5.92 kWh/ m2 day, a potential geothermal energy estimated up to 1000 MW, and few sites with annual wind speed higher than 6 m/s. The goal of this paper is, therefore, to assess an economic evaluation of different grid connected hybrid renewable energy systems to a residential urban house located in Tadjourah city (11.7913° N, 42.8796° E) in the North-Eastern part of Djibouti to reduce the cost of electricity from the grid. To reach this objective, a powerful software tool called HOMER (Hybrid Optimization Model for Electric Renewables) has been used to find the optimum hybrid energy system using real wind and solar irradiation data. The results obtained from this study show that the best economical suited combination of hybrid renewable energy system is a PV-Wind grid connected system. This study shows also that potentially the indigenous renewable energy contribution, in Tadjourah, can be as much as 77 % with 47 % of solar and 30% of Wind energy. The Net Present Cost, the Levelized Cost of Energy, and the operating cost of the optimal HRES are $337, $0.002/kWh and $1,025/year, respectively. When compared with the average cost of grid-only connection of $0.32/kWh, the optimal hybrid renewable energy system is more economical and will save 51 % of the cost that the customer must pay when using only the electricity from the grid.

Sizing of a Hybrid Energy System for Al Mazyouna Area

Natural gas and diesel currently are the main fuel for electrical power generation in Oman. Decreasing the dependence on national gas and diesel is one of the main goals for Oman’s vision of 2040. This paper discusses the optimum design of a hybrid stand-alone power generation system for the power station of Al-Mazyouna located west of Dhofar governorate using HOMER Pro Software. Real load data and solar radiation of Al-Mazyouna were utilized in the modelling approach. Different scenarios of power systems were investigated, using mainly, diesel generators, PV solar panels, and storage batteries to reach an optimal solution. The main factors that were considered to decide the wining setup of a power system are the net present cost, cost of energy and the amount of emissions. The optimum scenario resulted in a net present cost of $84.8 M and a cost of energy of $0.161/kWh compared to a net present cost of $99.4M and a cost of energy of $0.188/kWh for the current system. Additionally, the optimum scenario system limits toxic emissions significantly compared to the base system. The results of the winning scenario showed that the emitted quantities of harmful gases are all reduced by about 28% compared to the base system.

Numerical study on solar-driven methanol steam reforming reactor with multiple phase change materials

The multi-stage phase change material (PCM) fillings were proposed in the methanol steam reforming tube reactor driven by the parabolic-trough concentrated solar energy. Two-dimensional mathematical model of such surround filling reactor with numerical simulation was developed to evaluate its performance on eliminating the solar energy fluctuation. The effects of PCM with different thermophysical properties on chemical performance of the reactor were conducted when the sun is blocked. The optimal arrangement of multiple-stage PCMs was investigated and its performance under solar radiation fluctuations was investigated to improve the available latent heat of PCM and chemical performance of the reactor. The results showed that the PCM filling in the reactor significantly increased the time of methanol reforming reaction and improved the chemical performance when the heating by concentrated solar energy was ceased. PCM with lower phase change temperature and more latent heat could maintain the chemical reaction for a longer time. However, better chemical performance when PCM released latent heat could be achieved by PCM with higher phase change temperature. Compared to single PCM filling, Two-stage PCMs reached a maximum relative improvement in methanol conversion of 10.86%. Three-stage PCMs reached the maximum relative enhancement in methanol conversion of 11.36% compared to Two-stage PCMs. Under the cyclic and solar fluctuations, the multiple-stage PCMs reactor produced nearly twice as much hydrogen as that of the reactor without PCM. During a 6-h real solar radiation fluctuation, the multiple-stage PCMs reactor also have better methanol conversion. However, more than Three-stage PCMs arrangement improved the chemical performance of reactor only slightly.

Evaluation of energy recovery potential of solar thermoelectric generators using a three-dimensional transient numerical model

The solar thermoelectric generator (STEG) is regarded as a promising energy conversion technology to convert solar heat into electricity. Considering the real solar irradiance, impedance matching, and interface contacts, a comprehensive three-dimensional transient thermal-electric numerical model for the STEG is established to evaluate its dynamic response and energy recovery potential. The transient performance prediction of the STEG during the whole daytime is completed for the first time. Due to the temperature limitation of thermoelectric materials, the allowable concentration ratio for the Bi2Te3-based STEG is 150 suns, corresponding to the average daytime output power of 13.16 W and the average daytime conversion efficiency of 6.15%. Dynamic responses of output voltage and conversion efficiency present the same changing trend as solar irradiance. However, the steady-state numerical model underestimates the output power by 6.91% and overestimates the conversion efficiency by 1.85%, due to the ignorance of thermal inertia during thermal diffusion. The established transient model can predict more reasonable results and is well verified via transient experiments. It is obtained that the STEG can produce 491.4 kJ of electricity a day and 49.79 kW h a year, and the theoretical cost-recovery cycle for the cost of the thermoelectric generator module is 1.61 years.