Solar Conversion Research Articles

Light-driven phase change microcapsules modified by TiN/CNTs nanocomposites for enhancement of solar energy storage and solar photocatalytic efficiency

The development of microencapsulated phase change materials (PCMs) integrating solar photothermal conversion and storage holds significant for solar energy utilization. Herein, this study developed an efficient light-driven phase change microcapsule system by encapsulating paraffin within a brookite TiO2 shell through sol-gel interfacial polymerization, followed by wrapping titanium nitride (TiN)/carbon nanotubes (CNTs) nanocomposites on the shell surface. The microcapsule system exhibited a regular spherical core-shell structural morphology. The encapsulation of TiO2 and the introduction of the highly thermal conductivity enhancement phase increased the thermal conductivity of the microcapsule system by approximately 151.5 % compared to pure paraffin while maintaining latent heat of over 135 J·g−1. Furthermore, TiN/CNTs were combined with the microcapsule shell through hydrogen bonds and shared electron pairs, constructing localized surface plasmon resonance (LSPR)-enhanced heterojunction. The microcapsule system demonstrated excellent broad-spectrum light absorption capacity, resulting in a remarkable 112.01 % enhancement in the optimum photothermal conversion efficiency. Concurrently, the degradation rate of MB was increased by 59.52 % due to the synergistic catalytic action of photothermal, semiconductor, and LSPR effects. The microcapsule system also exhibited excellent thermal and cycling stability, with only 1.6 % latent heat loss after 500 thermal cycles. This study provides a promising strategy for developing energy storage microcapsule composite PCMs for the efficient collection and utilization of solar energy.

Solar Energy and Climate Change

Modern solar energy is based on photothermal, photovoltaic and hybrid solar radiation conversion and passive capture of solar radiation. Photothermal conversion of solar radiation takes place in low-temperature, medium-temperature, and high-temperature photoconversion systems. Flat collectors with water and air are used for low-temperature conversion of solar radiation. Solar concentrators are used for medium-temperature conversion of solar radiation. Concentrators with heliostatic fields and parabolic reflectors of solar radiation are used for hightemperature conversion of solar radiation. Solar cells made of different materials are utilized for the photovoltaic conversion of solar radiation. Stand-alone and photovoltaic systems connected to the electricity distribution network are used to supply consumers with electricity. Fixed tilt, single or dual-axis tracking solar power plants are designed with the aim to generate a larger amount of electricity. Hybrid solar collectors are used for the simultaneous conversion of solar radiation into heat and electricity. For passive capture of solar radiation, individual residential and other buildings are used, which are built in accordance with the principles of solar architecture. Solar energy uses mainly environment-friendly materials, except toxic As and Cd in GaAs and CdTe solar cells. Devices used in solar energy do not emit harmful substances and do not have an adversary impact on climate change.

Ultra-broadband and wide-angle solar absorber with hierarchical nanohole design based on MXene

MXene has received a lot of attention from researchers in the fields of photothermal and photovoltaic due to its excellent optical properties. However, research on MXene-based solar absorbers has rarely been carried out. In this work, we proposed a MXene-based solar absorber with absorption broadband, wide-angle, and polarization insensitive. The absorber has excellent light capture capability, with its average absorption in the solar band as high as 97.8 % and an energy absorption ratio of 98.9 % in the AM1.5 solar radiation spectrum. The electric and magnetic field distributions indicate that the unique hierarchical nanohole design can effectively excite multiple resonance couplings of surface plasmon resonance, cavity resonance, and guided mode resonance. The proposed absorber can still maintain the broadband absorption characteristics within a certain manufacturing tolerances. Moreover, the absorber is insensitive to polarization and has a high light absorption under a large incident angle. We believe that this work holds great promise for solar thermal conversion and heat utilization.

Synergistic solar-powered water-electricity generation: An integrated floating system on water

The global pursuit of sustainable development faces two critical challenges: the scarcity of clean water and the growing energy crisis. The integration of solar-powered hybrid systems that harness the photovoltaic effect and passive steam generation has emerged as a crucial strategy. While several thermally-localized multi-stage solar stills have been developed, they predominantly rely on ground-mounted designs. Herein, we present a groundbreaking integration concept that combines a floating solar panel with a five-stage membrane distillation (MD) device, enabling simultaneous clean water and electricity generation on water surfaces. Positioned on the reverse side of the photovoltaic (PV) cell, the Janus membrane-involved multi-stage architecture of the MD device passively cools the PV cell, captures and repurposes the waste heat and manages vaporization enthalpy recycling. Our research highlights the importance of optimizing heat and mass transport within each stage, boosting the photoelectronic and photothermal conversion of the whole system. As a result, the integrated system achieves an impressive water production rate of 4.14 kg m−2 h−1 while simultaneously maintaining a high electricity generation efficiency of 16.4 % under 1 sun, therefore maximizing the total solar energy conversion. The clean water production rate of 11.6 kg m−2 day−1 places our system among the best-performing solar stills operating under natural sunlight. This integrated system sets a pioneering example of clean water and electricity co-generation with minimized carbon footprint, extending the applicability of ground-mounted solar conversion systems to water bodies.

Flexible photothermal-triggered MOF-composite nanofibers textures for freshwater harvesting with high efficiency and stability

Vast freshwater reserves in the atmosphere have been investigated as a sustainable source of water for the alleviation of the water crisis with suitable sorbent-based atmospheric water harvesting (AWH) materials. In this work, we design a flexible photothermal-triggered MOF-composite nanofiber texture (PMNT), which is fabricated by combining nanofibers to be optimally integrated with UiO-66-NH2, carbon black and lithium chloride. PMNT achieves not only efficient water molecule uptake but also high solar thermal conversion efficiency. The PMNT effectively harvests atmospheric water to ∼ 1.44 g g−1 under 60 % RH in 80 min and quickly releases water over 30 min under 1 sun. In particular, PMNT outdoors collects water of ∼ 1.16 g g−1, even if the light intensity is ∼ 1.16 kW m−2 and the temperature is ∼ 34 °C, the RH is only 23 %. PMNT outdoors can achieve a total water yield of ∼ 4.61 g g−1 through 5 uptake-release cycles per day, along with stability and low energy consumption for AWH. It has been demonstrated that the as-harvesting water via PMNT meets the WHO standard. This study provides insight into the design of novel materials for AWH performance, which can be extended to practical applications, e.g., water engineering in arid regions, water harvesting devices and systems in industry.

Metallurgical slag modified monolayer graphene hybrid SA-based composite phase change materials for high thermal conductivity

Phase change materials are thermal energy storage materials with high heat storage density, low temperature loss and long cycle life. However, they also show a weak light absorption ability and low thermal conductivity, limiting their applicability for solar thermal conversion and storage technologies. In this paper, in order to improve the relatively low thermal conductivity of stearic acid and enhance its thermal conductivity, SGC-T composites with enhanced thermal conductivity were prepared using metallurgical slag, via the melt blending method. The SEM and EDS, surface scanning tests, were used to determine the morphology characteristics of the composite phase change materials and verify the addition of metallurgical slag. The physical phase composition, structure, and absorption coefficients were analyzed by XRD, FT-IR, and UV-Vis-NIR analyses. The thermophysical properties were analyzed by DSC. The thermal stability was explored using TG testing. The thermal conductivity was explored by measuring the thermal conductivity coefficient value of the samples at the testing temperature of 25 ℃ using the hot disk method/transient flat plate heat source method. The heat storage and exothermic capabilities of the samples were evaluated by the photo-thermal warming system/infrared thermography test. The results showed that the thermal conductivity of SGC was 0.663 W·(m·K)−1, and that of SGC-2 T, SGC-6 T, SGC-10 T, SGC-14 T, were 0.695 W·(m·K)−1, 0.758 W·(m·K)−1, 0.824 W·(m·K)−1 and 0.872 W·(m·K)−1, respectively, which are comparable to SGC. Compared with SGC, the thermal conductivity values of the four composite phase change materials increased by 4.8%, 14.3%, 24.3%, and 31.5%, respectively. SGC-14 T has the best heat transfer performance, which significantly improves the heat transfer performance during latent heat storage and release. Therefore, the SGC-14 T material reported in this work is a promising candidate in the field of energy-saving conversion, and further expands the applicability of phase change materials.

Renewable Energy Integration on a High Inflation Economic Scenario by Means of Firework Algorithm, Genetic Algorithm and Monte Carlo Simulation

This paper presents a solution to the Renewable Energy Integration Problem (REIP) by finding the Optimal Configuration of components required in a hybrid microgrid located in Kuwait, such that the cost of energy (COE) is minimized when considering several components such as: solar panels, wind turbines, electric batteries, converters, inverters, diesel generators and connection to the power grid. The optimal configuration is found by evaluating the interaction and effects of several combinations of components via Monte-Carlo simulation, and such configurations are in turn optimized by means of 2 alternative stochastic algorithms: The Genetic Algorithm and the Fireworks Algorithm. The two approaches are compared, concluding that the Fireworks Algorithm provides more variety of configurations along the iterations before reaching convergence. The evaluation by Monte-Carlo simulation is calculated, by means of Present Worth (PW) with a minimum attractive rate of return (MARR) set to 7 percent to represent a high inflation rate-scenario, concluding that both methods can be safely used to optimize the design of hybrid micro-grids under high economical stress.
 
 Received: 18 August 2023 / Accepted: 25 October 2023 / Published: 5 November 2023

SOLAR TRACKING SYSTEM FOR RENEWABLE ENERGY

Solar panel has been used increasingly in recent years to convert solar energy to electrical energy. The solar panel can be used either as a stand-alone system or as a large solar system that is connected to the electricity grids. The earth receives 84 Terawatts of power and our world extracts about 12 Terawatts of power per day. To extract maximum energy from the sun using solar panel and conversion from solar to electrical energy is the difficult task. To overcome this, the solar panels have to be positioned towards the sun. Thus the tracking of the sun’s location and positioning of the solar panel are important. The objective of this project is to design an automatic tracking system, which can locate position of the sun. The tracking system will move the solar panel so that it is positioned perpendicular to the sun for maximum energy extraction at all time. Hence the efficiency of the system may increased to about 16 percent to 20 percent. Light Dependent Resistors (LDR) will be used as sensors in this system. KEY WORDS : Solar panel, 555 IC, L293D IC, Light Dependent Resistor (LDR), 7805 Voltage Regulator, Battery, Battery Cap, Resistors, Capacitor, Light-Emitting Diode (LED), Switch, DC Gear motor.

Multimode Luminescent Properties from Tb3+-Yb3+ Codoped CaMoO4 for Solar Cell Spectral Conversion

NIR and visible emitting CaMoO4:Tb3+/Tb3+-Yb3+ phosphors were synthesized to harness the energy losses attribute to wavelength mismatch between response spectrum of incident solar photons and solar cells. The X-ray diffraction (XRD), field emission scanning microscopy (FE-SEM), fourier transform infrared spectroscopy (FTIR), UV–vis diffuse reflectance spectroscopy, photoluminescence (PL), up-conversion and life time measurements were used to characterized the prepared phosphors. XRD study followed by Rietveld refinement confirms the tetragonal crystal structure with space group I41a(88). The phosphors exhibit strong green emission (5D4→7F4) in visible region after an excitation wavelengths 378 nm and 980 nm, respectively through down-shifting (DS) and up-conversion (UC) processes. The UV photons (378 nm) are also split it into two NIR photons (2F7/2→2F5/2) through down-conversion process. Fluorescence quenching was observed by increasing concentration of Tb3+ and Yb3+ ions. Lifetime measurements clearly illustrates the energy transfer from Tb3+ to Yb3+ ions and mechanism involved is co-operative energy transfer. The estimated values of energy transfer efficiency (ETE) and corresponding theoretical internal quantum efficiency are achieved as 69% and 169% respectively.

Charging characteristics of finned thermal energy storage tube under variable rotation

Solar photovoltaic-thermal (PVT) systems effectively offset the drawbacks of intermittent solar and low photovoltaic conversion efficiency. Thermal energy storage (TES) tanks of PVT systems with high charging efficiency and consistent thermal safety might achieve efficient utilization of solar energy for building. A new variable rotational strategy has been proposed to optimize the charging characteristics for TES tubes, taking into consideration the non-uniformity of melting. A series of simulations based on the volume-averaged model are conducted to investigate the thermal energy storage property of TES tubes under variable rotary mechanism. Qualitative and quantitative comparisons are made between variable rotation (ω = 1.5–0.5, 1.5–1.0, 1.5–2.0 rad·s−1), constant rotation (ω = 1.5 rad·s−1), and stationary systems. The focus of the comparison is melting efficiency, temperature distribution, and natural convection. The results indicate that rotation effectively shortens charging time, with a 57.62% and 15.73% reduction with variable rotary mechanisms of 1.5–1.0 rad·s−1 when compared with stationary and constant rotating tubes. Meanwhile, in the final moment, the greatest medium-temperature (55–65 °C) proportion of 90.58% and less low-temperature (25–55 °C) and high-temperature (65–70 °C) paraffin occupation of 4.67% and 4.75% could be obtained, reflecting the completed latent heat storage and stable thermal safety. The optimal variable rotation achieves improvements of 47.84% and 106.73% in time-integral Grashof number (Gr) and heat storage rate, compared with traditional stationary tubes.

Energy Assessment of Solar Power Plant On-Grid Bi-direction 3 KW 1 Phase

The potential for generating electricity from solar energy as one of the renewable energies is suitable for rural areas, small populations, or communal systems. However, this type of power plant requires a high investment budget. Photovoltaic power systems must be designed to meet the demand for electrical energy but require a large supply. To build a more efficient system, it is necessary to build a communal system. For a small population, a 3000-watt power generation system is made. It will be distributed directly to users; a 5000-watt system is made for a larger area. It will be distributed directly to users and interconnected between generators with the principle of load control. In this study, a solar power plant (PLTS) was designed with an on-grid bidirectional system. Solar panels' conversion of electrical energy is channeled to users and stored in a battery backup system. This PLTS system produces a maximum power of 3000 watts by using 8 units of 450wp solar panels, an inverter with a 48-volt on or off-grid mode system, and 4 12V 200 Ah backup batteries. From the measurement results, the PLTS system will start converting DC current into AC with a radiation value of 356 to 1258 W/m2. Produce on-grid AC current energy, a maximum of 2297 watts, and charge backup batteries with DC current, a maximum of 14.3 A. This on-grid (bidirectional) backup PLTS system can convert DC current into AC, supply it directly to the network electricity (grid), and perform energy backups when solar energy is not energized.

Potentials of InxGa1-xN photovoltaic tandems

During the past few years a great variety of multi-junction solar cells has been developed with the aim of a further increase in efficiency beyond the limits of single junction devices. In this work, the solar power conversion efficiency of InxGa1-xN based tandem solar cells was investigated. With this intention, one simulation of the spectral response and the current-voltage characteristic was carried out using a simulation program designed under ‘Visual Basic 5’ language for this reason. Our cal culation indicates that the attainable efficiency can be enhanced up to 34 % and 37% for tandems with double and triple junctions respectively, obtained under 1-sun AM1.5 illumination and at ambient temperature, using realistic material parameters. A comparison has been made of our results with those of other models.

Performance assessment and resilience of solar mini-grids for sustainable energy access in Ghana

Mini-grids are increasingly adopted as a solution to extending electricity to remote communities in Africa. However, the system's resilience to meet increasing demand amidst degrading performance over time continues to be challenging. This study assessed mini-grid performance and explored factors that should be considered in scaling up mini-grids for sustainability in five island communities in Ghana's Volta Lake. Power generation and load data, visual inspection and thermal imaging data, and electrical systems performance characteristics data were collected and analysed using data loggers installed on site, the IEA PVPS Task 13 guidelines, and the IEC-TS 61724-3: 2016 guidelines, respectively. The study's findings indicate that the solar power conversion efficiency of the mini-grids was generally low and had a 25% - 45% performance ratio. This low efficiency was due to inefficiencies in the battery bank, distribution losses, and unused losses. The overall system efficiency of the mini-grids ranged from 4% to 7%. This is consistent with the literature, which reports that PV power systems in tropical climates have an efficiency of 5% – 15%. The research emphasises the importance of system maintenance, load management, and considering climate change's impact on mini-grid reliability and sustainability.

Comparative study between two maximum power point tracking (MPPT) techniques for photovoltaic system

Solar panels have a nonlinear voltage-current characteristic, with a distinct maximum power point (MPP), which depends on the environmental factors, such as temperature and irradiation. In order to continuously harvest maximum power from the solar panels, they have to operate at their MPP despite the inevitable changes in the environment. This is why the controllers of all solar power electronic converters employ some method for maximum power point tracking (MPPT). This paper presents a comparative study between two most popular algorithms techniques which are incremental conductance (INC) and perturb and observe (P&O) in order to optimize the efficiency of the solar generator. The MPPT techniques will be compared, by using Matlab tool Simulink.

Efficient photocatalytic hydrogen production by bacteriochlorophyll-a derivatives with different esterifying side chains

Ti3C2Tx MXene, a new family of 2D materials, has been successfully used as an ideal co-catalyst for enhancing photocatalytic activity due to its excellent physicochemical properties. Bacteriochlorophyll (BChl), one of the most abundant photosynthetically active pigments, has been studied in the field of artificial photosynthesis due to its constant and efficient absorption of solar energy and conversion of the excitation energy into chemical energy. In this work, five BChl-a derivatives with a range of different side chain groups in the C17 substituent were prepared and deposited on the Ti3C2Tx MXene surface by a solvent evaporation process to form BChl-n@Ti3C2Tx (n = 1∼5) composite photocatalysts, which were used for the visible light-driven photocatalytic hydrogen evolution reaction (HER) in an aqueous solution. Among the five BChls investigated, BChl-5 possessing a quaternary ammonium terminal showed the best performance and BChl-5@Ti3C2Tx composite exhibited an excellent hydrogen production activity of as high as 51 μmol/h/gcat. This is primarily attributed to the excellent photophysical and photochemical properties provided by the self-aggregation of BChl-5 in the BChl-5@Ti3C2Tx composite and the outstanding charge transport capability of the 2D Ti3C2Tx MXene. At the same time, the fast carrier separation and transfer capability between BChl-5 and Ti3C2Tx provides reliable charge transport for photocatalytic HER.

A novel solar-driven waste heat recovery system in solar-fuel hybrid power plants

Solar-fuel hybrid power generation can effectively reduce pollutants in fuel power plants and facilitate the efficient utilisation of solar energy. This study proposes a novel solar-driven waste heat recovery system for solar–fuel hybrid power plants. New system is integrated with parabolic-trough solar collector to drive the heat pump and optimise air pre-heating, offering unique advantages: solar energy amplification and upgraded utilisation. For a 600 MW unit, solar energy in new system generates an electric power of 9.0 MWe with a 0.67 % increase in thermal efficiency, almost twice that of conventional system. With waste heat recovery, the new system exhibits a solar-to-electricity efficiency of 42.12 %. The new system can increase boiler exergy efficiency from 47.78 % to 48.35 %, and decrease exergy loss of air pre-heating to 7.6 MWe. The essential energy saving mechanism of the new system can be attributed to the optimisation of air preheating. Owing to high thermal performance, new system can yield a net benefit of 13.82 million CNY/y, which is 2.6 times that of conventional system. The findings of this study can help for better understanding of solar energy amplification and and upgraded utilisation, thus opening new avenues for solar conversion in solar-fuel hybrid power generation systems.

Scalable Ultralight Wood-Inspired Aerogel with Vertically Aligned Micrometer Channels for Highly Efficient Solar Interfacial Desalination.

An ultralight material that simultaneously combines remarkably rapid water transportation, highly efficient photothermal conversion, and excellent thermal insulation is highly desired for solar-driven interfacial desalination but was challenging. In this work, inspired by the unique natural structure of wood, we developed an ultralight aerogel by ice-templated synthesis as an integrated interfacial evaporator for solar-driven water production. The interior features vertically aligned biomimetic microscale channels facilitating rapid transportation of water molecules, while an improved photothermal interface allows high solar absorption and conversion via nonradiative relaxation and molecular vibrations. The biomimetic aerogel is ultralight with a density as low as 0.06 g/cm3, especially its fabrication is size- and shape-programmable as a whole and easily scalable. Additionally, the outstanding thermal insulation of the aerogel focuses heat precisely at the evaporation interface, reducing ineffective heat loss, while the uniformly distributed large-sized channels promote the dynamic convection of high concentration salt ions on the evaporator surface. Consequently, the evaporator shows broadband light absorption of 92.7%, leading to a water evaporation rate reaching 4.55 kg m-2 h-1 under 3 simulated solar irradiations, much higher than that of other reported evaporators with randomly distributed pores. This work provides new insight into advanced hybrid aerogels for highly efficient and durable solar-driven interfacial desalination systems.

Photo-thermal conversion analysis of a medium-flux direct absorption solar system using gold nanoparticles with natural extract of Azadirachta Indica

Abstract Recently direct absorption solar collector (DASC) system had emerged a new class of solar collectors with much improved solar thermal conversion potential over conventional surface-based absorption solar collectors. Further, introducing noble metallic particles like Ag, Au, Al, TiN or Cu in the working fluids enhanced the optical properties of working fluid and hence the overall thermal performance of such DASC systems. But these novel thermal systems are prone to high emissive and radiative losses at high-temperature ranges. Additionally, the nanoparticles used in the working fluid are expensive, complex to synthesise and mostly non-biodegradable. In the present study, a medium-flux asymmetric compound parabolic concentrator (ACPC) based concentrating DASC system has been tested over clear sky days in the months of September and October 2022 at the composite climate of Jalandhar, India. A hybrid heat transfer fluid is prepared using Azadirachta Indica leaves extract and blended with gold plasmonic nanoparticles to improve the overall thermal performance of DASC system. Stored Energy Fraction (SEF) of hybrid heat transfer fluid at a depth of 2cm reached about 74.9%, which is about 67% higher than water. The outdoor experiments showed that hybrid heat transfer fluid had 10.4°C higher temperature gains in concentrating DASC system, and the photo-thermal efficiency was enhanced up to 40% as compared to water. The study demonstrates the advantage of an eco-friendly, low cost and highly stable hybrid heat transfer fluid as a potential candidate for a medium-flux DASC system.

Graphene-Based Cross-Shaped Surface Plasmon Resonance Solar Absorber Design for Solar Thermal Energy Converters

Graphene-Based Cross-Shaped Surface Plasmon Resonance Solar Absorber Design for Solar Thermal Energy Converters

Evaluation of Solar Conversion Efficiency in Dye-sensitized Solar Cells Using Natural Dyes Extracted from Alpinia purpurata and Alstroemeria Flower Petals as Novel Photosensitizers

Herein, we evaluate the conversion efficiency of dye-sensitized solar cells (DSSCs) photosensitized using two different natural dyes extracted from Alpinia purpurata and Alstroemeria flower petals. The appreciable absorption capacity of the extracts in the visible light region was examined through absorption spectroscopy. The functional groups of the corresponding pigments were identified through Fourier transform spectroscopy (FTIR) technique thus indicating the presence of cyanidin 3-glycosides and piperine in the flowers of Alstroemeria and Alpinia purpurata. The extracted dyes were immobilized on TiO2 on transparent conducting FTO glass, which were used as photoanode. The dye-coated TiO2 photoanode, pt photocathode and iodide/triiodide redox electrolyte assembled into a cell module was illuminated by a light source intensity 100 mW/cm2 to measure the photovoltaic conversion efficiency of DSSCs. The TiO2 anode and Pt counter electrode surface roughness and morphological studies were evaluated using atomic force microscope (AFM) and field emission scanning electron microscopy (FESEM), respectively. Through the photoelectric characterizations, it was promising to verify that the solar conversion efficiency was calculated with the photovoltaic cell sensitized by Alstroemeria and Alpinia purpurata. This was achieved with a yield (η) of 1.74% and 0.65%, with an open-circuit voltage (Voc) of 0.39 and 0.53 V, short-circuit current density (Jsc) of 2.04 and 0.49 mA/cm2, fill factor (FF) of 0.35 and 0.40, and Pmax of 0.280 and 0.100 mW/cm2, respectively. The results are promising and demonstrate the importance of the search for new natural dyes to be used in organic solar cells for the development of devices that generate electricity in a sustainable way.