Solar Unit Research Articles

A new solar, natural gas, and biomass-driven polygeneration cycle to produce electrical power and hydrogen fuel; thermoeconomic and prediction approaches

Nowadays, due to the limitations of fossil fuels utilization, renewable energies-driven polygeneration systems (PGSs) are becoming popular. In this article, the simulation and conceptual design of a PGS based on biomass and natural gas fuels to produce products such as electricity, hydrogen fuel, hot water (HW) and chilled water (CHW) is presented and discussed. The introduced PGS is integrated with units and cycles such as water electrolysis (based on polymer electrolyte membrane (PEM) electrolyzer), a ground source heat pump (based on geothermal well), and an absorption chiller. Additionally, in order to supply a fraction of the heat required for the cycle, a solar thermal unit (based on parabolic trough solar collectors, PTSCs) has been embedded. The proposed PGS is evaluated and analyzed from thermodynamic and exergoeconomic points of view. Moreover, as an innovative approach, a prediction on machine learning (ML) model is developed to predict and evaluate hydrogen production rate through biomass gasification. Besides, a state-of-art structure and configuration is considered for the proposed PGS, which had not been reported in the literature. The outcomes indicated that the considered PGS is capable of generating nearly 3.71 MW of electricity, 11.42 kg/h of hydrogen fuel, 5.7 kg/h of oxygen gas, 5.9 MW of CHW, and 2.95 MW of HW. In such a context, the energy and exergy efficiencies of PGS are yielded 74.2 % and 32.3 %, respectively. It is estimated that the implementation of such a system will require an investment cost of almost $ 3.9 million. It was also found that the HW unit exergy cost is approximately 37.8 % higher than that of CHW. Besides, the unit exergy cost of hydrogen fuel is almost 4.4-fold higher than that of electricity. In addition, a detailed parametric research is conducted to analyses the influence of the costing metrics on the PGS behavior under consideration. Finally, the results demonstrated that ML model had acceptable accuracy and could predict the hydrogen production rate through biomass gasification.

Productivity Enhancement of Solar Water Desalination Unit Using a Solar Electric Water Heater

The biggest problem faced by the world these days is pure drinkable water, and in a few years, pure drinkable water will not be easily available, as it is becoming brackish and saline due to pollution. By using solar energy, a solar still can produce pure water which can be used for drinking, cooking, and also for industrial purposes. In this research, a solar still based on clean technology using solar energy to drive the system is used that can be operated easily and with an approximately negligible maintenance cost. A pyramid solar water desalination unit with modification of the solar electric water heater (used to increase water temperature) is developed to increase the water yield per day. A theoretical model of the solar still unit is developed and performance is evaluated. Based on this theoretical design, fabrication is carried out and experiments are performed to predict the overall output. It is observed that the output distilled water has a total dissolved salts value much lower than the total dissolved salts of groundwater. Additionally, the average output of a solar water desalination unit with an electric water heater is found to be enhanced compared with the unit without an electric water heater.

Optimization of a grid-connected hybrid energy system: Techno-economic and environmental assessment

This study aimed to provide sustainable, secure, and clean energy for Tuzla campus of National Defense University Turkish Naval Academy. Research problem was to find technically and economically optimized hybrid energy system consists all or some of solar, wind, biomass, and battery sources in addition to grid and diesel generator of the campus. Greenhouse gas emissions of the optimum solution were calculated for environmental effect analysis. Additionally, the effects of the variables such as solar radiation, wind speed, expected inflation, and electricity unit prices on system were analyzed. The study conducted via Homer software under two scenarios based on legal regulations. As a result, the optimum system in both scenarios is a grid-connected hybrid system consisting of photovoltaics and wind turbines. Results presented reduction in net present cost of energy by 86.2%–90%, unit cost of energy by 92.7%–95.8%, operation & maintenance costs by $862,093–$933,695, emissions by 79%–82%. According to both optimization results and sensitivity analysis, no biomass generator was discovered in optimum solutions. It was also observed that batteries could be in the optimum system depending on economic variables. It is believed that this study, in which solar, wind, and biomass as well as battery, grid, and diesel generator were evaluated together under legal based scenarios, can be a reference for further researches due to its diversity in system components and its scenarios consisting legal aspects. The study also can serve as an example and a guide for other public university campuses.

Parametric study for optimizing double-layer microchannel heat sink for solar panel thermal management

The most significant issue affecting the electric efficiency of solar panels is overheating. Concentration photovoltaic (CPV) modules work by converting approximately 80% of sunlight to heat; this may exceed the cell operating temperature limits. Therefore, thermal management is the best choice for keeping such panels working under specified conditions. Prior to producing an actual solar indoor unit, the current research primarily focuses on optimizing the heat sink dimensions that affect the cooling performance of the solar panel. Two parametric studies were employed to optimize the microchannel heat sink design. First, a two-dimensional numerical study was implemented to optimize the best channel height for more uniform flow inside a double-layer microchannel heat sink (DL-MCHS); the width of channels was kept as a constant value. Second, a three-dimensional conjugate heat transfer model for fluid flow in the optimized heat sink was used to optimize the inlet/outlet header length. To evaluate the overall CPV performance, a further numerical case study was carried out for the optimized designs at a wide range of inlet mass flow rates and steady-state heat flux. The findings indicated that a channel height of 0.5 mm and a header length of 20 mm were the best design points for the suggested heat sink. To assess the effectiveness of a solar/thermal module, the selected design points were applied to a 3D model. The maximum electricity efficiency measured was 17.45%, nearly 40% greater than the typical CPV/T system.

MPC‐based DC microgrid integrated series active power filter for voltage quality improvement in distribution system

SummaryThis paper presents a DC microgrid integrated series active power filter (Se‐APF) to improve the voltage profile of the utility distribution system under sag, swell, and harmonics scenario. The DC microgrid encompasses a solar photovoltaic generation unit and a composite energy storage unit (CESU). A lithium‐ion battery and supercapacitor as a CESU are envisioned in this work. Compared to conventional Se‐APF supported by the capacitor/battery storage, the integrated DC microgrid prolonged the operational features of the Se‐APF for voltage quality improvement and feeding the localized dc loads or charging the CESU occasionally from the PV generation system. Further, a power management algorithm is implemented to coordinate the operations of the sources in the DC microgrid to accomplish the above‐mentioned features. The Se‐APF and associated power converters in the DC microgrid are regulated by a nonlinear controller based on optimal switching vector‐model predictive control algorithm. The proposed control method can be used to help distribution networks with voltage fluctuations by offering much faster and more precise voltage regulation. The feasibility and effectiveness of the proposed control strategy are verified in MATLAB/Simulink platform and then validated in a real‐time simulation platform using Opal‐RT Lab real‐time simulator OP4510.

Analysis of solar energy driven organic Rankine cycle-vapor compression refrigeration system

Integration of an organic Rankine cycle-vapor compression refrigeration system with an N series fully covered photovoltaic thermal compound parabolic collector is done in this study. The system is designed to produce electrical power and cooling effect simultaneously. The exergy efficiency (ηex), coefficient of performance (COPs), and the net mitigation of carbon dioxide per solar collector unit area (mCO2) have been selected as the performance assessment parameters based on energy, exergy, and environmental criteria. Moreover, the effect of expander inlet temperature (T7), packing factor (λcl), and the number of collectors (N) on the energy, exergy, and environmental performance of the system have been studied. Results show that the system's energy (COPs) and exergy (ηex) performance is maximum at an expander inlet temperature of 423 K and packing factor of 0.25. The corresponding maximum values of COPs and ηex are 1.81 and 5.8 %, respectively. However, the system has maximum environmental performance (mCO2 = 1999 g m−2) at the expander inlet temperature of 373 K and packing factor of 0.89. ηex and mCO2 are increased to 17.4 % and 8546 g m−2, respectively, as the number of collectors increased from 1 to 5.

Transient thermodynamic modeling and economic assessment of cogeneration system based on compressed air energy storage and multi-effect desalination

This study examined the design of a renewable system for producing electricity and freshwater based on the solar cycle and using thermal storage in different cities. The system comprised heliostat, gas turbine, multi-effect desalination, and compressed air energy storage (CAES) subsystems. The Engineering Equation Solver software was used for modeling and obtaining results by system analysis. Eight scenarios were examined by considering the charging time, discharging time, number of sunny hours, and various desalination effects. Finally, the best scenario was selected following a parametric study, which was scenario 5 with seven parameters, and it had the best performance. Specifically, the exergy round trip efficiency, round trip efficiency, power generation, and freshwater generation rate of the system were optimal. The number of heliostats and the turbine and compressor efficiencies influenced the system outputs. Based on an economic analysis of the system, the CAES, solar unit, and gas turbine costs were the highest among the system component costs. Moreover, based on an exergy analysis of the system, most exergy degradation corresponded to the heliostats, receiver, and gas turbine. Moreover, five cities—Esfahan, Dubai, London, Paris, and San Francisco—were compared in terms of the peak consumption time per year. Finally, the performance of the developed system was investigated for ambient temperature changes, solar radiation, and wind speed of the cities considered per year. The outcomes revealed that the system performed the best in the climate conditions of Esfahan during the peak consumption time.

Investigation on the Impact of Different Absorber Materials in Solar Still Using CFD Simulation—Economic and Environmental Analysis

Solar stills are one of the low water production desalination systems, but its low yield makes it necessary to investigate different design and performance parameters to improve its productivity. This paper aims to perform a parametric analysis of a solar still desalination system and study the effect of different absorber materials on the performance of a single-slope solar desalination unit employing computational fluid dynamics (CFD) numerical simulation via COMSOL® Multiphysics software. To consider the absorptivity of water with different absorbing materials, simulation was conducted with the application of effective emissivity for the solar still walls. In addition, the economic, exergoeconomic, and CO2 mitigation of solar stills were studied. The results revealed that the hourly water output of the solar desalination unit, with different absorbing materials (black ink, black dye, and black toner), reached the maximum values at 1:00 PM. On comparing the simulation results of solar stills with and without absorbing materials, it has been observed that the solar still painted with black toner shows the highest improvement in hourly productivity, the exergy of evaporation, and evaporative heat transfer coefficient with a maximum increase in respective values by 10.52%, 13.68% and 5.37%. The CO2 mitigation and enviroeconomic parameter of the solar still using black toner were equal to 31.4 tons and 455.3 USD, respectively. Moreover, the lowest cost per liter (CPL) of the solar still was obtained using black toner, which was about 0.0066 USD/L.

Exergo-economic comparisons of solar cooling systems coupled to series/parallel absorption chiller types considering the lowest heat transfer area

District solar assists cooling systems can make full use of local renewable resources, and reduce the fossil fuel consumption and greenhouse gas emissions. After modelling and validation of solar cooling systems, the exergo-economic method is carried out to explore the economic performance by considering the lowest heat transfer areas of two chiller types based on the yearly ambient parameters in Beijing, China. The sensitivity analysis of key parameters is searched to depict the impacts of initialized parameters. The results show that the solar cooling system coupled to parallel chiller needs the lowest solar installation area, 602 m2, and corresponds to the highest coefficient of performance, 1.15, and exergy efficiency, 21.91%. However, due to the higher heat transfer areas of parallel chiller, the specific exergo-economic cost of chilled water, 3.93 $/kWh, is higher than the one of series cooling system, 3.78 $/kWh. The sensitivity analysis demonstrates that except for temperatures of cooling water, returned chilled water, and temperature difference of driving steam from solar unit, other parameters have positive impact on exergo-economic performance.

Exploring the variability of the venusian thermosphere with the IPSL Venus GCM

Recent simulations of the Institut Pierre-Simon Laplace (IPSL) Venus Global Climate Model (VGCM) developed at the Laboratoire de Météorologie Dynamique (LMD) were performed with a model top raised from ∼10−5 (∼150 km) to ∼10−8 Pa (180–250 km; upper boundary). The parameterizations of non-LTE CO2 near infrared heating rates and of non-orographic gravity waves were improved. In addition, a tuning of atomic oxygen production was introduced to improve related effects (heating and cooling) and resulting thermospheric number densities. This work focusses on validating the modelled thermospheric structure using data from the Pioneer Venus, Magellan and Venus Express missions which cover similar and complementary (equator and pole) regions at different periods of solar activity, typically above altitudes of 130 km. This version of the IPSL VGCM shows good agreement with the diurnal evolution of the exospheric temperature at the equator reconstructed from the atomic oxygen scale height of the Pioneer Venus Orbiter Neutral Mass Spectrometer data. The model is also able to reproduce the sensitivity of the exospheric temperature and species density to the EUV flux of the solar high activity period (from 180 to 230 solar flux unit; s.f.u). However, to fit with the PV-ONMS density observations, it was necessary to increase the photodissociation of CO2 into CO and O above 135 km by a factor of 10. Indeed, our study points to the importance of an additional source of oxygen and carbon monoxide production above 130 km other than CO2 photolysis to explain the vertical profiles of CO and O number density in the thermosphere. Moreover, the presence of a GW drag at altitudes above 140 km has a significant impact on the nightside temperature value and its distribution.

Thermal performance and evaluation of a novel stratified and mixed flexible transformation solar heat storage unit

Thermal performance and evaluation of a novel stratified and mixed flexible transformation solar heat storage unit

Optimal design and performance assessment for a solar powered electricity, heating and hydrogen integrated energy system

Incorporating solar energy technologies into integrated energy systems (IES) plays an increasingly important role to mitigate energy supply shortages and climate challenges. However, the low efficiency of solar energy utilization and land limitation for system deployment greatly restrict the development of the solar powered IESs. In this paper, a solar powered electricity, heating and hydrogen IES based on photovoltaic (PV), photothermal (PT) and photocatalysis of hydrogen production (PH) is proposed and investigated. The system comprises solar radiation spectrum splitting technology, PV, PT, PH, electric heating device, compressive heat pump, solid oxide fuel cell, absorption heat pump and energy storage components. A component sizing method based on a region contraction algorithm is employed to find the system optimal design with minimizing the cost of energy. Two scenarios of the solar powered IES based on solar spectrum splitting unit and independent energy supply unit are analyzed and compared. The results show that the solar powered IES can completely meet the electricity, heating and hydrogen energy demands and achieve cost savings for consumers. Compared to independent energy supply unit-based IES, the use of solar spectrum splitting unit can significantly improve the total energy efficiency by 21.74% and reduce the land area for solar capture by 52.5%, but increase the cost of energy by 27.3%.

Analysis of Solar Power Generation Performance Improvement Techniques

The performance of solar power generation systems broadly depends upon the effectiveness of the solar cell placed in the architecture. The performance of the solar cell may vary with respect to the heat generated over its surface. Hence different types of cooling methods are employed over the solar power generation system to improve its power efficiency. Apart from solar cell cooling method, different types of optimization techniques are also implemented to the solar power generation unit for extracting a good power output. The maximum power point tracking algorithm is one of the primary methods used for matching the generated power to reach the required power in the connected battery system. The paper analyzes the research attainments and limitations of the various cooling models employed for the solar power generation system to develop an efficient system in future.

Energy and exergy analysis of a solar coffee roaster using concentrating scheffler-reflector

• An innovative solar coffee batch-type roasting system using a fixed-focus Scheffler reflector as a heat source. • Investigated thermal analysis of the solar roster unit based on energy and exergy. • Analysis provides clear insights into energy distribution and losses in the system. • The energy at the solar reflector was found to be 3680 W and out of which 66% (2449 W) was available for roasting coffee. • The integration of solar thermal energy into the roaster unit performs efficient decentralized roasting of coffee beans. The energy and exergy based thermal analysis was conducted on a newly developed solar coffee roasting system. The system is comprised of a rotating drum (diameter: 400 mm × length: 400 mm), electric motor with variable frequency drive, cooling tray (diameter: 500 mm × height: 100 mm), fan blower, and coupled with a heating source i.e., Scheffler fixed focus solar concentrator (8 m 2 ). Experiments were conducted using 2 kg coffee beans (variety Coffea arabica L .). The results revealed that the system is capable to process the complete batch in 21 ± 1 min at the temperature of 250 °C at corresponding solar radiations in the range of 800–850 W/m 2 . The specific product energy was calculated to be 1543 kJ/kg. The average exergy input, out, and loss of the solar roasting system were found to be 83.98, 47.58, and 36.40 kJ/kg, respectively. The results show that the average exergy efficiency and improvement potential factor of the solar roaster were 56.28% and 22.59 kJ/kg, respectively. Out of total available power (3680 W) at the solar reflector, 66% of energy was available for roasting coffee. The findings of this study show that the developed system could be a valuable tool for design and optimization of the energy distribution and losses at various components of the solar roasting system.

Energy Management System Based on Cost Optimization of Battery Aging and Hydrogen Consumption in a Microgrid

This paper introduces a new Energy Management System (EMS) approach for a stand-alone Hybrid Renewable Energy System (HRES) for residential application. The HRES comprises a solar photovoltaic unit (PV) as a master source, a hydrogen Fuel Cell (FC) as a standby source and a Hybrid Energy Storage System (HESS) combining a battery (Batt) and a supercapacitor (SC). The PV system works at maximum power point whereas the FC and the HESS act as support and storage system respectively. The adopted EMS not only aims at distributing the power between the FC, the Batt and the SC but also focuses on regulating the battery State of Charge (SoC) between two desired limits, while minimizing the cost of battery usage and hydrogen consumption. This is done via a gain scheduled low-pass filter where gain value is adapted online in order to increase flexibility of source’s use. Gain value should be pre-optimized by an optimization problem based on battery usage and hydrogen consumption cost. Numerical simulations using MATLAB/Simulink are carried out in order to evaluate the performance of the new method. Two other different EMS approaches have been utilized to serve the comparison with the proposed technique.

Solar remote monitoring unit

In this manuscript, a smart, IoT-enabled, solar-based datalogger, which can measure AC and DC voltage and current of solar panel accurately is presented. Combination of stand-alone current and voltage sensors are used to measure to develop the datalogger. The datalogger can measure the current non-invasively, without introducing disturbance to the circuit under test. The PCB is fabricated, and measurements have been made to evaluate the system's performance. The results demonstrate that sensed values give maximum accuracy compared to manually tested values. The main purpose of the study is to measure the electrical parameters of solar panels to achieve maximum accuracy, reducing the error rate, thus causing a reduction in electricity bills, and accessing the data remotely. The system can send data to the cloud so that a remote user can check the data through a web-application.

A hybrid fuel cell, solar thermal collector, and coal-fired power plant; energetic, exergetic, and emission analysis

ABSTRACT Although the nonrenewable energy-driven power plants have major limitations, but at present, more than 80% of the energy needed all over the world is met through these power plants. Among them, almost one-third is supplied through coal-fired plants. However, the major limitation in the exploitation of coal fuel is the increase in environmental harms due to the increased greenhouse gas emissions. In this regard, it is necessary to adopt solutions and integrate these plants with other clean and green energy production cycles in order to reduce the emission of pollutants and improve their behavior. In this paper, the thermodynamic-conceptual evaluation of a new coal-fired plant driven by lignite is developed. Besides that, the plant is coupled with a solid oxide fuel cell and two independent solar units (both based on parabolic trough collector (PTC) arrays) in order to reduce the environmental harms of coal. Additionally, the introduced power plant consists of two power generation units based on a Rankine cycle and a gas turbine-based cycle. Therefore, the introduced plant can produce electric power and hot water. Further, the integration of cycles based on renewable technologies can reduce environmental pollution and improve plant’s efficiency. Moreover, a comprehensive comparison is presented when changing power plant fuel from lignite to anthracite. The conceptual design of solar units based on the geographical characteristics of city of Karaj is also provided. The outcomes indicated that the gas released from the plant during the combustion process is approximately 94.1 kg per second. The considered plant can produce almost 270.2 MW of electric power and approximately 1572 kg of hot water per second. Additionally, the energetic efficiency was equal to 69.72% and exergetic efficiency was equal to 34.93%. The findings also indicated that the size of solar unit 1 under both types of anthracite and lignite coal is the same; while, by changing the type of coal from lignite to anthracite, the size of solar unit 2 can be reduced by almost 6.5 times.

Study of a solar HDH desalination unit powered greenhouse for water and humidity self-sufficiency

This study investigates the performances of a self-sufficient greenhouse powered by a solar humidification–dehumidification desalination unit. It aims to achieve an overall integrated system that produces enough fresh water to cover the irrigation demand as well as the air humidification needs of the greenhouse. The humidification–dehumidification operation was numerically simulated using the developed model along with the greenhouse microclimate. The greenhouse model was validated through an experimental real-scale greenhouse. To make the proposed system more flexible, an auxiliary control system is used to easily monitor the greenhouse needs and ensure its satisfaction. The findings revealed that the integrated system, with its two main subsystems and its regulation device, successfully ensures the greenhouse irrigation, the humidification needs and provides an optimal plant growth. For the case study, i.e. cucurbit greenhouse situated at El Hamma (Tunisia), the desalination system can cover more than 200% of the greenhouse water irrigation needs while keeping the greenhouse inside air at a humidity level of 60% at least. The maximum productivity and the best energy efficiency are respectively 5.1 m3/day and 63.25%.

Thermoeconomic assessment of a renewable hybrid RO/PEM electrolyzer integrated with Kalina cycle and solar dryer unit using response surface methodology (RSM)

In this research, a non-dimension model of renewable generation system encompassing a solar-geothermal driven Proton Exchange Membrane (PEM) electrolyzer in integration with Kalina cycle (KC), Single-effect Absorption Refrigeration Cycle (SEAC), and Reverse Osmosis (RO) unit is introduced. Cooling and heating loads, electricity, distilled water, Hydrogen, Oxygen, and dry air are the main products of the mentioned system. This scheme is investigated from the energetic, exergetic, and exergoeconomic (3E) standpoints by writing a code in engineering equation solver (EES) and is totally validated by the literature survey. Subsequently, to enhance the operating condition of the CCHP system devised, six decision variables are designated for the optimization procedure using the RSM via the Minitab software; the response variables are sum unit cost of products (SUCP) and exergetic efficiency. Here, the desirability of the accuracy of the regression models attained from the analysis of variance for the objective functions is entirely verified. Moreover, the optimal condition reveals the best exergetic efficiency and SUCP of 31.71% and 1.75 $/GJ, respectively.

Evaluating the Performance of a Solar Distillation Technology in the Desalination of Brackish Waters

Desalination is set to become a major source of drinking water in several Middle Eastern countries over the coming decades. Solar distillation is a simple power-independent method of water desalination, which can be carried out in active or passive modes. This study is among the first attempts to investigate the possibility of desalinating brackish groundwater resources under the threat of saltwater intrusion in the southern areas of Razavi Khorasan province in Iran. For this purpose, a pilot solar distillation unit was constructed to analyze the effects of the unit orientation, depth of the water pool, atmospheric conditions, input salinity, and flow continuity on the solar distillation performance. The results showed that the unit exhibited the highest efficiency when it had a 3 cm deep water pool. It was oriented facing southward while operating a continuous flow for at least 3 days under sunny weather conditions. It was found that among the studied parameters, the unit orientation and pool depth had the greatest impact on the water production performance for this type of water desalination system. Conversely, the water production efficiency was not very sensitive to the input salinity level. Overall, the solar distillation technology was able to reduce the salinity by 99.7% and the hardness by 94.7%.