Novel mixed solar cooker: Experimental,energy, exergy,and economic analysis

This work focuses on the structure, working, and testing of a new mixed solar cooker using a linear Fresnel collector, evacuated tube and box-type cooker. The low-cost components used in the construction of this cooker can help it satisfy the needs of both urban and rural inhabitants who need steady cooking temperatures above 140°C. A family of five can prepare four meals using this modified solar cooker, which costs about $250. The designed solar cooker was tested by conducting no-load and full-load tests. For the no-load test, the maximum temperature of the absorber plate and oil for the new mixed cooker was recorded as 160.26°C and 172.72°C, respectively. The absorber plate of the new mixed cooker and its oil both reached their highest temperatures during the full-load test at 141.14°C and 157°C, respectively. The energy efficiency of the new cooker is 58.776%, while its exergy efficiency is 13%. The heat transfer coefficient increased to 100.16 W/m² °C. This cooker provides an additional time savings of 60 min. An improvement of 27.5% in the highest temperature reached was seen when the developed cooker's performance was compared with those reported in the literature. Additionally, the new cooker's heat-storing capability enables up to 3 h of autonomy. The Levelized Cost of Cooking a Meal for the innovative mixed solar cooker is $0.034 per meal.     

Performance evaluation of a small‐scale sodium carbonate salt gradient solar pond

In this study, thermal performance of the salt gradient solar pond (SGSP), which of density gradient is artificially with sodium carbonate solution, was tested under Karabuk prevailing weather conditions in Turkey. A small‐scale prismatic glass tank was constructed with an area of 0.45 × 0.20 m² and a depth of 0.25 m as solar pond. A series of experiments with four different density levels were conducted in July–August 2004. The variations of the temperature and density profiles were observed for each of experiment for a week. It was found that the maximum temperature difference between the bottom and surface of the pond is 21°C and maximum temperature in the lower convective zone (LCZ) has been measured as 49°C at the first experiment. The efficiency of the pond was evaluated 13.33% weekly mean radiation intensity of 524 W m^?2 for the first experiment. Copyright © 2006 John Wiley & Sons, Ltd.     

A solar ejector air‐conditioning system using environment‐friendly working fluids

In this paper, the performance of the solar‐driven ejector air conditioning with several environment‐friendly working fluids is studied. The effect of the fluid nature and operating conditions on the ejector performance is examined. This performance is calculated using an empirical correlation. Thermodynamic properties of functioning fluids are obtained with a package REFPROP7. It appears that the refrigerant R717 offers the highest coefficient of performance (COP). For generator temperature T_B = 90°C, condenser temperature T_C = 35°C and evaporator temperature T_E = 15°C and with R717, the COP of ejector air‐conditioning system is 0.408. Using a meteorological data for the city of Tunis, the system performance is computed for three collector types. The air‐conditioning season and period were taken for six months from April to September. The daily period is between 8 and 17 h. For the solar air‐conditioning application, the COP of the overall system varied from 0.21 to 0.28 and the exergy efficiency varied from 0.14 to 0.19 with the same working conditions and total solar radiation (351–875 Wm^?2) in July. Copyright © 2008 John Wiley & Sons, Ltd.     

Efficiency analysis of a combined PEFC and bioethanol‐solar‐reforming system for individual houses

In this research, the development of a bioethanol reforming system for fuel cells (FBSR: fuel cell with bioethanol steam reforming) using sunlight as a heat source was investigated. The system was investigated using the experimental result of catalyst performance, and numerical analysis. If ethanol purity is high, the production method of the bioethanol used for the proposal system will not be limited. The overall efficiency of the production of electricity and heat power of this system was determined by examining its thermal output characteristic. The FBSR was introduced into standard individual houses in Sapporo, Japan, for analysis. The amount of hydrogen production, the production‐of‐electricity characteristic, and the thermal output characteristic were examined using meteorological data on representative days in March and August. Compared with the representative day in March (28.0 MJ day⁻¹), the solar radiation of the representative day in August (37.0 MJ day⁻¹) is large. However, the amount of solar radiation fluctuation of the representative day in August in this analysis is large compared with the representative day in March. It depends for the overall efficiency of the system on the amount of solar radiation fluctuation rather than the amount of solar radiation. As a result, the overall efficiency of the system, defined as the rate of power and heat output compared with the amount of solar heat collected, was calculated to be 47.4 and 41.9% on the representative days in March and August, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Comparative study of high concentrating photovoltaics integrated with phase‐change liquid film cooling system

In high concentrating photovoltaic systems, thermal regulation is of great importance to the conversion efficiency and the safety of solar cells. Direct‐contact liquid film cooling technique is an effective way of thermal regulation with low initial investment. Tilt of solar cells is common in concentrating solar systems. An evaluation of direct‐contact liquid film cooling technique behind tilted high concentration photovoltaics was performed using both experimental and computational approaches. In the experiment, deionized water was used as the coolant at the back of simulated solar cells. Solar cell inclination of 0° to 75° with inlet water flow rate of 100–300 L/hour and inlet temperature of 30°C to 75°C were experimentally investigated. A two‐dimensional model was developed using computational fluid dynamics technique and validated by experimental results. The effects of inclination on average temperature, temperature uniformity, and heat transfer coefficient were discovered in this paper. The results indicated that 20° is the optimum angle for liquid film cooling. In addition, optimum inlet width, temperature, and velocity for inclination over 30° are 0.75 mm, 75°C, and 0.855 m/s, respectively.     

Performance analysis of a solar cooker in Turkey

A box‐type solar cooker is designed and its thermal performance is analysed experimentally. The cooker tracks the sun in two axes, altitude and sun azimuth, by hand control for hourly periods. The experimental results show that the tested cooker may be assumed suitable in some cooking processes for specific country conditions. Copyright © 2002 John Wiley & Sons, Ltd.     

Thermodynamic analysis of the CO2‐based Rankine cycle powered by solar energy

Using carbon dioxide as working fluid receives increasing interest since the Kyoto Protocol. In this paper, thermodynamic analysis was conducted for proposed CO₂‐based Rankine cycle powered by solar energy. It can be used to provide power output, refrigeration and hot water. Carbon dioxide is used as working fluid with supercritical state in solar collector. Theoretical analysis was carried out to investigate performances of the CO₂‐based Rankine cycle. The interest was focused on comparison of the performance with that of solar cell and those when using other fluids as working fluids. In addition, the performance and characteristics of the thermodynamic cycle are studied for different seasons. The obtained results show that using CO₂ as working fluid in the Rankine cycle owns maximal thermal efficiency when the working temperature is lower than 250.0°C. The power generation efficiency is about 8%, which is comparable with that of solar cells. But in addition to power generation, the CO₂‐based solar utilization system can also supply thermal energy. Copyright © 2007 John Wiley & Sons, Ltd.     

Experimental investigation of a box-type solar cooker with a finned absorber plate

This article provides the results and finding of an experimental work undertaken in the desert of Algeria. That aimed to compare experimental performance of a box-type solar cooker equipped with a finned absorber plate to a similar box-type cooker which absorber plate without fins. Tests have been carried out on the experimental platform of the Renewable Energies Research Unit in Saharan Environment of Algeria at Adrar. Adrar is located at a latitude 27° 53′ North and a longitude 0° 17′ West. Fins that have been used in solar air collectors enhanced heat transfer from absorber plate to air. Experimental tests have been undertaken as part of this project where was applied this phenomenon to a box-type solar cooker. The results of the experimental investigation have been rigorously analysed and showed that the stagnation temperature for box-type solar cooker equipped with a finned absorber plate was about 7% more than box-type solar cooker equipped with an ordinary absorber plate. The time required for heating water up to boiling temperature in both box-type solar cookers was reduced with about 12% when a finned absorber plate was used.     

Experimental study on sulfur trioxide decomposition in a volumetric solar receiver–reactor

Process conditions for the direct solar decomposition of sulfur trioxide have been investigated and optimized by using a receiver–reactor in a solar furnace. This decomposition reaction is a key step to couple concentrated solar radiation or solar high‐temperature heat into promising sulfur‐based thermochemical cycles for solar production of hydrogen from water. After proof‐of‐principle a modified design of the reactor was applied. A separated chamber for the evaporation of the sulfuric acid, which is the precursor of sulfur trioxide in the mentioned thermochemical cycles, a higher mass flow of reactants, an independent control and optimization of the decomposition reactor were possible. Higher mass flows of the reactants improve the reactor efficiency because energy losses are almost independent of the mass flow due to the predominant contribution of re‐radiation losses. The influence of absorber temperature, mass flow, reactant initial concentration, acid concentration, and residence time on sulfur trioxide conversion and reactor efficiency has been investigated systematically. The experimental investigation was accompanied by energy balancing of the reactor for typical operational points. The absorber temperature turned out to be the most important parameter with respect to both conversion and efficiency. When the reactor was applied for solar sulfur trioxide decomposition only, reactor efficiencies of up to 40% were achieved at average absorber temperature well below 1000°C. High conversions almost up to the maximum achievable conversion determined by thermodynamic equilibrium were achieved. As the re‐radiation of the absorber is the main contribution to energy losses of the reactor, a cavity design is predicted to be the preferable way to further raise the efficiency. Copyright © 2009 John Wiley & Sons, Ltd.     

Finite time thermal analysis of ground integrated‐collector‐storage solar water heater with transparent insulation cover

A transparent honeycomb insulated ground integrated‐collector‐storage system has been investigated for the engineering design and solar thermal performance. The system consists of a network of pipes embedded in a concrete slab whose surface is blackened and covered with transparent insulation materials (TIM) and the bottom is insulated by the ground. Heat may be retrieved by the flow of fluid through the pipe. A simulation model has been developed; it involves the solution of the two‐dimensional transient heat conduction equation using an explicit finite‐difference scheme. Computational results have been used to determine the effect of such governing parameters as depth as well as pitch of the pipe network and collector material on the thermal performance of the system. The pipe network depth of 10 cm and the TIM cover made of 5 cm compounded honeycomb seem suitable for the proposed system. Solar gain (solar collection efficiency of 30–50% corresponding to collection temperature of 40–60°C) and the diurnal heat storage characteristics of the system are found to be of the right order of magnitude for solar water heating applications. Copyright © 1999 John Wiley & Sons, Ltd.     

Performance test of a box‐type solar cooker: effect of load on the second figure of merit

In this paper thermal performance test experiments for first figure of merit (without load) and second figure of merit (with load) of a box‐type solar cooker were conducted as per Bureau of Indian Standards. The values of second figure of merit (F₂) were determined for different loads of water and the results show that F₂ depends on the quantity of water loaded in a solar cooker. Therefore, it is recommended that the performance test method should specify the amount of water which is to be taken. Copyright © 1999 John Wiley & Sons, Ltd.     

Study on a direct‐expansion solar‐assisted heat pump water heating system

Analytical and experimental studies were performed on a direct‐expansion solar‐assisted heat pump (DX‐SAHP) water heating system, in which a 2 m² bare flat collector acts as a source as well as an evaporator for the refrigerant. A simulation model was developed to predict the long‐term thermal performance of the system approximately. The monthly averaged COP was found to vary between 4 and 6, while the collector efficiency ranged from 40 to 60%. The simulated results were used to obtain an optimum design of the system and to determinate a proper strategy for system operating control. The effect of various parameters, including solar insolation, ambient temperature, collector area, storage volume and speed of compressor, had been investigated on the thermal performance of the DX‐SAHP system, and the results had indicated that the system performance is governed strongly by the change of solar insolation, collector area and speed of compressor. The experimental results obtained under winter climate conditions were shown to agree reasonably with the computer simulation. Copyright © 2003 John Wiley & Sons, Ltd.     

Preliminary investigation of a transcritical CO2 heat pump driven by a solar‐powered CO2 Rankine cycle

In this paper, a transcritical carbon dioxide heat pump system driven by solar‐owered CO₂ Rankine cycle is proposed for simultaneous heating and cooling applications. Based on the first and second laws of thermodynamics, a theoretical analysis on the performance characteristic is carried out for this solar‐powered heat pump cycle using CO₂ as working fluid. Further, the effects of the governing parameters on the performance such as coefficient of performance (COP) and the system exergy destruction rate are investigated numerically. With the simulation results, it is found that, the cooling COP for the transcritical CO₂ heat pump syatem is somewhat above 0.3 and the heating COP is above 0.9. It is also concluded that, the performance of the combined transcritical CO₂ heat pump system can be significantly improved based on the optimized governing parameters, such as solar radiation, solar collector efficient area, the heat transfer area and the inlet water temperature of heat exchange components, and the CO₂ flow rate of two sub‐cycles. Where, the cooling capacity, heating capacity, and exergy destruction rate are found to increase with solar radiation, but the COPs of combined system are decreased with it. Furthermore, in terms of improvement in COPs and reduction in system exergy destruction at the same time, it is more effective to employ a large heat transfer area of heat exchange components in the combined heat pump system. Copyright © 2012 John Wiley & Sons, Ltd.     

Modeling of a solar receiver–reactor for sulfur‐based thermochemical cycles for hydrogen generation

Sulfur‐based thermochemical cycles for hydrogen generation from water have one reaction step in common, which is the decomposition of sulfuric acid, which is one of the most energy‐consuming steps. The present work deals with the development of a dynamic mathematical model of a solar reactor for this key step. One of the core parts of the model is a partial model of the reaction kinetics of the decomposition of sulfur trioxide, which is based on experiments investigating the kinetics of the used catalyst platinum coated on a ceramic solar absorber. Other partial models describe, e.g. the absorption of solar radiation, heat conduction in the absorber, convection between gas and the absorber walls and energy losses due to heat radiation. A comprehensive validation of the reactor model is performed using measured data, which is gained in experiments with a prototype reactor. The operating behavior of the real reactor is compared with the results of the numerical simulation with the model. The validation is, in particular, performed by reproducing the influences of individual parameters on the chemical conversion and the reactor efficiency. The relative deviations between the experimental data and the simulation results are mostly within the range of measurement accuracy. In particular, the good agreement of calculated values of the derived parameters, SO₃ conversion and reactor efficiency with those determined from the experiments qualifies the model for optimization purposes. Copyright © 2010 John Wiley & Sons, Ltd.     

Generation of typical solar radiation data for İstanbul,Turkey

Typical solar radiation data are very important as input in modelling, designing and performance evaluation of solar energy applications. In this study, typical solar radiation data were obtained for ?stanbul, Turkey both from measured data and synthetic generation. Firstly, a test reference year for daily global solar radiation on a horizontal surface was generated using 19 years measured data. The daily global solar radiation as typical data for ?stanbul was presented throughout a year in a tabular form. Secondly, the daily global solar radiation for ?stanbul was expressed with a trigonometric equation using long‐term measured data. It is expected that the typical data and the equation derived will be useful to the designers of solar energy systems as well as those who need to have fairly good estimates of daily global solar radiation for ?stanbul. Copyright © 2003 John Wiley & Sons, Ltd.     

Simulated production of electric power and desalination using Solar‐OTEC hybrid system

Ocean thermal energy conversion (OTEC) is an electric power generation method that utilizes temperature difference between the warm surface seawater and cold deep seawater of ocean. As potential sources of clean‐energy supply, OTEC power plants' viability has been investigated. However, The OTEC system has problems of low efficiency and high investment cost because the temperature difference between the surface and the deep sea is small and it has a long pipe line and high pumping cost for using cold deep water. Therefore, in this present study, the OTEC system is combined with a solar system. It evaluated the thermodynamic performance of Solar‐OTEC Convergence System for the simultaneous production with electric power and desalinated water. The performance analysis of Solar‐OTEC Convergence System was carried out as the fluid temperature, saturated temperature difference and pressure of flash evaporator under equivalent conditions. The results showed that the performance of solar‐open OTEC system is the highest at the flash evaporator pressure of 10 kPa. At this time, the system efficiency, electric power and desalination production enhancement ratios were approximately 3.9, 13.9 and 5.1 times higher than that of the base open OTEC system respectively. Also, the performance of solar‐hybrid OTEC system is the highest at the inflow fluid temperature of evaporator of 80 °C. The system efficiency, electric power and desalination production enhancement ratios were approximately 3.5, 3.5 and 14.5 times higher than that of the base hybrid OTEC system. Copyright © 2016 John Wiley & Sons, Ltd.     

Parametric analysis and yearly performance of a trigeneration system driven by solar‐dish collectors

Solar‐driven polygeneration systems are promising technologies for covering many energy demands with a renewable and sustainable way. The objective of the present work is the investigation of a trigeneration system, which is driven by solar‐dish collectors. The examined trigeneration system includes an organic Rankine cycle (ORC), which operates with toluene, and an absorption heat pump, which operates with LiBr/H₂O. The absorption heat pump is fed with heat by the condenser of the ORC, which operates at medium temperature levels (120°C to 150°C). The absorption heat pump produces both useful heat at 55°C and cooling at 12°C. The ORC produces electricity, and it is fed by the solar dishes. The examined ORC is a regenerative cycle with superheating. The total analysis is performed with a developed model in Engineering Equation Solver (EES). The system is investigated parametrically for different ORC heat‐rejection temperatures, different superheating levels in the turbine inlet, and various solar‐beam irradiation levels. Furthermore, the system is investigated on a yearly basis for the climate conditions of Athens (Greece) and for Belgrade (Serbia). It is found that the yearly system energy and exergy efficiencies are 108.39% and 20.92%, respectively, for Athens, while 111.38% and 21.50%, respectively, for Belgrade. The values over 100% for the energy efficiency are explained by the existence of a heat pump in the examined configuration. For both locations, the payback period is found close to 10 years and the internal rate of return close to 10%. The final results indicate that the examined configuration is a highly efficient and viable system, which operates only with a renewable energy source.