A solar thermoelectric refrigerator

It is shown that a thermoelectric generator, which draws its heat from the Sun, is a particularly suitable source of electrical power for the operation of a thermoelectric refrigerator. The theory of the combined thermoelectric generator and refrigerator is derived and the ratio of the numbers of thermocouples needed for the two devices is determined. It is found that this ratio can, in principle, be as low as unity, even for unconcentrated solar radiation, though practical considerations indicate that a ratio of 4:1 is preferred in this case. A 4-couple thermoelectric generator has been used to power a single-couple refrigerator. Temperatures below 0°C have been achieved for a temperature difference across the generator of about 40K.     

Experimental investigation on a thermoelectric refrigerator driven by solar cells

Experimental investigation and relevant analysis on a solar cell driven, thermoelectric refrigerator has been conducted. To make the device portable, daytime use and nighttime use of the refrigerator are treated in different ways. Solar cells are applied to power the refrigerator in the day. Storage battery, assisted by an a.c. rectifier, is used to provide electric energy in the night and in cloudy or rainy days. Experiment results demonstrate that the unit can maintain the temperature in the refrigerator at 5–10 °C, and have a COP about 0.3. It is expected that the refrigerator would be potential for cold storage of vaccine, foodstuffs and drink in remote area, or outdoor applications where electric power supply is absent.     

Experimental investigation and analysis on a thermoelectric refrigerator driven by solar cells

Experimental investigation and performance analysis on a solar cell driven, thermoelectric refrigerator has been conducted. Research interest focused on testing the system performance under sunshine. Experiment results demonstrated that the unit could maintain the temperature in the refrigerator at 5–10°C, and have a COP about 0.3. Further analysis indicated that the performance of the system is strongly dependent on intensity of solar insolation and temperature difference of hot and cold sides for the thermoelectric module, etc. There exist optimum solar insolation rates, which let the cooling production and COP achieve maximum value, respectively. It was expected that the refrigerator would be potential for cold storage of vaccine, food and drink in remote area, or outdoor conditions where electric power supply is absent.     

Design considerations for a thermoelectric refrigerator

Heat transfer at a finite rate and electrical resistive losses are necessarily irreversible processes and unavoidable in a thermoelectric device. It is shown that the internal and exernal irreversibilities in a thermoelectric refrigerator may be characterized by a single parameter, named the device-design parameter. The presence of this parameter in the equations for the refrigeration effect and the maximum input power, shows that a real refrigerator has a smaller cooling capacity and needs more input power than an ideal refrigerator.     

Thermodynamic investigation for developing solar refrigerator

The present study uses basic thermodynamic relationships capable of assisting in the design of a solar refrigerator for agricultural products refrigeration. The data used for calculation are daily average meteorological data collected over a period of five years in Hun city in Lybia, taking 1988 as a reference year and 2000 to 2003 for comparison. The investigated adsorption refrigeration cycle consists mainly of generator, condenser, evaporator and adsorber. The adsorption refrigeration cycle is assumed to be accomplished by the removal of heat through the evaporator at low pressure and heat rejection through the condenser at high pressure. The products refrigeration requires a temperature from 2 to 8°C. In these calculations, however, a temperature range from 0 to 8°C was taken into account in order to cover any losses. The calculations resulted in an average generator energy, Qg, of 4.59 kWh/m² per day, an average ammonia consumption, ma, of 0.0279 mass of ammonia per unit mass of activated carbon. The average coefficient of performance, COP, for the reference year was 0.555 and remained almost constant at 0.530 in the comparison years. The average evaporation energy Qe, was 2.460 kWh/m² per day for the reference year and did not change in comparison years.     

Design and testing of a microprocessor-controlled portable thermoelectric medical cooling kit

Blood cells, vaccines, and other drugs and biological products should be kept at a temperature within certain range. In this paper, a medical thermoelectric cooling kit is introduced. The kit keeps medical products at temperatures between 6 and 10 °C while being stored or transported. This range is within the standards recommended by WHO to keep biological, medical and food products. Tests were carried out under various environmental temperatures in laboratory conditions as well as outside the laboratory and on a transportation vehicle. Under all these conditions, the kit provided cooling at a satisfactory level. This paper presents the technical specifications of the kit, theory of its operation, and test results. The kit is supported with a microprocessor unit. The block diagram of the microprocessor program is also presented in the paper.     

Thermal,environmental, and cost analysis of effective solar portable vaccine refrigerator by COMSOL Multiphysics

A thermal, environmental, and cost analysis of an effective solar portable vaccine refrigerator is presented. Combining Peltier module with appropriate finned heat sink, choosing advanced software for thermal analysis, evaluating the environmental impacts of the combination, and comparing with other refrigerators are the key objectives of the present research. The Peltier module and the finned heat sink are professionally designed to enhance the thermal performance of the solar portable vaccine refrigerator. A competent solar panel is proposed to power the Peltier module for clean thermal energy. A set of equations are applied to calculate the overall surface efficiency and the total heat dissipation out of the refrigerator. COMSOL Multiphysics is employed to compute the temperature gradient and the heat flux of the Peltier module with the finned heat sink at steady‐state process. The thermal results show that the maximum overall surface efficiency is 78% with one Peltier module and 10 fins. The environmental results show that the values of the carbon footprint and total energy consumption of the solar portable vaccine refrigerator are reasonable according to the sustainability assessment methodology. The results also show that the manufacturing cost of the solar portable vaccine refrigerator is affordable as compared to others.     

Design and analysis of solar thermoelectric power generation system

This article reports on the design and performance analysis of a solar thermoelectric power generation plant (STEPG). The system considers both truncated compound parabolic collectors (CPCs) with a flat receiver and conventional flat-plate collectors, thermoelectric (TE) cooling and power generator modules and appropriate connecting pipes and control devices. The design tool uses TRNSYS IIsibat-15 program with a new component we developed for the TE modules. The main input data of the system are the specifications of TE module, the maximum hot side temperature of TE modules, and the desired power output. Examples of the design using truncated CPC and flat-plate collectors are reported and discussed for various slope angle and half-acceptance angle of CPC. To minimize system cost, seasonal adjustment of the slope angle between 0° and 30° was considered, which could give relatively high power output under Bangkok ambient condition. Two small-scale STEPGs were built. One of them uses electrical heater, whereas the other used a CPC with locally made aluminum foil reflector. Measured data showed reasonable agreement with the model outputs. TE cooling modules were found to be more appropriate. Therefore, the TRNSYS software and the developed TE component offer an extremely powerful tool for the design and performance analysis of STEPG plant.     

An experimental investigation on electrical performance and characterization of thermoelectric generator

Thermoelectric generator (TEG) is an attractive renewable energy source that utilizes waste heat energy from various sources to produce electricity. In this paper, a novel method has been proposed to investigate and characterize the TEG module by determining the exact maximum power point (MPP) and estimate the TEG module dynamic parameters. A DC-DC boost converter with a simple control method is proposed to obtain I-V and I-P characteristics and extract the exact MPP of the TEG module. The electrical performance and dynamic parameters such as Seebeck coefficient and internal resistance of the TEG module have been estimated at the MPP. MATLAB software package is used to model and simulate the complete system. Then, by using a low-cost Arduino microcontroller and a standard TEG module (HZ-14HV), a test rig is built to examine the electrical performance of the TEG. A comparison among simulation, experimental, and manufacturing data sheet is done to validate the accuracy of the proposed system. The proposed system tests and characterizes a TEG module at five values of temperature differences in the range from 377 K to 457 K and analyses the MPP generated in the range from 5 to 13.8 W . The obtained results confirm that there is good agreement among the simulation, experimental, and data sheet. To the best of our knowledge, it is the first time to use the boost converter to estimate the electrical characteristics and the dynamic parameters of the TEG. It can be said that the proposed DC-DC boost converter with the suggested control method is helpful for testing commercial TEG modules before implementing in a TEG system.     

半导体制冷电极工作性能的数值模拟

通过对稳定情况下半导体制冷器P型元件的工作模型分析,给出了其工作性能的分析解和数值解.结果显示对于单级制冷器,其制冷元件工作在较大温差下时,考虑温度对材料性能的影响是必要的.     

Design optimization of thermoelectric devices for solar power generation

We present an improved theoretical model of a thermoelectric device which has been developed for geometrical optimization of the thermoelectric element legs and prediction of the performance of an optimum device in power generation mode. In contrast to the currently available methods, this model takes into account the effect of all the parameters contributing to the heat transfer process associated with the thermoelectric device.The model is used for a comparative evaluation of four thermoelectric modules. One of these is commercially available and the others are assumed to have an optimum geometry but with different design parameters (thermal and electrical contact layer properties).Results from the model are compared with experimental data of the commercial thermoelectric module in power generation mode with temperature gradient consistent with those achievable from a solar concentrator system. These show that it is important to have devices optimized specifically for generation, and to improve the contact layer of the thermoelements accordingly.     

Experimental investigation of a novel steam ejector refrigerator suitable for solar energy applications

The paper presents the results of an experimental investigation of a novel steam jet refrigerator suitable for solar energy applications. The primary flow of the ejector is controlled using a spindle in order to provide fine tuning and for ejector operation as well as optimum coefficient of performance. The influence of the spindle position, and the boiler temperature, as well as that of evaporating temperature which denotes the cooling load temperature, on the performance of the ejector is assessed.     

Design construction and test run of a solar powered solid absorption refrigerator

The intermittent system used CaCl₂ and NH₃ as absorbent and refrigerant, respectively. The absorbent was mixed with 20% by weight of CaSO₄, as cement, and prepared as hard porous granules of 5–10 mm sizes.The double glazed collector/absorber/generator unit used clear PVC and plane glass sheets, with the former as the outer cover. Overall collector plate exposed area was 1.41 m². A stagnant water evaporative condenser was designed and constructed of re-inforced sandcrete, with steel condenser tubes, and was coupled to the system. The evaporator was a spirally coiled steel tube immersed in a pool of stagnant water. Absorbent cooling during absorption was by natural convection of air over the collector plate and tubes, coupled with sky radiation. All construction, except the collector covers and porous condenser walls, were of steel sheets and tubes.Ambient temperatures during absorption and generation ranged over (25°–35°C). Tests indicated that cooling capacities of the NH₃ condensed were around 714 KJ m⁻², while effective cooling obtained was equivalent to an ice production of 1 kg m⁻², per day.     

A low power,eco-friendly multipurpose thermoelectric refrigerator

There has been an immense endeavor to mitigate global warming in spite of which it has only been worse. This paper presents the design and implementation of a low power and eco-friendly refrigeration system using the thermoelectric effect. The conventional refrigerators make use of complex mechanisms which involves synchronous operation of various units, namely the compressor, condensers, expansion valves, evaporator, refrigerant and so on. But a thermoelectric refrigerator exploits the principle of the Peltier effect, thus avoiding the utilization of these complex components. This even helps curb the release of harmful chlorofluorocarbons (CFCs) into the atmosphere which contributes to the increase in global temperature. Moreover, the temperature can be controlled and set to required values with the help of a microcontroller. Hence, this can be used both for domestic and commercial purposes. The unit does not eject any harmful gases. Therefore, the heat expelled from the unit can be tapped for heating utilities, making the use of this device versatile in its application. Thus this proposal aims not only at reducing the air pollutants by not contributing to it but also at reducing the power consumption.     

Design, development and testing of a portable parabolic solar kitchen

In this project we describe the design, manufacture and testing of a new portable solar kitchen with a large, parabolic solar reflector that folds up into a small volume. Technical trials carried out with a prototype have determined that the solar kitchen reaches an average power scale of 175 W, with an energy efficiency of 26.6%. This power scale provides sufficient energy to cook a simple meal for two people in an average time of 2 h. Improvements in the design have reduced the weight of the solar kitchen to less than 5 kg and the assembly and disassembly times to 2 and 1 min, respectively. Moreover, its competitive price (48.62 €) encourages the substitution of solar energy for conventional energy. The parabolic solar kitchen described here thus provides a portable, inexpensive, environmentally friendly food heating system that can improve the quality of life of needy people in the Third World and reduce consumption of conventional energy.     

Development of a thermoelectric refrigerator with two-phase thermosyphons and capillary lift

A thermoelectric domestic refrigerator has been developed, with a single compartment of 0.225 m³, for food preservation at 5 °C. The cooling system is made up of two equal thermoelectric devices, each composed of a Peltier module (50 W) with its hot side in contact with a two-phase and natural convection thermosyphon (TSV) and a two-phase and capillary lift thermosyphon (TPM), in contact with the cold side.The entire refrigerator has been simulated and designed using a computational model, based on the finite difference method. Subsequently an experimental optimization phase of the thermosyphons was carried out, until thermal resistance values of R_TSV = 0.256 K/W and R_TPM = 0.323 K/W were obtained. These values were lower than those obtained with finned heat sinks.Finally, a functional prototype of a thermoelectric refrigerator was built, and the results which were obtained demonstrate that it is able to maintain a thermal drop (Ambient Temperature–Inside Temperature) of 19 °C. The electric power consumption at nominal conditions was 45 W, reaching a COP value of 0.45. The study demonstrated that by incorporating these two-phase devices into thermoelectric refrigeration increases the COP by 66%, compared with those which use finned heat sinks.     

Development of a hybrid refrigerator combining thermoelectric and vapor compression technologies

A domestic refrigerator with three compartments has been developed: refrigerator compartment, at 4 °C (vapor compression cooling system); freezer compartment, at −22 °C (vapor compression cooling system); and a new super-conservation compartment, at 0 °C (thermoelectric cooling system). The thermoelectric system designed for the super-conservation compartment eliminates the oscillation of its temperature due to the start and stop compressor cycles, obtaining a constant temperature and thus, a better preservation of the food.For the design and optimization of this application, a computational model, based in the numerical method of finite differences, has been developed. This model allows to simulate the complete hybrid refrigerator (vapor compression–thermoelectricity). The accuracy of the model has been experimentally checked, with a maximum error of 1.2 °C for temperature values, and 8% for electric power consumption.By simulations with the computational model, the design of the refrigerator has been optimized, obtaining a final prototype highly competitive, by the features on food preservation and power consumption: 1.15 kW h per day (48.1 W) for an ambient temperature of 25 °C. According to European rules, this power consumption value means that this new refrigerator could be included on energy efficiency class B.     

Absorbing photonic crystals for silicon thin-film solar cells: Design,fabrication and experimental investigation

In this paper, we present the integration of an absorbing photonic crystal within a thin-film photovoltaic solar cell. Optical simulations performed on a complete solar cell revealed that patterning the hydrogenated amorphous silicon active layer as a 2D photonic crystal membrane enabled to increase its integrated absorption by 28 % between 300 and 720 nm, comparing to a similar but unpatterned stack. In order to fabricate such promising cells, we developed a high throughput process based on holographic lithography and reactive ion etching. The influences of the parameters taking part in those processes on the obtained patterns are discussed. Optical measurements performed on the resulting “photonized” solar cell structures underline the regularity of the 2D pattern and a significant absorption increase above 550 nm, similarly to what is observed on the simulated absorption spectra. Moreover, our patterned cells are found to be robust with regards to the angle of incidence of the light.     

Theory and experimental investigation of a weir-type inclined solar still

A weir-type solar still is proposed to recover rejected water from the water purifying systems for solar hydrogen production. This consists of an inclined absorber plate formed to make weirs, as well as a top basin and a bottom basin. Water is flowed from the top basin over the weirs to the bottom collection basin. A small pump is used to return the unevaporated water to the top tank. Hourly distillate productivity of the still with double- and single-pane glass covers was measured and the latter showed higher production rates. The average distillate productivities for double- and single-pane glass covers are approximately 2.2 and 5.5 l/m²/day in the months of August and September in Las Vegas, respectively. Mathematical models that can predict the hourly distillate productivity are developed. These compared well with the experimental results. Productivity of the weir-type still with a single-pane glass was also compared with conventional basin types tested at the same location. The productivity of the weir-type still is approximately 20% higher. The quality of distillate from the still is analyzed to verify the ability of the still to meet the standards required by the electrolyzers.     

The theoretical and experimental investigation of the phase-change solar thermosyphon

The paper is concerned with the study of two-phase solar thermosyphon for domestic hot water (SDHW). Due to a combination of ideas of the heat pipe and classical thermosyphon, the heat transfer in the proposed installation is to be realised by the liquid - gas phase change, what should increase significantly both the heat efficiency of the system and the system applicability.