To evaluate the overheating temperature of solar cells in concentrator photovoltaic (CPV) modules during solar radiation conversion, we propose a method for determining the thermal resistivity between the solar cell and its environment (r(th)) in laboratory conditions at room temperature and in the absence of forced ventilation. The essence of this method is the measurement of the temperature change of the solar cells inside the CPV module under thermal load generated by direct current flow through the solar cell. The change in temperature of the solar cells in CPV modules under thermal load is determined by calculating the voltage difference across the module contacts during fast measurements of the I-V curve at room temperature and the I-V curve when the solar cells of the module are heated by direct current. The developed methodology eliminates uncertainties associated with the location of temperature sensors and unstable meteorological conditions. In the present work, this technique is used to study the overheating temperature of solar cells of "Small lenses, Multijunction cells, All from glass, Lamination, Fresnel, Optics, Concentration" design CPV modules varying in materials and thicknesses of heat sinks. In laboratory conditions, we determined the values of r(th) of small CPV modules and full-size CPV modules, containing, respectively, 8 and 128 pairs of Fresnel lens-triple-junction InGaP/InGaAs/Ge solar cells soldered to a metal heat sinks of similar design. Copper or steel was used as materials for the heat sinks.

The paper presents a promising solution for photovoltaic modules that provides overcoming the main conceptual limitation for the concentrator concept in photovoltaics—the impossibility to convert diffused (scattered) solar radiation coming to the panel of sunlight concentrators. The design of a hybrid concentrator-planar photovoltaic module based on heterostructure solar cells: A3B5 triple-junction and Si-HJT is presented. The results of initial outdoor studies of the module output characteristics are discussed and estimates of its energy efficiency are given.

The characteristics of concentrator photovoltaic modules based on a 120 × 120 mm Fresnel lens with secondary concentrators in the form of hollow aluminum focons with internal mirror walls are studied. The optimal sizes and configurations of secondary concentrators are determined to increase the efficiency of focusing systems of concentrator modules. The maximum value of the allowable misorientation angle was obtained, equal to ±0.75°, corresponding to a power drop to a level of 90

The paper presents a promising solution for photovoltaic modules that provides overcoming the main conceptual limitation for the concentrator concept in photovoltaics - the impossibility to convert diffused (scattered) solar radiation coming to the panel of sunlight concentrators. The design of a hybrid concentrator-planar photovoltaic module based on heterostructure solar cells: A3B5 triple-junction and Si-HJT is presented. The results of initial outdoor studies of the module output characteristics are discussed and estimates of its energy efficiency are given.

The characteristics of concentrator photovoltaic modules based on a 120 × 120 mm Fresnel lens with secondary concentrators in the form of hollow aluminum focons with internal mirror walls are studied. The optimal sizes and configurations of secondary concentrators are determined to increase the efficiency of focusing systems of concentrator modules. The maximum value of the allowable misorientation angle was obtained, equal to ±0.75°, corresponding to a power drop to a level of 90% relative to the maximum power value of the concentrator photovoltaic module at normal beam incidence. For a module with the most efficient focon 40 mm high and side face slope angles of 17°, the maximum efficiency of the module under laboratory conditions was obtained, equal to 35.15%. Under natural conditions, the efficiency value reached 33.8 The results obtained correspond to the level achieved for the best foreign analogues.

A combined module that combines a concentrator with planar photovoltaic circuits provides energy conversion of both parts of global terrestrial radiation: direct sunlight by concentrator solar cells and scattered (diffuse) sunlight by planar (non-concentrator) photoconverters. The decrease in Fresnel lens concentrating ability is usually associated with imperfections in the optical refractive surfaces, where some part of the direct light, which arrives normal to the surface of the Fresnel lens and is intended to be concentrated, becomes scattered and directed off the highly efficient concentrator solar cell. The diffuse light flux propagates inside the volume of the combined photovoltaic module. This flux undergoes multiple reflections from the structural elements, is partially absorbed, and ultimately reaches the photoconverters of the planar circuit. Thus, two types of diffuse light impinge the planar circuit: "external" from the atmosphere and "internal" produced by the Fresnel lens from direct light. This Letter proposes a method for determining the diffuse properties of sunlight concentrators such as Fresnel lens.

The measuring capabilities of a solar radiation simulator and computer simulation have been used in the study of concentrator photovoltaic modules with three-junction solar cells based on the GaInP/GaInAs/Ge structure. The possibility of using two methods together is shown to explain the processes occurring during the conversion of radiation in the concentrator—the solar cell system—and to predict the module parameters when the external focusing conditions change. The contribution of lateral currents to the formation of the photocurrent of the solar cell in the module is established. The possible causes of energy losses due to internal resistance in solar cells are determined for the Fresnel lens–cascade solar cell system. The output characteristics of the module are calculated using the method of computer simulation for various spectra of incident radiation.

The results of research and development of solar concentrator photovoltaic modules with an area of 0.5 m 2 based on Fresnel lenses with secondary solar concentrators in the form of inverted pyramids and multi-junction solar cells at the focus of Fresnel lenses are presented. The developed concentrator photovoltaic modules provide a high concentration ratio (up to 700×) and an optimal temperature regime for the operation of multi-junction solar cells. The photovoltaic modules are characterized by a high conversion efficiency over 32%, which matches the highest world level for such concentrator modules.

Предложена методика для исследования тепловых свойств фотоэлектрических концентраторных модулей в помещении в затемненных условиях, сочетающая в себе процедуру нагрева модуля за счет пропускания постоянного тока и последующего быстрого измерения вольт-амперных характеристик, в течение которого температура фотоэлементов не успевает значительно измениться за счет теплоемкости материала. Были проведены сравнения характеристик шести типов концентраторных модулей, отличающихся конструкцией, размерами и материалами теплоотводов. Для концентраторных модулей больших размеров исследовано влияние пространственного расположения модулей на эффективность теплосброса. Ключевые слова: концентраторные фотоэлектрические модули, тепловое сопротивление, p-n-переход, солнечные фотоэлементы, теплоотвод.

In this paper, a technique is proposed to study the thermal properties of concentrator photovoltaic modules indoor in darkened conditions. The technique combines the procedure of heating the module by passing direct current and the subsequent rapid measurement of the current–voltage characteristics, during which the solar cell temperature does not have time to change significantly due to the heat capacity of the material. The characteristics of six types of concentrator modules differing in design, sizes, and materials of heat sinks are compared. The influence of spatial arrangement of modules on the efficiency of heat removal was studied for concentrator modules of large sizes.

The paper outlines the results of research and development of solar concentrated photovoltaic modules with an aperture area of 0.5 m^2. Module design was based on Fresnel lenses with inverted pyramids as secondary concentrators of solar irradiance, and multijunction solar cells located in the focus of Fresnel lens. The developed modules are characterized with up to 700X solar concentration ratio and optimal operational thermal regime for solar cells. The efficiency of developed photovoltaic modules exceeds 32% which makes them on par with modules of the similar design developed and manufactured globally.

To study concentrator photovoltaic modules with GaInP/GaInAs/Ge triple-junction solar cells we used the measurement capabilities of a solar simulator accompanied by a computer simulation. The comparison of values of parameters for a module, Fresnel lens and triple-junction solar cell, obtained both experimentally and computed by means of the computer simulation, demonstrated good matching of results and high precision of calculations using the software. This allows to use both methods simultaneously to explain processes of radiation conversion in the system concentrator–solar cell and predict the values of module parameters under various external focusing conditions. The utilization of both methods revealed the impact of lateral currents on the total photo current of solar cells inside a module. For the system Fresnel lens–multi-junction solar cell we determined the possible cases of power loses associated with internal resistance of the cells. Output parameters of the module under varying spectrum of incoming radiation has been calculated using software.

High-efficiency concentrator photovoltaic modules have been developed and fabricated. The modules include a lens panel based on 32 Fresnel lenses (12 × 12 cm each), 32 multi-junction solar cells with secondary concentrators in the form of phocons, and heat-removing electrically insulating boards based on an aluminum oxide ceramic placed on the backside aluminum base. Efficiency measurements of a 0.46-m 2 module under a pulsed sunlight simulator (AM1.5D, 1000 W/m 2 ) yielded a value of 32.3%. An efficiency of 33.9% was obtained for a subunit with an area of 144 cm 2 .

The results of studies of characteristics of heat-removing electrical insulating plates of different designs based on heat-conducting AlN and Al 2 O 3 ceramics and aluminum-oxide plates based on aluminum plates are presented. Thermophysical parameters of the heat-removing plates were assessed by measuring the temperature of p – n junctions of the photoelectric converters mounted on the plates with thermal load applied to them. It was found that the minimum overheating temperature of p – n junctions, 45°C, was observed at the supplied thermal power of 13 W, when the photoelectric converters were installed on the AlN ceramics. In photoelectric converters installed on the Al 2 O 3 ceramics, the overheating of p – n junctions was 49°C, while it reached 70°C on the aluminum-oxide substrate.

High efficiency concentrator photovoltaic modules have been designed and manufactured. Each module consists of a lens panel with 32 Fresnel lenses 12x12 cm2 each, 32 multijunction solar cells with focons as secondary concentrators and electro insulated heatsinks made of alumina ceramics mounted on aluminum sheet. The module with a total area of 0.46 m2 measured under solar simulator with a spectrum AM 1.5D and irradiance 1000 W/m2 demonstrated an efficiency of 32.2%. Meanwhile, a single submodule with an area of 144 cm2 demonstrated an efficiency equal to 33.9%.

Concentrator photovoltaic units based on Fresnel lenses and secondary concentrators—hollow focons made of sheet aluminum—have been developed. To increase the efficiency of sunlight conversion, the optimal configuration of focons was determined and the photoelectric characteristics of the units were examined. The use of focons provided an increase in the admissible misorientation angle of the unit from ±0.45° (without a focon) to ±0.8° (with a focon) and in the unit efficiency from 29.2% (without a focon) to 32.8% (with a focon).

In the article the results of investigation of characterics of electro insulated heatsinks of different design are presented. For the material of the heatsinks AlN and Al2O3 ceramics along with alumina were chosen. Thermal characteristics of the heatsinks has been studied by measuring temperature of p-n junctions of solar cells mounted on heatsinks under thermal loading. The minimum overheating temperature of p-n junction was 45°C with input thermal power equal 13 W, when solar cells were mounted on AlN ceramic. In case of using Al2O3 ceramic and alumina heatsinks the temperatures were 49°C, and 70°C respectively.

Concentrator photovoltaic module with Fresnel lenses as primary optical elements and focons made of sheet aluminum as the secondary optical concentrators has been developed. To enhance the efficiency of conversion of solar energy into electrical the optimal focon design have been determined and the photoelectric characteristics of a module with such focons investigated. Implementation of focons in module design allowed to increase acceptance angle of the latter from ±0.45% (without focons) up to ±0.85% (with focons) and to increase the efficiency from 29% to 32.8%.

AbstractThe results of studying the effect of various conditions of heat dissipation on heating and temperature distribution in components of concentrator photovoltaic modules are reported. The modules based on Fresnel lenses and triple-junction solar cells InGaP/GaAs/Ge mounted on copper and steel heat sinks are studied. In order to determine the thermal characteristics, we use a method, which makes it possible to measure the temperature of the p–n junctions in the solar cells under laboratory conditions upon the simulation of thermal processes arising in the course of operation of the module under typical conditions. Further, the above temperature is used to calculate the value of the thermal resistance for a system consisting of a solar cell and the surrounding medium. The thermal processes in the module are simulated by transferring current through the solar cells in the forward-bias direction. The value of heating of the solar cells is determined by comparing the forward-voltage drops measured at the time of its rapid application or switching-off under various conditions of heat removal. The conditions of heat removal are varied using the generator’s air flow.

AbstractThe influence exerted by the heat removal conditions on the extent of overheating of photovoltaic converters of high-power (>10^3 W/cm^2) laser light has been studied. The temperature of the p–n junction of photovoltaic cells was measured by recording the instantaneous values of the open-circuit voltage generated by laser light. The effect of cooling in high-efficiency photovoltaic cells (efficiency = 55%) via removal of a substantial part of absorbed optical power by the photocurrent into the external load was demonstrated. It was shown that, at laser radiation power of 2.5 W, the overheating of a photocell with an area of 1.7 × 10^–3 cm^2 relative to the copper heatsink temperature is 48°C in the no-load conditions and 30°C in operation with the optimal load.