Alexander V. Chekalin

Progress In Developing HCPV Modules Of SMALFOC-Design

This work presents a module generation which has been named as “SMALFOC module design”. The abbreviation reflects the main features of the modules: Small-size concentrators; Multi-junction cells; “All-glass” structure; Lamination technology; Fresnel Optics for Concentration. Investigated modules have revealed a quite low over-heating temperature of cells in the MPP regime of operation and a real way for increasing the PV efficiency, if the rear glass base is supplied with an antireflection coating. Outdoor and high/low temperature tests have shown a good potential for long-term operation of such a type of modules.

Evaluation of the PV Cell Operation Temperature in the Process of Fast Switching to Open-Circuit Mode

A procedure for measuring the overheating temperature (ΔT ) of a p-n junction area in the structure of photovoltaic (PV) cells converting laser or solar radiations relative to the ambient temperature has been proposed for the conditions of connecting to an electric load. The basis of the procedure is the measurement of the open-circuit voltage (VOC ) during the initial time period after the fast disconnection of the external resistive load. The simultaneous temperature control on an external heated part of a PV module gives the means for determining the value of VOC at ambient temperature. Comparing it with that measured after switching OFF the load makes the calculation of ΔT possible. Calibration data on the VOC = f(T ) dependences for single-junction AlGaAs/GaAs and triple-junction InGaP/GaAs/Ge PV cells are presented. The temperature dynamics in the PV cells has been determined under flash illumination and during fast commutation of the load. Temperature measurements were taken in two cases: converting continuous laser power by single-junction cells and converting solar power by triple-junction cells operating in the concentrator modules.

Temperature of solar cells with regard to photoactive and non-photoactive light absorption in concentrator PV modules

A new method has recently been proposed by us for accurate measurement of the solar cell temperature in any operational regime, in particular, at a maximum power point (MPP) of the I-V curve (Tp–nMPP). For this, fast switching of a cell from MPP to open circuit (OC) regime is carried out and open circuit voltage Voc is measured immediately (within about 1 millisecond), so that this value becomes to be an indicator of Tp–nMPP. In the present work, we have considered a practical case, when a solar cell is heated not only by absorption of light incident upon its surface (called “photoactive” absorption of power), but also by heat transferred from structural elements surrounding the cell and heated by absorption of direct or diffused sunlight (“non-photoactive” absorption of power with respect to a solar cell). This process takes place in any concentrator module with non-ideal concentrators. Low overheating temperature of the p-n junction (or p-n junctions in a multijunction cell) is a cumulative parameter ch...

Current flow and efficiencies of concentrator InGaP/GaAs/Ge solar cells at temperatures below 300K

The forward dark current density – voltage (J-V) characteristic is one of the most important characteristics of multi-junction solar cells. It indicates that the mechanisms of current flow in the space charge region of photoactive p-n junctions. If one is to idealize the optical and electrical (coupling) elements of the solar cells, it is the J-V characteristic that determines the theoretically possible efficiency of the solar cell. In this paper, using the connection between the dark J-V and photovoltaic (η-Jg) efficiency – generated current density characteristics, the effect of current transport mechanisms in the space charge on the efficiency of multi-junction solar cells was investigated in the temperature range of 300 – 80 K. In the experimental J-V and η-Jg curves of the multi-junction solar cells, segments corresponding to the dominant current transport mechanisms were identified. The developed method, based on the analysis of forward dark J-V characteristics, makes it possible to identify the par...

HCPV modules of SMALFOC design in versions for PV and PV/T operation

The recently developed HCPV modules of SMALFOC design (Small lenses, Multijunction cells, All from glass, Lamination, Fresnel, Optics, Concentration) are characterized by structural and technological similarities with flat plate modules. In the paper, two variants of module usage are considered: (i) version for an “ordinary” generation of electricity; (ii) version for operation as a hybrid system, where a combined PV/Thermal approach is realized for producing both electricity and heated water. Water as a heat removing fluid is made to flow through a flat structure applied to the laminated back side of a HCPV module. PV and PV/T performances of the modules at different operation conditions are presented.

Influence of Heat Dissipation Conditions on the Characteristics of Concentrator Photoelectric Modules

The 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.

Indoor modeling of the wind pressure in solar installations with flat and step-like frames for HCPV modules

As a rule, the HCPV modules are mounted on solar trackers in a form of a flat panel. Wind pressure is one of the key factors limiting the operation capabilities of such type solar installations. At the PV Lab of the Ioffe Institute, the sun-trackers with step-like frame for modules have been proposed and developed, which have a potential for significant reduction of wind pressure. Such a reduction is realized in a wide range of the frame tilt angles the most typical for day-light operation of solar installations. In the present work, theoretical consideration and indoor experiments with mechanical models of installation frames have been carried out. A wind tunnel has been used as an experimental instrument for quantitative comparison in conventional units of expected wind loads on module frames of different designs.