• Energy Research

Abstract The paper presents a review of publications devoted to the use of thermal-electric analogy in the analyses of solar collectors’ performance, with special focus on the shortcomings of the proposed models of the equivalent thermal network (ETN). Additionally, the study describes the principles of construction of the ETN, especially for large-scale solar thermal circuits. The process of heating the working medium flowing through the collector battery was also shown. The ETN model was presented both analytically (nodal potential method) and with the use of the Simulink package (MATLAB), which made it possible to investigate the effect of operating conditions on the parameters of the solar collector.

Abstract The effects of solar systems operation can be compared only under very similar weather conditions. Diagnostics of the solar systems requires unequivocal determination of solar irradiation. Development of a method for precise identification of solar radiation day time profile is needed, as the methods used so far in the cloud cover determination are not satisfactory. The paper presents two optional methods, developed by the authors, for identification of the solar radiation profile. Advantages and disadvantages of the methods are also specified.

Abstract The flat-plate solar collector has been treated as a regulation object. An analog model of dynamics of the collector, based on the equivalent thermal network (ETN) method, has been proposed. The solar collector has been presented as an electrical circuit and has been calculated as a four-terminal network. Model was based on the construction and operating parameters of the collector, which allowed to shape the dynamics of work already at the stage of its design. An innovative solution has been proposed that has not yet appeared in the subject. The analog model has been verified on the digital model determined by experiment with using the parametric identification method. The models are to be used in designing of systems and algorithms for controlling of operation of hybrid supply systems. Transfer functions and step responses for both collector models (analog and digital) has been analyzed.

The parametric identification method was used for heat exchanger dynamics investigation. The transfer function of numerical models demonstrated oscillatory character in many cases. The thermo-electric analogy was used for transient heat transfer representation as the equivalent thermal network (ETN). The mutual changing of potential and kinetic energy in the electric network correspond to the oscillation. For this reason thermal capacity C, accumulating potential energy and thermal inductivity L – new element, accumulating kinetic energy were introduced in the ETN. The boundary values of L, by which oscillatory character of ETN should be observed and the values of L were calculated.