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• The laboratory and full-scale prototypes of the novel solar air collector were tested. • Fuel economy achieved in tests varies from 11% to 81% depending on weather conditions. • The increased concentration ratio of about 1.4 was obtained without a sun-tracking device. • The mathematical model of the collector was validated against experimental results. • The model was used to define the rational design parameters of the full-scale prototype. The application of greenhouse technologies is rapidly expanding in China and other regions of the world with the continental climate. Such technologies are characterized by a considerable consumption of fossil fuels, especially in winter periods. Various renewable energy technologies are used to reduce the energy demand in greenhouses, including solar heating. Simpler designs of water or air solar collectors are preferred without sun-tracking devices and reduced dimensions and weight. In this work, a novel solar multi-surface air collector with double-receiver tubes, which does not require a sun-tracking device is proposed and has increased concentration ratio and sun rays convergence and reduced thermal losses. The laboratory and full-scale prototypes of the proposed novel collector were manufactured and tested in laboratory conditions during the December-January period as a part of the greenhouse with the active-passive ventilation wall and latent thermal storage, located in the Beijing Region. Results of experiments demonstrate that the solar collector increases the average temperatures of the greenhouse north wall inner surface by 7.5 °C, indoor air during the night-time by 1.8 °C and indoor soil by 1.5 °C. The novel collector provided active heat gains of 11.831 GJ during the December-January period and satisfied from 11% to 81% of the heat load. A lumped parameter mathematical model of the proposed collector was developed, and the comparison of simulation results and experimental data demonstrate its high accuracy in prediction of the collector performance. The model was used to study the influences of outdoor meteorological parameters, air velocity in the receiver tubes and their length on the performance of the collector. This data was used to determine the rational design parameters and air velocity of the full-scale collector. The model was also used to rationalize the variation of air velocity in the receiver tube during the day. [ABSTRACT FROM AUTHOR]

• Rapid calculation of physical dimensions of passive solar greenhouses was derived. • The correctness of the proposed analytical method was experimentally confirmed. • The rapid calculation method is valid for a wide range of geographical latitudes. Space formation of passive solar greenhouses plays a dominant role in the creation of required lighing and thermal conditions and in increasing the efficiency of solar energy utilisation. In this study, the energy balance equation analysis was implemented in EnergyPlus software to numerically model the thermal performance of a passive solar greenhouse, located in the Beijing Region. Comparison of numerical and experimental data indicated a high prediction accuracy of the numerical model, which then was used to conduct a parametric analysis of the effect of main physical dimensions on the energy performance of such greenhouses. As a result, a range of rational values of physical dimensions was proposed for this type of greenhouses. The originality of the research approach is using parametric analysis data, obtained from the calibrated numerical model of greenhouses, to derive novel analytical correlations for rapid calculation of the main physical dimensions of passive solar greenhouses. The correctness of the proposed novel analytical method for calculation of main physical dimensions of passive solar greenhouses was experimentally confirmed in a series of comparative physical tests on various greenhouse models. The advantage of the proposed analytical correlations is that these are valid for a wide range of geographical latitudes in China and other regions, where a similar type of greenhouses can be exploited. [ABSTRACT FROM AUTHOR]