Vol 54, No 1 (2018)

An analysis of possible errors of laboratory studies of current–voltage (I–V) characteristics for solar cells based on Cu(In,Ga)Se₂ (CIGS) using different lamps is provided, and the possibility of simplifying the procedure of testing the cells and panels by calculations and modeling is presented. Formulas are presented to develop mathematical models of the correlation between the quantum efficiency and the spectrum of the used lamp to obtain (I–V) characteristics of solar cells based on CIGS, which simplifies the testing procedure and data collection.

The results of investigations to determine the convective heat-exchange coefficient in the inner heat-exchange channels (HECs) of the light-absorbing heat-exchange panels (LAHPs) of flat-plate solar water-heating collectors (FPSWHCs) are given based on the results of their short-term heat testing in fullscale quasi-stationary conditions. The research method is based on determining the value of the required parameter from the heat-balance equation formed for the inner surfaces of the LAHP HEC walls. The structures of the flow LAHPs with a sheet-piped and thin parallelepiped form are selected as the test objects. The thermal tests of the FPSWHC are carried out during the near-midday hours of the light day to ensure the quasi-stationary mode condition. The reliability of the proposed method and results of the investigations is proved by comparing the values of the thermal-efficiency coefficients of the FPSWHC LAHPs obtained using two independent approaches.

In order to study the effect of buoyancy on the performance of solar air collector, the theoretical analysis and experimental tests of four solar air collectors with different structures under natural convection and mixed convection are carried out. The results show that the air temperature rise of the protrusion-corrugated plate air collector is the highest in the natural convection, which is 9.17 Chigher than that of the flat plate collector, and the air outlet velocity is 0.19 m/s, increasing by 16.88% than that of the flat plate collector. Observing the effects on the heat transfer performance of mixed convection, it can be found, in addition to the protrusion-corrugated plate air collector, the buoyancy plays a positive role on the other three solar air collectors in the upward flow, while the buoyancy plays a negative role on the other three solar air collectors in the downward flow, and the enhanced degree of the buoyancy to the corrugated plate air collector is the largest, while the enhancement degree of the flat plate collector is the least.

The evacuated tube collector with U shape copper absorber tube is considered for the analysis. The experimental investigation is conducted on parabolic trough collector with U shape tube as absorber tube. The effect of the sudden fluctuations in the solar radiation on the performance of the collector is reduced by means of evacuated tube collector filled with thermic fluids. The analysis is performed with different thermic fluids such as dowtherm, therminol66, glycol water and ethylene glycol, are filled in the annular space between inner glass tube and U shape copper absorber tube. The experimentation is carried out at various mass flow rates from 20 to 100 LPH with the step-up flow rate of 20 LPH. A comparative study is carried out on various parameters such as effect of mass flow rate over instantaneous efficiency, useful heat gain and work input, etc. The characteristic curve of cylindrical parabolic trough collector (PTC) is also discussed. Experimental results show that, ethylene glycol gives better efficiency over mass flow rate and therminol66 gives best power heat ratio. Heat transfer mediums and its properties [specific heat capacity, thermal conductivity and dynamic viscosity] for all specified heat transfer fluids are also discussed. The results obtained with various specified heat transfer fluids filled in the annulus space of evacuated tube are compared with plain evacuated tube. It is observed that there is significant enhancement of overall instantaneous collection efficiency of the parabolic trough collector.

The solar-energy industry is currently concerned with improving software systems of sun-tracking concentrators. It is a feature of programmable tracking that there is no feedback from the tracked object, unlike in the case of optical tracking. In this regard, the accuracy of programmable tracking is affected by a large number of factors—in particular, axis-alignment errors. An error-checking algorithm is considered for the azimuth and zenith concentrator axes in programmable sun tracking. Effects of these errors on the accuracy of programmable tracking are assessed. It is shown that zenith axis errors have the same amount of influence as the vertical deviation of the azimuth axis, primarily affecting the azimuth angle, while its influence on the solar elevation can be neglected. The cumulative effect of axial errors is most noticeable when they have the same signs and lie in the same plane.

The deficiency in the energy for the space cooling is overcome by solar energy. Still the input energy is minimized by integrating both power and cooling cycle in common platform, such as working fluid, component and working parameters. The aqua-ammonia is used in both power cycle and vapor cooling cycle. The generator is common for cycles for the production of ammonia vapor. The analyses are made to find out the operational parameters for the cooling cogeneration cycle with solar as source. The analyses are done for the proposed cycle with various atmosphere temperatures. At absorber concentration of 0.42 and turbine inlet concentration of 0.90, with solar collector exit temperature of 155°C and atmosphere temperature of 30°C the generated power and cooling are 21.88 and 215.79 kW, respectively. The power and cooling output range can alter by varying turbine inlet concentration and temperature.

In designing generating solar-engineering devices, the first priority is the predesign study of the potential of local resources of solar energy at the places where they may be located. Currently, actinometric information is obtained in several ways. They include direct measurement of solar-radiation characteristics at meteorological stations or from satellites and analytical methods for calculating intensity of solar radiation. Despite the significant number of sources of actinometric information, it seems impossible to evaluate the potential of incoming solar energy in the region, to substantiate the composition and parameters of solar-power-plant equipment, and to predict its operation at the initial stage. Using the example of the town of Kamyshin in Volgograd oblast, the sufficiency of required actinometric information is analyzed for further solar-engineering calculations and the data accuracy and limits of their applicability are estimated.