Vol 52, No 1 (2016)

Epitaxial layers of the solid solutions (Si₂)_1–x(ZnSe)_x (0 ≤ x ≤ 0.01) of n-type conductivity on pSi base were cultivated by liquid phase epitaxy from a restricted amount of tin solution–melt. The spectral photosensitivity dependence of the pSi–n(Si₂)_1–x(ZnSe)_x structure was studied. A peak was discovered in the response level within the interval of photon energy from 2.67 to 3 eV conditioned by the energy band of ZnSe “quantum dots,” which is located ~1.55 eV lower than the ceiling of the silicon valence band.

This study deals with the energy and exergy analyses of natural circulation solar water heating (SWH) systems. The system comprises of a single glazed flat plate solar collector (FPSC) with absorber plate of 2 m², and a separate insulated well-mixed vertical water storage tank (WST) of 125 liters. The variable heat transfer coefficients, water inlet and outlet temperatures of the FPSC; and temperature of heated water stored in the WST are predicted theoretically for each interval. The daily energy and exergy efficiency of the FPSC, WST and SWH system are estimated to be about 39 and 4.36%, 67 and 38.55%, 27 and 1.01%, respectively. It is found that the water inlet temperature, optical efficiency and the solar radiation strongly influence the performance of the FPSC both energetically and exergetically. It is observed that change in the mass flow rate of water improves the exergy efficiency of the FPSC significantly. FPSC has been identified as a critical component of the system where exergy destruction of 308 W/m² takes place daily as compared to 24 W/m² in the WST against available solar exergy of about 663 W/m².

In this work, nanocrystalline P25 TiO₂ films with different thicknesses were deposited on FTO coated glass substrates by an electrophoretic deposition technique (EPD) and applied as the work electrode for dye-sensitized solar cells (DSSC) using cis-bis(isothiocyanato)(2,2'-bipyridyl-4,4'-dicarboxylato)(4,4'di-nonyl-2'-bipyridyl) ruthenium(II) (Z907, Dyesol) as sensitizing dye.The results showed that the increasing the thickness of TiO₂ films lead to increase the adsorption of the dye on the TiO₂ layers which in turns improved the short-circuit photocurrent (J_sc) and open-circuit voltage (V_oc), respectively. Furthermore, it was found that the effects of the surface states on the recombination of the photo-injected electrons (electron–hole pairs) in the TiO₂ films strongly depend on theTiO₂ electrode annealing temperature. Finally, a DSSC with a 32.82 μm thickness for TiO₂ film annealed at 600°C produced the highest conversion efficiency with an incident solar energy of 100 mW/cm² (η = 8.23%, J_sc = 15.98, V_oc = 0.73, FF = 0.7).

Today widespread application of energy-saving equipment based on heat pipes makes a significant contribution to the task of resources saving. Using the heat pipes as heat transfer and heat exchange design elements allows creating new effective equipment generation for solar energy systems. Heat pipes are widely used both to improve the outdated equipment, increase its efficiency, reliability and lifetime and in the creation of new high-quality and economic technology samples. Up to the present day there are the following systems and solar energy equipment where heat pipes are widely used: photovoltaic-thermal solar collectors, solar thermal collectors, concentrating photovoltaic and concentrating solar plant. The article presents an analysis of the current state and prospects of heat pipes using in solar energy systems.

The load characteristics of n-CdS/p-CdTe heterostructures were studied at different lighting levels with monochromatic light (λ = 632.8 nm) and white light with different spectra of radiation. It was established that the efficiency of conversation of a structure increases with increased temperature upon lighting with white light from an incandescent lamp. The results will help to optimize the structure of photocells based on CdTe polycrystalline films.

The neodymium-containing phosphorus oxychloride liquid laser material is studied as an active medium for pumping by concentrated solar radiation at the focus of small-size parabolic-dish concentrators. The possibility of increase its efficiency by means of frequency-down-shifting elements of solar spectrum is examined by simulation calculations by Monte-Carlo and ray-tracing methods using. More than 40% efficiency increase is obtained.