Solar Collector Surface Research Articles

Photovoltaic-Thermal Collector System for Domestic Application

Photovoltaic-thermal (PV/T) systems integrate photovoltaic and solar thermal technologies into one single system with dual production of electricity and heat energy. A typical arrangement is the direct attachment of PV modules onto a solar thermal collector surface. For a given collector surface area, the overall system energy performance is expected higher than the conventional “side-by-side” PV and solar thermal systems. In the development of PV/T collector technology using water as the coolant, the most common design follows the sheet-and-tube thermal absorber concept. Fin performance of the thermal absorber has been identified as one important factor that affects much the overall energy performance of the collector. Accordingly, an aluminum-alloy flat-box type PV/T collector prototype was constructed and tested in Hong Kong. Our test results indicate that a high combined thermal and electrical efficiency can be achieved. The primary-energy-saving efficiency for daily exposure approaches 65% at zero reduced temperature operation. With a simple and handy design, the product is considered to be very suitable for domestic application.

442 太陽集熱器の入射角依存特性が屋外集熱性能試験に与える影響について

A proposal of outdoor testing methods for the thermal performance of solar collectors is presented in this paper. The thermal performance of solar collectors is influenced by ambient temperature, wind speed, incident angle of solar beam to solar collector surface, conditions of cloud etc. This approach is a part of the research which goal is to establish outdoor testing methods for solar collectors. Five types of collectors were used for this study. Two of them are flat plate type collectors. Three of them are evacuated tubular collectors. Those types are representative collectors that have been sold in Japan.

99/03803 An optical system for the quantitative study of particulate contamination on solar collector surfaces: Biryukov, S. et al. Solar Energy, 1999, 66, (5), 371–378

99/03803 An optical system for the quantitative study of particulate contamination on solar collector surfaces: Biryukov, S. et al. Solar Energy, 1999, 66, (5), 371–378

Model of optimized solar heat engine operating on Mars

An endoreversible Carnot cycle is used to describe heat engine operation. This provides upper limits for real performance. The output power is maximized. Meteorological and actinometric data provided by the Viking Lander 1 are used as inputs. Four strategies of collecting solar energy are considered. Results concerning the following three parameters are briefly reported: (1) optimum solar collector surface area, (2) optimum solar collector temperature and (3) maximum output power.

Solar cells and batteries with unusual selective coatings for combined supply of heat and electricity by solar power stations

Abstract Optical coatings are used to increase the efficiency, extend the life, and to improve the electrophysical characteristics and stability of solar energy converters based on various physical principles, including semiconductor solar cells. When solar cells are placed on the exterior of collectors in photothermal systems, and generate both electric and thermal power, the optical coating applied to their surfaces gives them highly unusual selective properties, namely, reduced reflection of solar radiation (and high transparency in this part of the spectrum), which leads to higher integrated solar absorption coefficient, and enhanced infrared reflection which ensures that the thermal emission coefficient is as low as possible. Solar cells then not only generate electric power but, at the same time, covered by these coatings, act as selective optical surfaces for solar collectors.

Stable selective coating “black nickel” for solar collector surfaces

Abstract Electrodeposited black nickel coatings plated from chloride baths on metallic substrates have high solar absorptance coefficients (> 0,92) and low thermal emittances (

Etude par simulation de la stabilité des performaces d'une machine frigorifique solaire à adsorption solide

Solar refrigeration employing solid adsorption presents certain advantages over other methods, namely: simplified operation (no moving parts); total autonomy (no electricity and water requirements); and low operation and maintenance costs. Although this system has interested several laboratories it has some disadvantages due to the fact that the apparatus is inconvenient in certain respects. The intermittent and varying character of the operating conditions make the problems of cold compartment thermal regulation, energy storage and automatic operation difficult to solve. In the present work, a computer has been used to simulate the working conditions of this solar refrigerator. Numerical simulation has made it possible to study the behaviour of the performance of a solar refrigerator using the zeolite 13X-water adsorption couple, under various constraints. Particularly studied were the variations in coefficient of performance (COP) as a function of the quantity of zeolite per m 2 of solar collector surface, cold production as a function of solar radiation in relation to various component sizes, variations in exergetic efficiency as a function of evaporator temperature, and variation in the daily temperature in the solar collector when there were cloudy spells. The results obtained reveal the performance stability of such an apparatus, which operates fairly near the optimum even when sizing differs notably from the ideal. This fact enables us to more easily consider the problem of mass producing this kind of apparatus in order to lower production costs: a single size would be able to supply a relatively large range of cooling needs.

Materials for photothermal solar energy conversion

Commencally or potentially available selective and non-selective absorber surfaces for solar heat collectors are reviewed and the state-of-the-art of solar collector corrosion processes is outlined. The review of available published literature has indicated that a lack of quantitative information exists, relative to corrosion of collector surfaces. Available information (mostly qualitative) on durability aspects and corrosion of solar receiver surfaces is described to indicate potential corrosion problem areas and corrosion prevention possibilities. An outline of appropriate durability tests is presented.

Convective Heat Losses From Flat-Plate Solar Collectors in Turbulent Winds

This paper presents results for convective heat transfer coefficients on the surface of flat-plate solar collectors mounted on a single-family residential building and exposed to the wind. The results were obtained by testing a 1:32 scale model in highly turbulent nonuniform flows which simulated the natural wind. For full-scale conditions, the heat transfer coefficients are two to three times lower than those given by a commonly used correlation. The coefficients show some sensitivity to wind direction but are insensitive to the characteristics of the wind and to architectural details of the building.

Thermal degradation of solar collector surfaces

X-ray diffraction analyses indicate that electrodeposited black chrome and black zinc surfaces can be characterized by a metal-to-metal-oxide ratio that decreases (from 3.65 to 0.33 for black zinc and from 4.00 to 0.58 for black chrome) with increasing temperature of thermal exposure and this decrease correlates with the degradation observed in the optical selectivity ( α s ϵ t,H ) properties of these overgrowths. While black chrome surfaces are stable up to 500°C, black zinc surfaces (used in this study) degrade optically when heated to above 250°C. When the temperature of heat treatment is increased (from ambient to 300°C for black zinc and from ambient to 600 °C for black chrome) the particles comprising these surfaces increase in size (from 90 to 157 nm for black zinc and from 106 to 193 nm for black chrome) and exhibit a more spherical appearance in comparison with the more faceted particles comprising the as-plated surfaces.

Effect of Adiabatic Co-Planar Extension Surfaces on Wind-Related Solar-Collector Heat Transfer Coefficients

The heat transfer response to framing the thermally active cover surface of a flat plate solar collector with adiabatic co-planar extension surfaces has been investigated by wind tunnel experiments. Various framing patterns were employed (leading edge and/or trailing edge and/or side edge framing), along with frames of different width. The experiments were performed for various angles of inclination of the plate surface relative to the oncoming airstream and for a range of Reynolds numbers. It was found that the wind-related heat transfer coefficients can be substantially lower when the collector is framed than when it is unframed. An estimate of the possible reduction of the average heat transfer coefficient can be obtained from the equation h/h* = (Lc/Lf)1/2, where h and h* respectively denote the coefficients in the presence and in the absence of the frame. The quantity Lc is a dimension that is characteristic of the thermally active area of the cover surface, while Lf is a characteristic dimension of the outer edges of the frame. With respect to the reduction of the heat transfer coefficient, framing along the side edges appears to be more beneficial than framing along the leading and trailing edges, as is framing along the trailing edge compared with framing along the leading edge.

Cleaning agents and techniques for concentrating solar collectors

Tests were conducted to determine the nature of the soil which is irreversibly deposited on solar collectors during environmental exposure. Methods of removing this soil were investigated. The mechanism of attachment of the soil to the surface was determined as a potential aid to cleaning agent formulation. Reflector specimens were environmentally exposed at several industrial sites. Three types of reflector surfaces were studied: second surface silvered glass, aluminized FEK-244 film on aluminum substrate and RTV 670 on aluminum. Cleaning procedures were evaluated by microscopic examination of the solid surfaces before and after cleaning by measurement of specular reflectance. The effect of local environmental degradation specific to an industrial process on solar collector surfaces was investigated.

Systems Analysis of a Solar Industrial Process Steam Generating Plant

The systems analysis of a solar steam production plant is presented. The plant is designed to generate industrial process steam at 1034 kPag (150 lb/in.2g) for Dow Chemical Company’s Latex Manufacturing Plant located in Dalton, Ga. The project is intended to develop a demonstration unit with 929 m2 (10,000 ft2) of solar collector surface area. In this paper we have described an economic model developed for use in the systems analysis of solar steam plants, and discussed the systems analysis and optimization of the Dow solar steam plant. The economic model uses the annualized cost of a unit of fossil energy displaced by the solar steam plant as the cost-effectiveness parameter. The different factors that must be taken into account in developing this cost-effectiveness parameter are discussed. The concept selected for the detailed systems analysis uses an intermediate heat-transfer fluid in the primary loop. This fluid is circulated through the solar collectors to a boiler where steam is generated. Parabolic trough collectors are used in the system.

Selective absorbant surfaces for high temperature solar collectors

Selective absorbant surfaces for high temperature solar collectors

Calculation of the monthly-average transmittance-absorptance product

A method is presented for estimating the ratio of the monthly average transmittance-absorptance product for a solar collector surface to the value of this product for normal incidence. Theoretical and experimental determinations of the (direct) beam component contribution to the transmittance-absorptance product are discussed. A calculation of the monthly average daily solar radiation per unit area absorbed on a collector plate is given for the Madison, Wisconsin climate. (SPH)

A calorimetric method for determining the absorption for visible and near-infrared radiation of surfaces

The method consists of determining the power P1 absorbed by a surface from a beam of visible or near-infrared radiation, and of subsequently determining the power P2 absorbed by a black surface from the same radiation. The wavelength lambda of the radiation is determined by one of a set of bandpass filters. The temperatures are measured by means of thermistors. The optical system consists mainly of a 250 W lamp, a two-mirror collimator, a bandpass filter and a condenser lens. Results are given for three surfaces that may be considered as selective surfaces for flat-plate solar collectors, a copper oxide surface, a black nickel surface and a black enamel surface covered with tin oxide.

Optical properties of thin Au−Cr films and their application to solar energy conversion

Opaque Au and Au−Cr films were produced by rf triode sputtering onto a glass substrate at 150°C. Cosputtering of Au and Cr films has extended the solubility limits of Cr in Au from 19 at.% Cr to 48 at.% Cr. Electron microscopy showed polycrystallinity in the entire solubility range and electron microprobe analysis confirmed compositional uniformity of films. Reflectance measurements were made in the range 0.3−15 μ. Reflectance data were analyzed by the Kramers−Kronig method to obtain the optical constants n, k, ε1, and ε2. Good agreement is shown with the previous single crystal data on Au−Cr (up to 19 at.% Cr). The reflectance data are used to calculate α/ε ratio which is applied to the solar energy collector surfaces. Reflectance and transmittance data for very thin Au and Au−Cr films (100−400 Å) are used to calculate the figures of merit for the heat mirror type solar−thermal energy collector design.

Satellite solar power station

The finiteness of the Earth's fossil-fuel reserves are discussed and the world energy needs are projected to show that alternative energy sources to nuclear power merit consideration. A satellite solar power station is proposed to generate power to meet future requirements. Considerations are given to orbital location, solar energy conversion devices, transmittal equipment and Earth-receiving stations. The use of photoconductive organic materials to form thin film solar collector surfaces and generation of microwave radiation to transmit energy to an Earth-based antenna are discussed. The design considerations and the development tasks for a large satellite solar power station are reviewed and the potential technological needs are identified. The suggestion is made that the technology developed for the space program may find application in a satellite solar power station to generate power for use on Earth.

Addendum to: “Solar collector surfaces with wave length selective radiation characteristics”

Addendum to: “Solar collector surfaces with wave length selective radiation characteristics”

Solar collector surfaces with wavelength selective radiation characteristics

The use of porous materials through which a coolant is forced for the protection of surfaces exposed to high temperature gas streams has been discussed in a number of recent papers. The knowledge of the radiation properties of these materials is required if the designer is to be able to predict the porous wall temperatures to determine whether metallurgical limitations have been exceeded. With this application in mind, measurements were previously reported for the absorptivity for solar radiation of a number of porous surfaces. 1 Since that time total normal emissivity data have been obtained for the same surfaces. In viewing these results, it was discovered that these surfaces combined high absorptivity for solar radiation with a low emissivity value, and consequently their use as solar collectors is suggested. It is the purpose of this paper to describe the experimental apparatus used to obtain the radiation data and to compare the recent emissivity measurements with the solar absorptivity data for the same surfaces. For specified conditions, an efficiency is defined which allows a quantitative comparison of these with other surfaces as solar collectors.