Concentration of the solar radiation in a solar furnace

Energy concentration in a solar furnace is greatly influenced by the optical accuracy of the reflecting surface of the mirror. The highest density of a heat flux on the heating surface of a specimen is determined by its concentration and by the reflectivity of the mirror.

Since the apparent diameter of the moon is almost equal to that of the sun and the illumination of the moon may be adapted to the photographic determination of flux density, the rate of energy concentration in the authors' solar furnace was studied by the moon's image projected upon the heating zone in place of that of the sun.

As a result, about 300 watts per cm was obtained as the highest possible density of the heat flux in this solar furnace. This figure also agreed with the results of an optical analysis based on the practical finishing of the present mirror surface. With a heat flux of 300 watts per sq cm, in accordance with Stefan-Boltzmann's law of radiation, the highest temperature attainable is estimated to be approximately 2700°K. Besides the above, in actual experiment, approximately 2300°C was obtained in observing the melting points of binary mixtures, e.g., MgO---CoO and MgO---Cr₂O₃. Thus, the above-mentioned three approaches to the problem are in fairly good agreement.     

Calculating the solar contribution to solar assisted systems

After summarizing the methods for calculating the solar contribution for systems without thermal storage, this paper extends a previously proposed method which is based on using a frequency distribution of insolation data. This extension allows rapid hand calculation of solar contribution for most collector types and for any specified collector inlet and outlet temperatures. Typical results are shown to be accurate to within 1 per cent relative to dynamic computer simulation methods. The effect on the method of collector orientation and tilt is discussed, and a simple method of determining the maximum possible (i.e. infinite collector area) solar contribution for a given collector system is described.     

The effective size of the solar cone for solar concentrating systems

In this paper we define a virtual solar cone, whose principle axis is aligned with the solar vector, having a radial angular displacement containing a pre-defined proportion of the terrestrial solar radiation. By simulating various sunshape profiles, the angular extent of the energy distribution is established to give the effective size of the solar cone for a range of atmospheric conditions. Then, by simulating the reflection of these solar distributions off a set of non-ideal mirrored surfaces, accounting for non-specular reflection and mirror shape errors, the combined effect of sunshape and mirror properties on the solar image is obtained. Clear trends are presented that show the dependence of the effective size of the solar image on the accuracy of a mirrored surface for different sunshapes. We then identify the effective size of the solar image at the absorber plane that must be accommodated in the design and optimisation of solar concentrating systems.     

Some factors affecting the absorption of solar radiation in solar stills

The performance of a solar still can be affected to a significant degree by the build-up of reflecting layers of salt on the water surface and basin liner. This paper presents a method of quantitatively assessing the effect of these salt layers, taking into account the band absorption characteristics of water. A revised curve of the absorption of the solar spectrum in water is given.     

组合跟踪的槽式聚焦集热器太阳辐照量的研究

在建立太阳直射辐射计算模型的基础上，分析了聚先反射抛物面镜面在各种跟踪方式下接受到的瞬时太阳直射辐射量，得出了晴天时昆明各月平均日辐照量的变化图。通过对所得数据度曲线图的比较和研究，获得了聚光反射抛物镜面两种较好的组合跟踪方式，效率分别达到双轴跟踪的98．9％和99．34％。可为太阳能申高温跟踪系统的发展和运用提供新的思路。     

太阳能蒸馏器的试验研究

介绍了太阳能蒸馏器的原理和结构 ,通过用实验室制作的一台小型蒸馏器进行了实测 ,测试效率32 % ,效果良好     

On the effects of solar radiation variations on solar heating system performances

The effect of solar radiation availability on the performance of different solar heating systems has been studied. The systems include a solar water heater, passive solar houses and district solar heating systems with seasonal heat storage. Also, different collector orientations and collector types have been investigated. The hourly radiation data were generated by a simple computational simulation procedure. It was found that district solar heating systems with concentrating collectors and passive solar houses showed the largest variations for the given conditions.     

Quality control of solar radiation data within the RMIB solar measurements network

Assessment of the solar resource is based upon measured data, where available. However, with any measurement there exist errors. Consequently, solar radiation data do not exhibit necessarily the same reliability and it often happens that users face time series of measurements containing questionable values though preliminary technical control has been done before the data release. To overcome such a situation, a major effort has been undertaken at the Royal Meteorological Institute of Belgium (RMIB) to develop procedures and software for performing post-measurement quality control of solar data from the radiometric stations of our in situ solar monitoring network. Moreover, because solar energy applications usually need continuous time series of solar radiation data, additional procedures have also been established to fill missing values (data initially lacking or removed via quality checks).     

Computing the solar vector

High-concentration solar thermal systems require the Sun to be tracked with great accuracy. The higher the system concentration, the greater this accuracy must be. The current trend in solar concentrator tracking systems is to use open-loop controllers that compute the direction of the solar vector based on location and time. To keep down the price of the tracking system, the controller is based on a low-cost microprocessor. These two facts impose important restrictions on the Sun position algorithm to be used in the controller, as it must be highly accurate and efficiently computable at the same time. In this paper, various algorithms currently available in the solar literature are reviewed and a new algorithm, developed at the Plataforma Solar de Almería, which combines these two characteristics of accuracy and simplicity, is presented. The algorithm allows of the true solar vector to be determined with an accuracy of 0.5 minutes of arc for the period 1999–2015.     

Development of an embedded solar tracker for the enhancement of solar energy utilization

An embedded two‐axis solar tracking system using Laboratory Virtual Instrumentation Engineering Workbench to write the operation and control algorithms was developed for enhancing solar energy utilization. The system consists of a real‐time processor, two motion‐control modules, two step drives, two step motors, feedback devices, and other accessories needed for functional stability. The real‐time processor allows the solar tracker to be used as a stand‐alone, real‐time system that can operate automatically without any external control. The system combines two different solar tracking methods: the optical method and the astronomical method. Cadmium Sulfide (CdS) sensors are employed to continuously generate feedback signals to the controller, ensuring high‐precision solar tracking even under adverse conditions. The CdS sensor is a resistor whose electric resistance decreases with increasing incident light intensity. A database of solar altitude, azimuth, and sunrise and sunset times is provided by this solar tracking system. Other solar trackers operating in an astronomical method may access and use this database over the Internet. Solar position and sunrise and sunset times in the database were compared with those of the Astronomical Applications Department of the U.S. Naval Observatory. The differences were found to be negligible. Copyright © 2011 John Wiley & Sons, Ltd.     

Estimation of height-dependent solar irradiation and application to the solar climate of Iran

An explicitly height-dependent model has been used to estimate the solar irradiation over Iran which has a vast range of altitudes. The parameters of the model have been chosen on general grounds and not by parameters best fitting to any of the available measured irradiation data in Iran. The estimated global solar irradiation on the horizontal surface shows a very good agreement (4.1% deviation) with the 17-year long pyranometric measurements in Tehran, and also, is in good agreement with other, shorter available measured data. The entire data base of the Iranian meteorological stations have been used to establish a simple relation between the sunshine duration records and the cloud cover reports which can be utilized in solar energy estimations for sites with no sunshine duration recorders.Clear sky maps of Iran for direct solar irradiation on tracking, horizontal, and south-facing vertical planes are presented. The global solar irradiation map for horizontal surface with cloudiness is zoned into four irradiation zones. In about four-fifths of the land in Iran, the annual-mean daily global solar irradiation on horizontal surface ranges from 4.5 to 5.4 kWh/m².     

An assessment of solar energy availability in different regions of the solar spectrum

The use of spectrally sensitive devices such as solar cells for electricity generation and selective absorber coatings for solar heaters, require a knowledge of the spectral composition of solar energy arriving at the point of utilization. Work is in progress at the University of Bradford to measure the amounts of available energy in different regions of the solar spectrum.The solar spectral measurement system uses a circularly variable interference filter covering the wavelength range 0.3–1.06 μm.     

Enhancement of the yield of solar still with the use of solar pond: A review

A solar pond (SP) is a remarkable growth of renewable energy technology that has stored solar energy for storage purposes and is used in many solar thermal applications. It is also utilized for many purposes, such as heating, cooling, space heating, air conditioning, and many more. The present paper shows the use of an SP to improve the yield of solar still (SS) by providing hot water through the heat energy stored in it. It also reveals the use of shallow and mini SPs with SS to improve yield. Various future research works on SS using SPs have also been included in this paper. From the current review paper, it was concluded that the SP increases the yield of the SS.     

Monochromatic versus solar efficiencies of organic solar cells

The photovoltaic behavior in a perylene/phthalocyanine hetero-p/n-junction solar cell was investigated using intensity-dependent I/V-characteristics and short circuit photocurrent spectroscopy. It is concluded that the charge carrier generation occurs only in a very thin active region at the contact. By optimizing the light trapping, a maximum solar AM 1.5 efficiency of about 2% can be obtained. A further increase requires better material properties or new cell structures.     

Influence of solar heating on the performance of integrated solar cell microstrip patch antennas

The integration of microstrip patch antennas with photovoltaics has been proposed for applications in autonomous wireless communication systems located on building façades. Full integration was achieved using polycrystalline silicon solar cells as both antenna ground plane and direct current power generation in the same device. An overview of the proposed photovoltaic antenna designs is provided and the variation characterised of the electromagnetic properties of the device with temperature and solar radiation. Measurements for both copper and solar antennas are reported on three different commercial laminates with contrasting values for thermal coefficient of the dielectric constant.     

Measurement of solar radiation by silicon solar cell

Investigations into the use of a silicon solar cell to measure solar radiation intensity are described. The effect of optical path length ratio and atmospheric constituents are discussed. A survey is made of other photovoltaic devices. It is concluded that, on presently available data, the silicon cell is the most suitable for the purpose.

Comparisons are made between the signals obtained from a silicon-solar-cell radiometer and a Kipp thermopile type solarimeter used as a standard. One set of comparisons is made for 30-minute intervals on clear days and is analysed so that known effects due to angle of incidence are allowed for and variations in the signals caused by spectral quality of the radiation can be separated. This set of comparisons shows an extreme spread of ±13 percent on a reference constant determined for midday clear sky. This extreme spread includes variations of +6.5 to −3 percent at midday together with variations during the course of any one day.

A second set of comparisons made during whole days or long periods, during which conditions were stable, gave rise to two calibration constants, one for clear-sky and one for overcast-sky conditions.

If an over-all calibration constant is desired for all conditions, then a value of 15.79 mA cm⁻² min/Langley is obtained with a probable error of to percent. The skew effect here is because more readings were taken for clear-sky conditions, thus favoring the lower constant for these conditions.     

Performance of the brisbane solar house

A house with an absorption air conditioning system operated by flat-plate solar collectors has been built in Brisbane, Australia. After briefly describing the house and equipment, the paper gives the performance of the house for a typical clear summer day. It is suggested that the equipment performance should be adequate for the air conditioning of houses in the Australian tropics where reliable summer insolation is available. However, the results of a cost study of various types of air conditioned houses for the Australian tropics show that solar air conditioning is only marginally economic.     

Raising the efficiency of solar greenhouses

The aspects of the effective coupling of the covering coefficient and the thermal storage coefficient of a greenhouse as a function of the geometric parameters and the solar radiation energy input are considered.     

Assessment of the dye-sensitized solar cell

The field of solar electricity, or photovoltaics (PV), is rich in that there are many materials and concepts for converting sunlight into electricity. The technologies accepted as conventional are those well along in the process of commercialization. The dye-sensitized solar cell, developed in the 1990s, is a nonconventional solar electric technology that has attracted much attention, perhaps a result of its record cell efficiency above 10%. This paper reviews the technology, discusses new research results and approaches presented at a recent symposium of many of the world's important dye solar cell researchers, and presents an assessment of the dye-sensitized solar cell in a comparison with current conventional solar electric technologies. It concludes the dye solar cell has potential for becoming a cost-effective means for producing electricity, capable of competing with available solar electric technologies and, eventually, with today's conventional power technologies. But it is a relatively new technology and faces many hurdles on the path to commercialization. Because of its potential, this assessment recommends further funding for research and development (R&D) of the dye-sensitized solar cell technology on the basis of the promising technical characteristics of the technology, a strong US and worldwide research base, positive industry interest, and today's relatively small funding allocation for its R&D.