Solar Energy Density Research Articles

A Research on Control System of Solar Energy Collecting and Tracking

Solar energy density is low, only in the light of the sun vertical to irradiate on the solar battery board, can maximum efficiency in the use of solar energy. The existing technology of solar tracking apparatus is tracking of single direction of the sun, solar energy utilization efficiency of the bottom, this paper studies a suitable technology to track to track the sun in full range, with its the automatic judgment of real-time tracking solar irradiation intensity. Described the structure scheme, improved controller design, parameters of the experimental method, ensure the mechanism movement stable, accurate, experiments show that, this system has superior performance, low cost, high benefit, solar energy collection, novel.

Study on Solar Photovoltaic Tracking System Based on Servo Control

The demand on resource is increasing when human beings have entered the 21st century, as the one-time fossil fuels get mined-out, such as coal, natural gas and petroleum the energy crisis has become a central issue. Because the solar energy density is small and the solar orientation changes over time, it’s difficult to collect, transmit and store the solar energy. Therefore, the utilization of solar energy is improved by using the technology of high-power condenser and automatic tracking, and the scope of solar energy application is also expanded. Tracking photovoltaic system be made of sun sensor, automatic tracking control system, the tracking actuator, solar panel, battery. With the guidance of the sensor, the control system can accurately track the position of the sun, so that the solar panel is always vertical to sunlight, to maximize use of eventually reaching solar efficiency. Data show that the utilization efficiency of solar energy can be improved about 10%.

The effects of the solar radiant flux density on the properties of pyroceramic materials

The effect of the concentrated solar energy density on the microstructure and the properties of vitrocrystalline materials of pyroxene composition is studied. It is shown that the solar irradiation accelerates the processes of crystallization, formation of a perfect microstructure, and sintering of vitrocrystalline materials, thus providing high values of their properties.

Global Solar Free Magnetic Energy and Electric Current Density Distribution of Carrington Rotation 2124

Solar eruptive phenomena, like flares and coronal mass ejections(CMEs) are governed by magnetic fields. To describe the structure of these phenomena one needs information on the magnetic flux density and the electric current density vector components in three dimensions throughout the atmosphere. However, current spectro-polarimetric measurements typically limit the determination of the vector magnetic field only to the photosphere. Therefore, there is considerable interest in accurate modeling of the solar coronal magnetic field using photospheric vector magnetograms as boundary data. In this work, we model the coronal magnetic field for global solar atmosphere using a nonlinear force-free field(NLFFF) extrapolation codes implemented to a synoptic maps of photospheric vector magnetic field synthesized from Vector Spectromagnetograph (VSM) on Synoptic Optical Long-term Investigations of the Sun (SOLIS) as boundary condition. Using the resulting three dimensional magnetic field, we calculate the three dimensional electric current density and free magnetic energy throughout the solar atmosphere for Carrington rotation 2124. We found that spatially, the low-lying, current-carrying core field demonstrates strong concentration of free energy in the AR core, from the photosphere to the lower corona; the coronal field becomes slightly more sheared in the lowest layer and it relaxes to the potential field configuration with height. The free energy density appears largely co-spatial with the electric current distribution.

Assessment of Using Secondary Concentrators for Nonferrous Material Removal Applications

The paper investigates using a secondary solar concentrator to augment the solar energy density focused by a primary concentrator (a paraboloid dish). The secondary concentrator protects the focal point from cooling by convection from wind, and also would harness all the solar rays reflected by the primary concentrator, resulting in reduced losses due to aberration and other errors in finding the focal point. The intended application is the utilization of solar energy for nonferrous material ablation that could potentially replace or assist industrial lasers

Techno-economic optimization of hybrid power system using genetic algorithm

SUMMARY This paper presents an optimum sizing methodology to optimize the hybrid energy system (HES) configuration based on genetic algorithm. The proposed optimization model has been applied to evaluate the techno-economic prospective of the HES to meet the load demand of a remote village in the northern part of Saudi Arabia. The optimum configuration is not achieved only by selecting the combination with the lowest cost but also by finding a suitable renewable energy fraction that satisfies load demand requirements with zero rejected loads. Moreover, the economic, technical and environmental characteristics of nine different HES configurations were investigated and weighed against their performance. The simulation results indicated that the optimum wind turbine (WT) selection is not affected only by the WT speed parameters or by the WT rated power but also by the desired renewable energy fraction. It was found that the rated speed of the WT has a significant effect on optimum WT selection, whereas the WT rated power has no consistent effect on optimal WT selection. Moreover, the results clearly indicated that the HES consisting of photovoltaics (PV), WT, battery bank (Batt) and diesel generator (DG) has superiority over all the nine systems studied here in terms of economical and environmental performance. The PV/Batt/DG hybrid system is only feasible when wind resource is very limited and solar energy density is high. On the other hand, the WT/Batt/DG hybrid system is only feasible at high wind speed and low solar energy density. It was also found that the inclusion of batteries reduced the required DG and hence reduced fuel consumption and operating and maintenance cost. Copyright © 2014 John Wiley & Sons, Ltd.

A thin diffuse component of the Galactic ridge X-ray emission and heating of the interstellar medium contributed by the radiation of Galactic X-ray binaries

We predict a thin (scale height $\sim$ 80 pc) diffuse component of the Galactic Ridge X-ray emission (GRXE) arising from the scattering of the radiation of bright X-ray binaries (XBs) by the interstellar medium (ISM). The morphology of this scattered component is expected to trace the clumpy molecular and HI clouds. We calculate this contribution to the GRXE from known Galactic XBs assuming that they are all persistent. The known XBs sample is incomplete, however, because it is flux limited and spans the lifetime of X-ray astronomy ($\sim 50$ years). We therefore also use a simulated sample of sources, to estimate the diffuse emission we should expect in an optimistic case assuming that the X-ray luminosity of our Galaxy is on average similar to that of other galaxies. In the calculations we also take into account the enhancement of the total scattering cross-section due to coherence effects in the elastic scattering from multi-electron atoms and molecules. This scattered emission can be distinguished from the contribution of low X-ray luminosity stars by the presence of narrow fluorescent K-$\alpha$ lines of Fe, Si, and other abundant elements present in the ISM and by directly resolving the contribution of low X-ray luminosity stars. We find that within $1^\circ$ latitude of the Galactic plane the scattered emission contributes on average $10-30\%$ of the GRXE flux in the case of known sources and over $50\%$ in the case of simulated sources. In the latter case, the scattered component is found to even dominate the stellar emission in certain parts of the Galactic plane. X-rays with energies $\gtrsim 1$ keV from XBs should also penetrate deep inside the HI and molecular clouds, where they are absorbed and heat the ISM. We find that this heating rate dominates the heating by cosmic rays (assuming a solar neighborhood energy density) in a considerable part of the Galaxy. [abridged]

Organic, cross-linking, and shape-stabilized solar thermal energy storage materials: A reversible phase transition driven by broadband visible light

Broadband visible sunlight usage and shape-stabilized effect were achieved using organic, cross-linking, and shape-stabilized phase-changed materials (OCSPCMs) with broadband visible light absorption, which were obtained by cross-linking reticulation and color matching (yellow, red, and blue) according to solar irradiation energy density. The obtained OCSPCMs exhibited excellent form-stable phase-change energy storage and broadband visible light-harvesting. Under broadband irradiation (from 400nm to 700nm), the light-to-heat conversion and the thermal energy storage efficiency (η>0.74) of the OCSPCMs were significantly improved upon solar irradiation by color matching compared with those of OCSPCMs with single-band selective absorption of visible light (yellow, red, or blue). Differential scanning calorimetric results indicated that the phase change temperatures and latent heats of OCSPCMs ranged from 32.6°C to 60.2°C and from 120.1J/g to 132.7J/g, respectively. The novel materials show a reversible (more than 200 cycles) phase transition via ON/OFF switching of visible light irradiation.

Observational Evidence for a Double-Helix Structure in CMEs and Magnetic Clouds

We compare recent observations of a solar eruptive prominence as seen in extreme-UV light on 30 March 2010 by the Solar Dynamics Observatory (SDO) with the multi-tube model for interplanetary magnetic clouds (Osherovich, Fainberg, Stone, Geophys. Res. Lett.26, 2597, 1999). Our model is based on an exact analytical solution of the plasma equilibrium with magnetic force balanced by a gradient of scalar gas pressure. Topologically, this solution describes two magnetic helices with opposite magnetic polarity embedded in a cylindrical magnetic flux tube that creates magnetic flux inequality between the two helices by enhancing one helix and suppressing the other. The magnetic field in this model is continuous everywhere and has a finite magnetic energy per unit length of the tube. These configurations have been introduced as MHD bounded states (Osherovich, Soln. Dannye5, 70, 1975). Apparently, the SDO observations depict two non-equal magnetically interacting helices described by this analytical model. We consider magnetic and thermodynamic signatures of multiple magnetic flux ropes inside the same magnetic cloud, using in situ observations. The ratio of magnetic energy density to bulk speed solar wind energy density has been defined as a solar wind quasi-invariant (QI). We analyze the structure of the QI profile to probe the topology of the internal structure of magnetic clouds. From the superposition of 12 magnetically isolated clouds observed by Ulysses, we have found that the corresponding QI is consistent with our double helix model.

Optimal design and control of solar driven air gap membrane distillation desalination systems

A solar heated membrane distillation desalination system is constructed of solar collectors and membrane distillation devices for increasing pure water productivity. This technically and economically feasible system is designed to use indirect solar heat to drive membrane distillation processes to overcome the unstable supply of solar radiation from sunrise to sunset. The solar heated membrane distillation desalination system in the present study consisted of hot water storage devices, heat exchangers, air gap membrane distillation units, and solar collectors. Aspen Custom Molder (ACM) software was used to model and simulate each unit and establish the cost function of a desalination plant. From Design degree of freedom (DOF) analysis, ten design parameters were investigated to obtain the minimum total annual cost (TAC) with fixed pure water production rate. For a given solar energy density profile of typical summer weather, the minimal TAC per 1m3 pure water production can be found at 500W/m2 by varying the solar energy intensity. Therefore, we proposed two modes for controlling the optimal design condition of the desalination plant; day and night. In order to widen the operability range of the plant, the sensitivity analysis was used to retrofit the original design point to lower the effluent temperature from the solar collector by increasing the hot water recycled stream. The simulation results show that the pure water production can be maintained at a very stable level whether in sunny or cloudy weather.

Light–thermal conversion organic shape-stabilized phase-change materials with broadband harvesting for visible light of solar radiation

To achieve highly efficient utilization of sunlight, organic shape-stabilized phase change materials (OSPCMs) with light–thermal conversion and visible light (solar radiation) harvesting abilities were designed and synthesized through color matching (yellow, red, and blue) according to the solar irradiation energy density. These materials exhibited excellent rapid and broadband visible light-harvesting, light–thermal conversion, thermal energy storage, and form-stable (remained in the same state upon transition) effects. The chemical structures of OSPCMs were verified using Fourier transform infrared and proton nuclear magnetic resonance techniques. Differential scanning calorimetry results indicated that the melting temperatures and latent heats of the synthesized OSPCMs ranged from 48 °C to 64 °C and from 107.1 J g−1 to 138.5 J g−1, respectively. The novel materials show a reversible (more than 200 cycles) phase transition (crystalline state change) via ON/OFF switching of visible light irradiation. Colour matching showed that the light-to-heat conversion and thermal energy storage efficiency (η) of the OSPCMs significantly improved upon solar irradiation.

On the relationship between thermosphere density and solar wind parameters during intense geomagnetic storms

Total mass density measurements at 72°S, 0°, and 72°N latitude from the CHAMP satellite near 400 km altitude are used to provide a quantitative assessment of the relationship between solar wind energy input and density variations during intense (Dst ≤ −100 nT) geomagnetic storms that occurred between August 2001 and December 2006. Correlations between the thermosphere density variations and various solar wind parameters and coupling functions representing the energy input into the thermosphere reveal significantly different characteristics during different geomagnetic storms. Statistical analysis shows that, out of the chosen solar wind parameters including coupling functions, the Borovsky parameter correlates best with the global scale density variations. The correlations at the equator are significantly higher than those at high latitudes. Moreover, the correlations on the dayside are almost the same as those on the nightside at 72°S and 0° latitude, whereas the correlation on the nightside is slightly higher than that on the dayside at 72°N latitude. These results indicate that it might be possible to use solar wind measurements to improve predictions of thermosphere density perturbations and the resulting changes in satellite drag.

Magnetic clouds, cosmic ray decreases, and geomagnetic storms

Abstract The relationship between magnetic clouds, cosmic ray decreases and geomagnetic storms has been investigated by using some cosmic ray hourly intensities recorded with ground-based monitors at Alert, Deep River and Mount Washington, as well as the geomagnetic activity Dst index, and the interplanetary magnetic field (IMF) and the solar wind plasma (SWP) bulk-speed, density and temperature in the near-Earth space, on 28–30 September 1978, 24–26 April 1979, 13–15 January 1967, 3–5 January 1978, and 27–29 November 1989. Due to the interplanetary coronal mass ejection (ICME) impacting on slow solar wind, there is a sheath upstream of the ICME led by a fast forward shock. And the large IMF variations in this sheath, which sustain the depressions in the cosmic ray intensity during Forbush decreases (FDs), were found not to influence the main phase storm, but rather the southward IMF in the said sheath and magnetic cloud was the major source in triggering geomagnetic storms, by allowing a strong coupling between the solar wind and the magnetosphere. It was also observed that the initial set of the main phase storm always began in the sheath where, and when, the sustained southward-oriented IMF first occurred, but ceased when the IMF was rotated to a strong northward-orientation, only to resume at subsequent sustained southward-oriented IMF within the sheath and the leading (i.e., front) region of the magnetic cloud. The front boundary of the magnetic cloud was found to be well defined by the relatively high (≳10 nT) rms of the IMF components, which prominently separates both the Lull region of the sheath and the onset of the second decrease of the two-step FD, from the magnetic cloud. There were some instances where a two-step main phase storm, caused by the combination of a sheath and cloud structure, occurred, the two steps sometimes both starting in the sheath itself. Also, in some cases, the sheath and the leading region of the magnetic cloud together produced a single-step storm. In addition, enhanced IMF south latitude and IMF intensity in the sheath and magnetic cloud during the IMF sustained southern orientation, were each observed to produce enhanced geomagnetic activity, even for intense storms. And high SWP bulk speed was found to reduce the depth of the Dst index. Therefore, it appears that when the magnetosphere is exposed to a sustained southward-oriented IMF in the magnetic cloud and the sheath preceding it, a valve (i.e., valve-like IMF direction) opens and allows direct transfer of energy between the solar wind and the magnetosphere to trigger the geomagnetic storms, such that the stronger the sustained IMF south-ward orientation, the wider the valve opens, the higher the SWP bulk speed, the narrower the opening in the valve becomes. And the more the IMF strength during the IMF southern orientation, the larger is the solar wind energy density that is available for transfer through the valve. The valve closes when the IMF is rotated to a strong northward-orientation, and the geomagnetic storms cease. Index terms: 2104 Interplanetary Physics: Cosmic rays; 2111 Interplanetary Physics: Ejecta, driver gases, and magnetic clouds; 2139 Interplanetary Physics: Interplanetary shocks; 7513 Solar Physics, Astrophysics, and Astronomy: Coronal mass ejections.

Dependences of Postnoon Auroral Intensity on Solar Wind-Magnetosphere Coupling Functions

利用1997年和1998年南极中山站多通道扫描光度计的地面观测数据和Wind卫星在弓激波上游对行星际磁场和太阳风参数的观测数据,对午后高纬极光强度与太阳风-磁层耦合函数之间的相关性进行定量研究.研究表明,午后630.0nm极光强度与太阳风-磁层耦合函数间有很好的相关,而557.7nm的相关性差一些;在考察的所有耦合函数中,午后极光受太阳风电场和能量的影响更直接;同时,行星际磁场的时钟角对午后极光也有很强的控制作用.

High solar energy concentration with a Fresnel lens

The high solar energy density achieved in our simple and cheap Fresnel installation has been used for several surface modifications of metallic materials. This equipment is a very useful tool to apply concentrated solar energy in the field of high and very high temperatures (1500–2000 K). These temperatures are achieved in a few seconds and usually the materials treatments are completed in minutes. Fresnel lens installation is a serious alternative to the conventional equipment for material treatment and even to the large solar installations. In this work we review the surface modifications produced by concentration of solar energy with a Fresnel lens.

Finite size scaling in the solar wind magnetic field energy density as seen by WIND

Statistical properties of the interplanetary magnetic field fluctuations can provide an important insight into the solar wind turbulent cascade. Recently, analysis of the Probability Density Functions (PDF) of the velocity and magnetic field fluctuations has shown that these exhibit non‐Gaussian properties on small time scales while large scale features appear to be uncorrelated. Here we apply the finite size scaling technique to explore the scaling of the magnetic field energy density fluctuations as seen by WIND. We find a single scaling sufficient to collapse the curves over the entire investigated range. The rescaled PDF follow a non Gaussian distribution with asymptotic behavior well described by the Gamma distribution arising from a finite range Lévy walk. Such mono scaling suggests that a Fokker‐Planck approach can be applied to study the PDF dynamics. These results strongly suggest the existence of a common, nonlinear process on the time scale up to 26 hours.

Hydrogen-photovoltaic stand-alone power stations: A sizing method

Abstract Photovoltaic conversion appears as a very promising technology in order to achieve the technical and economic goals for penetration into the electric energy market. Nevertheless, a serious limit to the very large diffusion of PV systems is due to the intermittence of solar radiation. Hydrogen produced via water electrolysis can be considered as an useful means to store solar energy and overcome this limit. With reference to a stand-alone power plant configuration, a PV system, integrated with electrolytic hydrogen production and a fuel cell reconversion line, is examined in order to check the technical suitability of supplying electricity to a load with time continuity. A mathematical method, which utilizes as input data the monthly average values of solar energy density on a horizontal surface is presented, which permits us to size the PV array as a function of the annual load diagram for a given solar site. The results demonstrate that PV-H 2 systems are suitable for realizing a modular stand-alone solar power station able to supply continuously generic loads.

Wind and solar energy potential in Makkah (Saudi Arabia)—Comparison with Red Sea coastal sites

The characteristics of wind regimes and the availability of wind energy resources in Makkah, its outskirts and selected sites on the eastern and western coasts of the Red Sea have been studied. Statistical analysis of the wind speeds involving fitting of observed cumulative distribution to Weibull distribution function by least square technique, determination of the Weibull parameters and evaluation of wind power density by two methods, was carried out. The mean annual wind energy density at 10 m A.G.L. lies between 250 and 500 kWh/m 2 on the Red Sea coast sites and drops to about 50 kWh/m 2 in inland areas. Yanbu on the east coast has the highest resource while Makkah, affected by the Sarawat mountains, has the lowest wind energy density. The solar energy in all these areas is abundant. In Makkah and Port Sudan the mean annual solar energy density exceeds 2.0 MWh/m 2.

Comparison of plasma wave measurements in the bow shocks at Earth, Jupiter, Saturn, Uranus and Neptune

Plasma wave measurements from the Voyager 2 crossing of Neptune's bow shock are presented and compared with measurements from the bow shocks of Earth, Jupiter, Saturn, and Uranus. The wave amplitudes above 0.01fp, when normalized to the solar wind ion thermal energy density at each planet, are significantly higher at the outer planets than at Earth. Despite the differences in amplitude, the shock spectra of all the planets can be fitted to curves of similar form in this frequency range. The total normalized electric field energy densities exhibit an exponential dependence on ion thermal Mach number, Magnetosheath wave energies are comparable at all of the planets when normalized to the downstream plasma pressure.

Observations of the Earth's bow shock under high Mach number/high plasma beta solar wind conditions

Using 221 observations of the earth's bow shock by ISEE‐1 we investigate the magnetic field characteristics of the shock as a function of Mach number and plasma beta. We find that immediately behind the overshoot of the shock large amplitude waves develop preferentially with increasing Alfvén Mach number and/or plasma beta. Their probability of occurrence is very high in the parallel regime (θBN ≤ 10°), and declines to near zero probability when θBN reaches 75°. It is estimated that approximately 10% of the total solar wind energy density is dissipated by these waves.