scholarly journals Solar energy at high temperatures; researches at the Weizmann Institute of Science, Israel; 25 years of success

2016 ◽  
Vol 1 ◽  
pp. 1 ◽  
Author(s):  
Akiba Segal
Keyword(s):  
Solar Energy ◽  
High Temperatures ◽  
Weizmann Institute

scholarly journals Improvement of Phase Change Materials (PCM) Used for Solar Process Heat Applications

Molecules ◽  
2021 ◽  
Vol 26 (5) ◽  
pp. 1260
Author(s):  
Cristina Prieto ◽  
Anton Lopez-Roman ◽  
Noelia Martínez ◽  
Josep M. Morera ◽  
Luisa F. Cabeza
Keyword(s):  
Thermal Conductivity ◽  
Solar Energy ◽  
Phase Change ◽  
Effective Thermal Conductivity ◽  
High Temperatures ◽  
Phase Change Materials ◽  
Material Selection ◽  
Inert Atmosphere ◽  
Enhancement Effect ◽  
Process Heat

The high intermittency of solar energy is still a challenge yet to be overcome. The use of thermal storage has proven to be a good option, with phase change materials (PCM) as very promising candidates. Nevertheless, PCM compounds have typically poor thermal conductivity, reducing their attractiveness for commercial uses. This paper demonstrates the viability of increasing the PCM effective thermal conductivity to industrial required values (around 4 W/m·K) by using metal wool infiltrated into the resin under vacuum conditions. To achieve this result, the authors used an inert resin, decoupling the specific PCM material selection from the enhancement effect of the metal wools. To ensure proper behavior of the metal wool under standard industrial environments at a broad range of temperatures, a set of analyses were performed at high temperatures and an inert atmosphere, presenting a thorough analysis of the obtained results.

scholarly journals Temperature-Dependent Analysis of Solid-State Photon-Enhanced Thermionic Emission Solar Energy Converter

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1554
Author(s):  
Yang Yang ◽  
Wei Wei Cao ◽  
Peng Xu ◽  
Bing Li Zhu ◽  
Yong Lin Bai ◽  
...  
Keyword(s):  
Solid State ◽  
Solar Energy ◽  
High Temperatures ◽  
Open Circuit Voltage ◽  
Elevated Temperatures ◽  
Electrical Power ◽  
Thermionic Emission ◽  
Open Circuit ◽  
Temperature Dependent ◽  
Doping Density

Solid-state photon-enhanced thermionic emission (PETE) solar energy converters are newly proposed devices that can directly convert solar energy into electrical power at high temperatures. An analytical model based on a one-dimensional steady-state equation is developed to analyze the temperature-dependent performance of the solid-state PETE converter. The treatment used to derive the reverse saturation current density ( J 0 ) and open-circuit voltage ( V o c ) of the solid-state PETE converter is similar to that used in photovoltaic cells. Thus, their performances at elevated temperatures can be compared. Analysis results show that J 0 of the solid-state PETE converter with a GaAs absorption layer is approximately three orders of magnitude lower, and the decrease rate of open-circuit voltage ( − d V o c / d T ) is smaller than that of a practical GaAs photovoltaic cell. The improved performance of the solid-state PETE converter at high temperatures is attributed to the simultaneous use of diffusion and ballistic transport to harvest photo-generated electrons. The results presented in this paper demonstrate that, besides using wide bandgap materials and increasing doping density, harvesting solar energy via PETE effect can effectively improve the performance of solar cells at elevated temperatures.

High Temperature Thermochemical Energy Storage Using Packed Beds

2016 ◽  
Author(s):  
Qasim A. Ranjha ◽  
Nasser Vahedi ◽  
Alparslan Oztekin
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Energy Storage ◽  
Solar Energy ◽  
Latent Heat ◽  
High Temperatures ◽  
Heat Storage ◽  
Three Dimensional ◽  
Heat Transfer Fluid ◽  
Latent Heat Storage

Thermal energy storage units are vital for development of the efficient solar power generation systems due to fluctuating nature of daily and seasonal solar radiations. Two available efficient and practical options to store and release solar energy at high temperatures are latent heat storage and thermochemical storage. Latent heat storage can operate only at single phase change temperature. This problem can be avoided by some of the thermochemical storage systems in which solar energy can be stored and released over a range of high temperature by endothermic and exothermic reactions. One such reaction system is reversible reaction involving dehydration of Ca(OH)2 and hydration of CaO. This system is considered in the present study to model a circular fixed bed reactor for storage and release of heat at high temperatures. Air is used as heat transfer fluid (HTF) flowing in an annular shell outside the bed for charging and discharging the bed. The bed is filled with CaO/Ca(OH)2 powders with particles diameter of the order 5μm. Three dimensional transient model has been developed and simulations are performed using finite elements based COMSOL Multiphysics. Conservation of mass and energy equations, coupled with reaction kinetics equations, are solved in the three dimensional porous bed and the heat transfer fluid channel. Parametric study is performed by varying HTF parameters, bed dimensions and process conditions. The results are verified through a qualitative comparison with experimental and simulation results in the literature for similar geometric configurations.

scholarly journals EARLIER VEGETABLE CROPS WITH NEAR INFRA-RED TRANSMITTING MULCH

HortScience ◽  
1992 ◽  
Vol 27 (11) ◽  
pp. 1161d-1161
Author(s):  
Brent Loy ◽  
Otho Wells
Keyword(s):  
Solar Energy ◽  
Light Intensity ◽  
High Temperatures ◽  
Photosynthetically Active Radiation ◽  
Yield Response ◽  
Vegetable Crops ◽  
Active Radiation ◽  
Weed Growth ◽  
Infra Red ◽  
Black Plastic

Near infra-red (NIR)-transmitting plastic mulches transmit between 30 to 50% of the total solar energy to the soil, but block most photosynthetically active radiation (PAR). These mulches warm the soil more effectively than black plastic, but less effectively than clear mulch. Weed growth under NIR-transmitting mulches is suppressed through a combination of lowered light intensity and high temperatures under the mulch surface. With bell pepper and melons, IRT-76, a blue green, NIR-transmitting mulch, enhances growth to about the same extent as black mulch plus a floating rowcover. In turn, rowcover performance is enhanced by IRT-76 as compared to black mulch. In melons, early yield is about doubled and total yields increased by 20 to 30% with IRT-76 as compared to black mulch. Pepper yields are generally higher with IRT-76 as compared to black mulch, but the yield response to IRT-76 is less consistent than with melon.

scholarly journals Numerical investigation of solar collectors as a potential source for sintering of ZrB2

2021 ◽  
Vol 1 (2) ◽  
pp. 76-84
Author(s):  
Mohammad Vajdi ◽  
Saeed Mohammad Bagheri ◽  
Farhad Sadegh Moghanlou ◽  
Amin Shams Khorrami
Keyword(s):  
Solar Energy ◽  
High Temperatures ◽  
Focal Point ◽  
Good Alternative ◽  
Heat Radiation ◽  
Collector System ◽  
Alternative Material ◽  
Energy Consuming ◽  
Ultrahigh Temperature ◽  
Solar Heat Flux

Sintering of ceramics is an energy-consuming process that needs high temperatures, therefore, in the present work; solar energy is used to produce high temperatures for the sintering aim of different materials. Solar energy concentrators increase the intensity of incident energy to the receiver provides high temperatures. Ultrahigh-temperature ceramics (UHTCs) due to their high melting point can also be a good alternative for receiver materials. In the present work, ZrB2 is introduced as an alternative material for solar receivers which can withstand high temperatures of sintering. The governing equations, including heat radiation and conduction ones are solved numerically using the finite element method. Transient heat transfer in the concentrator-collector system is investigated to check the feasibility of high temperatures needs for sintering at the receiver. The highest temperature of 1680 °C was achieved after 15 minutes at the focal point of the concentrator when the solar heat flux of 6.86 w/mm2 used for the location of the city of Ardabil in Iran. The obtained temperature can be used to sintering of some groups of materials.

Rendez vous with Saturn's rings

1984 ◽  
Vol 75 ◽  
pp. 743-759 ◽  
Author(s):  
Kerry T. Nock
Keyword(s):  
Solar Energy ◽  
Electric Propulsion ◽  
Power Source ◽  
Propulsion System ◽  
Low Thrust ◽  
Ring Plane ◽  
The Earth ◽  
Total Impulse ◽  
Saturn's Rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

In situ REM imaging of surface processes on ceramic bulk crystals from 300 to 1670 K in a conventional TEM

1991 ◽  
Vol 49 ◽  
pp. 660-661
Author(s):  
Z. L. Wang ◽  
J. Bentley
Keyword(s):  
High Temperatures ◽  
Image Resolution ◽  
Atomic Processes ◽  
Crystal Surfaces ◽  
Beam Radiation ◽  
Surface Areas ◽  
Transmission Electron ◽  
Reflection Electron Microscopy ◽  
Gas Reactions

Studying the behavior of surfaces at high temperatures is of great importance for understanding the properties of ceramics and associated surface-gas reactions. Atomic processes occurring on bulk crystal surfaces at high temperatures can be recorded by reflection electron microscopy (REM) in a conventional transmission electron microscope (TEM) with relatively high resolution, because REM is especially sensitive to atomic-height steps.Improved REM image resolution with a FEG: Cleaved surfaces of a-alumina (012) exhibit atomic flatness with steps of height about 5 Å, determined by reference to a screw (or near screw) dislocation with a presumed Burgers vector of b = (1/3)<012> (see Fig. 1). Steps of heights less than about 0.8 Å can be clearly resolved only with a field emission gun (FEG) (Fig. 2). The small steps are formed by the surface oscillating between the closely packed O and Al stacking layers. The bands of dark contrast (Fig. 2b) are the result of beam radiation damage to surface areas initially terminated with O ions.

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