Solar Vacuum Research Articles

A material experiment for small satellites to characterise the behaviour of carbon nanotubes in space – development and ground validation

Over the last years, Carbon Nanotubes (CNT) drew interdisciplinary attention. Regarding space technologies a variety of potential applications were proposed and investigated. However, no complex data on the behaviour and degradation process of carbon nanotubes under space environment exist. Therefore, it is necessary to investigate the performance of these new materials in space environment and to revaluate the application potential of CNTs in space technologies.Hence, CiREX (Carbon Nanotubes – Resistance Experiment) was developed as a part of a student project. It is a small and compact experiment, which is designed for CubeSat class space satellites. These are a class of nanosatellites with a standardized size and shape. The CiREX design, electrical measurements and the satellites interfaces will be discussed in detail. CiREX is the first in-situ space material experiment for CNTs.To evaluate the data obtained from CiREX, ground validation tests are mandatory. As part of an extensive test series the behaviour of CNTs under solar ultra violet light (UV) and vacuum ultraviolet light (VUV) was examined. Single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT) and MWNT/resin composite (ME) were exposed to different light sources. After the exposure, the defect density was investigated with Raman spectroscopy. There is a clear indication that UV and VUV light can increase the defect density of untreated CNTs and influence the electrical behaviour.

Tri-direct CP in the Littlest Seesaw playground

We discuss spontaneously broken CP symmetry in two right-handed neutrino models based on the idea of having a different residual flavour symmetry, together with a different residual CP symmetry, associated with each of the two right-handed neutrinos. The charged lepton sector also has a different residual flavour symmetry. In such a tri-direct CP approach, we show that the combination of the three residual flavour and two residual CP symmetries provides a new way of fixing the parameters. To illustrate the approach, we revisit the Littlest Seesaw (LSS) model based on S4 and then propose new variants which have not so far appeared in the literature, with different predictions for each variant. We analyse numerically the predictions of the new variants, and then propose an explicit model which can realise one of the successful benchmark points, based on the atmospheric flavon vacuum alignment (1, ω2, ω) and the solar flavon vacuum alignment (1, −7/2, −7/2).

Daytime optical turbulence and wind speed distributions at the Baikal Astrophysical Observatory

Atmospheric turbulence limits the angular resolution of ground-based optical telescopes. The daytime turbulence conditions for solar observations are stronger and more complicated than the turbulence observed at night. The Baikal Astrophysical Observatory is the site of the 1-m Large Solar Vacuum Telescope (LSVT) located near Lake Baikal (East Siberia, Russia), which is the largest freshwater lake in the world. The region hosts unique weather regimes and natural phenomena, including local winds and giant ice rings. Because the LSVT has ongoing and planned programmes in adaptive optics (AO), statistical knowledge of atmospheric turbulence and wind speed distributions is essential for designing and optimizing AO systems. We present the first seasonal study of the vertical distribution of wind speed and daytime optical turbulence conditions at the Baikal Astrophysical Observatory. Site measurements of the daytime Fried parameter were collected using the Shack–Hartmann wavefront sensor in the LSVT AO system. Reanalysis data from the National Centers for Environmental Prediction (NCEP) and the National Centers for Atmospheric Research (NCAR) were used to characterize the wind speed distribution. The results demonstrate seasonal variation in both solar seeing and wind speed profile. The strongest wind speed was detected in winter and in November, while the weakest wind speed occurred during summer. The strongest daytime turbulence conditions were observed in the winter. The best solar seeing β0 ≈ 1 arcsec was detected in the summer.

Two-Mirror Adaptive System for Correction of Atmospheric Disturbances of the Large Solar Vacuum Telescope

Features of a two-mirror adaptive system for correction of atmospheric disturbances of the Large Solar Vacuum Telescope are described. The system has been developed with allowance for the correction of instrumental vibrations of the telescope in a wide amplitude-frequency range, with an open siderostat supply mirror. The light wavefront tilt and its deformations are corrected separately. The adaptive optics system is designed to work with extended light sources (the Sun), with low-contrast image details.

Performance analysis of solar vacuum membrane distillation regeneration

This paper proposes a novel solar vacuum membrane distillation (VMD) regeneration for liquid desiccant air conditioning (LDAC) system, and establishes a mathematical model of the VMD regeneration process and traditional thermal (TH) regeneration process based on the heat and mass balance. The corresponding simulation model was established by using Matlab software, and the model was verified by previous experiments. The results show that: the model results are consistent with the previous experimental results, and the maximum error is less than 6%. Model simulations are carried out to study the regeneration performance under various operating parameters and climatic conditions, meanwhile the comparison the solar power consumption for regenerating one kilogram desiccant between the VMD regeneration and TH regeneration. Results demonstrate that when the air temperature is less than 32 °C, the humidity ratio is higher than 19 g/kg, and the air flow rate is less than 0.13 kg/s, the VMD regenerator solution regeneration effect is better than the conventional thermal regenerator. VMD regeneration is more suitable for solution regeneration in wet areas than TH regeneration. Furthermore, when the solution temperature is lower than 60 °C, VMD regeneration outlet concentration is higher than TH regeneration. VMD regeneration is more suitable for low-grade energy. Analyze the solar power consumption for regenerating one kilogram desiccant found that the VMD regeneration saves 10–37% energy than TH regeneration. Through economic analysis, it is found that the VMD regenerator can save 582.4 kWh of electricity per year compared to the TH regenerator. According to the cost recovery calculation formula, the cost recovery period can be calculated as 13.8 years.

ANALYSIS OF CONDENSER PERFORMANCE DESALINATION OF SOLAR ENERGY OF THE NATURAL VACUUM SYSTEM AT THE TIME OF LOW RADIATION INTENSITY

Natural desalination device solar vacuum system has a main component of evaporator, condenser, and solar collector. The production of clean water from this appliance is strongly influenced by the performance of the condenser.On this research, condenser performance is performed when the intensity of solar radiation is low. The measurement data for 2 days when the sky is not bright is used to perform the condenser performance analysis. The result of analysis on the first day was found that the working energy of condensorsirippada was 141 J / day, while if without 29 J / day fins. So that the effectiveness of fins of 112 J / day. While on the second day found heat transfer using 122 J / day fins without fins 25 J / day to obtain fin effectiveness of 97 J / day. This is very influential on clean water production. The condensate rate on the 1st day is highest at 0.00018 kg / min, with an average of one day experiment 0.0001 kg / min, yielding fresh water of 0.8 Liter. On the 2nd day the highest condensate rate is 0.00019 kg / min with an average of condensate rate for one day 0.00011 kg / min, yielding fresh water of 0.81 Liter.

Optimal Number of Effects for Multi Effect Evaporation Seawater Desalination Process Using Solar Thermal Energy-Plate Evaporators

Seawater desalination using Multi effect-plate evaporators and solar energy is one of very promising ways to deal with fresh water shortage and pollution in the same time. Indeed, falling film plate evaporators are becoming more used in the desalination applications. This is because of their multiple advantages compared to tubular evaporators such as high heat transfer rate and low investment cost. This study presents the methodology used for sizing and optimization of plate evaporators for seawater desalination unit using multi effect evaporation and solar thermal energy. The pilot plant unit operates with hot water provided by solar vacuum tubes. The unit was designed for a production capacity of 5 to 7 m3/day of fresh water obtained from evaporation of 28 to 30% of feed seawater. The modeling equations are given at steady-state conditions and they are based on mass, heat balance and heat transfer equations, and thermodynamic and physical properties of each stream. MATLAB programming software is used to resolve the developed algorithm. This work focuses more on studying and analyzing the impact of the number of effects on the total required heat transfer area, the required thermal energy and therefore on the specific cost of water. The obtained results show that it is more beneficial to use nine effects, which gives the key solution for minimizing water production cost. The optimal design shows that the total required heat transfer area of evaporators and the last condenser is approximately equal to 42 m2 and the thermal energy needed to drive the pilot unit is about 64 kW.

Development of Components for Adaptive Optics Systems for Solar Telescopes

Wavefront aberrations at the entrance aperture of the Large Solar Vacuum Telescope were measured with a wavefront sensor of the adaptive optics system by a sunspot. To calculate the image shifts, a correlation algorithm with quadratic interpolation of the correlation function maximum position is used. The quality of astronomical vision, characterized by the Fried length, was estimated from the same experimental data as the statistical characteristics of the fluctuations of the coefficients of expansion of wavefront aberrations in Zernicke polynomials. The results were obtained at a Fried length of 51.6 mm in a sample 43 s long with a sampling frequency of 70 Hz. The means and standard deviations of the expansion coefficients are calculated. The analysis of the given spectra shows that the wavefront aberrations should be compensated in the frequency band 0–20 Hz for the effective correction of the images formed.

The development of the model of turbulent atmosphere on the astroplatform of Large Solar Vacuum Telescope as applied to image adaptation

The development of the model of turbulent atmosphere on the astroplatform of Large Solar Vacuum Telescope as applied to image adaptation

Two-mirror adaptive system for correcting atmospheric disturbances of the Large Solar Vacuum Telescope

Two-mirror adaptive system for correcting atmospheric disturbances of the Large Solar Vacuum Telescope

A working pair of CaCl2–LiBr–LiNO3/H2O and its application in a single-stage solar-driven absorption refrigeration cycle

In this paper, a working pair of CaCl2–LiBr–LiNO3(8.72:1:1)/H2O has been proposed for a single-stage absorption refrigeration system driven by solar energy collected with flat plate solar collectors or vacuum glass tube solar collectors. The crystallization temperature, saturated vapor pressure, specific heat capacity, and specific enthalpy of the proposed working pair were systematically measured. Results showed that under the same refrigeration conditions, the required solar collecting temperature of the single-stage absorption refrigeration cycle based on CaCl2–LiBr–LiNO3(8.72:1:1)/H2O was 7.7 °C lower than that based on LiBr/H2O. Furthermore, the COP of the cycle based on CaCl2–LiBr–LiNO3(8.72:1:1)/H2O was approximately 0.04 higher than that based on LiBr/H2O. The corrosion rates of 316L stainless steel as the structure material and copper as the heat exchange material for the proposed working pair were low enough for practical applications.

Golden Littlest Seesaw

We propose and analyse a new class of Littlest Seesaw models, with two right-handed neutrinos in their diagonal mass basis, based on preserving the first column of the Golden Ratio mixing matrix. We perform an exhaustive analysis of all possible remnant symmetries of the group A5 which can be used to enforce various vacuum alignments for the flavon controlling solar mixing, for two simple cases of the atmospheric flavon vacuum alignment. The solar and atmospheric flavon vacuum alignments are enforced by different remnant symmetries. We examine the phenomenological viability of each of the possible Littlest Seesaw alignments in A5, which preserve the first column of the Golden ratio mixing matrix, using figures and extensive tables of benchmark points and comparing our predictions to a recent global analysis of neutrino data. A benchmark model is constructed based on A5×Z6×Z5×Z5′.

Heat transfer in a directly irradiated ceria particle bed under vacuum conditions

Vacuum particle receivers have been proposed recently for the reduction of redox material in solar thermochemical redox cycles. To assess the performance of these receivers, it is essential to describe the heat transfer in particle beds correctly. A widely used model for effective thermal bed conductivity is the one developed by Zehner, Bauer and Schlünder, which was derived for the steady state case without interstitial gas flow. In this study it was investigated if the model is also applicable for suddenly irradiated ceria particle beds in a typical solar vacuum receiver environment. Therefore a particle bed of ceria was irradiated with a solar simulator under vacuum conditions to peak temperatures above 1300°C. Within the bed, temperatures were measured at different locations for various pressures between 25 Pa and ambient conditions. The experimental results were compared to heat transfer simulations in ANSYS Workbench incorporating the aforementioned bed conductivity model. A good agreement between experiment and simulation was found and the model was considered applicable.

Zero-discharge solution for blackwater treatment at remote tourist facilities

This study presents a novel decentralized sanitary separation system as a zero-discharge solution for blackwater (BW) (faeces, urine and toilet paper) treatment for remote tourist facilities located in sensitive areas. The system operates with low water and energy consumption, enables safe operation and requires low maintenance. The BW was collected from two vacuum toilets (VTs) (0.8 L flush water) and separated in peat filters (PFs) to obtain a liquid fraction (LF) and a solid fraction (SF) of the BW. The LF from the PFs was thereafter treated in a biofilter (BF) and finally evaporated in the evaporation module (EM) powered by solar vacuum collectors (SVC). In the PFs, particles larger than 1 mm were reduced from the BW by 96.5%. Furthermore, the total suspended solids (TSS) mass removal efficiency of the PFs averaged 51.5%. Reduction of ammonia through nitrification was noticeably enhanced after 100 days of the system operation (max. 55.8%). 21.2% or 0.54 kg of total phosphorus (TP) was retained in the PFs, to be further composted and reused for agricultural purposes. An additional 5% or 0.10 kg of TP was retained in the BF. The final step of the LF treatment was in the EM at a sanitizing temperature of >60 °C to prevent the release of human pathogens into environment. With a total electricity consumption of 9.1 kWh/day and a heat consumption of approximately 5.1 kWh/day gained by the SVC, the system successfully integrated different approaches to treating the BW, recycling nutrients, and removing pathogens.

LIFE CYCLE COSTING AND PAYBACK PERIOD EVALUATION OF A SOLAR THERMAL DESALINATION SYSTEM

Water is important for life and development. About 1.8 billion people will be living in absolute water scarcity by 2025.Non availability of safe drinkable water is the major source of diseases in the different regions of the world especially remote rural and coastal areas. About 97% of water on earth is comprised of seawater. Desalination of saline water is a prominent approach to handle the problem of water scarcity. Conventional desalination technologies cause economic and environmental problems due to their dependency upon fossil fuels. Solar flash desalination is one of the best desalination techniques in the developing stages. Solar energy, passive vacuum and recovery of latent heat of condensation make this system a sustainable option for desalination. In this paper, economic analysis of the solar thermal desalination system of saline water is presented. The unit cost of desalinated water is found to be US$ 0.0147 per litre. The energy and emission payback (EEP) period for vacuum chamber and solar collector has also been presented. The energy payback period of solar collector and vacuum chamber are found to be 1.3 years and 1.5 years respectively. The emission payback period of solar collector and vacuum chamber are found to be 1.8 years and 2.1 years respectively.

Thermal Analysis of a Solar Cooling Adsorption System by a Dynamic Model

Abstract—In this paper is shown the possibilities to implement an energy solar system, without auxiliary elements, made to cool. The new technologies (vacuumpacked tube, tanks of build-up with variable volume, etc.), allow the possibility to obtain easily a stand-alone refrigerating system. Today it is always more and more the case where during the summer season there is a surplus of thermal energy whose use is to be assigned within the energy optimization system. The most immediate solution to this problem is the ability to produce cold by means of simple adsorption solutions, thus contributing to the cooling problem with low COP values. The most beneficial adsorbent both for its thermal/physical and low cost is the silica gel, a polymer of silicon dioxide, commonly used for its dehydrating properties, especially in the preservation of electronic material [1,3,13].
 In this study we have developed a dynamic model with the software trnsys to verify the obtaining of appropriate warm fluid for an innovative cooling system absorption with gel of silica and water and it is tested on a real building as case study.
 The dynamic model analyzes the performance thermodynamic balance of a small size system has been made (about 20-50 kW), adequate to cool a Building of 900 sq m. and allow to assess the conformation (surface, storage volume, etc.). of a new generation solar power plant is able to guarantee a continuous operation during the summer period [2].
 We have tested a solar cooling system with solar vacuum collectors on a real Building with Meteo data of three Cities as Rome Milan and Tunisi and we have tested the model comparing the results obtained.
 The model in fact allows to make a preliminary design of principal part of the plant and to evaluate function cost-benefit of a complex investment for innovative technology The interesting results obtained allow at a later stage to make a prototype validating the theoretical results with experimental measures.
 Index Terms—Silica gel, Solar Cooling, Building

The use of solar energy for residential buildings in the capital city

Taking into account the conditions of sharply continental climate of Russia the implementation of the project of heating for an apartment house can be structured on the basis of solar vacuum collectors. A diagram of the operation of the vacuum solar collectors can be considered for heating and hot water. The calculations of effective angle of solar collectors also vary for stationary use in winter and summer. Consumption of centralized heat in the spring and autumn is reduced by 30 % due to the use of solar collectors. In summer the main problem of application of solar collectors is to protect the tubes from overheating. In winter, the use of solar heating is able to provide not more than 25 % of the needs regarding the utility and the results of experimental exploitation. It is shown that the main problem of using solar energy in Russia relies not in technology, but in the legislative field. The use of a vacuum manifold in Russia will be widely implemented in areas with a cold climate and in the modern houses after solving the issues of legislative support from the state and municipal authorities.

Adaptive optics system for solar telescope operating under strong atmospheric turbulence

New results obtained within Russian Science Foundation Project no. 15-19-20013 are presented. The project was started in the middle of 2015 and is aimed at the solution of actual problems of the development of the optoelectronic industry using adaptive optics for astronomy, laser, and other applications. The progress in the development of the up-to-date adaptive optics system for the largest Russian solar telescope, i.e., the 1-m Big Solar Vacuum Telescope of the Baikal Astrophysical Observatory, is described.

Heat transfer property of SiO2/water nanofluid flow inside solar collector vacuum tubes

Nanofluid is one of the innovative and promising heat-transfer fluids. In this work, SiO2/water nanofluid was prepared with two-step method by microfluidizer processor. The thermal conductivity and the transmissivity of SiO2/water nanofluid with mass fraction of 1%, 3% and 5% were tested in the experiment. The temperature variations and velocity distributions of working fluid including water and nanofluid were calculated via numerical simulation in order to discuss the heat transfer property of SiO2/water nanofluid flow inside the collector tube. According to the numerical model, water and SiO2/water nanofluid (5wt.%) were chosen as the working fluids of solar-collector vacuum tubes in insolation experiment, respectively. The results showed that the heat-transfer property of SiO2/water nanofluid were higher than that of water and increased with the mass fraction. Meanwhile, the influences of the placing time of nanofluid on heat transfer property were also referred. The results indicated that longer nanofluid placing time, easier nanofluid agglomeration and this phenomenon led to its heat transfer character became weak.

A developed solar-powered desalination system for enhancing fresh water productivity

A solar-powered desalination system using condenser integrated with flat-plate solar collector and vacuum pump was developed for producing fresh water and compared its performance with the ordinary solar desalination system without vacuum pump under different operational conditions. Systems temperatures added to ambient temperature were measured with hour intervals, under all experimental conditions for both solar desalination systems. Heat and mass transfer regimes were conducted for the used parallel condenser. Performance of the two systems was studied as a function of change in water salinity level and water tank flow rate and evaluated in terms of recorded temperatures, condenser efficiency, water productivity and cost. The experimental results reveal that the developed system increases water productivity for all water salinities compared with the ordinary system due to the presence of vacuum pump. The same results also reveal that water productivity increased and cost decreased by increasing water flow rate using the developed system while the vice versa was noticed using the ordinary system. Maximum fresh water productivity values of 10.94 and 7.27 L/d corresponding to cost values of 0.031 and 0.030US $/L were recorded at ground water tank flow rates of 0.80 and 0.40 L/h using developed and ordinary systems, respectively.