Benchmarking study between capacitive and electronic load technic to track I-V and P-V of a solar panel

<p>To detect defects of solar panel and understand the effect of external parameters such as fluctuations in illumination, temperature, and the effect of a type of dust on a photovoltaic (PV) panel, it is essential to plot the Ipv=f(Vpv) characteristic of the PV panel, and the simplest way to plot this I-V characteristic is to use a variable resistor. This paper presents a study of comparison and combination between two methods: capacitive and electronic loading to track I-V characteristic. The comparison was performed in terms of accuracy, response time and instrumentation cost used in each circuit, under standard temperature and illumination conditions by using polycrystalline solar panel type SX330J and monocrystalline solar panels type ET-M53630. The whole system is based on simple components, less expensive and especially widely used in laboratories. The results will be between the datasheet of the manufacturer with the experimental data, refinements and improvements concerning the number of points and the trace time have been made by combining these two methods.</p>

EVALUATION OF FIRE RESISTANCE OF FIRE PROTECTED STEEL STRUCTURES BY CALCULATION AND EXPERIMENTAL METHOD

Based on the developed geometric, physical, computer and finite element model, the fire resistance of fire-resistant steel structures was evaluated by calculation and experimental method. The adequacy of the developed computational-experimental method for assessing the fire resistance of fire-resistant steel structures in assessing the fire resistance of a fire-resistant I-beam steel column was verified. The results of tests for fire resistance of steel columns with fire-retardant coating at standard temperature of the fire without the load applied to them (temperature in the furnace, temperature in certain places on the surface of fire-retardant steel columns, the behavior of the investigated fire-retardant coating). The analysis of tests on fire resistance of fire-resistant steel columns exposed to fire at standard temperature (temperature in the furnace, temperature in places of measurement of temperature on a surface of columns, behavior of a fire-retardant covering) is carried out. A computer model of the «steel column – reactive flame retardant coating» system has been built for numerical simulation of non-stationary heating of such a system. Simulation of non-stationary heating of the system «steel column – fire-retardant coating» in the software package FRIEND with the specified parameters (geometric model, thermal effects, initial and boundary conditions, properties of system materials). The reliability of the results of numerical modeling with real experimental data on the duration of fire exposure at the standard temperature of the fire to reach the critical temperature of steel. Based on the comparison of experimental results and numerical simulations, a conclusion is made about the adequacy of the developed model to the real processes that occur when heating fire-retardant steel columns without applying a load under fire conditions at standard fire temperature. The efficiency of the proposed calculation and experimental method for assessing the fire resistance of fire-resistant steel structures has been confirmed.

EVALUATION OF FIRE-PROTECTIVE ABILITY OF NEWLY CREATED FIRE-PROTECTIVE COATINGS OF STEEL STRUCTURES

The results of the development of fire-retardant substances based on domestic materials to increase the fire resistance of fire-retardant steel structures are presented. New compositions of fire-retardant substances on the basis of domestic materials capable of swelling are developed. A series of experimental studies to determine the heating temperature of fire-resistant steel structures. For this purpose, samples of reduced size in the form of a steel plate with a flame retardant applied to the heating surface were used. Fire tests of fire-retardant steel plates coated with the developed fire-retardant substance forming a coating on the protected surface, in the conditions of their tests on the standard temperature of the fire using the installation to determine the fire-retardant ability of fire-retardant coatings. The results of experimental determination of temperature from an unheated surface of steel plates with a fire-retardant covering in the conditions of fire influence at a standard temperature mode of a fire are analyzed. Based on the obtained data (temperature in the furnace and from the unheated surface of steel plates with fire protection system) the solution of the inverse problems of thermal conductivity found thermophysical characteristics of fire protection coating (thermal conductivity and specific volume), which can be used for thermal calculation heating of fire-retardant steel structures at arbitrary fire temperatures. The thermophysical characteristics of the formed fire-retardant coating are substantiated to find the characteristics of the fire-retardant ability of the newly created fire-retardant coating and to ensure the fire resistance of fire-retardant steel structures. The efficiency of the developed fire-retardant coating for protection of steel structures is proved.

Determination of features of composite steel and concrete slab behavior under fire condition

Methods for calculating the fire resistance of steel-reinforced concrete slabs made using profiled steel sheets under the influence of a standard temperature regime for more than 120 minutes are considered and analyzed. Research has been carried out to determine the heating parameters and the stress-strain state of steel-reinforced concrete slabs made using profiled steel sheets under fire conditions for more than 120 minutes. The results of this study allow to obtain indicators of temperature distribution for assessing the fire resistance of such structures for fire resistance classes above REI 120. Accordingly, the results obtained are a scientific basis for improving the existing method for calculating the fire resistance of steel-reinforced concrete slabs made using profiled steel sheets. The temperature distribution in the cross-section of structures was obtained using a general theoretical approach to solving the problem of heat conduction using the finite element method. Using the obtained temperature distributions, the parameters of the stress-strain state were determined based on the method of limiting states. To carry out the calculations, appropriate mathematical models were created that describe the effect of the standard temperature regime of a fire, to determine the temperature distribution at every minute in the sections of steel-reinforced concrete slabs with profiled steel sheets. A method is proposed for dividing the section into zones to take into account the decrease in the indicators of the mechanical properties of concrete and steel. A simplified method for the design assessment of steel-reinforced concrete slabs made using profiled steel sheets is proposed, which is consistent with the current EU standards and can be effectively used to analyze their fire resistance when establishing their compliance with the fire resistance class REI 120 and higher.

THE EFFECT OF SHORT-TERM TEMPERATURE STRESS ON THE GERMINATION OF DILL SEEDS

New data on the process of germination of dill seeds of the first and second orders after short-term heat stress (40 ° C) have been obtained. Seed germination was carried out in a thermostat. Swollen seeds (four repetitions of 100 seeds) were exposed to a temperature of 40 ° C in accordance with the scheme of the experiment: 0 (control); 1; 2; 3; 4 and 5 days. After incubation, the seeds were transferred to standard (t = 20 ° C) conditions and germinated in Petri dishes on filter paper with-out access to light for 21 days. Methods of analysis of seed germination in dynamics are used. Log-logistic regression with three parameters was used to construct the seed germination curve: b, d, e. All statistical analyses were performed in R version 3.4.3. The duration of the action of high temperature, which has an inhibitory effect on the germination rate and the number of germinated seeds, was revealed. Seeds of the first order in the control and after incubation for 1-3 days germi-nated in a similar way, and with an increase in the incubation period to 4-5 days, the rate of ger-mination decreased sharply. The seeds of the second order were even less resistant to the action of a short high-temperature stressor, and when the seeds were incubated for 3 days and then trans-ferred to standard temperature conditions, germination did not occur. The germination time of 50% of seeds (T50) of the first order as a result of a sequential increase in the incubation period at 40 ° C increased from 0.92 ± 0.11 to 6.4 ± 0.49 (p<0.001) days, respectively. Seeds of the second order during incubation for 1-2 days also germinated significantly slower compared to the control, and in the future germination did not occur. The curves of changes in the index of maximum seed germination, especially for the second order of branching, had a sharp bend when the critical dose of the temperature factor was exceeded. After that, there was a sharp decrease in the speed of seed germination up to a complete stop. The maximum incubation time (at 40 ° C), after which germi-nation is possible under standard temperature conditions, was 3.69 ± 0.06 days for the first order, and 2.00 ± 0.19 days for the second order. The difference was significant at the significance level of p<0.001.

Investigation of the influence of the configuration of the fire furnace chamber on the temperature regime during the implementation of tests for fire resistance

The issue related to the conditions for creating the required temperature regime of fire when testing structures for fire resistance has not been studied in detail up to now. That necessitated determining the technical conditions under which it is possible to comply with the standard temperature regime of fire in the fire chamber of the furnace. The influence of the design parameters of the fire furnace chamber on the condition of compliance with the standard fire temperature regime when tested for fire resistance has been established. One of the most effective methods for examining such an impact is computer simulation. A computer model of the fire furnace was built on the basis of a comprehensive analysis and earlier work on the study of such furnaces, taking into consideration technical characteristics, in particular, geometrical parameters, fuel and air supply systems. The obtained research results are a prerequisite for scientific substantiation of the design parameters of fire furnaces and their engineering systems, which is necessary to comply with the standard temperature regime of fire in the furnace fire chamber. This makes it possible to provide the necessary conditions for testing building structures for fire resistance in compliance with the requirements of the relevant standards. The computer model constructed makes it possible to create the necessary temperature regime in the fire chamber of the furnace (in this study, the standard temperature of fire). As a result of the study, the technical parameters of the fuel supply and ventilation system were determined, which ensure compliance with the standard temperature regime in the fire chamber of the furnace. That makes it possible to build an automated complex of the testing process for fire resistance of building structures. In addition, the data obtained can be the basis for the design of such fire furnaces with the ability to comply with different fire temperature regimes without the intervention of the operator.

The use of underground thermal gradients as technique for soil radon mitigation

Diffusion coefficients of radon through minerals and rocks are characterised by Arrhenius linear plots, i.e., increasing with temperature. It has been observed, for example, that rocks with a mild heating (<100°C) translate into a radon release that can be enhanced 100–1,000 times than the normal release at STP (Standard Temperature Pressure (STP). Therefore, it is reasonable to think that if the soil is deliberately heated creating a thermal gradient, it could be possible, at least from a theoretical point of view, to thermally pump radon from soil because the radon atoms will escape preferentially from cold regions (low diffusion coefficient) towards hot regions (high diffusion coefficients) if a radon sink is located. In this short note, this approach for soil radon removal is investigated.

Investigation of the Limit of Fire Resistance of a Steel Beam at Loss of Integrity of a Fire-Resistant Lining

In this article, to solve the main problems, we determined the temperature regime of heating the steel beam, which took into account the fact of loss of integrity of the fire-retardant lining due to the thermal effects of fire. When calculating the temperature, the time of exposure to the standard temperature of the fire and the value of the heating temperature of the steel beam with mineral wool lining at which the latter loses its integrity was determined. Taking into account the geometrical parameters of the cross section of the studied I-beam, according to the finite-element scheme, the steel beam was divided into four elements of SHELL type with five points of integration in thickness in the Belichko-Tsai formulation. After the calculation, the corresponding results were obtained in the form of graphs of changes in the maximum deflection of the beam and the rate of increase of the maximum deflection depending on the time of exposure to the standard temperature of the fire. The critical values of the occurrence of the limit of fire resistance according to the graph of maximum deflection and the graph of the rate of increase of deflection were determined. The difference between the indicators shows that the time of the limit state of loss of bearing capacity is 70 min less, if not taking into account the loss of fire-retardant capacity of mineral wool fire-protection due to loss of integrity.