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Solar converters ensure uninterrupted operation of medical equipment***
Solar converters ensure uninterrupted operation of medical equipment
Yakimovich B.А.1, Kuvshinov V.V.2, Bereznyak V.А.3, 1,2,3,4 Sevastopol State University, Sevastopol, Russia, Universitetskaya St., 33, 299053
مؤلفون / Authors Results of the research
Energy-efficient charging solar panels based on semiconductor silicon photovoltaic converters with a nanomodified receiving surface are proposed to ensure the uninterrupted operation of the EMS apparatus.
photoelectric converter, nanomodified surface, EMS technology, uninterruptible power supply, solar panel.
and development of an electric power plant was carried out to ensure the uninterrupted The use of EMS technologies makes it possible to achieve high-quality treatment and rehabilitation for socially significant diseases (muscular atrophy, diseases of the musculoskeletal system, injuries, fractures, etc.). In the course of the work, a research operation of EMS apparatus with an uninterruptible power supply using a charging panel from silicon photoconverters with a nanomodified surface. The development and implementation of EMS apparatus with a backup power supply unit allows its use not only in medical institutions, but also at other facilities that do not have centralized power supply.
Sunlight is a renewable and inexhaustible source that is used to produce both thermal and electrical energy. In addition, solar energy is the most environmentally friendly and virtually has no harmful emissions. The total amount of solar energy reaching the Earth’s surface in a week exceeds the energy of all world reserves of oil, gas, coal and uranium [1]. Currently, the conversion of solar energy into electrical energy is one of the most promising directions [1]. The generation of electrical energy is carried out using photovoltaic converters, which are widely used for energy supply to the population, production facilities, space stations. The operation of the photovoltaic converters is based on the photovoltaic effect that occurs in inhomogeneous semiconductor structures when exposed to solar radiation [2]. In order to obtain research data on photovoltaic modules used in photovoltaic installations and to study their power losses, it is necessary to conduct full-scale tests at various angles of their operating modes. In particular, the change in their operating modes is directly affected by the change in their power characteristics associated with various factors. Such factors are a change in the angle of the impact of the sun's rays on their receiving surface, due to the movement of the Sun across the sky, a change in the intensity of the flow of solar radiation, due to cloudiness, a change in atmospheric temperature, the presence of snow cover, etc. However, the main problem for their large-scale use is the low power efficiency, low density and variability of the flow of natural solar radiation converted into electrical energy, and, as a result, a relatively high cost per unit of power [3], Semiconductor photovoltaic converters based on monocrystalline or polycrystalline silicon have become the most widespread. The efficiency of existing solar-to-electric energy converters is not high enough, which is one of the most important factors hindering progress in this area. One of the reasons is that the efficiency of the most common silicon solar cells does not exceed 25% [4]. In addition, a decrease in the generation of electrical energy occurs as a result of such reasons as a change in the angle of incidence of sunlight and heating of the surface of the modules. The negative influence of these factors similarly affects the thermal efficiency of solar thermal converters [5]. For this reason, work is actively underway to improve the technical and economic indicators of such devices [6]. Increasing the power of photovoltaic converters is possible, in particular, by forming plasmonic coatings on the receiving surface of solar cells [6]. The paper [7] presents data demonstrating a 20% increase in the power characteristics of solar cells as a result of modifying their surface with silver nanoparticles. An increase in electricity generation was also noted due to a more complete conversion of the incident solar radiation flow, even at small angles of incidence of sunlight on the receiving surface. Studies of the influence of temperature on the energy characteristics of photovoltaic converters have shown that the decrease in efficiency reaches up to 21% when their working surface is heated to a temperature of 70 °C [1]. In the case of monocrystalline and polycrystalline photopanels, the temperature power factor reaches a value of -0.45%, that is, there is a decrease in power by 0.45% for each degree of temperature increase. In this regard, the problem of cooling photodetector surfaces becomes urgent. At the same time, the conversion coefficient of solar radiation into electrical energy by modern serial silicon photovoltaic modules does not exceed 15-20%. Polycrystalline silicon-based solar cells have the cheapest watt of electricity, but their output is even lower. All these factors stimulate the search for an increase in the efficiency of photovoltaic converters [3-5], thus, the insufficient efficiency of existing solar engineering materials is one of the main reasons hindering the development of solar energy. In this sense, the task of improving the characteristics of industrially produced solar cells is certainly relevant.
Problem statement and objectives of the research Ensuring high-quality operation of medical equipment using energy-saving technologies and solar cells for the uninterrupted operation of EMS apparatus and medical equipment. In Fig. 1 you can see what EMS (Electric MioStimulation) equipment looks like.
Fig. 1. The appearance of EMS apparatus (Electric Mio Stimulation) A large number of different power supply systems are used for the operation of modern medical equipment. One part of these installations operates exclusively on AC power, the other uses built-in batteries. However, it is most effective to use combined power supply systems, in which accumulative uninterruptible power supply units are provided with the possibility of recharging from a common power system. But what to do if there is a prolonged absence of centralized power supply? It is most logical to use any improvised means that can generate low-power electricity and ensure uninterrupted operation. Such systems must meet certain requirements and during their operation, the quality and service life of auxiliary and main electrical equipment must not decrease. For the resort and recreational system (balneology, spa medicine, physical therapy, massage, etc.), various equipment is used, which has certain technical characteristics. In particular, there are so-called EMS technologies (EMS apparatuses) used for medical (rehabilitation) purposes. The objective of the work is to ensure the high-quality operation of medical equipment using energy-saving technologies and solar cells for the uninterrupted operation of EMS apparatus. Solar converters were used as a charging battery for an uninterruptible power supply in order to achieve this goal. However, constant use for work in non-stationary conditions and moving outside studios and medical salons can lead to equipment breakdowns. Therefore, photoconverters with increased energy characteristics were chosen to solve this problem. One of the objectives of the work was to create a charging energy-efficient solar panel based on a photovoltaic converter with a nanomodified receiving surface [5-7], which could be used to ensure the uninterrupted operation of EMS apparatus. The introduction of EMS technologies with backup power sources for resort and recreational facilities is a promising direction. To use backup power sources in electrical systems with solar cells for the operation of EMS apparatuses in “field conditions”, it is necessary to conduct additional experimental studies related to the determination of charge-discharge parameters. The main technical parameters that determine the quantitative, qualitative and cost characteristics of products (in comparison with existing analogues, including world ones) are: the technical characteristics of EMS apparatus with backup power sources are the electrical parameters of photo converters, battery capacity, number of solar cells, etc. To charge the battery of the backup power sources, a photovoltaic module (brand ARX-12, manufactured by SIMENS) is used, consisting of 36 photovoltaic cells connected in series, with a power of 12 watts with output current and voltage characteristics of 16 V and 0.6 A, a charge-discharge controller, and other auxiliary equipment. Additionally, a mini photovoltaic installation with polysilicon solar cells modified with silver ion nanoclusters will be used to charge the battery. The presented elements were processed in the spark plasma sintering laboratory (located at MSTU “Stankin” in Moscow) and have increased operational characteristics (service life, degradation during heating, hardness, etc.). Comparing with a similar device manufactured by Samsung Electronics Co., Ltd, which does not have photovoltaic converters, it is significantly superior in cost and inferior in charge quality. The cost of ARX-12 photovoltaic module is $30, the cost of additional photovoltaic cells with a nanomodified surface is $ 60. Design requirements (including technological requirements, reliability requirements, operation, maintenance, repair, storage, packaging, labeling and transportation) are: the prototype is a battery charger manufactured by Samsung Electronics Co., Ltd. containing an electric generator made synchronous and excitable by a permanent magnet, with a pneumatic drive consisting of one elastic chamber and the rigid partition, inside which the rectifier, the battery and the universal plug connector are located. The channel is also made, in which the impeller is located, placed on the shaft of the electric generator mentioned above. An additional device for charging the battery of EMS apparatus will be a solar battery with nanomodified elements. The elements presented from the spark plasma sintering laboratory of MSTU “Stankin” have increased operational characteristics, in particular, they have more heat-resistant characteristics, have significantly greater impact resistance than conventional silicon elements and increased efficiency values (20% higher than non-modified elements). These elements are more resistant to transportation and also degrade during operation. Patent protection requirements (availability of patents), essential distinguishing features of the product (technology) being created from the existing ones, providing the expected effect: the prototypes are battery chargers: portable folding solar panel Solar Charger SunPower 15Вт 15W, portable folding solar panel Solar Charger SunPower 6Вт 6W, which are used to charge tablets and have solar cells less effective than nanomodified photoconverters. There is also an analogue manufactured by Samsung Electronics Co., Ltd, containing an electric generator made synchronous and excitable by a permanent magnet, which does not have photovoltaic converters and is not adapted to work with EMS apparatus. The first stage: testing of ARX-12 photovoltaic module, investigation of the electrical and power characteristics of the module, assembly and testing of a solar installation with nanomodified elements. The second stage: assembly and testing of EMS apparatus with an uninterruptible power supply using a charging panel from ARX-12 module and silicon photoconverters with a nanomodified surface.
During the development of the electric power plant, silicon photoconverters with a working surface nanomodified with silver ions, were used to ensure the uninterrupted operation of EMS apparatus. The work was performed by the ion resonance method in the spark plasma sintering laboratory located at the Moscow State Technical University “Stankin” in Moscow [5-7]. The resulting solar cells have a high conversion coefficient, increased hardness and operational efficiency. Their power characteristics are shown in Fig. 2. As can be seen from the graphs, there is a 20% increase in the power characteristics of photovoltaic converters when applying nanocoatings on their working surface.
Fig. 2. Power characteristics of a nanomodified (solid line) and factory polysilicon (dotted line) solar cell. Under field conditions, changes in the angle of incidence of rays on the receiving surface of the photovoltaic module by a certain amount lead to a corresponding change in the illumination of the working surface of the EO module, which, in turn, affects the operation of the photovoltaic module [8-10].It is possible to simulate the situation of changing the illumination of the working surface when the sun moves along the horizon by changing the position of the installation angle of the photovoltaic module to the horizon for a short time and conducting direct measurements of the current and voltage of the module when the load resistance changes [7]. Fig. 3 shows theoretical and experimental characteristics.
Fig. 3. Experimental and theoretical power characteristics of photoconverters: nanomodified solar cell (solid line), factory element (dashed line), theoretical characteristic (dotted line).
As can be seen from the graphs, solar cells with a nanomodified surface transform the solar radiation flow more efficiently at critical angles of incidence [10]. Increasing the conversion of solar cells at small angles of incidence of sunlight can significantly increase the generation of electricity by solar modules. On the graphs (Fig. 2, 3) we can see a significant increase in the power characteristics of solar cells used in factory modules when coating them with silver nanoparticles and maintaining their power characteristics at small angles of incidence of solar radiation [4, 7]. The use of solar cells with nanocoating allows to increase the generation of electricity by photovoltaic installations due to a more complete conversion of the flow of incident solar radiation even at small angles of incidence of sunlight on the receiving surface [5-7]. The data obtained will contribute to the growth of the power characteristics of various types of solar cells, increase their conversion coefficient, increase the efficiency of photovoltaic installations and devices for various purposes, without increasing the area of their receiving surface, which will significantly expand the scope of use of solar power plants [6]. The use of polysilicon solar cells with a nanomodified surface for charging storage systems used for EMS apparatus. The use of backup power sources systems with photocells for the operation of EMS apparatuses outside the centers in “field conditions”, in the absence of access to the general power grid. The results of this work expand the understanding of the processes of formation of functional surfaces, the operation of photovoltaic energy converters, the influence of micro-impurities on the efficiency of photovoltaic converters. The established regularities allow us to evaluate the efficiency of modifying photovoltaic converters. The experimental data obtained shows that the use of polysilicon photovoltaic converters is much more effective in thermal photovoltaic installations, especially with a working surface modified with silver nanoclusters. When using modified elements with significant resistance to overheating, it becomes possible to cover the entire plane (and not just the lower part) of the thermal absorber, thereby providing an even greater increase in electricity generation by the solar installation module. In addition, the surface nanocluster layer will make it possible to abandon the use of an expensive selective coating, usually used on a heat-absorbing surface. Taking into account the slowdown in the rate of decrease in the efficiency of solar cells when the receiving surface is heated, the energy output of the thermophotovoltaic solar collector as a whole can be significantly increased, and the implementation of the results achieved can enhance the power electrical characteristics of solar plants by more than 25%.
The use of EMS technologies for hospitals and other medical institutions helps to increase the efficiency of rehabilitation centers and the recovery of people suffering from diseases such as muscular atrophy, diseases of the musculoskeletal system, etc. The expansion of the use of the proposed EMS apparatuses with uninterruptible power supply and charging units from solar panels contributes to better treatment. In the course of the work, it was revealed that the modification of the surface of solar cells with silver nanoparticles leads to an increase in power characteristics by 20% due to the initiation of the effect of surface plasma resonance. The use of solar cells with increased characteristics contributes to an increase in their service life and in the conversion coefficient. The introduction of solar installations in EMS technology contributes to a higher efficiency of the use of medical equipment by working in full-scale conditions in recreation areas at different times of the year.
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