Abstract
Content
- Introduction
- 1. Theme urgency
- 2. Description SPP structure
- 3. Simulation the solar battery
- Conclusion
- References
Introduction
In recent years, much attention has intensified the search for and development of alternative energy sources, which differ from fossil organic resources for its huge reserves, i.e. they are practically inexhaustible or renewed periodically. Contamination of the environment, the increase in energy prices and reduce their inventories justify the use of environmentally friendly and possibly cheaper sources of energy. These are the so–called renewable energy sources (RES). One of the most promising types of renewable energy is the energy of the sun. The sun, by human standards, – an inexhaustible source of energy. There are devices that convert solar energy into electricity. These solar cells to create solar power plant (SPP) solar cells combined in a battery and attached at the bottom for ease of final assembly and increase strength. This design called a solar panel, or a solar module. Now, the production of solar panels has reached significant proportions. Regarding the available solar modules have a coefficient of conversion of sunlight into electricity 7–18%. The maximum conversion rate is currently about 40%. However, the high cost of high–performance components does not allow them to create consumer power, because it is not economically feasible.
1 Theme urgency
The urgency of solar energy is growing because solar energy is environmentally friendly. The second reason for the relevance of the use of solar energy is its carrying capacity.
Total for 9 minutes the Earth receives more energy from the sun than humanity produces for the entire year. This energy is supplied free of charge and has no impact on the environment directly in your apartment.
Under the solar energy usually described as a sunlight conversion into heat. Solar energy used to produce hot water and heating system can support. Heat may very well be stored and available for several days. Convert solar energy systems used for heating and heated potable water.
Solar energy is a significant scope of investments in the face of declining oil and gas reserves. Solar energy helps to increase world consumption and an increase in fossil fuel prices.
Heat pumps used to ensure the circulation of energy in the environment. The refrigerant used for heat production. These components combine perfectly in a plant for the production of solar energy.
Operating costs for solar energy for heating is low, compared to comparable systems without the use of solar energy.
2 Description SPP structure
The basis of the solar power plant is a photoelectric converter. The principle of operation of the photoelectric converter is quite simple and as follows.
When illuminated by sunlight single silicon photoelectric converter generates an electrical voltage of approximately 0.5 V. Regardless of the type of the circuit and all (big and small) silicon solar cells generate a voltage of 0.5 V at no load and nominal value of insolation.
To increase the production of the individual PEC energy come together and form a photovoltaic modules which then connected into arrays (Fig 1.) To increase the output voltage of solar cells connected in series, and to increase the power – in parallel. The modular structure allows you to build different solar cells photovoltaic systems, depending on the power generation for various applications. Thus, the photovoltaic cell is a component of the photovoltaic systems.
Figure 1 – The photovoltaic element module and an array of PEC (animation: 4 frames, 7 repeating, 112 kilobytes)
Successive modules behave as energy consumers: they heat up when current flows and may break down wheeling diodes (as shown in Fig. 2) are used for protection.
Figure 2 – Series connection of solar modules reverse diode
In a parallel connection, and there is shading a separate item, it becomes locked and loaded for the other elements, as a result of the shaded element overheats and can fail. To protect against this mode is set in each branch of the locking diodes (Fig. 3).
Figure 3 – Location of locking diodes in parallel connection
Fig. 4 shows a diagram of a combined PV module with locking and reverse diode.
Figure 4 – The photovoltaic generator with backward and locking diodes
An effective way to solve the problem of shadowing is the parallel connection of bypass diodes to all elements, as shown in Fig. 5. The diodes connected so that when working solar cell, they are shifted back to the voltage of the element itself. Therefore, no current flows through the diode, and the battery is functioning properly.
Figure 5 – Parallel connection of shunt diodes
The circuit operates as follows. Suppose that one of the items obscured. In this case, the diode is forward–biased, and through it to the load current flows to bypass the faulty element. Of course, the output voltage of the entire chain reduced to 0.5 V, but eliminate the source of self–destructive force for the shaded solar cell.
A further advantage of this arrangement is that the battery continues to operate normally. Without the bypass diodes, it would be completely out of order.
In practice, inappropriate shunting each battery cell. It should be guided by considerations of economy and the use of shunt diodes based on a reasonable compromise between reliability and cost.
Typically, one diode is used to protect of 1/4 battery. Thus, the entire battery requires only four diodes. In this case, the shading effect will lead to a 25% (it is permissible) output power reduction.
3 Simulation the solar battery
Schematic diagram (Fig. 6), dubbed the model of the diode
, shows a solar battery cell. This model consists of a current generator, which connected parallel to the diode and shunt resistor Rsh (parallel resistance). Besides them to one of the alternator, terminals connected to the series resistance Rs (series resistance).
Figure 6 – Schematic model (equivalent circuit) solar batteries
Elements of the equivalent circuit diagram (Fig. 6) indicated as follows:
- Iph – photogenerated electric current [A],
- Id – diode electric current [A],
- Ud – diode voltage [V],
- I – output electric current [A],
- U – voltage to the terminal [V],
- Ish – shunt electric current [A],
- Rsh – parallel resistance [Ohm],
- Rs – series resistance [A].
The classical model of the semiconductor solar cell consists of a parallel–connected source photocurrent and bypass diode. Modelling of the solar panel element is produced using MATLAB/Simulink software, which is presented in Fig. 7.
Figure 7 – Solar battery model in MATLAB/Simulink
Based on this model have been calculated volt–ampere characteristics of the solar battery type for various lighting conditions, at ambient temperature of 25 degrees Celsius.
Fig. 8 shows the calculated current and power characteristics of solar panels for the solar cell light level E = 1000 W / m2 (under standard conditions). The figure shows that the highest efficiency solar panel occurs at a load corresponding to a fixed position of the operating point of maximum power.
Figure 8 – VAC and VVC normally
Shadowing modeled with a decrease in the level of insolation. The shaded state module also converts the energy and can give it to the common circuit, but the volt–ampere characteristics of the solar module (Figure 9) does not allow to use it with maximum efficiency, because the operating point of the shaded cell is near zero power and transformed the whole energy is dissipated in the module.
Figure 9 – VAC and VVC performance in shaded photocell
Conclusion
In the abstract, the problem of shading of solar cells and its effect on the work of SPP are described prevention measures are not effective work of the SPP and increase its efficiency in various lighting conditions. Just consider a model of the solar panel in the Matlab/Simulink environment, on the basis of which the calculation model of current–voltage characteristics of the solar cell were performed for various lighting conditions.
In writing this essay master's work is not yet complete.
Final completion: June 2017. The full text of work and materials on the topic can be obtained from the author or his manager after that date.
References
- Фролкова Н. О. Компьютерное моделирование вольтамперных характеристик солнечных батарей / И. В. Абраменков, Н. О. Фролкова // Тезисы докладов XIV международной научно–технической конференции студентов и аспирантов. – 2008. – С. 381–383.
- Шарифов Б. Н., Трегулов Т. Р. Моделирование солнечной панели в программе Matlab/Simulink. – 2015.
- Лунин Л. С., Пащенко А. С. Моделирование и исследование фотоэлектрических преобразователей. – 2010.
- Цигельман И. Е.
Электроснабжение гражданских зданий и коммунальных предприятий
М.1977. - Дьяков В. И. Типовые расчеты по электрооборудованию. – М.:Высшая школа, – 1976.
- Cole D. C. Extracting Energy and Heat from the Vacuum, Phys. Rev. E 48, 1562 (1993).
- Forward R. L. Extracting Electrical Energy from the Vacuum by Cohesion of Charged Foliated Conductors, Phys. Rev. B 30, 1700 (1984).