Efficient conversion of free rays of the sun into energy, which can be used to supply housing and other objects, is the cherished dream of many apologists for green energy.
But the principle of operation of the solar battery, and its efficiency are such that it is not yet possible to speak about the high efficiency of such systems. It would be nice to get your own additional source of electricity. Is not it? Moreover, even today, in Russia, with the help of solar panels, a lot of private households have been successfully supplied with “gratuitous” electricity. You still do not know where to start?
Below we will tell you about the device and the principles of operation of the solar panel, you will learn what determines the efficiency of the solar system. Video clips posted in the article will help you personally assemble a solar panel of photovoltaic cells.
The content of the article:
- Solar panels: terminology
The internal structure of the solar battery
- Kinds of photocell crystals
- The principle of the solar panel
- Solar Battery Efficiency
- The power scheme of the house from the sun
- Conclusions and useful video on the topic
Solar panels: terminology
In the subject of "solar energy" a lot of nuances and confusion. Often, newcomers to understand all unfamiliar terms at first can be difficult. But without this, it would be unwise to engage in solar power, acquiring equipment for generating solar current.
Unknowingly, you can not only choose an unsuitable panel, but also simply burn it when connected or extract too little energy from it.
The maximum impact from the solar panel can be obtained only by knowing how it works, what components and components it consists of and how it all connects correctly.
First, you need to understand the existing types of equipment for solar energy. Solar panels and solar collectors are two fundamentally different devices. Both of them convert the energy of the rays of the sun.
However, in the first case, at the output, the consumer receives electric energy, and in the second, thermal energy in the form of a heated coolant, i.e. solar panels are used to home heating.
The second nuance is the concept of the term “solar battery” itself. Usually, the word “battery” means a device that accumulates electricity. Or a banal heating radiator comes to mind. However, in the case of helio-batteries, the situation is radically different. They accumulate nothing in themselves.
The solar panel generates a constant current. To convert it to a variable (used in everyday life), an inverter must be present in the circuit.
Solar panels are designed exclusively for generating electrical current. It, in turn, accumulates to supply the house with electricity at night, when the sun goes down beyond the horizon, already in the batteries present in the object's additional energy supply system.
The battery here is meant in the context of a certain set of similar components that are assembled into something whole. In fact, this is just a panel of several identical photocells.
The internal structure of the solar battery
Gradually, solar cells are becoming cheaper and more efficient. Now they are used for recharging batteries in street lamps, smartphones, electric cars, private homes and satellites in space. They even began to build high-grade solar power plants (SES) with large volumes of generation.
Heliobattery consists of a set of photovoltaic cells (photoelectric converters FEP) that convert the energy of photons from the sun into electricity
Each solar battery is arranged as a block of the nth number of modules that combine sequentially connected semiconductor photovoltaic cells. To understand the principles of operation of such a battery, it is necessary to understand the work of this end unit in the device heliopanel, created on the basis of semiconductors.
Kinds of photocell crystals
Options FEP from different chemical elements, there is a huge amount. However, most of them are developments in the initial stages. At present, only silicon-based photovoltaic panels are being commercially produced.
Silicon semiconductors are used in the manufacture of solar cells because of their low cost, they cannot boast of particularly high efficiency
An ordinary photocell in a heliopanel is a thin plate of two layers of silicon, each of which has its own physical properties. This is a classic semiconductor p-n junction with electron-hole pairs.
When photons hit the FEP between these layers of the semiconductor, because of the heterogeneity of the crystal, a photo-EMF valve is formed, resulting in a potential difference and an electron current.
Silicon plates of photocells differ in manufacturing technology for:
The first have a higher efficiency, but the cost of their production is higher than the second. Externally, one option from another on the solar panel can be distinguished by form.
Single-crystal FEP has a homogeneous structure; they are made in the form of squares with cut corners. In contrast, polycrystalline elements have a strictly square shape.
Polycrystals are obtained as a result of the gradual cooling of molten silicon. This method is extremely simple, so these photovoltaic cells are inexpensive.
But their performance in terms of generating electricity from the sun’s rays rarely exceeds 15%. This is due to the “impurity” of the obtained silicon wafers and their internal structure. Here, the purer the p-layer of silicon, the higher the efficiency of the FEP from it.
The purity of single crystals in this respect is much higher than that of polycrystalline analogues. They are made not from melted, but from artificially grown whole silicon crystal. The photoelectric conversion coefficient of such FEP already reaches 20-22%.
In a common module, individual photocells are assembled on an aluminum frame, and to protect them from above, they are covered with durable glass, which does not interfere with the sun’s rays.
The top layer of the photocell plate facing the sun is made of the same silicon, but with the addition of phosphorus. It is the latter that will be the source of excess electrons in the pn-junction system.
The principle of the solar panel
When solar rays fall on the photocell, non-equilibrium electron-hole pairs are generated in it. Excess electrons and “holes” are partially transferred through the p – n junction from one semiconductor layer to another.
As a result, voltage appears in the external circuit. In this case, the positive pole of the current source is formed at the contact of the p-layer, and negative at the n-layer.
The potential difference (voltage) between the contacts of the photocell occurs due to changes in the number of "holes" and electrons from different sides of the pn-junction as a result of irradiation of the n-layer by the sun's rays.
The photocells connected to an external load in the form of a battery form a vicious circle with it. As a result, the solar panel works as a kind of wheel, along which proteins run electrons together. And the battery at the same time gradually gaining charge.
Standard silicon photoelectric converters are unijunction elements. Electrons flow through them only through a single p – n junction with an energy-restricted photon zone of this transition.
That is, each such photocell is able to generate electricity only from a narrow spectrum of solar radiation. All other energy is wasted. That is why the efficiency of the FEP is so low.
In order to increase the efficiency of solar cells, silicon semiconductor cells have recently been made multi-transition (cascaded) for them. In the new FEP transitions are already several. And each of them in this cascade is designed for its own spectrum of sunlight.
The total efficiency of the conversion of photons into electric current for such solar cells increases as a result. But their price is much higher. Here either the ease of manufacture with low cost and low efficiency, or higher returns coupled with high cost.
The solar battery can work both in summer and in winter (it needs light, not heat) - the less cloudiness and brighter the sun shines, the more heliopanel will generate electric current
During operation, the photocell and the entire battery gradually heats up. All the energy that did not go on the generation of electric current, is transformed into heat. Often the temperature on the surface of the heliopanel rises to 50–55 ° C. But the higher it is, the less efficiently the photovoltaic cell operates.
As a result, the same model of the solar battery in the heat generates less current than in frost. Maximum efficiency photovoltaic show on a clear winter day. There are two factors - a lot of sun and natural cooling.
Moreover, if snow falls on the panel, it will continue to generate electricity anyway. Moreover, the snowflakes will not even have time to lie on it, melting from the heat of the heated photo cells.
Solar Battery Efficiency
One photocell, even at noon in clear weather, produces very little electricity, only enough for the operation of the LED flashlight.
To increase the output power, several solar cells are combined in parallel to increase the constant voltage and in series to increase the current.
The effectiveness of solar panels depends on:
- air temperature and the battery itself;
- correct selection of load resistance;
- angle of incidence of sunlight;
- the presence / absence of anti-reflective coating;
- light output.
The lower the temperature in the street, the more efficient the photovoltaic cells and the solar battery as a whole. Everything is simple here. But with the calculation of the load situation is more complicated. It should be selected on the basis of the current generated by the panel. But its value changes depending on weather factors.
Heliopanels are manufactured with the expectation of an output voltage that is a multiple of 12 V - if you have to apply 24 V to the battery, you will have to connect two panels in parallel
Constantly monitor the parameters of the solar battery and manually correct its work is problematic. For this it is better to use control controllerwhich in the automatic mode itself adjusts the settings of the heliopanel in order to achieve the maximum performance and optimum operating modes from it.
The ideal angle of incidence of the rays of the sun on the solar battery is straight. However, with a deviation of 30 degrees from the perpendicular, the efficiency of the panel drops only in the region of 5%. But with a further increase in this angle, an increasing proportion of solar radiation will be reflected, thereby reducing the efficiency of the FEP.
If the battery is required to give maximum energy in the summer, it should be oriented perpendicular to the average position of the sun, which it occupies in the equinoxes in the spring and autumn.
For the Moscow region it is about 40–45 degrees to the horizon. If the maximum is needed in winter, the panel should be placed in a more upright position.
And one more thing - dust and dirt greatly reduce the performance of photocells. Photons through such a “dirty” barrier simply do not reach them, and therefore there is nothing to convert into electricity. The panels should be regularly washed or set so that the dust washed off by rain on their own.
Some solar cells have built-in lenses for concentrating radiation on solar cells. In clear weather, this leads to increased efficiency. However, in heavy clouds, these lenses only bring harm.
If the usual panel in such a situation continues to generate current, albeit in smaller volumes, then the lens model will stop working almost completely.
The sun battery of photocells should ideally illuminate evenly. If one of its sections turns out to be darkened, then unlit FEP turn into a parasitic load. They not only do not generate energy in such a situation, but also take it away from working elements.
Panels should be installed so that there are no trees, buildings and other barriers in the path of the sun's rays.
The power scheme of the house from the sun
The solar power system includes:
- Inverter (transformer).
The controller in this scheme protects both solar batteries and batteries. On the one hand, it prevents the flow of reverse currents at night and in cloudy weather, and on the other hand, it protects batteries from excessive charge / discharge.
Batteries for heliopanels should be selected to be the same in age and capacity, otherwise charging / discharging will occur unevenly, which will lead to a sharp decrease in their service life
For the transformation of direct current to 12, 24 or 48 volts into an alternating 220 volt needed inverter. Car batteries should not be used in such a scheme because of their inability to withstand frequent recharges. It is best to invest and purchase special helium AGM or fill-in OPzS batteries.
Conclusions and useful video on the topic
Principles of operation and solar circuit diagrams not too complicated to understand. And with the video materials we collected below, it will be even easier to understand all the intricacies of the operation and installation of heliopanels.
Accessible and understandable how a photovoltaic solar panel works, in full detail:
How are solar panels arranged in the following video:
Do-it-yourself solar panel assembly:
Every item in solar power system The cottage must be matched correctly. Unavoidable power losses occur on batteries, transformers and the controller. And they should definitely be reduced to a minimum, otherwise the rather low efficiency of the heliopanels will be reduced to zero altogether.
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