The principle of operation of a solar battery: how a solar panel works and works

Effectively converting free rays of the sun into energy that can be used to power homes and other facilities is the cherished dream of many green energy apologists.

But the principle of operation of the solar battery and its efficiency are such that there is no need to talk about the high efficiency of such systems yet. It would be nice to have your own additional source of electricity. Is not it? Moreover, even today in Russia, with the help of solar panels, a considerable number of private households are successfully supplied with “free” electricity. Still don't know where to start?

Below we will tell you about the design and operating principles of a solar panel; you will learn what the efficiency of a solar system depends on. And the videos posted in the article will help you assemble a solar panel from photocells with your own hands.

Solar panels: terminology

There are quite a lot of nuances and confusion in the topic of “solar energy”. It is often difficult for beginners to understand all the unfamiliar terms at first. But without this, it is unreasonable to engage in solar energy, purchasing equipment for generating “solar” current.

Unknowingly, you can not only choose the wrong panel, but also simply burn it when connecting it or extract too little energy from it.

First, you should 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 sun's rays.

However, in the first case, the consumer receives electrical energy at the output, and in the second, thermal energy in the form of a heated coolant, i.e. solar panels are used for home heating.

The maximum return from a solar panel can only be obtained by knowing how it works, what components and assemblies it consists of, and how it is all connected correctly

The second nuance is the concept of the term “solar battery”. Typically, the word “battery” refers to some kind of electrical storage device. Or a banal heating radiator comes to mind. However, in the case of solar batteries the situation is radically different. They do not accumulate anything in themselves.

The solar panel generates a constant electric current. To convert it to variable (used in everyday life), an inverter must be present in the circuit

Solar panels are designed solely to generate electric current. It, in turn, is accumulated to supply the house with electricity at night, when the sun goes below the horizon, already in the batteries additionally present in the facility’s energy supply circuit.

The battery here is meant in the context of a certain set of similar components assembled into a single whole. In fact, it is just a panel of several identical photocells.

Internal structure of a solar battery

Gradually, solar panels are becoming cheaper and more efficient.They are now used to recharge batteries in street lamps, smartphones, electric cars, private homes and on satellites in space. They even began to build full-fledged solar power plants (SPPs) with large generation volumes.

A solar battery consists of many photocells (photoelectric converters) that convert the energy of photons from the sun into electricity

Each solar battery is designed as a block of a certain number of modules, which combine semiconductor photocells connected in series. To understand the principles of operation of such a battery, it is necessary to understand the operation of this final link in the solar panel device, created on the basis of semiconductors.

Types of photocell crystals

There are a huge number of FEP options made from different chemical elements. However, most of them are developments in the initial stages. So far, only panels made from silicon-based photovoltaic cells are currently produced on an industrial scale.

Silicon semiconductors are used in the manufacture of solar cells due to their low cost; they cannot boast of particularly high efficiency

A typical photocell in a solar panel is a thin wafer 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 photovoltaic cell between these semiconductor layers, due to the inhomogeneity of the crystal, a gate photo-EMF is formed, resulting in a potential difference and an electron current.

Silicon wafers of solar cells differ in manufacturing technology into:

1. Monocrystalline.
2. Polycrystalline.

The former have a higher efficiency, but the cost of their production is higher than that of the latter. Externally, one option can be distinguished from another on a solar panel by its shape.

Monocrystalline solar cells have 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 by gradual cooling of molten silicon. This method is extremely simple, which is why such photocells are inexpensive.

But their productivity in terms of generating electricity from solar rays rarely exceeds 15%. This is due to the “impurity” of the resulting silicon wafers and their internal structure. Here, the purer the p-silicon layer, the higher the efficiency of the solar cell from it.

The purity of single crystals in this regard is much higher than that of polycrystalline analogues. They are made not from molten, but from artificially grown solid silicon crystal. The photoelectric conversion coefficient of such solar cells already reaches 20-22%.

Individual photocells are assembled into a common module on an aluminum frame, and to protect them they are covered on top with durable glass, which does not in any way interfere with the sun’s rays

The top layer of the photocell plate facing the sun is made from 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.

A real breakthrough in the field of solar energy was the development of flexible panels with amorphous photovoltaic silicon:

Operating principle of solar panel

When sunlight falls on a photocell, nonequilibrium electron-hole pairs are generated in it. Excess electrons and holes are partially transferred through the pn junction from one layer of the semiconductor to another.

As a result, voltage appears in the external circuit. In this case, a positive pole of the current source is formed at the contact of the p-layer, and a negative pole at the n-layer.

The potential difference (voltage) between the contacts of the photocell appears due to a change in the number of “holes” and electrons on different sides of the p-n junction as a result of irradiation of the n-layer with solar rays

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 like a kind of wheel along which electrons “run” together between proteins. And the battery gradually gains charge.

Standard silicon photovoltaic converters are single-junction cells.The flow of electrons into them occurs only through one p-n junction with a zone of this transition limited in photon energy.

That is, each such photocell is capable of generating electricity only from a narrow spectrum of solar radiation. All other energy is wasted. That is why the efficiency of FEP is so low.

To increase the efficiency of solar cells, silicon semiconductor elements for them have recently begun to be made multijunction (cascade). There are already several transitions in the new solar cells. Moreover, each of them in this cascade is designed for its own spectrum of sunlight.

The total efficiency of converting photons into electric current for such photocells ultimately increases. But their price is much higher. Here, either ease of manufacture with low cost and low efficiency, or higher returns coupled with high cost.

The solar panel can work both in summer and winter (it needs light, not heat) - the less cloudy and the brighter the sun shines, the more electric current the solar panel will generate

During operation, the photocell and the entire battery gradually heat up. All the energy that was not used to generate electric current is transformed into heat. Often the temperature on the surface of the solar panel rises to 50–55 °C. But the higher it is, the less efficiently the photovoltaic cell operates.

As a result, the same model of solar battery generates less current in hot weather than in cold weather. Photocells show maximum efficiency on a clear winter day. There are two factors at play here - a lot of sun and natural cooling.

Moreover, if snow falls on the panel, it will still continue to generate electricity.Moreover, the snowflakes won’t even have time to lie on it much, having melted from the heat of the heated photocells.

Solar battery efficiency

One photocell, even at noon in clear weather, produces very little electricity, only sufficient to operate an LED flashlight.

To increase the output power, several solar cells are combined in a parallel circuit to increase the DC voltage and in a series circuit to increase the current.

The efficiency of solar panels depends on:

• temperature of the air and the battery itself;
• correct selection of load resistance;
• angle of incidence of sunlight;
• presence/absence of anti-reflective coating;
• luminous flux power.

The lower the temperature outside, the more efficient the photocells and the solar battery as a whole work. Everything is simple here. But with load calculation the situation is more complicated. It should be selected based on the current supplied by the panel. But its value varies depending on weather factors.

Solar panels are produced with an output voltage that is a multiple of 12 V - if 24 V needs to be supplied to the battery, then two panels will have to be connected to it in parallel

Constantly monitoring the parameters of a solar battery and manually adjusting its operation is problematic. For this it is better to use control controller, which automatically adjusts the settings of the solar panel in order to achieve maximum performance and optimal operating modes from it.

The ideal angle of incidence of the sun's rays on a solar battery is straight. However, if the deviation is within 30 degrees from the perpendicular, the efficiency of the panel drops by only about 5%.But with a further increase in this angle, an increasing proportion of solar radiation will be reflected, thereby reducing the efficiency of the solar cell.

If the battery is required to produce maximum energy in the summer, then it should be oriented perpendicular to the average position of the Sun, which it occupies on the equinoxes in spring and autumn.

For the Moscow region, this is approximately 40–45 degrees to the horizon. If the maximum is needed in winter, then the panel should be placed in a more vertical position.

And one more thing - dust and dirt greatly reduce the performance of photocells. Photons simply do not reach them through such a “dirty” barrier, which means there is nothing to convert into electricity. The panels must be washed regularly or placed so that the dust is washed off by rain on their own.

Some solar panels have built-in lenses to concentrate radiation onto the solar cell. In clear weather this leads to increased efficiency. However, in heavy clouds, these lenses only cause harm.

If a conventional panel in such a situation continues to generate current, albeit in smaller volumes, then the lens model will stop working almost completely.

The sun should ideally illuminate a battery of photocells evenly. If one of its sections turns out to be darkened, then the unlit solar cells turn into a parasitic load. Not only do they not generate energy in such a situation, but they also take it away from the working elements.

The panels must be installed so that there are no trees, buildings or other obstacles in the path of the sun's rays.

House solar power supply diagram

The solar power supply system includes:

1. Solar panels.
2. Controller.
3. Batteries.
4. Inverter (transformer).

The controller in this circuit protects both solar panels and batteries. On the one hand, it prevents the flow of reverse currents at night and in cloudy weather, and on the other, it protects the batteries from excessive charge/discharge.

Rechargeable batteries for solar panels should be selected the same in age and capacity, otherwise charging/discharging will occur unevenly, which will lead to a sharp reduction in their service life

To transform direct current of 12, 24 or 48 volts into alternating current 220 volts you need inverter. Car batteries are not recommended for use in such a circuit due to their inability to withstand frequent recharging. It is best to spend money and purchase special helium AGM or flooded OPzS batteries.

Conclusions and useful video on the topic

Operating principles and solar panel connection diagrams not too difficult to understand. And with the video materials we have collected below, it will be even easier to understand all the intricacies of the functioning and installation of solar panels.

It is accessible and understandable how a photovoltaic solar battery works, in all its details:

See how solar panels work in the following video:

DIY solar panel assembly from photocells:

Each element in solar power system cottage must be chosen correctly. Inevitable power losses occur in the batteries, transformers and controller. And they must be reduced to a minimum, otherwise the already rather low efficiency of solar panels will be reduced to zero.

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