Photovoltaic systems - the principle of operation

Kategoria: Aktualności

Every PV system is made up of several basic components, including photovoltaic panels and an inverter. How is electricity generated and how is it possible to use it to power a house? What is the photovoltaic phenomenon?

A photovoltaic (PV) system consists of devices that generate electricity from solar energy. Every PV system is made up of several basic components, including photovoltaic panels and an inverter. How is electricity generated and how is it possible to use it to power a house? What is a photovoltaic phenomenon? How efficient are photovoltaic modules? Read this article to find out.

Photovoltaics - how does it work?

Photovoltaics, which has become increasingly popular in recent years, is a branch of science dealing with the conversion of solar energy into electricity. This transformation takes place thanks to the photovoltaic phenomenon, also known as the photovoltaic effect. It was first noted and described in 1839 by Alexandre Edmond Becquerel, a French physicist and physical chemist. In photovoltaic systems, this effect is used to convert light into electricity, which is needed to power multiple appliances in homes, businesses, and farms.

What components make up a photovoltaic system?

Each photovoltaic system, which allows its owners to reduce their electricity bills and become independent of energy suppliers or cyclical increases in electricity prices, consists of two basic elements. These include photovoltaic panels, incorrectly called solar panels or solar modules, mounted on the roof of a building or the ground, and an inverter, which converts direct current into alternating current that flows in the electrical sockets of our homes and other facilities. 

The safety and reliability of the installation are ensured by overvoltage protection designed to protect against electrical discharges and surges. A bracketed support system and cabling are also mandatory components of the installation.

What is the structure of a photovoltaic cell?

The above-mentioned photovoltaic panels, the key component of a PV system, are made up of individual photovoltaic cells. As these are semiconductor materials, silicon, in the form of polycrystalline or monocrystalline wafers, is most often used in their production. Due to their physical and chemical properties, silicon is a great initiator of piezoelectric phenomena in the panels. Silicon modules, on the other hand, are composed of cells that are connected in series or parallel. By dividing the panel into modules, only part of it becomes less efficient when shadowed, and not the entire photovoltaic system.

 

The top and bottom of the modules are laminated with transparent EVA (ethylene-vinyl-acetate) film, which protects the cells from the influence of external factors. The tempered glass, on which the sun's rays fall, protects the module from mechanical damage and, at the same time, reduces the amount of reflected solar radiation, thus limiting energy losses. From the bottom, the cells are protected with an electro-insulating film, the so-called backsheet, which is responsible for the desired colour effect. White, black, and transparent films are most commonly used. In addition, a single PV module consists of an aluminium frame and a connection socket with the necessary cabling.

A photovoltaic system - how does it work?

To be able to answer the question of how a photovoltaic installation works, you first need to know what the phenomenon occurring in a single photovoltaic cell is all about. The so-called photoelectric phenomenon consists of a change in the electrical properties of a cell made up of semiconductors under the influence of solar radiation. 

Each silicon wafer consists of two layers, separated by a so-called potential barrier. The upper layer, directed towards the sun, or more precisely, towards the stream of photons which are the smallest unit of light, is negatively doped. This means that there are excessive electrons in it. The bottom layer is positively doped, which means that it is electron deficient. 

As a result, an electric field emerges in the barrier area as the energy of a photon incident on the photovoltaic cell causes the release and movement of the additional electrons in the upper layer. This creates a potential difference, i.e. electrical voltage. Once the circuit with an electrical consumer is closed, current flows between the plates. 

Where to install a photovoltaic system?

The efficient operation of a photovoltaic system depends on exposure to sunlight. Therefore, PV panels are mounted on roofs, and in certain cases on the ground, facing south and titled to 30-40 degrees. On flat roofs, PV systems are installed using special support systems that ensure the optimum tilt angle of the PV modules, which translates into improved power generation capacity. Please note that the PV system must not be shaded. This aspect is particularly important in autumn and winter when the sun travels relatively low on the horizon so that any tall trees or neighbouring buildings can cast a shadow on the PV modules and interfere with their operation.

How to use the power generated by a photovoltaic system?

Photovoltaic modules generate direct current (DC). To be able to use this electricity in your home, it needs to be converted into alternating current (AC). This is done by the inverter, which, next to the PV panels, is the most important component of any photovoltaic system. 

PV panels generate direct voltage using solar rays. In our sockets, however, there is AC voltage with parameters that correspond to the low-voltage network (230/400 V 50 Hz). To use the electricity produced by the system, the two voltages must be mutually adjusted, and this task is implemented by an inverter. 

 

This device automatically converts the DC voltage to the appropriate AC voltage. The resulting alternating current can be used to power household devices and the surplus can be sent to the power grid and collected in periods of increased demand, which usually occurs in winter when the days get shorter and it gets dark quickly. 

 

However, do not forget that prosumers can collect the surplus electricity stored with the power company at a loss, which is currently 20% or 30%, depending on the capacity of their photovoltaic system. According to the Renewable Energy Sources Act, owners of PV systems whose capacity does not exceed 10 kWp can collect from the grid 80% of the generated energy. Investors, in their turn, whose photovoltaic installations have a capacity between 10kWp and 50 kWp settle a 1:0.7 ratio with the power company, which means that during the balance period they can collect 70% of the stored electricity. However, with a bi-directional meter, it is possible to track the current flow and continuously monitor the amount of electricity produced by your system and collected from the grid. In addition, the inverter is also responsible for monitoring the condition of the system and checking its operation. Inverters also allow for verifying the amount of energy produced by the photovoltaic system, as well as readings on the DC and AC sides.

Photovoltaic systems and their types?

A photovoltaic installation can operate in several ways: as an on-grid, off-grid, or hybrid system. On-grid systems, which are integrated into the electricity grid, consume the energy generated on an ongoing basis and send the excess back to the utility company. An on-grid PV installation is an effective way to reduce electricity bills. 

The option of transmitting the excess generated energy is also beneficial as the RES Act provides for a system of rebates for prosumer installations (the so-called net-metering). In practice, an owner of a micro-installation, who has the option to send surplus energy to the public grid, can also collect it from the grid within one year, in the period of reduced production, as mentioned above. Storing electricity in the grid is a very cost-effective solution that makes the PV plant owner resistant to electricity price increases.

 

By contrast, in an off-grid system, the PV plant is not connected to the grid. All the electricity produced is stored in batteries. Hybrid systems combine features of on-grid and off-grid approaches. In this case, the system is not only connected to the public grid but also integrated with energy storage. In this way, the self-consumption of the generated energy is optimised, which further increases the profitability of RES investments. The energy storage, in turn, guarantees increased independence from energy supplies. It is especially useful in the event of power cuts and when it is impossible to connect to the power grid.

How much energy do photovoltaic panels generate?

Every investor interested in photovoltaics would probably ask this question. The amount of electricity a photovoltaic panel can generate depends on its power, which is determined by factors such as:

 

  • current weather conditions,

  • panel dimensions,

  • arrangement of the modules in relation to one another,

  • intensity of solar radiation,

  • roof inclination angle,

  • shading of the modules,

  • technology of the photovoltaic system. 

 

The efficiency of a single photovoltaic panel, which determines how much electricity it can produce under standard conditions (understood as the panel's peak power output), is expressed in kilowatt-peaks (kWp). It is assumed that a south-facing 1 kWp photovoltaic panel will generate on average 900-980 kWh of electricity per year.

What power should I choose for my photovoltaic system?

Just like any other investment, the photovoltaic system needs to be profitable. However, the return on investment period depends on many factors, which you should get to know well before deciding to install PV panels. When estimating the power of your micro installation, first of all, you should analyse your current electricity bills. They will tell you how much electricity you consume. A certain margin needs to be accounted for in the calculations, especially if your plans for the upcoming years include an electric car, a bigger family or air conditioning. Each additional device plugged translates into greater electricity consumption. 

 

Assuming an average consumption of ca. 3,000 kWh per year, a 3 kW installation should be sufficient. However, this is a very rough estimate and should be weighed against information on:

 

  • the place of installation,

  • the size of the roof or ground slope for the planned investment,

  • access to sunlight (the more shade, the lower the electricity output),

  • orientation in relation to the directions of the world,

  • angle of inclination.

 

It must not be forgotten that the power of photovoltaic modules decreases over time. Although warranties from leading manufacturers usually cover 12, 15, or even 25 years, the linear warranty after 25 years is on average between 80% and 85% of the initial PV panel performance. In case of doubts or difficulties in estimating the energy needs of your household, company, or farm, ask experienced fitters for help. They are familiar with market conditions and can help you choose a solution perfectly tailored to your needs avoiding both under- or over-sizing your photovoltaic system.

 

How does a photovoltaic system work with a heat pump?

Due to the growing ecological awareness of our society, photovoltaics are often discussed in the context of choosing forms of heating for modern homes, especially heat pumps. Where does this trend come from? The reason is simple: the two systems complement each other. A heat pump extracts energy from the natural environment; air, ground, or water; but it also needs electricity to work. 

If this is obtained using a photovoltaic system, the cost of operating the heat pump, and thus heating the house, is significantly reduced. The combination of these two systems thus brings tangible benefits to prosumers, regardless of the season. The surplus electricity stored in the period of greater insolation can be successfully used by the heat pump in winter when electricity production is lower due to less insolation. 

How does a photovoltaic system work with solar panels?

When getting to know the principles of operation of photovoltaic systems, also note the possibility of combining the benefits of their use with a solar system. Although the terms photovoltaic panels and solar panels are often used interchangeably, they are completely different types of systems and are intended to be used differently as well. A photovoltaic system, as we already know, is used to convert energy obtained from the sun into electricity. Solar panels, on the other hand, convert solar energy into heat and are capable of heating a water tank to 70º C in just a few hours. If you choose to invest in both systems, you can use the electricity produced by photovoltaics to power electrical water heating devices. The hot water costs will then be significantly reduced. 

Operating a PV system - what mistakes to avoid?

Each and every investor dreams of the efficient and failure-free operation of a photovoltaic system. Therefore, a strategy of acquiring electricity from the sun should be well analysed at the design stage. It is very important to carefully verify the quality of individual components of the PV system. Remember that its average service life is estimated at 25 years. For the funds invested in photovoltaics to pay back after an average of 6-8 years, you need to choose photovoltaic panels and inverters with boast good parameters: efficiency, speed of operation and compatibility with other system elements. The length and scope of warranty or the reputation of the manufacturer also deserve some attention. Well-known and respected manufacturers of PV panels include brands such as Encor, Q.Cells, Risen Energy, DMEGC SOLAR, LG, Jinko Solar, Ja Solar, Longi Solar, Bruk Bet, Zn Shine, Sharp, Selfa and Sun Power. Among the inverter manufacturers worth mentioning are Solar Edge, Sofar Solar, Fronius, SMA, Sungrow, Huawei, Fimer, Growatt, Afore and Enphace.

The correct operation of a photovoltaic system also depends on project design. Incorrect estimation of the load-bearing capacity or surface area of the roof, as well as inappropriate cable routing, may result in the need to correct the system design at the installation stage, which can translate into higher costs due to delays in the work. 

It is also a common mistake for investors to choose unproven contractors with no experience in the industry. As photovoltaics grow in popularity, the market has unfortunately seen the emergence of many pseudo-specialists. It should be noted that the quality of a photovoltaic system translates into its failure-free operation and the ability to generate electricity without any downtime, which in turn makes the return on investment quicker. This is also important with regard to fires of photovoltaic systems or possible surges. Therefore, if you decide to install photovoltaics, learn exactly how a photovoltaic system works and hire reliable professionals to implement the project. 

The CORAB Partner network currently includes over 120 verified contractors of photovoltaic systems from all over Poland. If you cooperate with one of the fitters associated with our network, you can be sure that they will use the highest quality components for the installation and they will provide comprehensive services, from estimating the system’s power, through its assembly, start-up and connection, to warranty service. What is important, they will also help in choosing the best form of co-financing.

Photovoltaics - an effective way to reduce electricity bills

Systematic increases in electricity prices make investments in photovoltaic systems attractive for a growing number of individuals, farmers and entrepreneurs. According to information made available by the Polish Photovoltaic Industry Association, the Polish market of photovoltaic micro-systems is worth nearly PLN 6 billion. At the same time, there appears to be no change in this trend. Therefore, it is worth getting to know the principles of operation of a photovoltaic system to adjust its power to current needs and take advantage of the numerous photovoltaic subsidies available. This would help to significantly reduce the monthly bills from the energy company and benefit the environment. 

The third edition of the My Current 3.0 programme, launched on 1 July 2021, allows for obtaining up to PLN 3,000 for the installation of a photovoltaic system with a capacity of 2 to 10 kWp, which has been commissioned after 31 January 2020. Applications for subsidies of photovoltaic systems should be submitted electronically, through the Generator of Subsidy Applications or GWD for short. The previous two editions of the programme enjoyed great interest from beneficiaries and the pool of funds was quickly exhausted. Therefore, if you wish to benefit from RES in the upcoming years, apply for a subsidy as soon as possible.

Farmers, in turn, may benefit from the Agroenergia programme, with two forms of support. The first one is a non-refundable grant of up to PLN 25,000. The second one is a loan granted on preferential conditions. According to the programme's assumptions, farmers may obtain up to 100% of financing for a photovoltaic system and repay the incurred obligation within the period of up to 15 years. 

Entrepreneurs, in turn, may use the Energy Plus Programme as one of the forms of support for investments in RES. Similar to farmers, they can count on co-financing in the form of a loan or a grant. Loan granted to finance a photovoltaic system may not exceed 85% of the total eligible costs, while a grant may cover up to half of the costs. Leasing of photovoltaic installations or loans offered by reputable banks on favourable terms also enjoy a lot of interest from entrepreneurs.

Will photovoltaic systems continue to dominate the Polish market?

An analysis of market trends to date indicates that the popularity of photovoltaics will remain high in the coming years. This is not only due to consumer behaviour but also to legal circumstances and requirements set by the European Union. In the face of rising electricity costs and falling prices of individual components of photovoltaic systems, investors are attracted by the benefits of renewable energy sources. 

For individual investors, the benefits mostly translate into finances. Available subsidies or the possibility to take advantage of thermal modernization allowances provide some opportunities for real savings. On the other hand, entrepreneurs investing in RES, apart from the economic aspect, also work on improving their reputation. For many companies, especially in production, taking care of the environment is an important element of their development path. In this context, photovoltaics are, and will remain, an important development factor, determining market opportunities and increasing the competitive advantage of enterprises.

Anyone who wishes to learn how a photovoltaic system works is invited to take part in periodic webinars and training organised by CORAB and run by experts in the field of RES. Additionally, make the best you can of our knowledge base on our website. We will advise you and share our experience to make your photovoltaic system work efficiently and bring measurable benefits in the form of free electrical power. We know all too well that the profitability of your investment depends on making good choices, based on reliable information. With the experience of CORAB experts, you can be sure that the photovoltaic system installed in your house, farm or company will work trouble-free without any downtime.

 

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