FAQ – questions and answers. Photovoltaics – a guide

Photovoltaics is a branch of the energy industry, a branch of science that deals with the conversion of solar energy into electricity using the photovoltaic effect/phenomenon. The photovoltaic effect is a reaction that occurs in a semiconductor – the photovoltaic cell (silicon) – when exposed to sunlight.

When sunlight reaches the surface of a photovoltaic panel, electrons are excited in the silicon crystals, resulting in the production of direct current. Then, with the help of a voltage converter – inverter, which is also the heart of the entire Photovoltaic system, the direct current (DC) is waved and converted into alternating current (AC) with appropriate parameters. Alternating current is the one, which we can already use in our homes or companies to power electrical devices.

What is photovoltaics? Conversion of direct current into alternating current

A photovoltaic system – how does it work?

1. Photovoltaic panels with a mounting system adapted to the type of roofing and location;
2. Photovoltaic inverter with WI-FI communication module or LAN connection and necessary wiring and electrical equipment
3. Energy storage / batteries, which act as emergency power supply for the internal electrical network of the facility and allow for storage of specific amounts of energy, necessary for the operation of electrical loads;
4. Electrical switchgear – the place of connection of the photovoltaic system;
5. Internal grid – home/company electrical grid, which is powered by the electricity produced by the photovoltaic panels. In the most commonly installed photovoltaic systems in Poland, the green energy from the sun is first transferred to storage batteries, then it is further transferred to the home/business grid to power all electrical appliances. Finally, surplus electricity that is not used at any given time is sent to the electricity grid of the operator;
6. Bidirectional electricity meter, installed by the electricity system operator after the installation of the photovoltaic power plant, whose function is to record the amount of energy produced from the photovoltaics and that taken from the grid. The operator shall replace the meter with a bidirectional meter on the basis of an application submitted by the photovoltaic system owner or the installer within 30 days of receipt of a complete set of documents;

A properly selected and designed photovoltaic system is a system that should work faultlessly for at least 25-30 years. The right choice of photovoltaic installer and photovoltaic components of the highest quality, coming from a proven photovoltaic wholesaler, is a guarantee of long-term efficiency of the system and high savings on electricity.

Before installing photovoltaics on your house or on the roof/ground of your company building or farm, it is very important to:

1. Verify the reliability and reputation of the installer’s company: a company with a good reputation will most often prepare your photovoltaic system with attention to all the details, according to art and with the necessary standards.
2. Be sure of the number of references: it’s a good idea to go through and check the latest photos of the Photovoltaic system, this way you can be sure that the installer has professional installation teams, has
3. Professional supplier of high quality photovoltaic and electrical components: choose a photovoltaic wholesaler, an authorised distributor/importer or a representative of a photovoltaic component manufacturer in the country. Before setting up a photovoltaic system, it is mandatory to analyse the photovoltaic wholesaler’s offer, the most commonly offered and sold models of photovoltaic panels, inverters and PV protection systems, to make sure that you buy equipment with the certificates and declarations of conformity to the European standard required by the system operators. It also means security and confidence that in the event of equipment failure, your product will be repaired quickly and without problems under the product warranty.

Photovoltaic systems are usually mounted on the roofs of buildings or on the ground, using a special support structure. The place of mounting of photovoltaics is extremely important from the point of view of its efficiency and profitability. The correct positioning of the PV plant, taking into account the optimum orientation of the PV modules towards the south, allows its owner to obtain more kWh of free electricity per kWp of installation benefits. When selecting a PV installation site, it is also important to take into account the conditions that may affect its secure fastening to the roof sheathing. Mounting structures are selected to suit the prevailing wind zones in the country. Similarly, there is a need to minimise potential damage caused by such factors as corrosion or degradation caused by atmospheric agents, including brine water (coastal areas) or ammonia (rural areas).

Wind zones in Poland. Where is the best place to install photovoltaics?

Photovoltaic installation usually takes 1-2 days. The time from start to finish depends on the efficiency and experience of the installation team. Unfavourable weather conditions often have a big influence on the installation time. Larger photovoltaic systems are governed by slightly different laws. Photovoltaics is installed in several design stages, and very often there are additional requirements related to obtaining building permits or environmental approvals. The assembly of large PV projects can take from a few to even several months.

Find out more about the types of photovoltaic panel installation:

The service life of a photovoltaic system in Poland is at least 25-30 years. It depends mainly on the prevailing weather conditions, the location of the PV system and the quality of the components used. High-quality mounting structures, photovoltaic modules and inverters extend the service life of PV. The most important issue to consider when selecting photovoltaic panels are their parameters, especially those related to solar panel efficiency. The largest manufacturers of photovoltaic panels, such as PhonoSolar, Astronergy, Jinko or JA Solar, have in recent years been outdoing themselves in constructing products that allow for increasingly better technical parameters. The parameter that largely determines the lifetime of a Photovoltaic system is the Linear Performance Guarantee. This parameter can be found on the technical data sheet of the photovoltaic panels and indicates the annual degradation factor of the modules in a perspective of usually 25 or 30 years.

What is the lifetime of a Photovoltaic system?

Jinko Solar – the largest photovoltaic module manufacturer in the world in the technical characteristics of its Jinko Solar 470W photovoltaic panels model JKM470M-7RL3 indicates that the linear performance guarantee is 25 years. The annual decrease in module efficiency over this period is 0.55%. This means that after 25 years of use, a PV installation on these PV modules under standard test conditions (STC) will have reached a guaranteed efficiency of 84.8% of its initial value. The electrical measurements of the photovoltaic panels take place in laboratories where standardised conditions prevail, in the case of STC tests the intensity level of solar radiation is 1000 W/m2 and the temperature of the photovoltaic cells of the module being illuminated reaches 25°C. In the same way, products of all photovoltaic manufacturers in the world are tested under identical conditions.

How much energy can be obtained from photovoltaic panels? Insolation in Poland

Yes, a photovoltaic system designed and built by an installation company with many years of experience and using high-quality panels, inverters, electrical equipment and solar cables is a very safe electrical equipment. The danger of electrocution or the risk of fire is most often the result of mistakes in the design or mistakes made by the installation team. The fire safety regulations concerning photovoltaics, amended on 19 August 2020, increased the restrictions, so that the risk of faulty installation is now lower. According to the new regulations, any installation with a capacity higher than 6.5 kWp requires the project to be agreed with a fire protection expert and the authorities of the State Fire Service to be notified.

Do you want to find out more about the fire safety of photovoltaics?

Based on historical weather data collected in all regions, it is assumed that the level of insolation in Polish climatic conditions is on average 1000 kWh/m2/year. This result puts us on a par with Germany or the Netherlands. In Warsaw the insolation amounts to 1100 kWh/m2, which is the same as in Berlin. Such a result of the average insolation in Poland means that each 1 kWp (kilowatt-peak; 1kWp=1000 Wp) of the power of a photovoltaic system can produce about 1000 kWh of green electricity.

For example, a 10 kWp ground-mounted photovoltaic array consisting of 28 AstroSemi 355 Mono Half-Cut Full Black panels at 355 Wp each, will produce about 10,000 kWh of renewable electricity per year.

Since 2020, Poland has seen a strong increase in interest in photovoltaics. Poles, thanks to widely available subsidies for photovoltaics in the form of “Mój Prąd” subsidies, have joined the country’s energy transformation. At the same time, we are also observing a technology race among the world’s largest photovoltaic panel manufacturers. Just two years ago, the most popular photovoltaic modules in Poland in terms of unit power were panels in the 270-300W range.

In 2021/2022, this range has already increased to 400-460W. Extremely popular in 2021 in Poland were Jinko Solar 470W photovoltaic panels, characterised by extremely high efficiency, as high as 20.93%. However, not all photovoltaic panel manufacturers have followed the same path as Jinko. Some of them introduced modules with increasingly higher power, which was not always accompanied by a clear increase in efficiency. Higher power was achieved simply by increasing the size of the modules.

The standard dimensions of photovoltaic modules are approximately: 170 x 100 cm. Full technical parameters of photovoltaic modules are provided by manufacturers on data sheets, which are made available by the installer, distributor or photovoltaic wholesaler before purchasing the equipment.

Example 1:

AstroSemi 355W Full Black photovoltaic panels have the following dimensions: 1765 x 1048 x 35 mm.

Below the technical data from the data sheet of AstroSemi 355W, modules from the offer of Photovoltaics Wholesaler Solmix.

What are the dimensions of photovoltaic panels? AstroSemi 355 full black modules

Example 2:

JA Solar 540W photovoltaic panels already have dimensions that are much larger, i.e.: 2279 x 1134 x 35 mm

Half cut technology is a solution that is very often used in the production of photovoltaic modules. It consists in cutting the cell in half, thanks to which the performance of the photovoltaic module can be significantly improved. An additional advantage of the half-cut panel is a lower risk of microcracks occurring due to smaller dimensions of the cells in the PV module. This extends the life of the photovoltaic panels.

Half Cut technology advantages

1. Higher panel efficiency in low light conditions,
2. Higher PV panel lifetime – lower risk of micro-cracks and hot spots,
3. Higher yield over the entire life cycle – reduces resistance losses,
4. Modules work efficiently even at high temperatures,
5. Resistance to PID,
6. Increased mechanical resistance of PV modules and resistance to severe weather conditions,

Do you want to know which photovoltaic panels to choose? Read our entry in the guide:

Photovoltaic panels can be mounted on the vast majority of roofing materials, such as metal roofing tiles, ceramic and concrete roofing tiles, plain tiles, corrugated and trapezoidal sheeting. On the other hand, it is not advisable to install on roofs covered with eternit, polycarbonate or ondulin. A prerequisite for the safe installation of the system is the good technical condition of the roof. Photovoltaics can be mounted on roofs with different pitches – sloping and flat roofs – and in different orientations to the cardinal directions. The most optimal solution is to install the system on a sloping roof covered with roofing sheets or tiles with a pitch of approximately 35-40 degrees and oriented to the south. Such an arrangement of PV modules guarantees high efficiency of the photovoltaic system and high yields of green energy from the sun.

By default, to estimate the roof space occupied by a photovoltaic system with an optimum slope, it is sufficient to assume approximately 6 m2 per kilowatt. In order to verify exactly how much space the photovoltaic system will take up on the roof, it is recommended to use a ready-made tool prepared by the specialists at the photovoltaic wholesaler Solmix:

The photovoltaic calculator is a very useful solution for designers or installers, which facilitates the correct selection of PV system power to be mounted on the roof of buildings. To estimate the area necessary for installing photovoltaics, as well as the power of the system, simply select a photovoltaic module model from the list and enter the dimensions of the roof pitch. After indicating the roof pitch, base pitch length and roof length, the calculator will indicate the necessary number of rows of panels in two arrangements: horizontal and vertical. The whole algorithm is based on the technical parameters of the photovoltaic panels.

Example of the calculation of a roof area for photovoltaics:

SERAPHIM 370 Mono Half-Cut photovoltaic panels in black frame

Roof dimensions:

1. length of pitch base = 5m
2. length of roof = 10m
3. 3. roof pitch = 35 degrees

Photovoltaic calculator – example of calculation. How much space do photovoltaic panels take up on a roof

An ON-GRID Photovoltaic system is a photovoltaic system that is connected to the external electricity grid of an operator. This solution makes it possible to transmit energy in both directions, thanks to a bidirectional meter. The surplus electricity produced by the installation is fed into the grid. At times of lower energy production or in the evenings or at night, the energy deficits are supplemented and balanced directly by the electricity retailer on the basis of a comprehensive electricity contract. In the event of a grid failure, the ON-GRID photovoltaic system shuts down automatically. The PV system starts up when power is restored.

ON-GRID installations are the photovoltaic system type most often chosen by investors. You can buy pre-assembled photovoltaic kits with different power ratings for self-assembly from the photovoltaic wholesaler solmix: Check out the pre-assembled PV kits.

An OFF-GRID photovoltaic system is a photovoltaic system that can operate off-grid, without being connected to the grid. Excess unconsumed electricity from the photovoltaics must be stored in batteries, which are an integral part of the set. Off-GRID installations are most often used in places where there is no access to the operator’s grid, i.e. in holiday homes, boats or yachts.

Hybrid installations, which combine the functionality of on- and off-grid installations, have become very popular in recent months. They allow the safe use of green electricity from the sun in homes or businesses, thanks to the use of hybrid inverters and energy storage, and also serve to ensure continuity of operation during temporary power outages in the electricity grid. Hybrid photovoltaic systems will receive support this year in the form of the 4th edition of the “Mój Prąd” subsidies programme, which is planned to be launched at the beginning of the second quarter of 2022.

The cost of photovoltaics depends on many factors, including the type and power of the photovoltaic inverter or the photovoltaic module manufacturer chosen. The most important of these is the total power of the solar power plant needed to power your home or business. The average cost per kWp of a photovoltaic system ranges between 4500 and 5800 PLN net. The largest percentage of the total cost of a photovoltaic system is the installation cost, so the higher the installation capacity, the lower the cost per kWp.

The cost of the PV system can be reduced by the amount of thermo-modernization relief (PIT relief) or thanks to subsidies for photovoltaics, e.g. from the programme Mój Prąd.

In addition to photovoltaic panels, mounting structures, wiring, security and labor costs planning to install photovoltaics, you should also consider the cost of the inverter. Prices of inverters for photovoltaics are on average between 4000 and 6500 PLN. The price of the inverter depends on the power, manufacturer, as well as technical parameters and quality of the inverter. The lowest price is for single phase photovoltaic inverters.

When looking for a suitable supplier of photovoltaic inverters, it is worth checking inverter prices at the online photovoltaic wholesaler solmix.pl. Users registered in the e-wholesaler get access to wholesale inverter prices.

How much does an inverter cost? Current inverter prices at the photovoltaic wholesaler – May 2022:

Single phase inverter price – May 2022:

Three-phase inverter price – May 2022:

A key component of any photovoltaic system is the inverter. In order to select the right inverter for your photovoltaic panels, you need to pay attention to several important factors. Proper selection of the inverter for the installation is based on matching its power to the parameters and total power of the photovoltaic panels. It is also important to take into account where and how the photovoltaic modules are located and their orientation with respect to cardinal directions.

According to design science, it is important that the inverter is optimally loaded: the total power of the PV modules should be between 105 and 120% of the inverter power. Nowadays, installers usually use professional PV SOL software at the design stage of a photovoltaic system to prepare estimates of the annual energy yield and the efficiency of the photovoltaic inverter with a given hardware configuration.

The FoxESS T10 3PH 2MPPT three-phase inverter is the best choice for a 10 kW Photovoltaic system. The inverter is designed for three-phase domestic and small commercial installations. It is ideal for a small business where electricity consumption is around 10-12 MWh of electricity per year. The FoxESS T10 inverter comes with a 12-year manufacturer’s warranty against defects and faults. The Wi-Fi communication module available as standard allows you to track your current electricity production using a mobile app.

In order for the FoxESS T10 inverter to start operating the voltage on the photovoltaic module chain must exceed 180V. This usually happens a few dozen minutes before sunrise. When the inverter’s MPP system (maximum power point search) starts working, the voltage on the module string decreases and it is important that it does not drop below the minimum permissible value (i.e. 160V). Importantly, even if there is sufficient voltage on a given string of PV modules, but the irradiance is still too low for the modules to produce current, the inverter will not inject energy into the grid. Only when the irradiance is high enough for current – and therefore power – to be produced, will the inverter begin feeding energy into the grid.

Technical data sheet of the FoxESS T10 three-phase inverter:

At what voltage does the inverter switch on? Technical data sheet of the FoxESS T10 inverter

New prosumer billing rules come into force from 1 April 2022. The rules were introduced by an amendment to the Renewable Energy Sources Act in December 2021. The new billing regime solutions introduced create additional opportunities for a faster and more sustainable development of the civic energy system in Poland. The Act introduces a new Net-Billing system, i.e. a system of value-based settlement of surplus energy produced by a prosumer in a Photovoltaic system. The existing Net-metering system remains open only to prosumers who report their micro-system to the grid before 1 April 2022.

Considering the acquired rights, the existing prosumers and those who apply to the Distribution Network Operator (DSO) by 31 March 2022 to connect their micro-system to the grid will remain in the discount system, which they will benefit from for 15 years.

New photovoltaic energy billing system – Net-Billing

Net Billing aims to:

• Implement the provisions of Directive (EU) 2019/944 of the European Parliament and of the Council of 5 June 2019 on common rules for the internal market in electricity and amending Directive 2012/27/EU, to which EU Member States are obliged.
• Ensure that end users actively participate in the energy market by being able to sell surplus electricity produced at attractive prices.
• Ensure the operational security of the electricity grid by integrating the growing number of prosumer micro-systems into the electricity system.
• Provide access to a new system of value accounting of the produced surplus of energy not consumed at the place of its production. Settlement will take place according to exchange prices at the average price of the previous month. The volume-weighted average price on the DAM (Day-Ahead Market) was 525.89 PLN/MWh in February 2022).
• Introduce from mid-2024 of settlements with prosumers at an hourly price consistent with the applicable dynamic tariff, which will ensure prosumers’ informed participation in energy market processes.

Net-Billing – Prosumer billing system effective from 1 April 2022.

Photovoltaic energy billing. Under the photovoltaic billing system the prosumer will:

• be billed under the net-billing system – value billing for surplus energy;
• bear the costs of the variable distribution fee;
• benefit from net-billing for 15 years;
• be able to settle the value of surplus energy produced for 12 months;
• exempt from the obligation to pay PIT, excise tax and VAT.

Net-billing is a new system for settling surplus energy from photovoltaics, which will be introduced in Poland after 1 April 2022. The system is intended to provide prosumers with an incentive for greater self-consumption of green energy from photovoltaics. Additionally, it is expected to increase the popularity and investment in backyard energy storage.

The net-billing system is an equally cost-effective and simple settlement mechanism for prosumers as the currently operating system of discounts (net-metering). The calculation of the value of surplus energy in the prosumer’s account will be carried out by the distribution system operator. The biggest change is that the settlement will concern the value, and not the quantity of electricity – as it is now. Settlement of energy with the operator will be made in money (PLN) and not in kilowatt hours (kWh).

AlphaESS Smile energy storage system.

What is the net-billing system (principles of operation):

• The prosumer is an active participant in the energy market. He will seek to feed electricity into the grid when prices are high, and to take energy from the grid when prices are low.
• The prosumer is guaranteed a market-based way of accounting for surplus electricity injected into the grid.
• The net-billing system creates an incentive for renewable energy prosumers to increase self-consumption of generated electricity and to adjust the size of the installation according to electricity demand.
• The prosumer gains greater awareness of energy market rules and motivation to manage and store electricity in the household (shaping electricity consumption patterns).
• Reduction of the increase in electricity supply costs for consumers.
• The net-billing system contributes to the flexibility of the national electricity system and energy efficiency.

Net-metering, also known as the discount system, is a billing system for prosumers (producers and consumers of photovoltaic energy), available to all who apply to the operator for connection by 31 March 2022. The discount system is based on a cashless settlement of the surplus electricity generated in the PV micro-system and injected into the grid and the energy taken from the grid by the prosumer.

Under the discount system, the prosumer:

• benefits from the system of discounts 1:0,7 / 1:0,8 – benefits from the quantitative settlement of the produced energy;
• does not bear the costs of the variable distribution fee;
• benefits from the settlement under the discount system for 15 years;
• may account for surplus energy for 12 months;
• may voluntarily decide to switch to net-billing.