Would like to find out how you can cooperate with Soltec? Perhaps you need a little extra knowledge about PV systems?
Our FAQ’s will answer those questions and more!
Our FAQ’s will answer those questions and more!
Photovoltaic module
Yes, these terms can be used interchangeably. A module or panel is a set of interconnected photovoltaic cells that produce electricity in the form of direct current.
The term “panel” appeared in Poland as an English loanword and has been in use on our market for several years.
It is also useful to know what a photovoltaic cell is. It is a single junction of P-type and N-type semiconductors that converts solar energy into electricity. The cells, often called wafers, generate a low DC voltage when exposed to light. For the most common silicon cell, it is about 0.6 V. To obtain a useable voltage (around a few dozen volts), the wafers are connected in rows by solder or glue. The standardised number of 60 silicon cells can achieve around 40 V. The voltage of a single cell will vary depending on the material of the semiconductor. Therefore, string lengths vary, which directly affects the electrical performance of the entire photovoltaic module.
Strings of cells are often connected in parallel to obtain more power for the entire module.
A module is a collection of individual cells, so the wrongly derided name, “photovoltaic cell battery,” is the correct one.
In contrast, the term “solar collector” should not be used as it means a device used to convert solar energy into thermal energy.
Sunlight is a stream of photons. When it falls on a photovoltaic cell, i.e., a P-N junction, it causes the electron-hole pairs to break apart. The released negatively charged electrons and positively charged holes accumulate at opposite poles of the cell, generating a constant flow of voltage. When the electrical circuit is closed, electrons travel from cells connected in rows toward positive holes through metallised contacts to equalise the potential. The electrical current created in this manner can be processed by a photovoltaic inverter or used, for example, to power DC loads.
It can be said without any doubt that PV installations are an investment for years. Photovoltaic modules are long-lasting devices, made to ensure their reliable operation for several decades – even in extreme weather conditions. Manufacturers provide up to a 30-year warranty on the module’s power output and failure-free performance. Over time, however, each module slightly loses its efficiency. Depending on the manufacturer, materials used, and the manufacturing technology, the guaranteed efficiency loss is between 0.2 and 0.7% per year.
The long lifetime of PV modules can be demonstrated by an example from Germany. In the 1990s, our western neighbours launched the “1,000 roofs” programme to encourage Germans to switch to alternative sources of energy. 20 years later, scientists at the Chemnitz University of Technology tested the modules that were installed at that time. The performance of all installations significantly exceeded 80% of the initial capacity.
Yes, there are mounting structures dedicated to different roof coverings and roof angles. Thanks to their easy adjustability, they can provide a solid foundation for photovoltaic modules while maintaining the durability and airtightness of the roof.
The slope and azimuth angle of the roof surface largely determine the performance of the installation. In Poland, the highest efficiency is obtained with PV modules facing south with an angle of about 35°. Flat roof owners can take advantage of special designs that optimise the angle of the panels to increase the installation’s safety and annual energy yield.
The only constrains of installing PV modules are the building’s poor structural condition and shaded areas of the roof.
This is something that the installer or an advisor should assist the customer with. They will be able to calculate the required capacity of an installation based on electricity bills from recent years and an analysis of the technical parameters of the roof to help their customer choose the appropriate type and number of modules.
The home’s power requirements are an important consideration. The installer, along with the investor, must also consider whether major investments are planned in the coming years. Installing air conditioning, a heated driveway, or an electric car charger will all significantly increase power requirements. It is worth it to include these plans in the design.
Yes, it does. For silicon photovoltaic cells, low temperature has a beneficial effect on the operation of the photovoltaic system. This is because the cell voltage increases as the temperature decreases. The design of the modules allows them to work in very low temperatures, which is why we can use them even in Antarctica.
However, keep in mind that winter days are relatively short, and the intensity of sunlight is smaller than in the summer. As a result,, energy production will be lower than in sunny seasons.
If you are not a licensed installer – we strongly advise against installing a PV system yourself. Attempting to set up a photovoltaic system on your own without proper training is putting your health and life at unnecessary risk. An untrained “installer” can be electrocuted or fall from a great height. What is more, poorly installed systems will also operate less efficiently and may be more prone to faults and fires and also void manufacturer’s warranty.
Please contact experienced companies that specialise in PV installations.
A polycrystalline module is made from polycrystalline semiconductor cells, while a monocrystalline module uses monocrystalline cells.
Producing monocrystalline silicon requires more energy than producing polycrystalline silicon, which means that the former is more expensive. However, monocrystalline cells have higher solar conversion efficiency compared to polycrystalline cells, while amorphous cells rank last. This translates into the size of the area occupied by the modules. Respectively, monocrystalline cells occupy the smallest area of those listed, so they require less money for the mounting structure and installation itself.
Polycrystalline cells are cut from blocks of polycrystalline silicon, so they are square in shape. Monocrystalline silicon is made with the Czochralski method to form a cylinder, which is then cut into wafers after milling the side edges. The substrate of a mono cell has a characteristic shape like a square with rounded off corners.
Monocrystalline cells are very dark blue, almost black – much darker than blue or navy polycrystalline cells.
From a performance standpoint, it does not make a significant difference. A photovoltaic generator of a certain capacity, regardless of the type of modules used – polycrystalline or monocrystalline – will produce almost the same amount of power per unit time. When choosing cell technology, programs that simulate the yield of PV installations usually do not distinguish between poly and monocrystalline modules, only between crystalline and amorphous. However, in recent years, more emphasis has been placed on the development of monocrystallisation technology, so these cells feature, among other things, improved temperature coefficients that contribute to the increased efficiency of monocrystalline PV modules.
In most manufacturers’ modules, PV cells are connected using a metal strip designed to conduct electricity. Busbars are places prepared for soldering this tape, located on the back and front of the cell.
A traditional PV module is typically made up of 60 square cells. In half-cut modules, the cells are cut in half, thanks to which the panel is made up of not 60 but 120 rectangular cells. These are 2 strings of 60 half-cells connected parallel to each other. By changing the structure of how the cells are joined together in the module, resistance to the flow of current is reduced, resulting in an increase in the device’s efficiency of between 1.5 and 3%. In addition, the panel handles partial shade better.
PV inverters
PV modules produce electricity in the form of direct current. The inverter’s job is to convert this energy into alternating current that is compatible with the electricity in the power grid.
Micro-inverters are devices that enable the conversion of direct current to alternating current from one or more PV modules. Unlike standard string inverters, which are placed further away from the modules, for example, on a wall in the service room, micro-inverters are fitted directly underneath the PV module. This minimises losses as less DC wiring is required, and it cuts out the cost of DC circuit protectors which are needed for string inverters. Such configuration significantly improves the installation’s safety as the maximum DC voltage that flows through the system is that of a single module. In addition, there is no need for any protection on the DC side. Micro-inverters are connected in parallel to one or three phases of AC wiring that leads directly to an AC switchboard.
Hybrid inverters are multi-functional devices that are connected to at least the power grid as well as an energy storage system. You can configure them according to your specific preferences, so the inverter will send the energy produced directly to the electrical appliances in your home. If the PV installation produces more energy than is required at the time, the excess energy does not have to be sent to the grid. It is possible to use it to charge an energy storage system. This allows the prosumer to enjoy free electricity after sunset when their PV system is not producing power.
Choosing the right inverter depends on the size of the system and the number of phases supplied. According to Polish regulations, owners of PV installations with a capacity exceeding 3.68 kW must choose a three-phase inverter. For smaller installations, there are no such restrictions, and it is possible to purchase both single-phase and three-phase inverters. A general rule of thumb for matching inverter’s power to the system’s power is that PV panel power should be in the range of 0.8-1.2 of the device’s AC power. If you want to find the perfect inverter for your installation, use our tool “TOOLTEC”. If you have more questions about selecting the right inverter, please contact Soltec Customer Service.
Check whether the inverter switch is in the “I” position and make sure that the circuit breakers in the switchboard are engaged. If the inverter only operates at certain times, try to determine when the problems occur, and pay attention to weather conditions when they do. Gather as much information as possible and contact your installer.
Due to summer weather conditions, the inverter reaches higher temperatures during operation, but this does not affect its lifetime or failure rate.
Directly connecting a typical inverter and a micro-inverter is not possible. A PV system with a classic string inverter can be expanded by installing another separate PV system based on micro-inverters.
The principles of operation are the same as in a typical system. During the day, the prosumer uses the electricity produced by the PV system. Excess energy goes back into the grid.
In addition to the basic components such as panels, a mounting system, and electrical protections, you still need to purchase a control panel that manages all the micro-inverters in your installation.
Yes, provided the inverter is IP65 rated. It is good practice to protect the inverter by building a small canopy in order to shield it from the sun, rain, and hail. For important information on how to install the inverter, refer to the unit’s instruction manual.
Energy storage systems
Energy storage is a particularly effective way to increase your energy autonomy. During the summer, daytime power production often exceeds the demand at any given time. In a standard installation, the excess is sent to the grid and the prosumer can collect it later. However, the grid owner takes 20–30% of the energy received. Whereas installations equipped with an energy storage system, redirect the electricity straight to the batteries, and the installation owner does not lose any kilowatts produced.
Owners of inverters with UPS or ESS function are also protected against power outages. The inverter will switch to emergency power mode and begin drawing power from the charged batteries. The prosumer will therefore be able to use electrical appliances despite the lack of electricity in the area.
Achieving full energy independence under current technical conditions is justified in places where there is no power grid. The optimal solution is to increase self-consumption in on-grid installations by using batteries.
The first step is to determine energy requirements. To do this, the prosumer should contact their installer or an advisor and analyse electricity bills from recent years as well as additional needs, such as protection against power outages.
In its simplest form, a PV system with energy storage consists of a hybrid inverter and a size- and type-matched energy storage system in the form of a battery. Other components of the PV system are the same as in a typical installation. A major difference is the need for the space to install the battery.
The Victron MultiPlus inverter, unlike many hybrid inverters, offers the ability to connect to an existing PV installation. It is a perfect solution for those who want to expand their installation with an energy storage system that has a UPS function.
Yes, in most cases the cables to connect to the inverter are included.
PV installation designs
Yes, our design team can create a complete design of any installation up to 3 MW and prepare all necessary documents. Please contact your account manager for details.
The time of execution and pricing of the design is an individual matter which depends on many factors. In most cases, this should take no more than 7 business days. Please contact your account manager to discuss details.
The building design of a PV system includes a section on fire protection systems. A simple PV installation concept does not.