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!
PV installation designs
Can Soltec design the entire installation and prepare the necessary documentation?

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.

How long does it take for Soltec to prepare a PV installation design and how much does it cost?

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.

Does the design of a PV installation include a section on fire protection systems?

The building design of a PV system includes a section on fire protection systems. A simple PV installation concept does not.

Photovoltaic modules
Are modules and panels the same thing? Structure of a photovoltaic modules.

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.

How does a PV module work?

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.

What is the lifetime of a PV module?

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.

Can PV modules be installed on every roof?

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.

How many modules need to be installed on the roof for the PV system to meet the customer’s needs?

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.

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PV inverters
What is an inverter?

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.

What is the difference between an inverter and a micro-inverter?

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.

What is a hybrid inverter?

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.

How to choose the best inverter for a given installation? How do models differ from each other?

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.

My inverter is not working. What should I do?

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.

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Energy storage systems
Do energy storage systems guarantee independence from the grid?

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.

How to choose an energy storage system?

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.

What does an energy storage kit consist of?

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.

What is the difference between a Victron MultiPlus inverter and a hybrid inverter?

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.

When I buy a battery, does it come with cables to connect to the inverter?

Yes, in most cases the cables to connect to the inverter are included.

Other questions
What does a PV installation consist of?

The basic components of any PV systems are the photovoltaic modules and the inverter. Photovoltaic modules are the muscles of the installation that are responsible for production of energy. The inverter converts direct current generated by the panels into alternating current and monitors the operation of the entire system. Thanks to the inverter, we know how much electricity the home power plant has generated. It is the brain of the entire system.

An installation also includes connecting cables that connect the modules to the inverter and the inverter to the switchboard. A vital component is the mounting structure, which ensures that the PV modules are securely attached to your roof or the ground.

Building your own PV system is expensive, so it is important to make sure it is safe. Electrical protections such as surge arresters are an important part of this.

To maximise energy yields, it is also worthwhile to consider purchasing power optimisers.

For those who want to store the energy produced, we propose to enhance the installation with an energy storage system.

How do Tigo power optimisers work?

Tigo power optimisers search for maximum power point at the level of a given module to which they are connected. These allow the module to achieve the highest possible capacity it can at any given time, regardless of how much power other modules are generating. An installation without optimisers works as well as the weakest panel that is, e.g., in the shade. By using optimisers, we improve the operation of the weakest panels so that the entire installation works even better.

This is a perfect solution, for example, when the module is partially shaded or when the roof has many slopes.

The big advantage of Tigo power optimisers is that they are fully compatible with most inverters and that they can be fitted to modules that require it and not to all modules in the installation.