What is photovoltaics?

The word photovoltaics is a combination of two words related to physics, i.e. the word “photo” meaning light and “volt” meaning the unit by which we express voltage of current. Photovoltaics is a field of science and an economic sector that focuses on converting solar energy into electricity.

The basic element of a photovoltaic power plant are photovoltaic modules (popularly called solar panels). Photovoltaic panels consist of semiconductor elements that convert solar energy into electricity as a result of the photovoltaic phenomenon. The cell is composed of two layers of semiconductor – n-type and p-type and connected electrodes – upper and lower. As a result of the impact of sunlight on photovoltaic cells, electrons are knocked out by photons. As a result of knocking out, a potential difference is created, followed by a direct current.

First of all, it should be remembered that PV installations are not solar collector installations, which are only used to heat water. The energy generated by photovoltaic cells can be either stored using batteries or fed back to the grid for storage or sale. Therefore, photovoltaic installations are divided into two types:

1.On-Grid photovoltaic power plants

It is a type of photovoltaic installation integrated with the public grid. This type of installation is most often chosen in Poland due to the relatively low investment cost and good and simple settlement rules. The grid inverter returns the surplus to the Energy Plant and, depending on the settlement method, we can sell the surplus or put it into storage and collect it in the winter.

Pursuant to the Polish Act on Renewable Energy Sources, a natural person can easily and quickly settle electricity in the “discount” system. All you need to do is become a prosumer, i.e. sign a new contract with the energy company regarding the introduction of micro-installations and the extra electricity from photovoltaics is stored at the distributor. We can receive this electricity when we have a shortage, e.g. in winter (higher electricity consumption, lower panel yield resulting from shorter days, more cloudy days, etc.). If we have an installation smaller than 10kW, we can collect 80% of the previously produced electricity (the energy company collects 20% as storage costs).

The undoubted benefits of network installations include:

• current use of energy produced by solar panels,

• sending surplus energy to the grid.

2. Off-Grid photovoltaic power plants

This is a type of photovoltaic installation that consists of a regulator, converter, solar panels, batteries and a controller. This type of installation is most often chosen in allotment houses that do not have access to the public grid or in villages, where uncomfortable power outages often occur (on-grid photovoltaics does not work when we do not have electricity from the grid). This system is a much more expensive solution due to the high prices of individual energy storage (components).

We have already discussed the principle of operation of solar panels in the previous part of the article. In order for a photovoltaic installation to be complete and to function properly, it also needs the “heart of the installation”, i.e. an inverter, also known as an inverter. The inverter loads the panels by searching for the maximum power point (MPPT – link) from the string of panels, achieving the optimal power of the string. The inverter also changes direct current (DC) from the panels to alternating current (AC) and feeds the electricity into the building’s network. Then the obtained electricity goes to the sockets and is used to meet the current consumption of electrical devices in the house (TVs, household appliances, air conditioning, electric stoves, lighting, etc.). Modern inverters are equipped with monitoring functions, i.e. information about the production of a given installation is sent to the manufacturer’s server using built-in WIFI modules. The user can conveniently monitor the operation of his power plant using an application on his smartphone or web browser.

The more solar panels and the sun’s rays falling on them, the greater the energy yield the investor achieves. That is why photovoltaic panels are more often mounted on the roof than on the ground – the roof usually has a slope close to the optimal one (about 35 degrees), and its high position also means that the panels are free from shading, which has a very harmful effect on the efficiency of the installation (check the effects of shading – link). The sun’s rays are free, so the investment in photovoltaics pays off after a few years. Additionally, the installation is completely maintenance-free, so it does not generate any additional costs.

Elements of a photovoltaic installation – photovoltaic sets

In addition to the previously mentioned solar panels and the inverter, you need a number of accessories and photovoltaic components that make up the COMPLETE PHOTOVOLTAIC SET (available in our store). The solar kit consists of:

• Photovoltaic modules

• Inverter

• Aluminum structure (PV rail profiles, tile hooks, trapezoidal bridges)

• Stainless steel load-bearing elements (PV double-threaded screws)

• Connecting elements (PV clamps, Allen screws, rail entries)

• Solar cables

• MC4 connectors

• Ground wires

• DC PV surge protectors

• PV switchboards (photovoltaic distribution boxes)

• Electrical accessories (MC4 crimping tools, ferrules, eyelets)

Thanks to the system of discounts for prosumer installations (so-called net-metering), the owner of a photovoltaic installation can send surplus electricity to the grid and collect it within one year (the next billing period). In other words, the user of a photovoltaic power plant has the right to annual energy balancing, i.e. settling the difference between electricity consumption and electricity production on an annual basis. This means that the owner of solar panels on the roof can receive electricity when its production is low, e.g. in winter. The prosumer contract therefore allows for full independence from electricity prices.

Installing a photovoltaic power plant on the roof does not require changing the electrical installation. The PV installation is most often connected to the central switchboard in the building, i.e. to devices that already exist and do not require modification. Depending on the existing electrical installation in the building – single or three-phase, an appropriate photovoltaic installation is selected for 1 or 3 phases.

The bidirectional counter is an essential component for the correct accounting of current flow in the discount system. The bidirectional meter balances the amount of energy taken from the grid with the amount of energy released into the grid from the photovoltaic installation. Its task is to measure current in two directions. Depending on the type of inverter you have (single-phase inverter or three-phase inverter), an appropriate counter is installed.

Replacing the meter with a bidirectional one is the responsibility of the energy company. After submitting an application to connect a new photovoltaic installation, the relevant facility has 30 days to consider the application and replace the meter at its own expense. Therefore, the investor of a micro installation does not pay either for a new meter or for its replacement.