Against the backdrop of rising energy prices, people's desire to be energy independent has also increased. Photovoltaic panels or heat pumps are the alternative that more and more Romanians are turning to. Today we are discussing photovoltaic panels . We all know that the sun emits huge amounts of energy daily. Some reaches ground level, and some is absorbed by the atmosphere or reflected back into space. The amount of energy that reaches the Earth in a single day is greater than the energy consumed by the inhabitants of the planet in a whole year.

What are photovoltaic panels?

Photovoltaic panels are the energy collector within a photovoltaic system. With the help of photovoltaic cells, the energy of photons is converted into electrical energy. A panel comprises several photovoltaic cells that are electrically connected and laminated between sheets of vinyl acetate. The photovoltaic cell absorbs part of the light particles that fall on their surface, also called photons . In turn, photons contain a small amount of energy, and when it is absorbed it releases an electron from the solar cell material. Finally, the photovoltaic cell will produce electricity that can be used instantly or stored in batteries .

Photovoltaic cells are connected either in series or in parallel. The amount of electricity produced at the cell terminals is determined by the level of radiation, temperature, air quality and length of day. Most of the time photovoltaic panels are mounted on the roof of a house. Lately they have been installed including on the roof of apartment blocks or supermarkets. 

The performance of photovoltaic systems is directly related to their orientation, degree of inclination, shading and temperature . Therefore, methods of capturing solar radiation can vary between fixed-orientation systems or systems with the possibility of orientation along one or two axes and ground-level locations.

Types of photovoltaic systems

Photovoltaic systems are divided into 3 categories:

• on-grid system – connected to the public grid. Specifically, the energy produced by the panels during the day is used for household consumption. If the production is higher than the consumption, the surplus energy is injected into the network and reaches other consumers. If an on-grid system does not capture enough solar energy, then the difference in consumption is covered from the public grid. At the end of the month, users of such a system will only pay the difference between the energy produced and that consumed. Bills can be reduced by up to 100%, and if the monthly production is higher than the consumption, you will receive money for the amount of energy injected into the network. The only downside is that you will still be dependent on an electricity supplier that you have to sign a contract with. Even so, the dependency will be quite low.
• off-grid system – ensures the energy independence of the home with the help of accumulators that store additional energy and use it in times of low production, such as at night or on cloudy days. The household will benefit from electricity both day and night. In addition, you will not depend on the public system at all and will not have to sign a contract with a supplier. The unpleasant part is that you risk running out of electricity if the system is not designed and sized efficiently.
• hybrid system - combines the advantages of the above. It is equipped with an inverter and has many settings. Among the possible variants we mention: consumption from photovoltaic panels and additional as needed from the public network, consumption from panels and storage of additional energy in batteries or consumption from panels, charging batteries from the network during the night and consuming the energy stored there as needed. The steep price is the only downside of this system.

Advantages & disadvantages

Regardless of the option chosen (on-grid, off-grid or hybrid), the advantages of photovoltaic panels are numerous.

• friendly solution for producing electricity compared to classic systems;
• fixed price for electricity produced by the photovoltaic system, so you will not be hit by periodic price increases;
• does not emit any sound;
• it can be mounted on any type of roof or on the ground;
• renewable energy source;
• reduce current bills;
• low maintenance costs;
• long life span of about 20-25 years.

Regarding the disadvantages of photovoltaic panels, they are fundamental, not functional:

• expensive investment;
• they depend on the weather – PV panels can also work on cloudy days or in winter, but the efficiency is lower.
• storing the energy produced in batteries is quite expensive;
• space needed – the more energy the household needs, the more panels will be needed.

How many panels fit on the roof?

Photovoltaic panels are always mounted on the south side of the roof to benefit from as much light as possible. First of all, you need to measure the roof or you can take the exact measurements from its technical project. The next step is to find out the size of the photovoltaic panel. The last step requires a division operation: the roof area is divided by the area of ​​a panel, resulting in the number of panels that fit on your roof. In general, a standard photovoltaic panel has the size of 100 x 164 x 4 cm, which is approximately 1.7 square meters.

How do you calculate the need for photovoltaic panels?

Manufacturers are of the opinion that establishing the need for panels is not necessarily related to the surface of the roof or the number of people, but to the actual energy consumption. Many people aim for a number of panels directly proportional to the area of ​​the house or the people who live there. Wrong!

Calculations are made starting from the daily energy consumption . For example, a household records a monthly consumption of 300 kWh, i.e. 10 kWh daily. The daily consumption is divided by a coefficient of 3.3 (daily annual average) resulting in the installed power of 3 kW. If you opt for a classic 250 W panel, then you will need 12 photovoltaic panels.

What type of photovoltaic panels should I choose?

After you have chosen the type of system and determined the panel requirements, the next step is to actually choose the panels. There are several types of panels on the market that we will detail below:

• monocrystalline panels – have a high level of efficiency and produce the largest amount of energy. They are durable and can be mounted even on smaller surfaces. Color dark black;
• polycrystalline panels - do not withstand high temperatures so well. They are cheaper and the level of efficiency is somewhat lower. Dark blue color;
• panels with a thin layer (Thin Film) – they are flexible and can be installed on large surfaces. Energy efficiency and production will not be affected by temperatures or shade;
• hybrid panels – contain monocrystalline cells that have a thin layer of amorphous solar film. Their role is to attract as much solar energy as possible, especially when the light is weak. They can convert solar energy into electricity or heat water. They are not recommended for very large roofs;
• flat panels – consist of flat copper plates that are placed on fiberglass insulation and covered with a special material that captures the sun's energy. They are effective regardless of the type of climate and can also heat domestic water.
• vacuum tube panels – capture solar energy using pressurized or non-pressurized vacuum tubes. They are much easier to maintain than flat panels and the level of efficiency is high.

Components of a photovoltaic system

A photovoltaic system is generally composed of 6 basic components:

• photovoltaic panel;
• charge controller;
• battery bank;
• inverter;
• utility meter;
• electrical network.

The installation must be done on a stable structure that supports it and resists weather conditions such as wind, rain or corrosion. It is good to know that the wear of solar panels is given by the environment and the way they are mounted.

How are photovoltaic panels mounted?

Please note that installation should only be carried out by specialists. Here are the steps:

• choose the right place - either on the roof or on the ground, it is important that they are exposed to the sun and oriented to the south or east.
• installation of the mount - gives stability to the panels in the face of environmental factors and prevents water from leaking from the roof into the house;
• mounting the panels – the mobile rails and the metal support are installed. It is mounted on the roof at a height of at least 6 cm from the roof. The panels will be fixed with an adhesive that prevents their movement.
• tilt angle calculation – helps capture more light. The angle is calculated according to the latitude of the house from which 15 degrees are added in winter or subtracted in summer.

How much does it cost to install photovoltaic panels?

Photovoltaic panels are a very expensive investment that pays off over time. Prices differ from project to project. For example, a single-phase off-grid system with a power of 5 kW costs about 4400 euros. In contrast, an on-grid system with a power of 10 kW ends up costing twice as much, while a hybrid system can even exceed 10,000 euros.

Documents required for the installation of photovoltaic panels

Nothing without roads, papers and bureaucracy. Although since 2019 the law has eliminated the need to have a permit for the installation of photovoltaic systems , those wishing to do so must notify the City Hall of the changes made to the home before the work begins.

It is necessary to obtain a series of approvals:

• sanitation notice – issued within 15 days by the local sanitation company. The fee is set by the company in question;
• the ISU opinion – is issued within 30 days by the Inspectorate for Emergency Situations;
• telephone notice - is issued within 15 days by the telephone provider. The fee varies between 3 and 9 euros (without VAT);
• energy supplier location notice – is issued within 15 days by the electricity distributor. The fee is 55 lei (without VAT);
• technical approval for connection - is issued within 30 days by the electricity distributor. The fee is 42 lei (without VAT);
• the electricity production and accreditation license - these are two documents issued by the National Energy Regulatory Authority (ANRE) within 60 days and 30 days, respectively;
• the connection certificate – is issued free of charge within 30 days by the electricity distributor.