5 Essential elements in a photovoltaic solar system: complete guide

Installing a photovoltaic solar system is an increasingly popular choice for those looking to reduce their energy bills and contribute to environmental sustainability. But which elements are truly essential to ensure the proper functioning and efficiency of a photovoltaic system? In this article, we will look at the 5 indispensable components of a photovoltaic system, which are absolutely necessary to achieve maximum performance.

1. Photovoltaic modules (solar panels)

Photovoltaic modules are the beating heart of every system. Composed of silicon solar cells, their task is to convert solar energy into direct current (DC) electricity. The choice of panels depends on:

Efficiency

Efficiency indicates the percentage of solar energy that the panel can convert into electricity. Depending on the technology, the values vary:

• Monocrystalline panels: offer high efficiency, generally ranging from 18% to 21%.

• Polycrystalline panels: slightly less efficient than monocrystalline ones, but they can perform better in variable light conditions throughout the day.

• Thin-film panels: characterized by lower efficiency, but they perform well in diffuse light or high temperatures.

Technology

The main available technologies are:

• Monocrystalline: made from monocrystalline silicon, recognizable by their uniform dark color. They are appreciated for their high efficiency and durability, which can exceed 25 years.

• Polycrystalline: made from polycrystalline silicon cells with randomly oriented crystals. They feature an intense blue color and slightly lower performance compared to monocrystalline.

• Thin-film: made with materials such as amorphous silicon or cadmium telluride, they have a uniform dark appearance and are well-suited to various architectural solutions thanks to their flexibility.

Rated power

The rated power of a panel, expressed in Watt-peak (Wp), indicates the maximum power the module can generate under standard test conditions (STC), i.e., with irradiation of 1000 W/m² and an ambient temperature of 25°C.

2. Photovoltaic inverter

The inverter is a key component in every photovoltaic system. Its main function is to convert the electricity produced by the panels, which is in direct current (DC), into alternating current (AC), making it usable for domestic consumption or feeding it into the power grid.

Several types of inverters are available, each designed for specific needs:

• String inverters: Connect multiple solar panels in series, forming "strings." The direct current produced is then converted into alternating current. A critical point is that the efficiency of the entire string can decrease if even one panel is shaded or malfunctioning.

• Microinverters: Installed directly on each panel. They allow each module to operate independently, improving overall efficiency, especially in systems subject to partial shading or with different orientations. Their main disadvantage is a higher initial cost compared to string inverters.

• Centralized inverters: Mainly used in large installations, such as industrial or ground-mounted plants, they can handle energy from numerous strings and convert it into alternating current. Ideal for managing high volumes of energy production.

• Hybrid inverters: Combine the functions of a standard inverter with the ability to manage energy storage systems. In addition to converting energy, they regulate the charging and discharging of batteries, facilitating self-consumption and optimizing the use of the produced energy.

3. Mounting structure

The mounting structure's role is to securely anchor the solar panels to the roof or directly on the ground. It is usually made of highly resistant materials such as galvanized steel or aluminum, capable of ensuring strength and durability even in adverse weather conditions, easily withstanding wind and snow loads.
When designing and installing a mounting structure, it is essential to consider some key parameters:

Tilt angle

The efficiency of the panels also depends on the angle at which they are tilted. This value varies depending on the installation site's latitude. In Italy, the recommended tilt is between 30° and 40°. More specifically:

• In northern regions, a tilt between 35° and 40° is preferable.

• In southern regions, a tilt between 20° and 30° is recommended.

Orientation

The ideal orientation to maximize solar energy production is facing south. However, slightly shifted orientations, such as southeast or southwest, also provide good results, with efficiency losses generally below 5-10%.

Resistance certifications

It is essential that the structure complies with current regulations and holds certifications attesting to its resistance to wind loads, snow, and other stresses required by local standards.

4. Storage system

More and more users choose to integrate their photovoltaic system with a storage system. Batteries allow the energy produced during the day to be stored and used in the evening or during periods of low solar irradiation.
The main battery technologies are:

Lithium batteries

Advantages:

• Have a long lifespan, supporting thousands of charge and discharge cycles.

• Offer high efficiency, with yields exceeding 95%.

• Require little maintenance, not needing refilling or regular checks.

• Can be discharged up to 80-90% of their capacity without compromising their useful life.

Disadvantages:

• The purchase cost is higher than traditional batteries.

Lead-acid batteries

Advantages:

• Generally cheaper at the time of purchase.

Disadvantages:

• Have a shorter lifespan and support fewer charge/discharge cycles compared to lithium batteries.

• Require periodic maintenance, such as checking and refilling the electrolyte.

• Have lower efficiency, varying between 70% and 85%.

• It is advisable not to discharge them beyond 50% to avoid rapid deterioration.

5. Electrical panel and safety devices

To ensure safety and reliability for the entire photovoltaic system, some fundamental components are indispensable:

• Protection electrical panel: Works as a control unit that organizes all safety devices. It ensures order in electrical connections and facilitates control and maintenance operations.

• Residual current circuit breakers (RCCBs): Protect against electric shocks by detecting current leakage to the ground and immediately cutting off the circuit in case of anomalies.

• Miniature circuit breakers (MCBs): Provide protection on two fronts: the thermal component handles prolonged overloads, while the magnetic one reacts promptly to short circuits, protecting the system and reducing the risk of fires.

• Surge protection devices (SPDs): Protect the system from voltage spikes caused by events like lightning. They divert excess energy to the ground. It is recommended to install them on both the direct current (DC) and alternating current (AC) sides.

• Bidirectional meters: Allow monitoring of both energy drawn from the grid and fed into it, facilitating energy management and participation in incentive schemes or net metering.

These devices work together to ensure an efficient and safe system, protecting both the equipment and the users.

Carefully selecting all the elements of a photovoltaic system is crucial to guarantee efficiency, safety, and long-term durability. Only in this way will it be possible to fully benefit from this technology.