One of the most critical components ensuring the efficient and safe operation of solar energy systems is the often overlooked but vital solar cable. So, what exactly is a solar cable, and what types of cables are used at different points in a solar power plant (SPP)?
What is a solar cable?
Solar cable is a type of cable specifically designed and manufactured to safely transmit direct current (DC) electricity produced by solar panels in photovoltaic (PV) systems to the inverter. Its main difference from standard electrical cables is its resistance to the harsh outdoor conditions to which solar energy systems are exposed.
The essential characteristics of a solar cable are:
Solar cables, constantly exposed to sunlight like solar panels, have a special outer sheath to protect against wear, cracking, and discoloration caused by ultraviolet (UV) rays. Temperatures can reach extreme levels or, conversely, freezing temperatures in environments where solar panels are installed on roofs or in the ground.
Solar cables are manufactured to operate without losing performance in a wide temperature range, such as -40°C to +120°C. They are also resistant to weather events such as rain, snow, and wind.
To maximize safety, solar cables generally have a double-layered insulation structure. This minimizes the risk of electrical leakage and provides extra protection against mechanical impacts. They are manufactured from halogen-free materials that slow the spread of flames in the event of a fire and do not release toxic gases when burned. This is a vital safety feature, especially in building and roof applications.
Thanks to their structure, which does not obstruct visibility in case of fire and produces little smoke, they facilitate evacuation and intervention operations.
They are resistant to chemical effects in industrial areas and ozone in the atmosphere.
These properties generally require solar cables to be manufactured in accordance with international standards such as EN 50618 and TÜV 2 PfG 1169. These standards certify the quality and reliability of the cable.
Types of Cables Used in Solar Energy Systems
A solar energy system is not just about solar cables. Different cables with different characteristics are used at different stages of the system. We can basically divide these cables into three main categories:
- DC Cables (Solar Cables)
As explained in detail above, these cables are used in the DC section of the system, i.e., between the solar panels and the inverter. They are called DC cables because they carry the direct current (DC) produced by the panels. They are usually found in cross-sections such as 4 mm², 6 mm², or 10 mm², and choosing the correct cross-section according to the system’s power, the current to be carried, and the distance is critical to preventing energy losses.
- AC Cables
The inverter converts the direct current (DC) from the panels into alternating current (AC), which is used by devices in our homes and industry. This is where AC cables come into play. All connections from the inverter output to meters, distribution boards, and the grid connection point are made with AC cables.
Although these cables are not exposed to the same harsh outdoor conditions as solar cables, they must be selected according to the current capacity to be carried and voltage drop calculations. Standard low-voltage cables such as NYY or NYM are generally used in this section. Copper or aluminum can be preferred as conductor materials.
- Grounding Cables
In solar energy systems, safety is just as important as efficiency. Grounding ensures that excess electrical load is safely transferred to the ground in case of any electrical leakage or lightning strike. This protects the safety of people and prevents damage to valuable equipment in the system (panels, inverter, etc.).
The metal frames of the solar panels, the metal construction of the mounting system, and the chassis of devices such as inverters are connected to the grounding line with grounding cables of appropriate cross-section and usually yellow-green in color. Grounding cables are also expected to be resistant to corrosion and external factors.
Cable Usage According to System Type
The cables used may also differ depending on whether the solar energy system is connected to the grid (on-grid) or off-grid.
On-Grid Systems
In these systems, DC solar cables, AC cables, and grounding cables are used as standard. AC cables provide the connection from the inverter to the bidirectional meter and from there to the electricity grid.
Off-Grid Systems
These systems also include battery storage units. Therefore, for connections between the inverter and battery groups, and between the battery groups themselves, battery connection cables with an appropriate cross-section, usually thicker and more flexible, are used. It is essential that these cables can safely carry high currents.
Choosing the right cable is a fundamental requirement not only for the current performance of a solar energy system but also for its long-lasting, safe, and efficient operation. These “hidden heroes,” which directly affect the quality and safety of the investment, ensure that energy from the sun is integrated into our lives without loss and without problems. Therefore, it is crucial to adhere to the standards and cable types specified by expert engineers during system design and installation.