ENERGY ACT FOR UKRAINE FOUNDATION
How solar power plants work
Today, renewable energy sources (RES) play a crucial role in ensuring Ukraine's energy security and combating climate change. Hybrid solar power plants are becoming a reliable solution for stable and efficient electricity generation. These systems use solar energy to generate electricity, while providing the ability to operate both from batteries and the grid. This approach allows optimal use of solar energy even during blackouts or periods of low sunlight.
The main components of a hybrid solar station
A hybrid solar power plant consists of three main components:
-
Photovoltaic modules (PV)
-
Inverters
-
Rechargeable batteries (batteries)
Photovoltaic modules
Photovoltaic modules, or solar panels, are the main element of a hybrid solar power plant. They convert solar radiation into electrical energy using the photovoltaic effect. PV modules consist of solar cells made of semiconductor materials, most commonly silicon. When sunlight strikes these cells, the photons' energy is transferred to electrons, releasing them and creating an electric current. This is direct current (DC), which is then sent to the inverter. During installation, the panels are positioned in such a way as to minimise shadow on their surface and to maximise access to sunlight throughout the day and year. The optimal tilt and orientation of the panels also depends on the geographical location of the installation. For modern panels, the percentage of solar energy converted into electricity is usually between 15% and 22%.
Inverters
The inverter is a key component of a hybrid solar plant, as it converts the direct current (DC) electricity generated by the PV system into alternating current (AC) electricity used in domestic and commercial electrical systems. In addition, the inverter can be programmed to manage the charging and discharging of batteries, keeping them healthy and efficient. The inverters have a minimum of two connection points on the alternating current (AC) side - one for the external grid and one for the consumer - and a minimum of three on the direct current (DC) side - two for solar panels (PV) and one for the battery. Some models also have the ability to connect additional power sources, such as generators.
Rechargeable batteries
Batteries store excess energy generated by PV modules for use when solar power is not available, such as at night or on cloudy days. Batteries provide continuous power supply to critical consumers. Typically, the percentage of stored energy that can be reused ranges from 80% to 95%. The most commonly used batteries are lithium iron phosphate (LiFePO) batteries, as they have a longer operating life and reliability. However, lead-acid batteries also exist and are used, which is a traditional type of battery that is less efficient and less durable.
How a hybrid solar station works
1. Generation of electricity: PV modules are installed on a roof or other open surface. The sunlight that hits the panels generates direct current (DC) electricity. Since one panel on average has a generation voltage of 49 V, and the inverter must receive a minimum of 160 V and a maximum of 1000 V from the PV system (the final values may vary depending on the inverter model), in order to provide this voltage, the panels are connected in series with each other and this chain of panels is called a string. Each such string is connected to the corresponding inputs to the inverter, and their number is limited by the inverter's power. For example, a 10 kW inverter can be connected from 2 to 8 strings, a 50 kW inverter can have up to 16 strings.
2. Conversion of electricity: So after installing the solar panels and connecting them into strings, they are connected to the inverter, as the direct current (DC) must be converted into alternating current (AC), which is suitable for use in domestic and commercial electrical systems. The number of connection points for both AC and DC depends on the make and model of the inverter. Two on the AC side and three on the DC side are the minimum possible number.
3. Energy storage: Excess energy that is not used at the time of generation is stored in the battery for later use when solar energy is insufficient. The battery is connected to the inverter at the appropriate inputs so that it can invert direct current to alternating current. Whether the battery will be charged by the grid or the PV system depends on the amount of electricity generated by the PV system and the internal consumption of the facility where the solar power plant is installed. The location of the battery and the inverter cannot be too far apart. It is ideal if the inverter is located above or near the battery installation site to use the minimum amount of cable.
Modes of operation of a hybrid solar station
1. Energy storage mode: The batteries are charged from the public grid or through an inverter that supplies the generated energy from the PV system. The battery charge and discharge levels are regulated to maintain optimal performance.
2. Mode of supplying excess electricity to the grid: Excess electricity is fed into the grid using the net billing scheme, which reduces electricity costs. If this option is not enabled, the plant limits its electricity production according to actual consumption.
3. Emergency mode: During a power outage, hybrid stations continue to generate power. The automatic transfer switch (ATS) switches the facility's power source from the grid to the battery, ensuring continuous operation.
Conclusion
Hybrid solar power plants represent a sophisticated and effective approach to meeting today's energy needs. By seamlessly integrating solar energy generation, conversion and storage, these systems offer a sustainable solution for uninterrupted and cost-effective power supply, especially during blackouts. As technology advances, hybrid solar plants will become an even more important component of the global energy landscape, providing reliable and efficient renewable energy for a variety of applications.