Solar power plant (Photovoltaic plant)
At a time of fluctuating energy prices, it is often thought about self-sustainability. The source of energy that is the most available, and recently more and more accessible, is solar energy. The energy in question belongs to renewable energy sources. The technology of solar power plants has reached a level where the installation of a smaller power plant on the roof of a house becomes economically affordable.
TECHNICAL CHARACTERISTICS
The energy produced by the solar power plant depends on the position and layout of the power plant itself. Annual solar insolation, angle of inclination and the azimuth are the main characteristics of photovoltaic panels. The azimuth of the sun (šS) is the angle between the projection of the sun’s rays on a horizontal surface and the north-south direction in the horizontal plane. The ideal angle of inclination and azimuth changes during the day and the year. If the panels are installed on an existing building, the azimuth and angle of inclination depend somewhat on the geometry of the roof. There are systems that track the sun to optimize tilt angle and azimuth for maximal insulation, but they add significantly to the investment cost of a power plant . The location of the solar panels should preferably be in the shadow of other buildings and plants (e.g. trees) for as little as possible during the day. Shading of the panel reduces the efficiency of the panel.
Technical data that is important to keep in mind when choosing equipment is the efficiency of solar panels and inverters. As the angle of inclination affects the amount of solar insolation, the efficiency of the panels and inverters also affect the overall efficiency of the system.
From the aspect of planning the solar power plant, at the very start it is necessary to decide whether it will be connected to the public power distribution network or will work independently off grid. In case you want to supply electricity to a place where there is no distribution network, the off grid power plant is the right solution.
| Advantages | Disadvantages | |
| Connected to network | – excess energy is transferred to the network and no batteries are needed – the power of the power plant should not cover the peak power because the lack of sun is covered by the network | – the electric power network should be ready to receive excess electricity |
| Off grid | – it is not necessary to do the main design and to obtain the conditions for connection to the network | – need for batteries – must satisfy the peak power of the consumer |
DESIGN
In which network mode the solar power plant works depends on which elements need to be foreseen in the design phase. In case the power plant is connected to the power distribution network, the main elements are the inverter, photovoltaic panels and protection devices. According to the conditions given by the distribution network operator, if the power plant is designed to be connected to the network, then there must be protection against switching to off grid operation. In the case of a power plant that is designed for off grid, in addition to the inverter, photovoltaic panels, protective devices, the batteries, battery charger and battery monitor system (BMS) must also be selected.
Currently, the construction of solar power plants and their connection to the existing power system is carried out based on: Zakona o tržiÅ”tu elektriÄne energije (NN 111/2021), Zakon o obnovljivim izvorima energije (NN 138/2021), Pravilnik o opÄim uvjetima za koriÅ”tenje mreže i opskrbu elektriÄnom energijom (NN 100/2022), Pravilnik o jednostavnim i drugim graÄevinama i radovima (NN 112/2017).
According to the currently valid regulations, legal entities and individuals who have a solar power plant connected to the electricity network, annually produce less electricity than they consume, do not enter the tax system as an electricity producer. The tax obligation is an important information for an investor when choosing the size of a solar power plant. Another important aspect when connecting a solar power plant to the network is that the quality of the supplied energy must be satisfactory. This is verified by a seven-day quality measurement of electricity at the time when the solar power plant is connected to the power network. The acceptable quality of electricity is prescribed by the network operator through the electricity approval(EES). In case the quality of electricity is not acceptable, it is possible to improve the quality of electricity by installing an active filter. The filter is designed to remove harmonic interference and compensate for reactive energy.
APPLICATION
Integrated solar power plants are mostly used for self-consumption. They are installed on the roof or facade of buildings. The positive side of integrated solar power plants is that they do not occupy areas for agriculture. While unintegrated solar power plants are placed in areas that are suitable for agriculture. Just as a solar power plant needs the sun to produce electricity, so plants need the sun to photosynthesize. This brings us to the important question, should non-integrated solar power plants be built on agricultural land? Taking all things into account, mankind needs both food and energy.
The largest solar power plant currently being built by HEP is about 10 MW (SE Donja Dubrava). This year in the north of Poland in Zwartow, a solar power plant with a power of 204 MW was put into operation (when it is completed, it will have installed 290 MW). Spain, which has one of the better positions in Europe for the production of electricity from the sun, has the largest power plant with an installed power of 590 MW.
| Croatia’s annual electricity consumption in 2021 | Croatia’s annual electricity production in 2021 | Estimation of electricity production of SE Donja Dubrava in one year |
| 16,837 GWh | 10,801 GWh | 12,596 MWh |
| 100.00% | 64.15% | 0.07% |
FIRE PROTECTION
Whether you’re a homeowner looking to reduce your electricity bill or a corporation looking for ways to reduce your carbon footprint, installing solar power on your roof or facade increases your fire risk. Like any other electrical installation, an integrated solar power plant presents a fire risk. The main causes of fire are component failure, improper installation and inadequate maintenance.
As an example for fire on an integrated solar power plant we can take Amazon. A global company that has office buildings around the world whose roofs are suitable for integrated solar power plants. In a period of 15 months, they had a fire at 6 out of 47 (12.76%) plants in the USA. According to Amazon’s official statement, the reasons for the fire were a malfunction or improper installation of the system.
All buildings that have integrated solar power plants should have a sign visible to the firefighters when they arrive on intervention. So they can adapt adequate fire fighting tactics. An essential part of the solar power plant system in terms of fire protection is the switch that disconnects the photovoltaic panels from the grid. The switch in question should be as close as possible to the panels so that the minimum extent of electrical installations remains under voltage. As a result, the panels remain energized, and the rest of the wiring is de-energized. Such a situation allows firefighters to extinguish the fire with water on the rest of the building.
Solar energy is often called free energy. But when looking at the necessary equipment, installation process, permits and risks involved in the production of electricity from the sun, it can be concluded that it is an investment that needs maintenance and supervision throughout its life. At the moment, a trend of switching to renewable energy sources can be noticed in Europe, which makes solar power plants more and more accessible with incentives, changes in the legislative framework and the development of technology.