What are photovoltaic inverters and what are they for?
The main benefit of having a photovoltaic installation is independence from the most expensive use of electricity and its production for your own needs. However, to be able to speak of a comprehensive installation of photovoltaic energy, it is necessary to install several of its necessary elements, one of the key elements is the inverter.
- How to make the best choice for this device?
- What must be taken into account when selecting an inverter for a photovoltaic installation?
We answer the most important questions in our post.
What are photovoltaic inverters and what are they for?
The inverter is also known as a solar inverter or frequency converter .
Many industry specialists call it the “heart” of photovoltaics. Its main function is to convert the direct current generated by the photovoltaic system into alternating current and to control and protect the photovoltaic installation.
The inverter works very well during a breakdown, when the voltage in the grid disappears. Then, thanks to the inverter, it is possible to disconnect the photovoltaic system and interrupt the power supply to the electrical grid. It can be safely stated that the function of the inverter is also to supervise the operation of the entire photovoltaic installation. It’s worth adding that many of the newer devices have built-in software . It is thanks to him that it is possible to detect and diagnose any failure almost instantly. In addition, all the information on the irregularities detected is sent to those responsible for the repairs and maintenance work related to the photovoltaic installation.
Using a properly selected PV inverter allows you to minimize the risk of power shortages. Therefore, it is clear that the selection of a good inverter is a key issue when mounting a photovoltaic installation.
Which inverter for photovoltaics: the most important parameters of the device
When choosing an inverter for a photovoltaic installation, it is worth paying attention to the important parameters of this device. Which are?
It is worth looking for an inverter that is as reliable, durable and with a high protection class as possible. In addition, it is extremely important to have a comprehensive, long-term warranty and the appropriate certificates; one of the most desirable are those that comply with PN-EN 61000-3-2 and PN-EN 61000-3-3 (below 16A), PN-EN 61000-3-12, PN-EN 61000-3 -11 (between 16 and 75A) and PN-EN 50438. Furthermore, it is also important that the investor has a declaration of conformity with Directive 2014/35 / EU and 2014/30 / EU.
In addition, an important criterion when choosing an inverter is also the maximum power level of the device and its professional installation.
Photovoltaic inverter: single phase or three phase
Inverters are devices that can be classified according to their use and the number of phases to which the device is connected.
Therefore, there are single-phase and three-phase inverters. The first of them are especially recommended for installation in small photovoltaic installations. Those investors who want to use the functionality of larger photovoltaic installations (those with a power greater than 3.68 kW) should choose a three-phase photovoltaic inverter. This one, of course, will definitely differ in price – it is even several dozen percent more expensive than a single-phase inverter.
However, investing in a more expensive solution also brings numerous financial benefits down the road. They will be influenced by the higher efficiency of the inverter and the uniformity of the energy input in each of the phases. This, in turn, is related to the implementation of the idea of a uniform distribution of loads in the building between the phases. In addition, the current value in each of the phases is significantly limited, which has an impact on the overall stability of the local network.
Inverter for photovoltaic panels – important IP resistance class
An important factor determining the quality of the inverter is its IP resistance class . It is an indicator that shows how the inverter handles water and different types of dust. Defines the resistance of the device and its tightness.
It is worth knowing that inverters with a minimum resistance class of IP65 are worthy of interest. Of course, each higher class means even greater protection for photovoltaic installations.
It is worth paying special attention to this parameter when you want to install an inverter dedicated to working in difficult conditions, also in open areas.
Some Opinions about Investors
Before deciding to buy a specific solar inverter, it is worth knowing the opinions about the inverters available in the market . It is good to do this step regardless of whether you plan to transfer power to the grid or consume all the energy from the electricity produced. It is also worth knowing the opinions regardless of the size of the power of the future photovoltaic installation. It is also good to know the opinion on the quality of a specific inverter, its operating parameters or the individual modules used in it.
In addition, it is worth knowing what the fault-free level of a given investor looks like. It is good to use industry proven PVEL tests . The tests make it possible to determine the resistance of the inverter to the variability of the operating conditions of the photovoltaic modules, taking into account, for example, the temperature.
Another important indicator that will generate satisfaction with the performance of the investor will be the CEC efficiency level . Here, when choosing a device, it is worth aiming for a value of at least 97%; of course, the higher it is, the better.
How to correctly choose the power of the inverter?
Which solar inverter will be the most suitable? Without a doubt, one whose power is optimally adapted to the power of the photovoltaic modules that make up the entire photovoltaic installation.
As a general rule, it is recommended to use an inverter that has the highest possible load. This allows you to achieve a situation where the efficiency of your operation is as high as possible.
It is worth considering the power of the inverter in the context of the fact that photovoltaic panels provide energy with different power. This fact depends not only on the temperature and the level of sunlight, but also on the time of day. It should be remembered that it is extremely important that photovoltaic panels provide energy with a power close to the maximum power of the inverter for as long as possible. At the same time, you should also try to avoid wasting energy. This, in turn, is possible when the panels will generate more power than the maximum power of the inverter.
It is not surprising then that, according to the recommendations of the photovoltaic panel manufacturers, the power of the modules should be in the range of 80-125% of the inverter power. However, it is worth emphasizing that the highest efficiency of a photovoltaic system is achieved when the power of the panels is oversized in relation to the power of the inverter and varies from 105 to 120%. It is also assumed that the optimal value of the recommended power depends on several factors. These will be mainly the location, type and orientation of the photovoltaic modules and the method of their connection to the inverter .
Smaller investor: why is it worth it?
Why is it worth using an inverter smaller than the power of photovoltaic panels? There are at least several benefits of such a solution.
Although the instantaneous power of such a device is lower, the energy efficiency will be higher in the long term. All this is possible thanks to the higher efficiency of the inverter and its longer operation during the day: the operation extends up to 1 – 2 hours a day.
Another benefit will be energy losses of only about 1% of annual production . These losses will occur mainly in spring, during the lowest temperatures. In addition, it is worth knowing that a smaller inverter will be better suited to the longer operation of the entire photovoltaic installation. This, in turn, is due to the fact that the natural degradation of the panels causes a decrease in their power of approximately 0.5% per year. And one more benefit, this time economic. The smallest investor is definitely cheaper than the largest. Therefore, the savings are autonomous.
When is it worth considering choosing a larger investor? This decision will come true when investors plan to expand their PV installation in the future. However, it should be emphasized that by that time, the efficiency of the entire system may be several percent lower.
Important monitoring of photovoltaic installations
The photovoltaic inverter is in charge of the monitoring and control of the photovoltaic installation systems, guaranteeing the total safety of its operation . Thus, it is responsible not only for the immediate notification of undesirable situations, but also ensures the possibility of obtaining maximum efficiency from the entire system.
This monitoring is also very important from the point of view of the maintenance and continuous service of the photovoltaic installation. The timing and accuracy of the immediate report of any irregularities in the operation of the photovoltaic installation is of great importance: it allows you to immediately locate and, if necessary, eliminate the cause of the failure.
The purpose of such actions is one: to minimize the possible losses incurred by the investor.
The reliable operation of the inverter is of utmost importance for the correct and optimal operation of the photovoltaic system.
The most important criteria that must be taken into account when deciding to buy an investor are:
- high device efficiency,
- maximum operational reliability,
- the ability to maintain a point of maximum power
- and a high degree of protection (minimum IP65).
It is also important if the investor selected by us will comply with all the rules and regulations in force or if they will have a local service in the country and the complete documentation in Polish. It is worth choosing such an inverter, necessarily from a good manufacturer in the industry!
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