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Choosing the size of a solar power plant?

Next I will explain how to choose the size of the solar power plant. Choosing the size of  a solar power plant is  not always easy and obvious. It is not always worth trusting the opinion of the installer, because in many cases they always try to sell the largest possible installation guided by their profits. 

A solar power plant should be selected so that it reduces our energy bill to almost zero and does not generate unnecessary additional kWh that we will not be able to use. The following article will bring you closer to the selection of the size of a domestic photovoltaic installation.

Choosing the size of a solar power plant?

Selection  of solar panels should be estimated initially based on the amount of electricity consumed by the customer. It does not make sense to build a photovoltaic installation that is too large, since in the future we will not be able to consume all the electricity produced or balance it. An average household with 4 people consumes around 2000 – 2500 kWh per year. 

This is an example of a typical home without additional energy receivers such as pumps, heating controllers, etc. For the average annual consumption of 2500kWh, we should assume the construction of a solar power plant with a photovoltaic panel capacity no greater than 30kWp. . Such a power plant should produce around 3000kWh on average per year, which will fully satisfy the electricity demand of the whole house with interest in the event of a periodic increase in energy consumption.

However, if we design a photovoltaic installation for a house, which is equipped, for example, with a heat pump, hydrophor or other large energy receivers, the annual consumption of the whole house must be carefully controlled. It can often be much higher than the assumed average and a solar power plant may need to be built with a capacity of up to 10 kWp or more.

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Choosing the size of a solar power plant?

Choosing the size of a solar power plant: what type of solar panels to choose?

The choice of the type of solar panels is of secondary importance. Yes, if we have a small space to develop and we want to obtain the highest possible power, it is worth opting for monocrystalline panels. They are more efficient, which means that we can place more solar panels on the same surface. However, the differences end there. A 300W polycrystalline or monocrystalline solar panel will work the same and we will not notice any difference or performance improvement in our photovoltaic. The inverter:  the voltage converter  , which connects the solar panels to the grid,  has a significant impact on efficiency  .

Single-phase or two-phase installation?

This is dictated by the type of installation we have in our home as well as the size of the photovoltaic installation. In fact, most of the solar installations that do not apologize for the 3 kWp of solar energy are single-phase installations. Installations with higher powers are already three-phase. The type of installation in our facilities is also important. It is not possible to install three-phase with single-phase connection. However, it is possible to build a single-phase solar power plant and connect it to only one of the three phases. However, these technical solutions are rarely used.

Chinese or German investor?

Before answering this question, each of us should answer how long we want our photovoltaic installation to work. The estimated average life of a solar power plant is 25 years. At least everyone would like their power plant to last that long and to be undamaged. At this point, you need to consider the price of a grid inverter with an exemplary popular power rating of 5kW. A branded product, for example from Fronius, SMA or Steca, will cost around PLN 6,000 gross. The same power of a Chinese inverter, for example Growatt, costs about 3,000 PLN gross. Each of us should answer the question whether such a price difference is due only to the margin and the fact that we pay for the manufacturer, or maybe there is another reason, such as a drastic difference in the quality of the devices. Unfortunately, by choosing cheaper alternatives, we always lose in the amount of electricity produced and also in the durability of the device. In the case of the cheaper solutions, we should not expect a durability of 25 years, but should be between 3 and 5 years of use without failures.


Choosing the size of a solar power plant?

Balancing energy of solar power plant

Each solar power plant produces electricity at any given time. It does not have a battery to store excess energy for later use, for example at night. Balancing the electricity in a power plant is helpful. Equilibrium occurs most often over a half-year period, but surpluses produced must be used within 351 days from the date of production. 

This means that we have a whole year to use the overproduction of energy from the day it occurs. Depending on the type of installation we have, the rates will be set. 0.8 kWh of return for every 1 kWh injected into the grid for photovoltaic installations with power lower than 10kWp and 0.7 kWp for installations greater than 10kWp to 40kWp.

Thanks to the energy balance, we can afford to heat the house in winter, as long as we have an electric heating installation. By having a photovoltaic installation large enough, we can produce surplus in summer to use in winter to heat the building, hot water or use it for other utility purposes.

Solar Power Plant – Summary

When building our first solar power plant, it pays to pay attention to the components that went into building it. We must also actively participate in the selection of power and not rely solely on the opinions of the installer. The solar power plant must work for many years not only without failures, but also in an optimized way.

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