How to choose the right PV module for your roof

· About Solar Panels

Especially in times like these, when electricity and energy sources such as oil and gas are becoming increasingly expensive and there is a great deal of uncertainty about supply, it is becoming increasingly important and urgent to find alternative sources of energy.

The most popular and efficient renewable energy source is solar energy, which is not only relatively cheap, but also very friendly to the environment in the long run and guarantees you a greater degree of independence from central energy suppliers.

However, installing a photovoltaic system for your roof is a long-term and not insignificant investment decision. Therefore, when choosing the right PV module, you should know exactly what is important and what is best for your home?

In order to provide you with all the information you need to make an informed purchasing decision, Maysun Solar will examine the following for your information.

·What is a photovoltaic module and what can it do?

·What types of PV modules are available?

·What is known as power rating and how does it affect your electricity production?

·How does a PV module optimiser work?

·What is the difference between a 300w PV module and a 400w PV module?

What is a PV module?

Firstly, we need to know exactly what a PV module is and what tasks it performs in a PV system.

A PV module, whether it is a 12V PV module or a 24V PV module, refers to the whole of all the solar cells that are coupled together to absorb solar energy and convert it into electricity.

PV modules, also known as solar panels, are therefore one of the most important components of a PV system, because without solar cells, solar energy cannot be harnessed and converted into electrical energy production.

The electrical energy produced by the solar panels is direct current.

In order to make the energy available for normal household appliances, it must be converted into alternating current. This task is carried out by an inverter. The inverter is an important part of the photovoltaic system and completes the conversion process from solar energy to the electricity we extract from the socket.

What types of solar cells are there? 

There is in fact a wide variety of photovoltaic modules, and they consist of different types of solar cells.

In terms of materials, we can divide solar cells into three categories.

·Polycrystalline silicon solar cells

·Monocrystalline solar cells

·Thin-film solar cells

The different types will differ in their performance, measured in Wp (watt peak), and in their price range.

There are three main types of thin film PV modules currently in production: cadmium telluride, copper indium gallium selenide and amorphous silicon. Their general disadvantage is that their photoelectric conversion efficiency is too low and although they are cheap, they are only used in individual niche scenarios, with a market share of less than 5%.

The third generation of thin film technology, calcium titanite cells, which has been developing rapidly in recent years, is expected to be a breakthrough. In the more spacious BIPV field, thin-film cells are more suitable than crystalline silicon cells. And chalcogenide batteries are expected to become the mainstay of new energy-saving building materials.

As far as current technology is concerned, crystalline silicon modules are clearly more suitable for individual users than thin film modules. They have a significantly higher rated output and can therefore generate a large amount of electricity even in small spaces.

Polycrystalline silicon PV modules achieve a nominal output of up to 330 Wp and have for a long time held a large share of the market due to their price advantage compared to monocrystalline solutions.

Now, however, more than 95% of crystalline modules on the market are monocrystalline, and almost all new PV systems for private homes are opting for monocrystalline PV modules. They have a nominal peak output of up to 400 watts and therefore require very little space to produce a significant amount of energy.

In addition to the nominal power, the efficiency factor is an important key figure in calculating the efficiency of a PV module.

The efficiency indicates the maximum percentage of available solar energy that can be converted into electrical energy.

Of the three types of modules mentioned above, monocrystalline PV modules achieve the highest mass production efficiency to date, currently ranging from 20% to 22.5%.

When choosing a module, the smaller your roof area, the higher power and higher conversion efficiency you will need to select. For private homes, monocrystalline PV modules are generally recommended.

PV module power optimisers

If you really want to produce the maximum amount of electricity, you should consider purchasing a power optimiser or ensure that it has been integrated into the system.

A PV module optimiser ensures that the total output of the module is not reduced by individual solar cells being shaded.

Without such an optimiser, a group of solar cells connected in series will only produce the power produced by the weakest one.

As a result, the overall performance is sensitively weakened by individual cells that are in the shade, for example, because the power output is shaded by a tree or something similar.

12V vs 24V

Specifications in watts and volts can sometimes cause confusion and lead us astray, so we take this opportunity to clarify and answer a frequently asked question.

Do you need a 12V or 24V module?

Volts are necessary to measure voltage and, as the name "photovoltaic" suggests, this voltage is a key factor in solar power generation.

However, 12, 24 or 48 volts are used for so-called stand-alone off-grid PV systems, such as PV module campers, where the electricity produced is consumed directly by the producer.

On the other hand, on-grid rooftop PV systems feed rich electricity into the public grid and require higher voltages, in the range of several hundred volts.

 

Design and weather resistance

Of course, in rainy, windy and sometimes snowy Germany (as in Austria and Sweden), weather resistance is an important aspect that should not be overlooked.

In windy areas, it is necessary to consider the angle and direction of the slope of the roof when installing solar systems.

Particularly near the coast in northern Germany, wind is a big issue when purchasing and installing PV modules.

The experts at MaySun are certainly well aware of this situation and adapt their advice and installation work to the prevailing weather conditions.

In northern Germany, heavy snowfall sometimes occurs, which places an additional load on the solar modules. The snow quickly reaches a considerable weight, exerts pressure on the system and can lead to damage. In snowy areas it is therefore important to ensure that the system has a high resistance in pascals. The higher the Pascal value, the more snow per square metre can be carried without causing damage.