The photovoltaic system is one of the many alternatives when it comes to sustainable and environmentally friendly energy especially for residential consumers. A photovoltaic system transforms light energy, or solar radiation, into electrical energy by the help of solar cells. But to go from planning an energy policy to actual implementation is a huge step.

photovoltaic power plant

Photo: Public Domain Shannontanski

The function of a photovoltaic system

A photovoltaic system produces electricity with the help of individual solar cells in a process called the “photoelectric effect”. When the suns rays (photons) hits the silicon solar cells they stimulate neutrally charged particles, thereby releasing electrons.

The power is collected from the cell by the means of small metal contacts, the electrons are then forwarded to the consuming device. Afterwards a self-contained circuit conducts the electrons back into the solar cell where they once again meet up with positively charged particles (holes). This brings them to a neutral charge. This process is repeated continuously, the photovoltaic system thus generates electricity. The individual solar cells are connected to form PV modules, because a single cell is unfortunately not in a position to produce sufficiently high voltage.

The electricity generated by a PV system is as direct current (DC), this current either needs to be used up immediately or stored. Storage can be done with the help of an accumulator (battery). Feeding it into the public electricity grid is also possible.

To release the generated solar electricity into the public grid an inverter is needed. This is because in contrast to the Direct current (DC) that comes from the solar panels, the power grid operates with alternating current (AC). For the electricity that is fed into the public grid, the state pays the owner of the PV system a feed-in tariff.

 

How is the photovoltaic system mounted on the roof?

When it comes to the mounting of a photovoltaic system, two main systems can be identified. The modules could be set up with an on-roof system (frequent use, easy to implement) or be mounted as an in-roof system.

On-roof mounting

When we talk about an on-roof system, the photovoltaic system is mounted on top of the roof with the help of scaffoldings. This system is suitable for sloping tile roofs, metal roofs, slate roofs and corrugated sheets. The installation is relatively easy and inexpensive.

TIP:  The ventilation of the PV system is important it gives the PV modules a chance too cool down on hot days

photovoltaic system

On roof photovoltaic system Photo: Public Domain Jusben

In-roof mounting

If you plan to refurbish your roof or thinking of buying a new one, usually the in-roof solar system is to be recommended. However this type of installation is not possible for every roof. For metal roofs and asphalt roofs In-roof mounting is not recommended. Furthermore it must be a pitched roof. Only with the help of a decent sloping an easy water runoff can be ensured during rainfalls.

The In-roof mounting system is more aesthetically pleasing than the on-roof system because the system is integrated with the rest of the roof shingles. Ventilation is unfortunately not possible with this solution. That’s why roof-integrated modules can easily heat up, diminishing the performance and yield of the Photovoltaic system.

in roof photovoltaic system

In roof photovoltaic system License Some rights reserved by jsbarrie

Solar roof tiles

For high quality building projects or just for those who are extra picky, an extra esthetically pleasing photovoltaic system is now available in the form of solar shingles. These solar tiles are barely visible because they visually match the houses original roof tiles. The function is the same as normal roof tiles as well. However, solar shingles are more expensive to buy and less efficient in their power generation. This is why they are often only used on buildings where the looks and feel is of utter importance.

Find out more about solar roof tiles here >>

solar shingles

Solar roof tiles License: Some rights reserved by Moralist

How to plan for the purchase of a photovoltaic system

When you are planning to buy a photovoltaic system there are a number of different choices to make, for example, what type of panels to buy, how to mount them, where to put them and so on. How you set up your solar system will depend on many factors that are individual just for your home. Here are a number of questions that you need to ask yourself to help you on the way

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  1. How much roof space is available?
  2. What inclination angle does your roof have?
  3. Which direction is your roof facing?
  4. Will there be problems with shading? (Dormers, chimneys, trees, adjacent buildings, etc.)
  5. Are you planning on going totally off grid or staying on grid?
  6. What kind and what quality do you expect from the photovoltaic modules?
  7. How should the economical funding look like? Loan, upfront payment, free funding
  8. What feed-in tariffs and other subsidies can you expect?

Prices for photovoltaic systems

In addition to the cost of the photovoltaic panels themselves comes a cost for the inverter, wiring, assembly and the electricity meter. And then there are the running costs that would entitle things like maintenance costs, cleaning costs and insurance premiums. These additional costs are about 2 percent of the initial cost per year.

 

PV – modules

Generally photovoltaic modules can be divided between monocrystalline and polycrystalline. Most often polycrystalline modules are used. They offer good value for money, but also have a lower efficiency. The monocrystalline modules are correspondingly more expensive but come with a higher efficiency.

A third type of photovoltaic module is the thin-film module. Thin-film modules are becoming increasingly popular and have acquired a wide range of users around the world. They are inexpensive, produced by a low amount of raw material and have a high efficiency under diffuse light conditions. The disadvantage is however a lower efficiency overall.

When deciding what type of photovoltaic modules to buy one should read through the questions above and answer them accordingly to their needs and environmental conditions.

More info on the 3 types of solar modules can be found here >>

 

Photovoltaic subsidy – the feed-in tariff

According to the Renewable Energy Sources Act (EEG) Those that obtain a photovoltaic system have the opportunity to get compensated by the state for the electricity their new PV modules generate. This applies even if owner uses up all of the electricity himself. The subsidy is guaranteed for 20 years. The amount of compensation depends on various factors.

For example:

  • The Year of commissioning: the sooner, the better – fall in tariffs
  • The system size: the smaller the plant, the higher the pro rata payment
  • Type of installation: on top of houses is higher than in open areas

NOTE: The feed-in tariff has fallen sharply in recent years. But you can still sell excess energy that you don’t use up to your power company and get paid for that.

 

Maintenance of a photovoltaic system

The great thing about photovoltaic is that once their up they are practically maintenance free. With the exception of a non tilted system you don’t even have to clean your solar modules. Mother Nature will do that for you. The only thing is that you will probably have to exchange your inverter after about 10 years, they don’t have the same life expectancy as the actual panels themselves. A solar panel comes with a warranty of 25 years but in reality it can keep producing clean energy for almost the double amount of years. By going solar you would get almost a lifetime supply of free electricity. With the prices of energy only rising further and further up the calculation that tells you a photovoltaic system is a good deal is fairly simple.

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