Die Donauer Photovoltaik Fragen

Solar power facts & FAQ

What does photovoltaics mean?

The word "photo" comes from ancient Greek and means light. Voltaics is the conversion into electrical current. Photovoltaics is therefore the generation of electricity through sunlight. To do this, you need solar cells made of silicon. Silicon is produced from melted sand and, in this respect, is infinitely available.

What are monocrystalline modules?

As the name already suggests, the monocrystalline solar panels consist of one single crystal. A particularly high efficiency is achieved by precisely aligning the crystal structure. Manufacturing such modules, however, is a particularly complex endeavor, which is why these cells are significantly more expensive than conventional cells.

What makes a solar power system so climate-friendly?

Generating electricity using fossil fuels releases carbon dioxide (CO2), which was previously locked in oil, gas, wood or coal. CO2 is a natural element of air and is not toxic. However, the release of massive quantities of CO2, as we have seen since the beginning of the industrial revolution, produces an unnaturally strong increase of the greenhouse effect. The consequences yield the much-debated climate change. No CO2 is released when electricity is generated using photovoltaics.

What is behind the designations IEC 61215 and IEC 61646?

They are certificates indicating the quality, mechanical stability and compliance with electrical parameters.

What does operating voltage / MPP voltage mean?

MPP is the abbreviation for maximum power point. This point specifies a module's voltage value at which the maximum electrical power can be output.

What does STC stand for?

STC is the abbreviation for standard test conditions. If you compare various solar panels with one another, for example, to determine which one works the most effectively, standard test conditions are established that apply worldwide. These conditions include: a radiation of 1000 W/m², a module temperature of 25°C and an air mass of 1.5.

What does module efficiency mean?

The module efficiency indicates how efficiently a solar module operates. That is to say, how much electrical energy can be produced from solar energy for every square meter.

What is a performance guarantee?

A guarantee from the manufacturer on a module's minimum performance. Generally, this applies over a longer period of time. You should make sure to read the fine print. Here, you will find the maximum permitted deviation from the minimum rated output after using over 10, 20 or even 25 operating years.

What does performance tolerance mean?

It describes the maximum deviation from the rated output and generally fluctuates between 0 and 10 percent.

Should I insure my system?

We recommend insuring the system against natural hazards, such as storms and hail. In general, such hazards are already covered in the building insurance. Broad coverage provides all-risk insurance that also insures the system against theft, lightning protection, surge voltage or yield loss.

Can lightning destroy the system?

Solar pv systems are technologically highly sensitive and a direct lightning strike would definitely destroy it. There is also yet another hazard, as a lightning strike could create surge voltage near the solar power system and these surge voltages can also destroy the system. Which is why many manufacturers integrate surge-voltage protectors into the inverter. However, since these components only discharge small voltage peaks, you should consider using protective devices in individual cases. By the way: The probability that lightning will directly strike your house is not increased by photovoltaic systems.

Can hailstones damage the modules?

The probability that the modules will be destroyed by hailstones is relatively low. We use hardened special glass for our photovoltaic systems, which must withstand ice balls in a shot test with a diameter of 75 mm and projected at a speed of 140 km/h.

Does the photovoltaic system require regular cleaning?

Rain automatically cleans the modules and the rainfall in Germany is sufficient to keep the module clean. In areas with heavy air contamination, however, the modules require an additional cleaning from time to time. A system installed at more of a level, below the minimum angle of 15°, can mean that the rainfall will not be sufficient to permanently keep the system clean.

Does the system require maintenance?

Compared to wind turbines, solar power systems are very rarely maintained, since they operate without any rotating parts, bearings or other high-maintenance components. However, we recommend regularly checking the yield values to detect any failures immediately.

How long will the system last?

A solar power system generally operates for between 30 and 35 years. Our manufacturers provide a 25-year performance guarantee on our solar modules and a 5-year manufacturer’s warranty on solar grid inverters, which can be optionally extended up to 10 years.

Is a permit required to install a solar power system?

Roof-parallel installations do not require a permit. This does not apply to protected historical buildings for which an authorized representative for monument protection or in case of doubt, regional conservator must make a decision.

What happens when the sky is cloudy?

Photovoltaic modules not only use direct sunlight, but they also use diffuse radiation under cloudy conditions. However, the following generally applies: The brighter it is outside, the more performance the modules achieve – regardless of whether the sun is directly visible or not.

How profitable are the solar radiation conditions in Germany for a photovoltaic system?

Each year in Germany, 300 billion kilowatt hours of solar energy hit the Earth's surface. That equates to 1000 kilowatt hours per square meter annually, which converted corresponds to a calorific value of around 100 liters of heating oil. A 10 square meter photovoltaic system therefore saves around 1000 liters of heating oil.

Is it worth having guided modules that track the sun?

Modules that automatically track the sun achieve up to 45 percent more yield. Here, a distinction is made between time-dependent and brightness-dependent systems.

How can I install a solar energy system on a building?

There are four different ways to mount a solar pv system: on-roof, flat roof, roof-integrated and façade installation.

What conditions make a building suitable for a solar power system?

Almost every building is suitable for a solar power system. A roof or façade surface that faces south, east or west is critical for a building. The highest yield is generally generated on a surface facing south with a tilt angle of around 25°. A deviation towards the southwest or southeast or angles between 25° and 60°, however, only slightly reduces the energy yield. Shade caused by trees or neighboring buildings or anything similar should be avoided.

Where should the inverter be mounted?

Solar grid inverters should be installed at a cool location that has very little fluctuation in temperature. For example, a cool roof or basement is ideal. Heat damages the inverter.

How does the system automatically disconnect from the grid if the power supplier interrupts its grid?

The MSD system stops the system from feeding electricity into the grid within seconds if the grid is disconnected.

Which documents do I need to submit to the power supply company for the grid connection?

All the required documents are prepared and assembled by the installer and must be handed over with the test reports during commissioning. The documents in detail include: site plan, overview plan of the solar power system with nominal data of the individual components, description of the protection devices specifying the type, brand, switchgear and function, conformity declaration for the inverter, specifications on the short-circuit strength for the switch, meter request and installation certification.

How can I obtain the money?

You make a feed-in contract with the power supply company, which lists the legal regulations, such as how the remuneration as well as the payment methods and fees are regulated. In most cases, the additional meter fee is not included in the annual invoice, which saves you 40 euros.

How do you measure the electricity that is fed into the public power grid?

The metering system is expanded by an additional meter. If a free field is still available in the metering system, it can be used after consulting the electricity supplier.

What does kWp mean?

kWp stands for kilowatt peak and is the unit for the peak performance of a PV generator under standard test conditions. See also STC.

How much electricity will my system produce in a year?

That depends very much on the general conditions. Does the system face south? What is the tilt angle of the solar modules? How high are the irradiance values at the location? How bright is the weather throughout the year? The following value can be assumed as a rough planning aid: 800 to 900 kWh per year for each kWp of installed power.

What happens with my photovoltaically generated electricity?

Due to the increased feed-in tariff with a grid-connected PV system, all of the solar power produced is generally fed into the public grid and sold to the grid operator. The renewable energy law (EEG) has been in effect since 2004. This law treats PV systems concerning the feed-in tariff as follows.:

  1. The system size
  2. The location where the system is installed
  3. The year of the installation
  4. How much power does a solar cell produce?

    An individual solar cell that is 10 x 10 cm in size generates approximately 0.5 volts and 3 amperes of electricity in full sunlight. That corresponds to approximately 1.5 watts of output. In most cases, these values, most importantly the low voltage, are too low for practical use. Therefore between 36 and 72 solar cells are typically connected together (in a row), the entire unit is called a module. Such a photovoltaic module generates current and voltage values that provide sufficient current for usage. Depending on the model, a module with a surface of one square meter generates between 120 and 180 watts of output.

    What are amorphous and micro-amorphous modules?

    Amorphous or micro-amorphous modules are very effective under light conditions without direct solar radiation, for example, under cloudy conditions or at sunrise. They also achieve higher power outputs than crystalline modules, which are the most commonly installed in Germany. In addition, they are more cost-effective, since they only require 1% of the silicon quantity of conventional modules. Simplified production processes also help significantly reduce the manufacturing costs over crystalline modules. Today, the major challenge is increasing the efficiency in crystalline module technology.

    What are polycrystalline modules?

    Polycrystalline or also multicrystalline modules offer a good price/performance ratio, since the manufacturing process is not entirely so complex and expensive as manufacturing monocrystalline cells. Semiconductor-grade silicon is melted under protective glass in the negative pressure range. Due to the casting process, the individual crystals are not uniformly aligned and are arranged freely. This produces the characteristic cell block diagram. All additional work steps are identical with all crystalline modules. The blocks or columns are cut into silicon slices that are 0.2 mm to 0.4 mm thick and are then cleaned. This intermediate product is referred to as cell or wafer. Various chemical processes are carried out to form typical conductor paths on the wafers, which are arranged and connected on the glass pane and laminated in foil. High-purity silicon is not necessary to manufacture polycrystalline material, making it more cost-effective to manufacture. Furthermore, the block casting method (poly) is less complex and more cost-effective compared to the Czochralski process (mono). Due to increased purity and fewer recombination sites (grain boundaries with polycrystalline structures), monocrystalline modules achieve higher efficiencies.

    How does personal consumption function in my photovoltaic system?

    You can feed electricity that you generate with a solar power system into the public grid or also consume it yourself in the household, which is referred to as personal consumption. If you use the solar power produced yourself, you save electricity costs from your power supply company. You also receive a state subsidy for each kilowatt hour you use yourself, because it relieves the power grids throughout Germany. The bonus and saved electricity costs for the kilowatt hour yield a higher profit than the full feed-in of solar power. And with conventional electricity costs on the rise, this advantage will even increase over the next few years. To use the power generated yourself, you only need a feed-in and consumption meter, which is only slightly different to install than a standard system. Inform youself with the solar pv calculator.

    How can I make optimum use of the generated power?

    The ideal way to use the electricity produced is to have electrical devices switched on when the power is generated. However, since the electricity is produced during the day, this is not so simple. Control units are now available, however, which automatically switch the electrical devices on and off depending on the power produced. For example, you can let your washing machine and dryer run while you are at work. In addition, some manufacturers are currently working on developing batteries that can store the power generated by your system so that you can also use it late at night. The first of these storage buffers will be marketable in the foreseeable future. We will be happy to notify you once they are that far.