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18.06.10
Donauer Solartechnik presents new Off Grid brochure
The growth of the population and the economy leads to an increased demand for energy in many regions of the world. Many networks and power plants are ...
16.06.10
Donauer Solartechnik introduced a number of innovations at Intersolar Europe 2010.
Employees provided information on the company’s innovations to hundreds of customers and attendees at the nearly 400-m² booth.
Frequently asked questions and answers concerning solar technology
What does photovoltaics actually mean?
Photovoltaic (photo = light, volt = unit of electrical current) is the technical term for solar-generated electricity.
That means solar energy is converted into electrical current. Silicon is the main component of a solar cell and is melted from sand, which is available in limitless quantities. Silicon only conducts when there is solar radiation. The top of a solar cell is sprayed with phosphorous and the underside is sprayed with boron. The top side has 5 electrons and the underside has 3 electrons. The electrons try to establish a balance (each 4 electrons). Since silicon has 4 electrons, it is used as a transport medium (semiconductor).
What are monocrystalline modules?
Monocrystalline cells currently have the highest efficiency (up to 17.5%, already up to 25% in the laboratory) of all photovoltaic modules and have a service life of at least 30 years.
As the name already suggests, the cells consist of one single crystal. Due to the exact identical orientation of the crystal structure in one direction, it achieves a high level of efficiency. However, this also entails an extremely high expenditure during processing. For this reason, the cells are by far the most expensive.
How does a solar energy system contribute to preserving the environment?
A solar energy system generates energy and thus correspondingly reduces the need for conventional energy gained from oil, gas, coal or uranium. Using solar energy systems reduces environmental pollution caused by CO2 emissions (not compared with nuclear energy). In addition, it also prevents environmental pollution caused by transporting, extracting and processing raw materials or by the permanent disposal of consumed energy sources.
What do IEC 61215 and IEC 61646 mean?
If a solar module is IEC 61215- (crystalline) or IEC 61646- (thin-film) certified, this is a sign of quality as regards mechanical consistency and the compliance of the electrical parameters.
What does operating voltage / Mpp voltage mean?
It specifies the level of voltage at which the best output can be delivered under STC. A modules maximum power point is known as its MPP. (Maximum Power Point)
What does STC mean?
STC = Standard Test Conditions. In order to effectuate an output comparison between solar modules, uniform test conditions are applied. Irradiation of 1000W/m²; temperature 25 degrees Celsius and AM 1.5 (AM= air mass; designation gauges the thickness of the atmosphere; at the equator, the air mass is AM=1.0, in Europe it is approximately 1.5). The solar cell's sensitivity changes in accordance with the spectral composition of the sunlight.
What does module efficiency mean?
Renders the ratio between power emitted and power irradiated for a solar module based on the module surface.
What does performance warranty mean?
This specifies the maximum permitted deviation from the rated output after use over 10, 20 or even 25 operating years.
What does performance tolerance mean?
This specifies the maximum deviation from the rated output. The module manufacturers indicate this with 2.5%, 5% and also with 10%.
Should I insure my system?
We recommend insuring the system against natural hazards (storms, hail, etc.) After consulting your insurance provider, these damages are usually covered within the building insurance. All-risk insurance offers higher insurance protection that also includes theft, lighting, surge voltage, yield loss, etc. Theft prevention is possible in our Intersol mounting systems.
Can lightning destroy the system?
Yes. A direct lightning strike will destroy the system. A solar power system, however, does not increase the probability of a direct lighting strike. It is more likely that nearby lighting strikes will induce surge voltages into the solar power system. These surge voltages can destroy the system. Therefore, inverters are delivered with integrated overvoltage protectors.
Can hailstones damage the modules?
In general, the modules are well protected against hailstones. The special glass used is hardened and for testing purposes, ice balls are fired at the modules. In accordance with the IEC standard, these tests are conducted with ice balls with a diameter ranging from 12.5 mm up to 75 mm. The highest impact speed is 140 km/h. The probability that the modules will be destroyed by hailstones is relatively low.
Does the photovoltaic system require regular cleaning?
Fortunately, it does not! The precipitation accumulated in Germany alone is sufficient for the cleaning required for operation. However, there are regions with a higher level of air pollution (industrial systems), where cleaning may be required in greater time intervals.
Does the system require maintenance?
In general, solar power systems require no or only very little maintenance. There are no rotating parts, bearings or other high-maintenance components. We recommend checking the plausibility of the yield value by regularly controlling the feed meter or performing balancing calculations using a computer/data logger to detect any system failures as quickly as possible.
How long will the system last?
The solar modules have a performance warranty of 25 years. Inverters have a 5-year manufacturers warranty that can be optionally extended up to 10 years. You can generally expect the system to have a service life of 30-35 years.
What happens when the sky is cloudy?
Not only do photovoltaic modules use the direct sunlight that only occurs when skies are clear, but they also use diffuse radiation from the clouds. It is actually very simple: The brighter it is outside, the more performance the modules achieve regardless of whether the sun is directly visible or not.
Is it worth having guided modules that track the sun?
Yes, by using a tracking system, the solar energy system can achieve higher yields of up to 45%. We offer 2-axial tracking systems that align themselves toward the sun. On cloudy days, the module surface moves into a flat position to absorb the greatest quantity of diffuse sunlight possible.
How can I install a solar energy system on a building?
The following installation types are available:
- On-roof installation
- Flat roof installation
- Roof-integrated installation
- Façade installation
What conditions make a building suitable for a solar power system?
Basically, almost every building is suitable for a solar power system. A building requires a roof or façade surface that faces south, east or west. A surface facing south with approximately a 30° angle is ideal for an optimum yield. A deviation towards the southwest/southeast or angles between 25° and 60° only slightly reduce the energy yield. However, shade caused by trees or neighboring buildings should be avoided.
Where should the inverter be mounted?
The inverter should possibly be installed at a cool location that has very little fluctuation in temperature. A cool roof or basement is ideal. Heat adversely affects the inverter.
How does the system automatically disconnect from the grid if the power supplier interrupts its grid?
There is an automatic device integrated into the inverters. The MSD system stops the system from feeding electricity into the grid almost immediately if the grid is disconnected
How is electricity 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. Otherwise, an additional small-scale meter cabinet is installed.
How much do the components cost?
You can expect to pay between 6,000 and 8,000 for standard systems. Special solutions or larger-scale systems should be calculated individually.
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.
How much electricity will my system produce in a year?
The answer to this question heavily depends on several conditions. Orientation of the system (south?), system inclination (what is the inclination of the roof), irradiance value at the location and last but not least, the weather. The following value can be assumed as a rough planning aid: 800-900 kWh per year for each kWp of installed power.
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 2.4 amperes of electricity in full sunlight. That corresponds to approximately 1.2 watts of output. In most cases, these values, most importantly the low voltage, are too low for practical use. Therefore several solar cells are typically connected together (in a row) and the cells are also packed between sheets of glass or plastic to provide better protection against environmental influences. The entire unit is called a module. Such a photovoltaic module generates current and voltage values that provide sufficient current for usage. Modules with 36 cells as well as large-scale modules with up to 2.5 m2 of surface, for example, are often used. On a clear sunny day here in Germany, the sun radiates approximately 1,000 watts per m2. 1,000 watts corresponds to the output of a medium-sized hot plate, for example. Under these conditions, a 1 m2 module generates approximately 120 watts.
The PV module is the basic unit of a photovoltaic system and contains a specific number of solar cells that are electrically interconnected. Several modules are connected to the generator. The direct current produced by the solar cells is routed through the DC lines to the inverter. In a grid-connected PV system, the inverter converts the direct current into alternating current which is then is fed into the public power grid by a meter.
In a stand-alone system, the solar power is mostly stored in batteries or accumulators and used at a later point in time.
What are amorphous /micro-amorphous modules (thin-layer)?
Amorphous or micro-amorphous modules are vaporized on float glass and are made of silicon. Compared to conventional silicon modules, materials usage for consumed silicon within the manufacturing phase makes up only 1%.
As a result, these modules are more cost-effective, however; the efficiency is lower than that of conventionally produced modules. However, the most important advantage is that amorphous/micro-amorphous modules are considerably more dynamic. That means that they harvest excellent electricity yields with only diffuse light conditions (during sunrise and sunset, as well as under cloudy sky conditions).
What are polycrystalline modules?
Polycrystalline or also called multicrystalline modules have an excellent price/performance ratio. In other words, the price per KwP is sufficiently favorable. That is due to the less expensive manufacturing process.
Semiconductor-grade silicon is melted under protective glass in the negative pressure range and cast into moulds in which it solidifies as the temperature is increased. The multicrystalline blocks are then further processed into columns with a squared cell surface using extremely fine saws. Using annular saws, the columns are cut into multicrystalline silicon slices that are 0.45 mm thick and are then cleaned. This intermediate product is also referred to as a wafer.