• A
  • Accumulator

    On photovoltaic systems where there is no grid supply, the generated energy can be stored in an accumulator working with direct current. This energy can be used when there is no sunlight, i.e. at night or in bad weather.

  • Amorphous solar cells

    A variant of thin-film solar cells. They are produced by applying a thin, non-crystalline silicon layer to a substrate such as glass or metal by means of vapor deposition. As a result, less silicon is needed than for crystalline solar cells. They are also cheaper to produce, although the efficiency factor is lower.

  • Azimuth angle

    This angle describes how far the direction in which the system is pointing deviates from the south (azimuth angle of 0°). Towards the east, the angle is negative; towards the west it is positive. The following azimuth angles arise as a result: east –90°; south-east –45°; south-west 45°; west 90°.

  • B
  • Backup system

    This emergency power system switches itself on in a matter of milliseconds should there be a power failure, guaranteeing an autonomous power supply using the stored energy from the accumulator.

  • Bypass diode

    If a single module or a string of modules is shaded or damaged, this semiconductor component allows the power to bypass this point, still allowing the operation of the rest of the system.

  • C
  • Charge controller

    On island systems which are independent of the grid, this component monitors and controls the power flow between the solar plant, the consumers and the accumulator in order to prevent an overcharge or deep discharge.

  • Conversion sites

    Ecologically burdened areas which were previously used as commercial, transportation, residential or military sites – such as former airports, barracks, landfill sites or brownfield land – are funded by the EEC with particularly high feed-in tariffs when they are converted into solar parks.

  • Crystalline solar cells

    These solar cells are made of highly pure, crystalline silicon, which is cut into thin slices (or wafers) during production. Depending on the crystal structure, these could be monocrystalline or polycrystalline solar cells. Crystalline solar cells have a higher efficiency factor than thin-film solar cells, but they are also more expensive.

  • D
  • Diffuse radiation

    On cloudy days or if there is dust or there are other particles in the atmosphere, the sun’s rays still reach the earth. This diffuse radiation can be used with photovoltaics, although there is considerably less energy than with direct radiation.

  • E
  • Efficiency factor

    The efficiency factor describes the proportion of solar radiation that is converted into power, i.e. the efficiency of a solar cell or system.The efficiency factor depends on the material used:

    Monocrystalline silicon    14 to 17 %
    Polycrystalline silicon 13 to 15 %
    Amorphous silicon 5 to 7 %
    CIS / CdTl 7 to 11 %
  • Energy payback period

    This time period denotes the length of time a photovoltaic system requires to generate the energy that was used for its production. This is usually between three and seven years; in systems with amorphous solar cells, energy payback periods of between 17 and 41 months are even possible. Incidentally, coal-fired power plants and other power plants that use fossil fuel do not have an energy payback period, because they constantly require new sources of energy.

  • EPC

    The abbreviation for engineering, procurement and construction is used internationally to describe the handling of the entire construction project by a general contractor like SYBAC Solar. The contractor undertakes to hand over a turnkey project on a given date – usually at a fixed price.

  • EVA

    The abbreviation stands for ethyl vinyl acetate. During production, the solar cells are hermetically sealed into this film material to permanently protect them from moisture and corrosion. First the EVA is melted and then the cells are embedded. This process is also known as laminating.

  • F
  • Façade system

    A photovoltaic system installed on the façade of a building or integrated in the building walls. A south-facing solar module installed vertically yields around 30% less power than a pitched-roof system facing the same direction.

  • Feed-in tariff

    Renewable energy is funded by this payment for every kilowatt-hour fed into the grid, which is fixed for 20 years from the point at which the system starts generating power. The fed-in power is recorded using a calibrated feed-in meter and invoiced to the power grid operator. The EEC envisages that the feed-in tariff will be reduced year on year – so-called degression. From 2009 to 2011 this degression was fixed; in 2012 it firstly depends on how many new power plants with renewable energy have been connected to the grid during the previous year. The more newly constructed systems there are, the less funding in the following year.*

    * This applies to Germany only. Other countries may have different arrangements.

  • G
  • Global radiation

    Global radiation denotes the overall solar radiation that lands on a horizontal area of the earth. It is made up of direct radiation and diffuse radiation, which is scattered by water and dust particles in the atmosphere.

  • Grid feed-in

    Grid-connected photovoltaic systems feed the generated energy into the public power grid, for which the grid operator pays a stipulated feed-in tariff. To feed-in the power, the direct current in the system is converted to alternating current by an inverter. With this kind of system, an accumulator is not necessary.

  • Grid parity

    This point is reached when the generating costs for solar power have dropped to the same price charged by the electricity supplier. From this point, solar power pays off even without grants. Experts expect that grid parity will be reached soon.

  • I
  • Inverter

    An important connecting element that converts the direct current generated by the solar power plant into alternating current, so that it can be used in the user’s own mains supply or fed into the public grid.

  • Island systems

    Systems that are not connected to the grid and, unlike grid-connected systems, do not feed energy into the grid, but merely produce it for the user’s own consumption – especially in remote areas.

  • L
  • Light absorption

    This value denotes how much light radiation a solar cell is capable of absorbing and using as energy. Accordingly, it is a crucial factor in determining the efficiency factor – the higher the absorption, the higher the efficiency factor.

  • M
  • Maximum power point (MPP)

    How much electricity a solar cell produces depends on the solar radiation, the voltage and the temperature. The MPP describes the point at which the solar cell reaches its maximum performance. The MPP doesn`t have a constant value, but is continuously determined by the inverter.

  • Monocrystalline solar cells

    These cells are made of a single crystal and have a black/bluish colour. They have the highest efficiency factor and, at more than 20 years, the longest life expectancy. They are predominantly used in areas where space is limited.

  • MWp

    The output of solar power plants is measures in megawatts. The small ‘p’ at the end stands for ‘peak’. This value denotes the power rating of solar modules and photovoltaic systems achieved under standard test conditions (STC) at a radiation rate of 1,000 W/m² and a module temperature of 25 ºC.

  • O
  • Own consumption

    If a photovoltaic system does not feed all the power it generates into the public grid, but instead retains some of the power to be used locally, this proportion is known as 'own consumption'.

    Even this proportion can be supported with public funds. A two-way meter records how much power is fed into the grid and how much is taken and consumed.*

    * This applies to Germany only. Other countries may have different arrangements.

  • P
  • Photovoltaics (PV)

    Direct conversion of radiant energy into electrical energy. When exposed to sunlight, positive and negative charge carriers are released through the so-called ‘photo effect’, producing direct current. Depending on the orientation, sunlight and type of module, around 1 kWp of power can be generated with a 10 m2 area, which corresponds to approximately 800 to 1,000 kWh of power per year.
    The term is composed of the Greek word for light (‘phos’) and the name of Alessandro Volta, pioneer of electricity who gave his name to the electrical unit ‘volt’. Photovoltaic technology was first used in 1958 to sustain the energy supply of satellites.

  • R
  • Rear ventilation

    The yield of a photovoltaic system declines if it heats up too much. Therefore, during the planning and installation phase, sufficient rear ventilation for cooling purposes has to be taken into account.

  • S
  • Shading

    Temporary shading due to dirt or snow, permanent shade in certain locations caused by buildings, trees or power lines, or shading due to other modules in the system – particularly in the case of elevated systems – significantly affect the output of a photovoltaic system. Due to the serial connection, a shaded module influences the entire string and a considerable proportion of the total output. Any form of shade should be avoided and partially shaded areas should not be populated with any modules at all. The shading analysis using a solar path indicator or other suitable devices is a crucial part of the planning process.

  • Silicon

    More than 80% of the solar cells produced around the world are made of silicon. As a semimetal, this chemical element (abbreviated to Si) belongs to the group of semiconductors and it is the second most common chemical element after oxygen, making up more than 25% of the weight of the earth’s crust. Besides siliceous minerals, it is mostly found in the form of silica sand, which consists of pure silicon dioxide. Silicon is extracted from this sand through chemical treatment.

  • Solar cells

    Commercially available solar cells are entirely semiconductor cells and thus work in a very similar way. Even the usual square shape is standardised, with an edge length of 125 mm or 156 mm, or even 210 mm, which is being used ever more frequently. However, there are differences in the structure and material used. Here is an overview of the most important solar cell types:

    Material thickness    Thick-film/thin-film
    Material Si, CdTe, GaAs oder CuInSe
    Crystal structure Monocrystalline/polycrystalline/amorphous

     
    Various construction types are also possible – e.g. in terms of the structure of the surface or the integration of the contacts (e.g. slim or transparent) or the stacking arrangement of the different materials, allowing the solar spectrum to be exploited to the fullest possible extent.

    More expensive semiconductor materials than silicon are used on the ground in so-called concentrator systems. Researchers are working on further designs and materials – polymer, organic or even dye solar cells could become reality in the future.

  • Solar module

    Solar cells are not installed individually, but are interconnected to modules using conductor paths on the front and rear, and installed between the glass panels or plastic film. The modules are held together by frames, which are also used to secure them to the substructure later on.

    The solar cells on a module are usually connected in series. This allows the voltage of the individual cells to accumulate and means that thinner cables can be used than would be the case in a parallel setup. To ensure that individual cells can cope with breakdowns or shaded periods in spite of this series setup, bypass diodes are used.

  • Solar radiation

    The sun is not only strong enough to use for energy production in southern countries, but also in Germany. In summer, up to 1,000 watts of radiation power per m2 are possible. In order to optimally harness the power of the sun, solar plants in Germany should face due south at a tilt angle of 30°.

  • String

    A string is a series of solar modules arranged next to each other.

  • T
  • Temperature coefficient

    An index of the extent of the power loss for a solar panel. A coefficient of –0.4% indicates that for every degree over 25˚C the maximum power output of the panel is reduced by 0.4%.

  • The German Renewable Energy Act (Erneuerbare-Energien-Gesetz – EEG)

    The Act for Granting Priority to Renewable Energy Sources is part of a package of measures implemented by the Federal Republic of Germany to achieve a 21% reduction in CO2 emissions by 2012, as agreed in the Kyoto Protocol, and to reduce the country’s dependence on fossil fuels and nuclear power. According to this law the amount of renewable energy in the German power-mix should be at least 20% by 2020. The law also regulates how renewable energy sources are to be used to generate heat, the feed-in tariffs for regenerative power and a biofuel quota for road traffic.*

    The model for feed-in tariffs has been adopted by almost 50 countries around the world.

    * This applies to Germany only. Other countries may have different arrangements.

  • Thin-film solar cells

    Also known as amorphous solar cells. These dark brown, almost black cells have a non-crystalline silicon layer which is applied to a substrate such as glass or stainless steel by means of vapour deposition and is thus a hundred times thinner than crystalline solar cells. The efficiency factor of thin-film solar cells is lower and as a result they require a larger surface area than crystalline modules. Nonetheless, they can be used more flexibly in a wider variety of situations and are advantageous in diffuse light or at high operating temperatures; even the complex job of cutting up the silicon blocks can be dispensed with.

  • Tilt angle

    The angle between the solar modules and the horizontal axis is known as the tilt angle. From an angle of 15° the solar modules are cleaned by rain. The optimal angle is around 30°.

  • Tracking

    When particularly high yields are required, the solar modules can be installed on movable structures, which automatically and precisely follow the path of the sun using electric motors. There are uniaxial and biaxial tracking systems. Compared to a fixed system, up to 30% higher revenues per year are possible.

  • W
  • Wafer

    The very thin silicon wafers with a thickness of 200 to 300 µm are an essential part of the solar cells. They are cut or sawn from large bars or ingots.