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Solar Glossary: A C D E G H I K L M N O P R S T V W Accumulator or solar battery Is used to store solar power for stand-alone energy supply systems to decouple power generation and power consumption times. Amortisation, energy payback period The time span a solar system requires to generate the energy required for its production. Energy payback periods of photovoltaic systems are between three and a maximum of seven years: According to a study by the Technical University of Berlin, PV systems based on amorphous silicon have an energy amortisation period of only 17 to 41 months. PV systems therefore have a positive energy balance. Power plants fired with fossil fuels do not have energy amortisation because more fuel is continually being used. Amortisation, economic For solar power system, revenues from the sale of electricity (in line with the Renewable Energies Law) are compared to investment costs. Ampere (A) The unit for electrical current. Alignment A solar power system attains the highest energy yield when its modules are aligned southwards. The energy yield is still cost-effective even if alignment is not absolutely perfect. Azimuth angle To use the sun's rays as effectively as possible, modules and collectors are aligned such that the solar yield is as high as possible. The angle of incidence of the sun, the "azimuth angle" and the tilt angle of the modules/collectors are important here. The Azimuth angle specifies by how many degrees the module surfaces deviate from the precise south alignment. The angle of tilt applies to the deviation from the horizontal. Tests confirm that systems with an azimuth angle of 0° and an angle of tilt of 30° are aligned perfectly. But minor deviations are not necessarily problematic: Around 95% of the possible yield can still be achieved with south-easterly or south-westerly orientation. Carbon dioxide (CO2) Carbon dioxide (CO2) is produced by burning fossil fuels. Being a greenhouse gas, it takes its share of responsibility for the warming of the earth's atmosphere. Central inverter Central inverters are particularly well suited to the design of photovoltaic systems with a homogeneous structure (modules of the same type with identical alignment and tilt). They are used for systems specified at 100kW or greater and are usually designed for outdoor installation. CO2 reduction The amount of carbon dioxide (CO2) prevented as a result of using the solar system depends on the fuel (gas, heating oil, coal) or the conventional energy (electricity, district heating) used and is proportional to the fuel/energy saving. The CO2 emission prevented is calculated from multiplying the saving with the emission factor (unit kg CO2 per kWh fuel saving or ton CO2 per MWh). The CO2 reduction figure is a measure of the contribution a solar system makes to climate protection. Data communication There are different data communication systems for monitoring photovoltaic systems. These are usually installed in addition. They record information on the amount of electricity produced and provide information on the proper operation if the system. Monitoring is possible via Internet, e-mail, mobile and large displays. Data logger A data logger stores the operational data of the inverter and allows functional control of the solar power system over a longer time period. Degree of efficiency The degree of efficiency specifies the ratio of usable to used energy. As an illustration: Conventional light bulbs transform about 3-4% of the energy used into light. Photovoltaic systems, or solar cells, currently reach an efficiency level of 11-17%. Direct current how it is produced by solar cells/modules and stored in batteries. Electricity purchase Electricity purchase is regulated by the Renewable Energies Law which first came into force on 01.04.2000. In Germany, an allowance is paid for electricity (generated from renewable energies) fed into the national grid. The Renewable Energies Law commits grid operators to collect all the electricity and to make payment at the rates specified by the law. The following allowance table is from the law:
Energy source The first, and biggest, energy source for the earth, from which all other energy sources have been created, is the sun. It keeps water circulating and is hence the "engine room" for hydro-power, it grows plants and has also been instrumental in the creation of coal, crude oil and natural gas. Global radiation Denotes the sun rays falling on a horizontal area on the surface of the earth. This is made up of direct, diffuse and reflected rays (such as those from snowfields). The angle between sun ray and surface area is decisive for the accurate calculation of the energy that falls on an area. This changes according to time of day and time of year. Over a year, the average global radiation falling onto a horizontal area in Germany is about 1000 Kilowatt hours. This figure is higher in some regions and lower in others. Southern Bavaria and Freiburg benefit most. High voltage High voltage is used for regional and nationwide energy transmission. The voltage level is defined between 60,000V and 150,000V (60kV and 150kV). The usual voltage level is 110 kV. Inverter The DC current generated by the solar cells is transformed into grid-compatible AC current by the inverter. It is therefore the connecting link between the solar modules and the electricity grid. kWh Kilowatt hour 1 kWh = 1000 Watt over a period of one hour. Unit of electrical work. Electrical work or electrical energy is the product of power and time. kWp Kilowatt Peak Peak power of the PV generator at maximum sun ray intensity under standard test conditions, STC. Loan programs Loan programs are used for improved cost-effectiveness of renewable energies and energy saving measures. These should reduce CO2 emissions and create an improved market for companies working in the renewable energy sector. In Germany, the federation, states, cities, local authorities, tax authorities as well as several public utility companies are making funds available to promote the use of renewable energies. Maximum Power Point (MPP) Operating point of the photovoltaic generator in which it delivers the highest possible power. The position of the MPP changes continuously, e.g. in relation to radiation and temperature. Module inverter Module inverters are attached directly to the photovoltaic module so as to draw the maximum power from the individual modules. They are used mainly when they become obstructed during the course of the day since the interconnection of several modules always determines the weakest overall power of the system. Drawback: The specific costs (Euro per Watt) are considerably higher than for inverters with higher power. Control units and monitoring equipment must be provided x times, depending on system size. MPP tracker Device that sets current and voltage of the photovoltaic generator such that it is operated at its "Maximum Power Point". Multi-String Inverter Inverter that broadly combines the benefits of several string-inverters (separate MPP - control of individual strings) and one central inverter (low power-specific costs). Network operator The network operator is your electric utility company. In accordance with the Renewable Energies Law, it is obliged to collect the electricity stored by you and to make payment as laid down by the law. On-roof installation The solar power generator is installed 5-15cm above the roofing using special installation kits made of zinc-plated steel, aluminium or stainless steel. Parallel circuit The electrical voltage at each resistor is identical in a parallel circuit. The current is inversely proportional to the resistance values (i.e. the lower the resistance, the higher the current flowing through it). Peak Oil Explanation: Production peak of oil production. Being a fossil fuel, there is not an infinite supply of crude oil - unlike sun and wind power for example: The bottom line is that our world-wide oil reserves are becoming increasingly sparse. This does not become a problem when we run out of oil, but rather when the production peak is reached. The most widely accepted model on this topic is from geophysicist Dr. M. King Hubbert, the so-called "Hubbert curve". The Hubbert curve approximates the shape of a bell in which crude production first increases, reaches its peak and then drops off continually. The highest point of the curve is the production peak, also referred to as "Peak Oil". This drops off together with the point in time at which 50% of reserves have been used up. The supply rate sinks year on year from this point on - in the face of increased demand from China and India. Experts expect this point will be reached by 2010 at the latest, perhaps even earlier. The consequences are continually rising oil prices and harder-fought distribution battles - with unforeseeable consequences for industrial nations in particular. Oil supply is guaranteed over the next several decades, but the key here is when we run out of cheap oil and from when we can expect bottlenecks in supply. Some scenarios forecast we will be facing the consequences of global warming at the same time - the result of the greenhouse effect by burning fossil fuels. Please refer to http://www.peakoil.com for more information Photo effect The photo effect is the release of positive and negative charge carriers in a solid body through light irradiation. Photovoltaics Made up from the Greek word "Phos" (light) and the name of the physicist Alessandro Volta. The term describes the generation of electrical current from solar energy. "PV" is the abbreviation for photovoltaic. Photovoltaic generator Generators convert other forms of energy into electricity. In solar technology, only the collective interconnected photovoltaic modules are denoted the generator or solar power plant. Photovoltaic generators integrated into buildings Photovoltaic modules are increasingly being used as integrated parts of facades and roofs. On roofs, these components are replacing conventional roofing (in-roof installation). In facades, they are replacing glass, natural stone and metal cladding. The integration of photovoltaics into buildings is an especially attractive solution. This can be used for new buildings and for the renovation of roofs and facades. Photovoltaic module A photovoltaic or solar module comprises of several interconnected solar cells that are embedded in-between two glass or plastic panes, providing protected from the elements. Modules are generally fitted in a frame on the roof or a carrier frame. Planning permission Installation of a photovoltaic system on the roof of a house does not generally require planning permission. Permission is only required for listed buildings. However, systems erected in open spaces are treated separately because they are classified as stand-alone structures. Power Electrical power denotes the intensity with which energy is generated or converted at a particular point in time (power = work per time). The higher the power of an electrical device, the more energy (i.e. work) is converted within a unit of time. Unit: Watt (W) or Kilowatt (kW). Renewable energies All energies available in infinite quantities in relation to human time scales - solar energy, wind power, hydropower, biomass and geothermal power. Silicon Silicon (Si) is the second most common element on earth - after oxygen. A chemical process extracts it from silica sand. It is then cleaned and used in the electronics industry and for the production of solar cells. Solar cells In solar cells (usually silicon), positive and negative charge carriers are released under the application of light or heat (photo effect), producing a DC current. Different material compositions result in different degrees of efficiency - monocrystalline silicon 14 to 17%, polycrystalline silicon 13 to 15% and amorphous silicon 5 to 7%. Solar energy "Solar power", i.e. energy from sunlight or other solar radiation such as thermal and UV radiation. Solar radiation Solar radiation is made up of direct and indirect radiation. Indirect radiation is, for example, reflection radiation from the surroundings, such as that from snow-covered areas and blue sky. The angle between sun ray and surface area is crucial when accurately calculating the energy falling on an area. This changes according to time of day and time of year. Irradiance can reach 1000 Watt/m2 in summer. Stand-alone systems Stand-alone systems allow autarkic energy supply and are used mainly in areas not connected to the public grid. In the event of an excess of power, the solar power generated is stored in batteries to guarantee permanent energy supply. STC Standard Test Conditions, see kWp String Denotes the combination of several electronic solar modules connected in series. String inverter In string technology, the photovoltaic generator is divided into individual module surfaces and each of these individual strings is assigned its own string inverter. This technology reduced system costs, the installation is simplified considerably and energy yield and system availability are increased. Supply The DC current generated in the solar cells is converted into AC current by an inverter and fed/delivered to the public grid. Supply meter Since the introduction of the Renewable Energies Law in Germany, photovoltaic systems coupled up to the grid must be fitted with a supply meter. It is installed alongside the existing consumer meter and measures the amount of electricity generated by the solar power system and the electricity fed into the national grid (in Kilowatt hours, kWh). System coupled to the grid A photovoltaic system that feeds the electricity generated into the national grid is known as grid-connected. Tilt angle The tilt angle the roof components of a solar system are installed at is important for the yield. Because the sun takes a different trajectory depending on season, a flatter tilt angle is used in summer and a steeper one in winter. Averaged over the year, the best tilt angle for photovoltaic systems is 20° to 60°. Thin layer cell Photoactive semiconductors are applied to a backing material (glass, high-grade steel film) and form a thin layer on it. The low manufacturing costs, low susceptibility to obstructions and high degree of flexibility in regard to design are all benefits of thin layer cells. One drawback is the low efficiency compared to pure crystalline silicon cells. Tracking To increase yields, larger systems are equipped with electric motors to track the sun. The module surface follows the path of the sun during the course of the day. This way the annual yield for our latitudes can be increased by about 30% compared to a system aligned in a fixed southerly direction. The mast elevation of tracked solar systems allows the selection of the best possible installation site. A shade-free angular sweep of 180° is provided irrespective of structures/buildings. Transformer The conversion from one voltage level to another is usually performed by transformers. A transformer either increases or decreases electrical voltage. Transformers are used to e.g. reduce the high voltage of outdoor power lines to the low voltage in our power sockets. Volt (V) Unit of electrical voltage. Named after the Italian physicist Alessandro Volta (1745-1827). The voltage denotes the difference in electrical charge at the poles of a current source. Electricity in most households in European countries is 230 Volt. The larger unit for voltage is 1 Kilovolt (kV) = 1000 Volt. Electricity from large power plants is brought up to higher voltages using transformers (up to 500kV in Europe) so as to reduce transport losses as a result of conductor resistance. The supply is then transformed back to 220/230V nearer to the consumer. Watt (W) Unit of electrical power. The work performed in the time unit of 1 second is called power. For example, the power of a device specifies how much energy it can transfer per second. The faster the work is performed, the greater the power. |
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