Electricity from PV systems how does it work?

Transcription

1 Electricity from photovoltaic systems Bosch Solar Energy

2 2 Electricity from PV systems Electricity from PV systems how does it work? Photovoltaics: This is the name given to direct conversion of radiant energy, primarily sunlight, into electrical energy. In short: solar power. The name itself is composed of the roots 'photos' the Greek word for light and Volta, an homage to Alessandro Volta, a pioneer in the field of electrical engineering. For a PV system, the solar electricity is generated using solar cells that capture the sunlight and convert it to electrical energy. A PV system typically includes multiple solar modules, each containing solar cells that are installed and wired together. An inverter is wired to the PV system to convert the direct current into the alternating current used on the power grid. The volume of electricity produced depends on the length and intensity of sunlight falling on the system and the type and quality of solar cells and components used within the solar module. Principle function of a PV System Solar generator Generator connection box Inverter Meter Grid connection 5 4 3

3 Electricity from PV systems 3 Modern photovoltaic systems can be used on buildings or stand alone systems and can endure extreme weather conditions such as rain, storms and hail. They are long lasting and represent a good investment for private homes. PV systems also make an important contribution to environmentally friendly energy supply. Figures Units Terms Kilowatt (kw): Measure of output. For example, the sun radiates an output of 1 kw per square meter and hour of sunshine onto the earth's surface. (1 kw Watt) Kilowatt hours (kwh): Measure for energy corresponding to the electrical output of one kilowatt that is applied for one hour (1 kw x 1 hour). Wp/kWp: The size of a PV system is typically not defined in square meters, but rather in terms of its rated electrical output. This output is cited under standard conditions and in watts Wp or kilowatts kwp (The p stands for 'peak'). Difference from solar thermal: A solar thermal system uses the sun's energy to capture heat, which is then used for heating or warm water supply.

4 4 Electricity from PV systems What's the best way to get optimal results? Some of the factors that dictate the energy yield for a PV system cannot be influenced. This includes natural conditions such as the number of hours of sunshine and the intensity of the sunshine as it falls on the PV system's location. The map of sun intensity in Germany indicates the annual radiation level that vary in intensity in different locations across the country. Map of sun intensity in Germany The radiation volume in Germany totals between 981 and 1200 kilowatt hours (kwh) per square meter and year. That's the same amount of energy that is produced by 100 liters of fuel oil. Annual total in kwh/m The sun map is based on values provided by the German Weather Service ( No responsibility assumed for correctness of the information. Updated:

5 Electricity from PV systems 5 Having these conditions it is possible to achieve optimal capturing of the energy. That means that the existing sunlight should hit the solar cells optimally to enable as much of the sunlight as possible to be converted into useable electrical energy. This requires professional evaluation and meticulous layouting by a qualified PV systems technician: Roof orientation Under optimal conditions the modules should be oriented toward the south. If this is not possible, then the following rule of thumb applies: The closer to south, the better the chances for optimal capture of energy. Hence, the stronger the tilt of the module, the stronger the effect of the orientation for the ultimate energy generation. Roof pitch The energy output from a PV system is statistically at its highest when the sunlight hits the solar cells at a right angle. The optimal tilt for fixed PV modules in Germany is degrees. In general PV systems should be tilted between degrees. The tilt angle can be adjusted using elevation systems. Shading* Architectural and topographic factors that lead to shadows falling on the solar module reduce the energy generation and should be avoided. Each factor (roof orientation, roof pitch and shadows) has an impact on the rated top output of the solar unit in proportion to its deviation from ideal conditions. * The manufacturer's respective installation instructions provide detailed information about the effects of shadows on the solar module.

6 6 Electricity from PV systems Clean, safe, independent the benefits of photovoltaic systems PV systems offer independence from fossil fuels Oil, coal and gas are growing more scarce and expensive. Those willing to take the step to produce their own free and clean energy from the sun are gaining independence from fossil fuels and atomic power, and also don t have to worry about the anticipated price increases by energy utilities. Photovoltaic systems are a secure investment in and for the future. PV systems cut energy costs and deliver long-term planning security The use of solar power does more than just make future price increases by traditional electrical utilities into a minor issue; it also cuts your current energy costs. PV systems make your own electricity supply more secure and forecastable for the long term. That cuts your energy costs for the long run. PV systems are unbeatably clean Running your own PV system will improve your household's CO 2 balance, which promotes both the coming switchover to cleaner energy and with it a healthier environment. Solar power offers numerous benefits, since the PV system converts the sunshine directly into electricity without the hazardous byproducts involved in conventional power generation. Self-consumption pays off! The sinking feed-in tariffs combined with constantly climbing electricity prices make self-consumption an important factor for the profitability of PV systems. The key is to increasingly use as much of the solar power you generate as possible to cover your own needs. Self-consumption of solar power has positive effects in a variety of ways: Independence Future security Potential savings Increase of savings effects For more information on this topic, please read our brochure "Self-consumption of solar power."

7 Electricity from PV systems 7 PV systems pay for themselves PV systems pay themselves off over the course of their service lives in two ways. The first is through feed-in tariffs for the local distribution grid; the second is through a reduction in energy costs by using the power you create on your own. The first factor involves a fixed price for each kwh of electricity that is fed into the general power grid, starting from the first year of operation and running for 20 years thereafter. Depending on the location and size of the system, the system operator receives a fixed compensation for solar power fed into the grid. After amortization the point where the system has earned back the money it costs it then begins delivering long-term yields. You earn through the sun. Self-consumption of solar power Self-consumption of solar power is the portion of the energy that is directly consumed at home, like when you run your own washing machine. Self-consumption of solar power

8 8 Electricity from PV systems Photovoltaics Energy generation with a positive balance Energy Pay-Back Time In photovoltaics, as with the entire field of energy engineering, the 'Energy Pay- Back Time' describes the period required by the PV system to generate the same volume of energy as was required to produce it. A misconception stubbornly maintains that PV modules don't produce as much energy that was required to manufacture them. The state of production technology and processes for monocrystalline modules Energy pay-back time in years Average energy pay-back time for monocrystalline PV modules in European mass production, 2009/2010. Units: years Mono 0,18 0,75 0,95 1,18 1,27 The energy pay-back time for solar cells thus totals approx. 1 year, 3 months. That means that a solar cell generates the same amount of energy during that time as was used to produce it, including the raw and semi-finished products. Silicon raw materials Wafer Cells Laminate without frame Frame (Source: UPDATE OF ENERGY PAYBACK TIME DATA FOR CRYSTALLINE SILICON PV MODULES, Dr. Thomas Wetzel, Florian Feuerstein, Karlsruhe Institute of Technology KIT)

9 Electricity from PV systems 9 as practiced during 2009 and 2010 translate into an energy pay-back time of 1.27 years. That means that a monocrystalline solar module from Bosch will produce as much energy as was required to manufacture it in under one and a half years. Nor has the effort ceased to drop that number even further. Quite the contrary, we're working continiously to improve our products and the processes used to manufacture them. Ratio of energy consumption to energy yield Yield (kwh): Energy payback time Energy produced by a solar module during its lifetime Service life of a module (t) The energy pay-back time and energy yield, regarded over a service life of 25 years, stand in a 1.27:25 ratio. (Source: UPDATE OF ENERGY PAYBACK TIME DATA FOR CRYSTALLINE SILICON PV MODULES, Dr. Thomas Wetzel, Florian Feuerstein, Karlsruhe Institute of Technology KIT)

10 10 Electricity from PV systems Environmental protection on the roof? Active and sustainable protection of our climate and environment with PV systems Each installed PV system achieves a drop in CO 2 emissions compared with conventional energy generation, meaning an active and sustainable protection of the environment. Environmentally sound and sustainable production location Through its products, Bosch Solar Energy does more than just contribute to sustainable energy and environmental policies. It also draws its suppliers and production processes into the equation. During the supplier selection process, each potential Bosch supplier must agree in writing to adhere to transparent, binding standards. Bosch Solar Energy also uses the conditions present at its production facilities to protect and preserve the environment. The large plant in Arnstadt, for example, uses solar Reduction of the CO2 emissions Rooftop system South orientation Creates kwh electricity annually Family of 4 Corresponds to washing kg of laundry Corresponds to 1580 kg Co 2 savings Solar unit: Stuttgart, rooftop system, south facing 30, 10 c-si M 60, 4 person household CO 2 emissions per kwh of conventional power production: 0.59 kg (Source: Internationales Wirtschaftsforum Regenerative Energien (IWR))

11 Electricity from PV systems 11 energy to heat showers for the employees, while waste heat from production is used to heat the buildings. Not surprisingly, open spaces, roofs and facades are used for the installation of PV systems. The production processes are also constantly monitored and optimized, leading to reductions in emissions, energy consumption and CO 2 release. A professional filtering of all unavoidable wastewater and emissions is also a standard part of our processes, with monitoring around the clock at multiple locations. Quality and sustainability are given top priority at Bosch, even when our products reach the end of their life cycle. This applies in particular for legal specifications about environment protection. For the PV cycle, for example, we are committed to an industry-wide recycling program for old modules and invest large amounts in R&D to ensure that future products will be even more environmentally friendly. Recycling procedures Separation of cardboard,wood and plastic T hermal utilization Separation of copper, glass, steel Solar energy Solar module Raw materials Chemical handling

12 Your specialist installation company will be delighted to help you further! The high quality of Bosch Solar Energy solar modules forms the essential basis for long-term high energy yields above all, they play an important Bosch Solar Energy AG Robert-Bosch-Strasse Arnstadt Germany Tel. +49 (0) Fax +49 (0) You can get more information about solar energy from: Printed on 100 % recycled paper. Updated 05/2012 role in protecting our environment.