Electricity from photovoltaic systems

Bosch Solar Energy

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

Electricity from PV systems how does it work?

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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.

Solar generator

Generator connection box

Inverter

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Figures Units Terms

Kilowatt (kW): Measure of output. For example, the sun radiates an output of 1kW per square meter and hour of sunshine onto the earth's surface. (1kW 1000 Watt)

Kilowatt hours (kWh): Measure for energy corresponding to the electrical output of one kilowatt that is applied for one hour (1kW 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 condi-tions 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.

Modern photovoltaic systems can be used on buildings or stand alone sys-tems 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 contri-bution to environmentally friendly energy supply.

Map of sun intensity in Germany

What's the best wayto get optimal results?Some of the factors that dictate the energy yield for a PV system cannot be influenced. This includes natural condi-tions 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 indicatesthe annual radiation level that vary in intensity in different locations across the country.

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1181 1200

1161 1180

1141 1160

1121 1140

1101 1120

1081 1100

1061 1080

1041 1060

1021 1040

1001 1020

981 1000

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/m2

The sun map is based on values provided by the German Weather Service (www.dwd.de). No responsibility assumed for cor-rectness of the information. Updated: 12.2010

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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 evalua-tion and meticulous layouting by a quali-fied 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 pitchThe 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 28 30 degrees. In general PV systems should be tilted between 20 60 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.

PV systems offer independence from fossil fuelsOil, 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 gain-ing independence from fossil fuels and atomic power, and also dont have to worry about the anticipated price increases by energy utilities. Photovol-taic systems are a secure investment in and for the future.

PV systems cut energy costs and deliver long-term planning securityThe 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 elec-tricity supply more secure and forecast-able for the long term. That cuts your energy costs for the long run.

PV systems are unbeatably cleanRunning your own PV system will improve your household's CO2 balance, which promotes both the coming swi-tchover 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.

Clean, safe, independent the benefits of photovoltaic systems

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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:

For more information on this topic, please read our brochure "Self-consumption of solar power."

Independence

Potential savings

Future security

Increase of savings effects

PV systems pay for themselvesPV 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 com-pensation for solar power fed into the grid. After amortization the point where the system has earned back the money it costs it then begins deliver-ing long-term yields. You earn through the sun.

Self-consumption of solar powerSelf-consumption of solar power isthe portion of the energy that is directlyconsumed at home, like whenyou run your own washing machine.

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Self-consumption of solar power

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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

Silicon raw materials

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Cells

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(Source: UPDATE OF ENERGY PAYBACK TIME DATA FOR CRYSTALLINE SILICON PV MODULES, Dr. Thomas Wetzel, Florian Feuerstein, Karlsruhe Institute of Technology KIT)

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 pro-duce it, including the raw and semi-finished products.

Mono 0,18 0,75 0,95 1,18 1,27

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 manu-

facture it in under one and a half years. Nor has the effort ceased to drop that number even further. Quite the con-trary, we're working continiously to improve our products and the pro-cesses used to manufacture them.

Ratio of energy consumption to energy yield

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Energy pay-back time

Energy producedby a solar module during its lifetime

Service life of a module (t)

Yield (kWh):

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)

Active and sustainable protection of our climate and environment with PV systemsEach installed PV system achieves a drop in CO2 emissions compared with conven-tional 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

Environmental protection on the roof?

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Reduction of the CO2 emissions

Corresponds to washing 17868 kg of laundry

Corresponds to 1580 kg Co2 savings

Rooftop system South orientation Creates 2680 kWh electricity annually

Family of 4

Solar unit: Stuttgart, rooftop system, south facing 30, 10 c-Si M 60, 4 person householdCO2 emissions per kWh of conventional power production: 0.59 kg(Source: Internationales Wirtschaftsforum Regenerative Energien (IWR))

energy to heat showers for the employ-ees, 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 opti-

mized, leading to reductions in emis-sions, energy consumption and CO2 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.

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Recycling procedures

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.

Separation of cardboard,wood and plastic

Solar energy

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T hermalutilization

Separation of copper, glass, steel

Chemicalhandling

Bosch Solar Energy AG

Robert-Bosch-Strasse 199310 ArnstadtGermany

Tel. +49 (0)361 2195-0Fax +49 (0)361 2195-1133www.bosch-solarenergy.com

Your specialist installation company will be delighted to help you further!

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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 role in protecting our environment.