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PV System Components. Advanced Engineering The Technology Academy @ Landstown High School. What is a solar cell?. Solid state device that converts solar energy directly into electrical energy Efficiencies from 10%- 80%% No moving parts No noise Lifetimes of 20-30 years or more.
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PV System Components Advanced Engineering The Technology Academy @ Landstown High School
What is a solar cell? • Solid state device that converts solar energy directly into electrical energy • Efficiencies from 10%- 80%% • No moving parts • No noise • Lifetimes of 20-30 years or more
How Does It Work? • The junction of dissimilar materials (n (+) and p (-) type silicon) creates a voltage, • Energy from sunlight knocks out electrons, creating a electron, • Connecting both sides to an external circuit causes current to flow, • In essence, sunlight on a solar cell creates a small battery with voltages typically 0.5 volt DC,
Combining Solar Cells • Solar cells can be electrically connected in series (voltages add) or in parallel (currents add) to give any desired voltage and current, • Power (Watts) output is calculated P = I x V • Photovoltaic cells are typically sold in modules (or panels) of 12 volts with power outputs of 50 to 100+ watts. • These are then combined into arrays to give the total desired power or watts.
Other System Components While a major component and cost of a PV system is the array, several other components are typically needed. These include: • The inverter – DC to AC electricity • DC and AC safety switches • Batteries (optional depending on design) • Monitor – (optional but a good idea) • Ordinary electrical meters work as net meters
The PV Market Solar Calculators REMOTE POWER • Lighting • Buoys • Communications • Signs • Water Pumping • Mountain Cabins
The PV Market • As prices dropped, PV began to be used for stand-alone home power. • If you didn’t have an existing electrical line close to your property, it was cheaper to have a PV system (including batteries and a backup generator) than to connect to the grid. • As technology advanced, grid-connected PV with net metering became possible.
NET METERING • In net metering, when the PV system produces excess electricity, it is sent to the grid system, turning the meter backwards. • If you are using more power than is being produced, or it is at night, the electricity is received from the grid system and the meter turns forwards. • Depending on PV size and electrical consumption, you may produce more or less than you actually use. • Individual houses may become power producers.
BATTERIES • Batteries can be used to provide long-term or short-term electrical supply in case of grid failure. • Many grid-connected houses choose to have a small electrical battery system to provide loads with power for half a day in case of outage. • Larger number of batteries are typically used for remote grid-independent systems.
2 KW PV on Roof with battery storage. Solar hot water collectors and tank
PV On Homes • PV can be added to existing roofs. • While south tilted exposure is best, flat roofs do very well. • Even east or west facing roofs that do not have steep slopes can work fairly well if you are doing net metering since the summer sun is so much higher and more intense than the winter sun. • The exact performance of any PV system in any orientation is easily predictable.
Other Mounting Systems? • If it is impossible or you don’t want to put a PV system on your existing roof, it is possible to pole mount the arrays somewhere near the house as long as the solar exposure is good. • Pole mounted solar arrays also have the potential to rotate to follow the sun over the day by installing a sun tracking system, • Sun tracking systems can provides a 30% or more boost to the PV system performance.
Roof Integrated PV • If you are doing new construction or a reroofing job, it is possible to make the roof itself a solar PV collector. • This saves the cost of the roof itself, and offers a more aesthetic design. • The new roof can be shingled or look like metal roofing. A few examples follow.
Roof Integrated PV (objects below chimney are solar hot water collectors)