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

Cross Section of Solar Cell

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.

Cells, Modules, Arrays

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 Photovoltaic Array with its other electrical components

PV was developed for the space program in the 1960’s

PV Price and Quantity Manufactured Relationship

The PV Market

Solar Calculators

REMOTE POWER • Lighting• Buoys• Communications• Signs• Water Pumping • Mountain Cabins

Photovoltaic Array for Lighting

Telecommunications Tower

Remote Water Pumping in Utah

Recreation Vehicle Outfitted with Solar Panels

Solar Lanterns for Landscaping

A Solar Driven Band

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.

Net Metering can be done with or without a battery backup

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.

Photovoltaic Array on Roof and as an Overhang

½ KW PV System Installed along Roof Ridge

California Home PV Installation

PV on House

2.4 KW System under Installation in New Hampshire

PV Installed at Roofline on Building at Frost Valley, NY

PV Panels on Tile Roofs in Arizona

PV on Roof in California

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.

Pole Mount for Solarex Modules

Pole Mounted PV

Pole Mounted PV

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.

Solar Roofing Shingles

Roof Integrated Photovoltaics in Misawi, Japan

Roof Integrated PV in Japan

Roof Integrated PV in Maine

Roof Integrated Photovoltaic System in Colorado

Roof Integrated PV (objects below chimney are solar hot water collectors)

PV Installation in Planned Community in Germany