How a System Works

System Components:

1. Solar Panels
Electricity can be produced from the sunlight through a process called photovoltaics. Photo refers to light and voltaic to voltage. The term describes a solid state electronic cell that produces direct currrent electrical energy from the radiant energy of the sun. Photovoltaic cells are made of self-conducting material, most commonly silicon, coated with special additives.
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2. Inverter system
Inverter: A device that takes DC Voltage and changes it to AC voltage so that the Ac voltage can be used to operate home appliances.

DC breaker box: Holds all the breaker safety switches for all the DC voltage devices.

AC breaker box: Holds all the breaker safety switches for all the AC voltage devices.

Charge controller: A device that regulates the amount of voltage to charge the battery bank.

Digital display controller: A device that is used to program all the settings in the system

3. Battery Bank

These batteries used are called a Deep Cycle battery. The batteries are used to store the energy produced by your solar array. They can be discharged and recharged several times. Deep cycle batteries are measured in amp hours. The size of battery bank that you need is determined by how many amp hours it takes to run all the devices in your house and for how long without recharging.

The System:

The solar panels collect light from the sun, to create electricity. The dc voltage from the solar panels can be 12 to 140 volts DC. The dc voltage is connected to the charge controller. The charge controller is programmed to determine what voltage your battery bank is. A battery bank can be 12,24, or 48 volts DC. The charge controller will take what ever voltage that is coming from the solar array and change it to match the voltage of the battery bank. It will charge the battery bank until it is full and then will direct the excess to the inverter. This excess electricity can be used to operate your house or sometimes can be sold back to the hydro utility supplier. The inverter takes the Dc voltage from the battery bank or the solar array and changes it to AC voltage. AC voltage is the electricity that we use in our houses. Sometimes when the S un has not been out long enough to fully charge the batteries we can use the inverter as a charger. This is another component within the inverter. This will take the Ac voltage and change it to Dc voltage so that we may recharge the battery bank when necessary. We can do this by means of a generator or from the hydro utility system.

AC: Alternating current, Electricity current in which the direction of the flow is reversed at frequent intervals, 120 times per second

DC: Direct current, electric current in which electrons are flowing in one direction only.

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More on Photovoltaic Systems......

A photovoltaic (PV) system consists of one or more photovoltaic (PV) modules, the basic building block of PV-systems. One PV-module consists of about 40 photovoltaic solar cells; the cells convert the light into electricity. The PV modules are connected either in series or In parallel and they are called the PV field. Because PV-fields are built with PV modules of 50 or 100 watts each, photovoltaic systems are exceptionally modular, which provides for easy transportation and rapid installation, and enables easy expansion if power requirements increase.

To be able to use the generated electricity, more components need to be added to the system. PV systems for stand-alone applications (also called off-grid applications) may comprise also a control, storage (e.g. battery), cables and a load (e.g. lights, radio, television). PV systems for grid connected applications need an inverter to convert the direct current (d.c.), generated by the PV-modules, into alternating current (a.c.).

Photovoltaic cell converts light into electricity

The photovoltaic cell is the component responsible for converting light to electricity. When sunlight strikes a photovoltaic cell, part of the light particles (photons), which contain energy, is absorbed by the cell. By the absorption of a photon a (negative) electron is knocked loose from a silicon atom, and a positive "hole" remains. The freed electron and the positive hole together are neutral. Therefore, in order to be able to generate electricity, the electron and the hole need to be separated from each other. Therefore a photovoltaic cell has an artificial junction layer, also called the pin-layer. Now, the freed electronics cannot return to the positive charged holes. When the electric contacts on the front and rear are being connected through an external circuit, the freed electrons can only return to the positively charged holes by flowing through this external circuit, thus generating current.

As shown in the image, a photovoltaic cell has more layers. The upper layer of multicrystalline silicon cells looks blue, due to a anti-reflection coating, which is used to optimize the absorption of light by the cell. Both the upper layer and rear layer have contacts, to enable the freed electrons to flow through the external circuit from the negative layer to the positive layer. The silicium part, the actual photovoltaic cell, also has a negative (N-layer) and positive (P-layer), which both are chemically polluted: the upper layer consists of material of which the atoms have one electron extra than silicum, whereas the layer on the rear side is made of material of which the atoms have one electron less than silicium.

The photovoltaic effect will continue as long as light strikes the photovoltaic cell: every time the photons will create new electron/hole-pairs. This implies that no materials are being wasted; it is a renewable process.

The electrical power that can be extracted from a photovoltaic cell is proportional to its area and to the intensity of the sunlight that hits the area, and is measured in watt (W).