A typical Solar pv electrical law is described to refresh our basic electrical knowledge. This knowledge will allow us to be comfortable with the found of our pv solar law and have confidence that it is not over or under designed.
The pv Solar energy System: A pv Solar law has the four major components.
Pure Sine Power Inverters
1) The Solar Panel: This is the component that receives photons from the sun and converts the photon energy into electricity. The panels are rated in Watts.
2) charge Controller: This component insures that the storehouse batteries are not overcharged and damaged.
3) storehouse Batteries: The batteries store our collected electricity until we use the energy to power our appliance. Our electricity is store as the possible energy rated in Volts.
4) Inverter: This component changes the current from our batteries, which is stored in direct current (Dc), to an alternating current (Ac) which is compatible with our household appliance.
Conversion of Sunlight to Electricity: Photovoltaic energy is the conversion of sunlight into electricity through a photovoltaic (pv) cell, generally called a solar cell. A photovoltaic cell is a non mechanical expedient normally made from silicon alloys.
Sunlight is composed of photons or particles of solar energy. These photons consist of discrete amounts of energy corresponding to the different wavelengths of the solar spectrum. When photons charge a photovoltaic cell, they may be reflected, pass right through, or be absorbed. Only the absorbed photons contribute energy to originate electricity. When sufficient sunlight (energy) is absorbed by the material (a semiconductor), electrons are dislodged from the material's atoms. Extra treatment of the material face during manufacturing makes the front face of the cell more receptive to free electrons, so the electrons naturally migrate to the surface.
The production of a solar panel is normally stated in watts, and the wattage is carefully by multiplying the rated voltage by the rated amperage. The recipe for wattage is Volts times Amps equal Watts. So for our example, a 12 volt - 60 watt solar panel measuring about 20 X 44 inches has a rated voltage of 17.1 and 3.5 amps .
V X A = W
17.1 volts times 3.5 amps equals 60 watts.
Our solar panel rated as 60 watts exposed to 6 hours of peak sun will furnish 360 watt hours of power per day. An typical; home will want 4000 watts of Dc generating power to furnish sufficient kwh to cover annual electrical consumption. This equates to 67 - 20 X 44 inches solar panels from the example above.
Wiring the System:
Solar panels can be wired in series or parallel to growth voltage or amperage respectively, and they can be wired both in series and in parallel to growth both volts and amps. Series wiring refers connecting a unavoidable concluding of one panel to the negative concluding of an adjacent panel. This association will furnish voltage as the sum of the two panels and the amperage will remain the same as the production panel. Two 12 volt and 3.5 amp panels wired in series will furnish 24 volts at 3.5 amps.
Solar panels can be wired in parallel by connecting unavoidable terminals to unavoidable terminals and negative terminals to negative terminals. Two 12 volts and 3.5 amps panels wired in parallel will furnish 12 volts and 7 amps.
A series/parallel wired law refers to doing both to the above. This wiring task would furnish 24 volts and 7 amps from our two 12 volt and 3.5 amps panels.
Inverter:
An inverter is a expedient which changes Dc power stored in a battery bank to standard 110 / 240 volts Ac. Nearly all our lighting, appliances and motors are designed to use Ac power. Inverters come in sine wave and modified sine wave output. Most 11o volts devices can use the modified sine wave output. However, Extra devices that use lasers or silicon controlled rectifiers will want the pure sine inverter which is more expensive.
Auto exchange switching is a base internal highlight which enables switching from one Ac source to someone else and / or from utility power to inverter power for designated loads. Battery temperature compensation, internal relays to control loads, self-acting remote generator starting and stopping and many other programmable features are available.
Charge Controller:
A charge controller monitors the battery's state of charge to insure that when the batteries need current when required and also insure that the batteries are not overcharged. Connecting a solar panel to the batteries without a charge controller seriously risks damaging the batteries and potentially causing a security concern.
Charge controllers are rated based on the estimate of amperage they can furnish from a solar array. If a controller is rated at 20 amps you can join together up to 20 amps of solar panel current output. Industrialized charge controllers utilize Pulse-Width-Modulation which insures the most productive battery charging and extends the life of the batteries. Even more Industrialized controllers can consist of Maximum Power Point Tracking which maximizes the estimate of current going to the batteries by lowering the panel's production voltage.
Many Industrialized charge controllers offer Low Voltage Disconnect and Battery temperature recompense as optional features. The Low Voltage Disconnect allows the terminals to be voltage sensitive. If the battery voltage drops too far the panels are disconnected thus preventing damage to the batteries. The Battery temperature recompense adjusts the charge rate based on the temperature of the battery since batteries are sensitive to temperature variations above and below about 75 F degrees.
Batteries:
The batteries for our law should be Deep Cycle units which are designed to be discharged and then re=charged hundreds or thousands of times. Batteries are rated in Amp Hours (ah) and are normally rated at 20 or 100 hours. Amps hours refer to the estimate of current which can be supplied by the battery over the periods of hours. An example would ne a 350 ah battery could contribute 17.5 continuous amps over a 20 hour period.
Like solar panels, batteries are wired in series and/or parallel to growth voltage to the desired level and growth amp hours.The capacity of the battery amp hour capacity requires true sizing for the conditions under consideration. Longest periods of no sun or cloudy conditions, availability of generator or grid backup or a standby generator with battery charger are among the conditions for consideration. The size of the battery bank will depend on the storehouse capacity required, the maximum extraction rate, the maxium charge rate, and the minimum temperature at which the batteries will be used.
Overall Design:
As with all electrical systems there are voltage losses as the electricity is carried across the wires, batteries and inverters and these losses are dependent on the efficiency of each component. These efficiency losses vary from component to component, and from law and can be as high as 25 percent. A trained technician will be required to fine tune the law for efficiency.
overview of a Pv Solar power theory