Photovoltaic
Mar 5th, 2008 by solarbill
- Grid Tie
A grid tie system is the most common form of Photovoltaic(PV) system for a household. These are systems that use an inverter to match the voltage and frequency of the electricity coming from the utility. The power from the utility is often referred to as grid power or just the grid. The inverter pushes the electricity being produced by the solar panels into the house wiring system. If the system is producing more electricity than the house is using the difference is sent back into the grid to be used elsewhere. This return of electricity turns the meter backwards. When the solar is producing less electricity than the house is using the grid makes up the difference. If the grid goes down the system shuts off. This protects linesmen from being shocked by the power from the solar when they think they have shut the power off. This is the least expensive solar solution as it does not need batteries or dedicated circuits.
- Off-Grid
An off grid system is a stand alone system. Such a system would be seen where connecting to the grid is not practical. These systems use the panels to charge batteries. Some loads such as pumps can be run directly off of the batteries. Other loads that require 120v or 240v are supplied through an inverter. These inverters usually have the ability to start a generator in the event that there is not enough power stored in the batteries.
- Battery Backup Systems
Are a hybrid of the above two systems. When the grid is up the system functions much as the grid tie does. It also keeps batteries charged. When the grid goes down certain circuits are kept powered these are referred to as the critical circuits. These may include lighting, refrigeration, heater fans and computers. These systems are used by households and businesses that are concerned that an interruption of power would be too inconvenient or damaging.