Solar Power Systems
A solar electric system (sometimes known as a photovoltaic or solar PV system) captures sunlight using solar (PV) cells made from a semiconductor material. Capturing sunlight in these PV cells increases the energy of the electrons within, which are then released through the photoelectric effect to produce a flow of electrons. It is this flow of electrons that we all know as electricity.
There are three main ways that a solar electric system can provide electricity to you.
To the surprise of many, the most commonly installed solar electric systems do not have batteries. That's right – no batteries. This is called a grid-tied solar electric system. The solar electric system is connected directly into your main breaker box. When the sun is shining on your PV cells and you are generating electricity, this electricity will be used by the electric circuits in the main breaker box. If there is more solar energy generated than is currently being used, the excess electricity is exported out through the utility meter back out onto the grid. You are now selling electricity to your utility – and in most cases, you are selling at retail price. When there is no sun or insufficient sun to generate electricity for your needs, you simply continue to buy electricity from your utility. In essence, the utility is now acting as your battery.
A grid-tied solar electric system usually proves to be the most cost-effective solution when you have utility electric service available.
Grid-Tied with Battery Backup
Grid-tied solar electric systems with battery backups are essentially the same as grid-tied solar electric systems with one key advantage: during grid power outages, the battery bank continues to provide power to specific electrical circuits. The system owner will identify 'critical loads', such as a well pump, refrigerator, freezer, heating system controls, internet router, and others to have available when the grid is absent. By identifying only those 'critical loads', the battery bank can be kept smaller and more affordable. Customers that experience frequent outages or find that they cannot tolerate even short power outages find this system provides them the security of an uninterruptable power source.
Off-Grid (Stand Alone System)
Off-grid systems are not connected to the utility grid and require a battery bank to provide all the electricity when there is little or no solar resource. These systems are generally installed when there is no utility service available, or when the cost of bringing in electric service is outrageous. The solar system works in tandem with a generator (propane, wind or both) to provide electricity to loads and/or recharge batteries when there is an insufficient solar resource. The off-grid system is for the customer that wants to be completely self-reliant.