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A brief description of Solar Photovoltaic Technology

We want our customers to understand how our systems work, and what they are doing. there are several different configurations, from simple stand alone, to complete Net Metered systems with battery and generator backups integrated into them. Which one to use depends on your situation, and specific needs. While there are many possibilities, on this page we will briefly describe some of the more common configurations.

A Solar Photovoltaic system is a method for generating electric power by using solar cells packaged in photovoltaic modules, often electrically connected in multiples as solar photovoltaic arrays to convert energy from the sun into electricity. To explain the photovoltaic solar panel more simply, photons from sunlight knock electrons into a higher state of energy, thereby creating electricity.

Solar cells produce direct current electricity from light, which can then be used to power DC equipment or to recharge a battery. In order to provide the common household 115v AC power, an inverter is used. This unit converts the DC voltage from the Solar arrays into an AC voltage suitable for household use. In the case of a Grid-Tied system, the same inverter unit will also include the majority of the electrical components necessary to connect the solar arrays to the utility grid. These units are know as 'Grid-Tie' inverters, and are carefully regulated and certified.

These two major components are what comprise the typical residential Grid-tied system. There is no need for batteries, or other electrcial storage means. In a Grid-tied system the utility power grid serves to power the home whenever there is insufficient sunlight to power the solar arrays. In a Net Metered system, excess electrical power produced by the solar panels is temporarily 'stored' in the utility grid until the home needs it. In actuality, this is a 'paper' process of credits. THe utility gives you credits for any power you supply to them. These credits can then be used to offset the cost of any utility electrcity you use later. There is also a process wherein you can actually sell excess electrcity to the Utility provider. The limits on this type of setup are being removed. In all cases, the home based equipment is virtually identical.

Finally, some solar PV systems incorporate storage and backup supplies in the form of batteries, or generators, or normally both. These systems are typically used where utility grid power is either nonexistant, or highly unreliable. The addition of batteries and/or a backup generator add greatly to the cost of the system, and it's maintenance costs.

Below are some brief examples of these systems

In these examples, the first one is the most typical residential grid tied system. In the drawings, allowance is made for powering DC loads from the system. If used, this could consist of LED lighting, emergency equipment, or, in the case of a standalone system a major part of the household may be run off of the DC output to avoide the losses inherent in the inverter (approximately 12% of the power generated is lost in the conversion from DC to AC).

Basic Grid-Tied system without backup

This is the basic Grid-Tie system without any backup or storage capacity. DC Electricity generated by the PV array is fed directly into a Dc to Ac inverter. The AC output of the inverter is tied to the homes circuit breaker box. If the house is using more electricity than the PV system is supplying, then the remainder comes from the electric utility grid. Conversely, if the PV system is producing more electricity than the house is using, the excess electricity is fed back to the Utility Grid through your meter. This results in energy credits at the utility.

Basic Grid-Tied system including battery backup

This system is essentially the same as the basic grid-tie system above, with the addition of a storage batery. This will ensure on site power even during dark periods when the PV system is not producing electricity. In this sytem, allowance is made to run certain critical loads from the battery/PV system when the power grid supply is not available. It is not however large enough to run the entire house without supplimental power from the utility.

Stand alone Non-Grid Tied system including battery

This system would be used where there either is no utility power grid avaiable, or to power items completely separate from the grid. The batteries, which are usually much larger than a grid-tied system, will supply all the elctrical power during periods where the PV panels are not producing electricity.

Stand alone Non-Grid Tied system including battery & generator backup.

This is the system that would be used in an area without utility grid power to provide continuous power in any situation. It is the same as the stand alone system above, except that it adds a generator for periods when the battery supply may be used up, or to supply intermittant loads that are larger than the PV system alone can supply.