Catalog Pg. 42

Grid-Tie Solar Electric Kits

Grid-Tied Solar Systems are the most efficient way to utilize solar power if you are tied to the grid (have utility power) and do not need a system which can supply power if the grid fails. The major benefits of grid-tied systems are ease of installation, lower equipment costs (no batteries are needed) and more efficient use of the solar modules. Since the solar array doesn't charge batteries, battery charging inefficiency (15%) is avoided. Also, all the voltage (power) the modules generate will be used. When charging batteries usually only about 12 to 14 volts of 17 volts available is being used and of course when the batteries are fully charged, the array ceases to make any power!

The kits listed on the next page are examples of high-voltage grid-tied systems. In all cases more solar modules may be added although a minimum number per string is necessary. The Sunny Boy 1800 requires at least 139 volts DC to operate which translates into at least five 24 volt solar modules per string. For example, instead of one string of eight 24-volt modules, two strings of five each 24-volt modules could be used. Some have already figured out that 5 times 24 only equals 120 volts, not 139. Remember that "24 volts" refers to nominal voltage, not working voltage, which is 34 volts for a 24-volt module. The maximum array size for the 1800 is about fifteen 150W modules, or 2250 watts and the maximum size for the 2500 is about twenty 150W modules or 3000 watts. As long as the voltage requirement is met, any size module can be used. For example, one could use five 120 watt modules instead of five 150 watt modules. If you were to use 12V modules, ten would be the minimum required in a string.

The kits on the next page supply all that is necessary to set up a grid-tied system with the important exception of the conduit and wire needed to connect the array combiner box, the DC disconnect, the Sunny Boy and the AC disconnect together. Since we have no idea what these distances will be it is impossible for us to place this material in a kit. This wire and conduit are standard electrical items and can be supplied by you or your electrician.

Before starting a grid-tied system, you must contact your electric company to see what they will require for system installation. Most electric companies require an outdoor AC disconnect box which we have included in the kits. They may also require a new metering system as well. See page 55 for a description of the Sunny Boy inverters and page 54 for more discussion on solar electric grid-tie systems.

The question of "pay-back" time is a difficult one to access when referring to solar electric systems. In terms of cents per kilowatt hour generated by a solar electric system, pay-back will take many years. In terms of "investment" in green energy, pay-back is immediate. Don't forget the investment value to your home when a solar electric system is added. It is truly a long-term investment because solar modules will outlive you and me! In some states subsidies are available to help pay for the cost of a grid-tie system. 103 Kit #GT8

Note: Grid-Tie Solar Electric Kits are continued on the next web page.

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