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Grid-Tied (or Utility-Intertie) and Back-up power systems
Out of all the technology we use in renewable energy systems, the battery is the least environmentally friendly. Batteries require periodic maintenance, are only 80% efficient at best, contain toxic substances and have a high failure rate (in comparison to the other equipment used). If we were to eliminate the battery, it would improve the system longevity and minimize the system’s environmental effects. It is possible for you to connect your renewable energy system through an inverter directly to the utility grid. Connected this way, there is no need for the system to have batteries. Energy produced and not used by the system is “stored” on the utility grid. When energy use exceeds production, the grid supplies the extra needed. In this way, ordinary citizens can produce and supply renewable energy to the utility grid. These intertie systems can be any size. One 100 to 300 watt solar module can be connected through a small intertie inverter. AC Modules like our Sunsine and the Eversun are pre-assembled and tested units that allow a homeowner to “plug in the sun” and the utility grid easily. This allows individuals to start with a very small system and add modules as they wish. For 1000-1500 watts of solar modules and up, it is more cost effective to use a single intertie inverter, (like Trace Utility-tie inverters and the AEI CG-1000). Intertie inverters have all the needed protective electronics to synchronize with the utility grid and to automatically disconnect from the grid in the event of an outage. Intertie systems utilitizing intertie inverters are installed and working safely in every state in the United States. The intertie system/utility connection varies from state to state and is rapidly changing. Some states are encouraging intertie systems and have passed laws to allow for net metering and streamlined the connection of intertie systems. Solar rebates and tax credits are also available depending on the location of the system. Under a net metering arrangement, homeowners who use solar systems run their electric meter backwards as they feed extra electricity back to their utility. This means that the utility “pays” the customer the retail rate for the electricity produced. Not all utilities offer net metering to their customers. Some require two electric meters to be installed, one for measuring the electricity used, one for electricity produced. This allows them to pay a different price for the produced electricity, often at a lower rate that the consumer pays for electricity. A lockable disconnect is also often required. The systems offered here satisfy the requirements for the California Buydown Program, a solar rebate in California, and other renewables incentives. Check the DSIRE web site for information about incentives in your area at: www-solar.mck.ncsu.edu

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