For informational purposes, we’ll break this section down into two sub-sections.
The first type we will discuss is the grid tied system which uses the available solar power, then switches to the grid for support. This is a typical type of solar system where the utility does not allow intertie’s for “sell back”.
The second type is for use as a “sell back” system, but with frequent power outages or brownouts, allows the client to have an almost seamless switchover to battery power when the grid is down.
When we are designing these systems we talk with the customer about how much battery capacity they might need as well as what percentage of their power they might like to make from solar.
In a battery based, grid tied system with a utility intertie (sell back) agreement with the local power company, your batteries will be kept at a preprogrammed level (float voltage)and any residual power being made by your soar panels not being used by the home in the moment will be sent back to the utility grid. A bi-directional meter measures that outgoing power and the utility puts that power in a power “bank account” for you. Each month the utility subtracts what you put back onto the grid from the total household usage. You get to use your power “credit” toward your bill. If you made more than what you used the power stays in your power “bank account” until it is needed. The current utility agreement allows the utility to keep the power for themselves if you have not used it one year from the month you made it. This is why proper design is important. We only want you to make the power you will use, not oversize the system and allow the utility to keep your excess power.
|Grid tie system with batteries in Bahamas