After reading some of your posts about grid tie systems, I see that when the grid goes down, the solar operator that doesn't use batteries won't have electricity even though he is generating his own power via solar panels (during daylight of course).
I obviously need to learn more about grid tie systems, I just always assumed (there is that word again, it gets me every time) that the homeowner would still have power as long as it was daylight. Is this done this way for safety reasons so that the lineman don't get nuked from other forms of energy entering into the grid ? but if that were the case, then I would think they (the utility company) would allow for automatic cutoff/bypass switches to be used to disallow power from backfeeding into the grid until utility power was restored..... like they do with emergency generators. Thanks
The inverters used in grid-tied systems do automatically disconnect the solar system from the service panel when there is a power outage. That is a performance test the inverter has to pass to be okayed for use by the utility grid it is being installed on. In practical terms, there is a list of utility approved inverters a person can use.
I know it bothers people that they cannot make use of the power generated on a sunny day while the utility power is out. First of all, for a typical outage how often is it a nice clear sunny day and the sun is somewhere south of due east and due west? On long daylight summer days, the sun spends a goodly number of morning and evening hours north of due east and west--it is behind your panels unless you have a tracking system. Night hours are out, snow, rain or just heavy storm cloud periods are out. No or no appreciable power is being generated in those times and conditions. Even a sunny day with haze can take 30%-40% of your output away.
The second limiting factor in a grid-tied system is that it is designed to draw from the grid as needed, like when a motor starts, or an electric water heater cycles. Such things may well exceed the capacity of the system. Even if it is only momentary, you have a brownout problem. The same is true for any size load if a thick cloud passes over; your power output is going to fall like a rock.
Your home appliances are designed to receive constant power, and as much of it as they need when they need it. That isn't what a grid-tied system is designed to provide.
An off-grid system uses the solar panels and charge controller to charge a large battery bank. The power you use in the home comes from the batteries, not from the panels. The battery bank and output inverter are sized to satisfy the appliances you use and has enough reserve capacity to act like the grid in a grid-tied system.
Grid-tied and off-grid comparisons are really apples and oranges.
