Combine Solar and Grid Power without connecting to the Grid

[LightningJimmy]

Does anyone know of any device/way that can combine the power from solar panels and a wall outlet? I am trying to save money on a server that uses 600 watts of power. Therefore, the device should be able to output at least 600 watts on a standard U.S. outlet. I am thinking of buying two 160watt off grid solar panels and have no intention of connecting them to the grid. If anyone has any ideas, please respond.

[sensij]

A proper grid-tied installation will allow solar power to reduce the amount of power drawn from the grid. Whether or not it saves you any money (eventually) depends on the details of your existing service and potential installation.

You can't safely add a solar panel to an existing residential load circuit, if that is what you are thinking.

[SunEagle]

To backup what sensij is saying, to totally isolate the power coming from the solar panel and the power from the grid would be to build an off grid solar / battery system.

Unfortunately once you add a battery and charger into the mix you end up paying much more for the electricity generated by the solar / battery then what you would have paid using the grid.

Best way to save money is to find ways to use less electricity or go with a grid tied pv system.

[solarix]

What you are talking about is called an "off-grid inverter with grid backup". Also known as an "Uninterruptible Power Supply" or UPS
Most off-grid inverters (well - not the cheap ones) have an AC input for connecting a generator, or the grid to do charging of the batteries. Off course all these use a battery, but 600watts is a pretty small load and you have many choices of suitable inverters. If you need 600 watts on a 24/7 basis, that is about 15kWh per day or about a 600Ah, 48V battery using 50% depth of discharge. This is a fairly large battery even though the load is small.

[LightningJimmy]

What you are talking about is called an "off-grid inverter with grid backup". Also known as an "Uninterruptible Power Supply" or UPS
Most off-grid inverters (well - not the cheap ones) have an AC input for connecting a generator, or the grid to do charging of the batteries. Off course all these use a battery, but 600watts is a pretty small load and you have many choices of suitable inverters. If you need 600 watts on a 24/7 basis, that is about 15kWh per day or about a 600Ah, 48V battery using 50% depth of discharge. This is a fairly large battery even though the load is small.

I'm not exactly sure how Uninterruptible Power Supplies work, but the solar panels would generate 320 watts max. Will it combine power from both or will it just use the grid power?

[jflorey2]

What you are talking about is called an "off-grid inverter with grid backup". Also known as an "Uninterruptible Power Supply" or UPS

More specifically a double conversion UPS.

I'm not exactly sure how Uninterruptible Power Supplies work, but the solar panels would generate 320 watts max. Will it combine power from both or will it just use the grid power?

If you are careful you can set the charge voltage of the solar charge controller higher than the voltage of the AC charger; this would result in most of the load being carried by the solar (when available.) When voltage drops at night the AC charger takes over.

Needless to say this is far more expensive than a similarly sized grid tie system.

[inetdog]

You would need what is called a dual-conversion or always on UPS. It would take at least 300W of the 600 from grid during peak sun hours and 600W from the grid the rest of the time.
You do not want to actually cycle the UPS batteries since they are not designed for that use and will quickly die.
I do not see a practical way to get DC from the panels and mix it with DC from the grid without at the same time cycling the battery voltage.

[Mike90250]

Does anyone know of any device/way that can combine the power from solar panels and a wall outlet? I am trying to save money on a server that uses 600 watts of power. Therefore, the device should be able to output at least 600 watts on a standard U.S. outlet......

I think you saw some "plug in grid tie inverters" on flea bay or some online store. Those are expressly illegal to connect to your house wiring by plugging them into an outlet. Yes, you can buy glass pipes too, but the police will arrest you if they see it,
Most of the cheap plug in inverters are not efficient, and fail quickly anyway. They are not safety tested and will void your fire insurance if your house burns.