I am new to this forum, but i joined mainly because its an active forum which is great.
I am looking to install a grid tied PV system. I have gathered nearly all the stuff needed, listed below.
12 300w Panels
Single Axis Tacker
6000N Linear Actuator
DC Circuit Breaker
AC Circuit Breaker
Wires and Construction materials.
As you can see I am missing the Inverter. I know that when the grid goes down so does the PV system. I have recently heard of some systems that don't go down though. I learned new terms "AC Coupled", "transformerless", "islanding", "anti-islanding"
and all this just confused me on what i should actually be looking for. From my understanding an AC Coupled System requires a separate inverter connected with a battery that basically comes online when the grid fails and tricks the main inverter into believing the grid is still up and power from the panels can still be used. The power cannot however be sent to the grid, any excess above the load and recharging the battery is wasted.
I am looking to see if there is a way to still use power from the panels when the sun is up and the grid is down with only 1 inverter and no batteries, and if thats not possible and AC Coupled is the only way then what is the smallest size backup inverter that i can use.
Chuck, you are in luck! SMA makes just the thing for your situation. The Sunny Boy inverters with SPS (secure power supply) are a great device. We have a dozen or so of these inverters in the field and you will have up to 15a at designated outlets or a critical loads sub panel when the grid is down.
They cost the same per watt as any other inverter in their class and the SMA gear over the years have been rock solid reliable- good stuff.
You will not need an traditional ac coupled system unless you later decide that a serious backup is needed.
The SB3800 is a good fit for your wattage, arguably you could use the SB3000. Use the specs from your modules and the SMA sizing tool.
Chuck does not require a battery,
I suggest that people who have the SPS and would like a small battery back up, can simply plug in an off the shelf UPS from office depot or other and recharge it while the sun shines for night time lighting and communications during an extended grid outage.
When it is used for evil, then watch out! When it is used for good, then things are much nicer. Like this tiny ad: