Grid Tied PV with backup power when the grid is down

[peakbagger]

Sunny Boy has released a inverter for Grid Tied PV that has a 120 volt plug on the base of it. If the sun is out and the grid is down, the unit supplies up to 15 amps with no batteries. Its roughly a $300 extra cost compared to similar inverters. It obviously doesn't work at night but may be enough for some folks to have a bit of backup when the grid goes down. I expect that someone might be able to plug in a UPS (if it doesnt draw too much juice) and use the UPS to extend its usefulness. I will let the pellet folks figure out if it will work for them.

There are battery based grid tied units out there but the overall cost bump is significant (as well as their capabilities). I am also not sure if many leasing companies will install these as most of them use microinverter based PV as its a lot easier to plan install with less front end design albeit at a higher cost than a central inverter.

Given the ongoing federal solar tax credit and many state incentives, this may be the thing that convinces some folks on the fence to make the install. Of course if the power is out due to a storm like what hit the Atlantic coast it was a few days before the clouds cleared out. With my 2KW array I still get some power even on cloudy days so there may be some power available but they may have a low end cutout of some sort.

I unfortunately missed out on this with my new system.

 

[begreen]

Good idea. I wanted to put in a Sunny Boy/Sunny Island system, but that would have added non-WA components and thus dramatically reducing the payback.

 

[Redbarn]

Thanks for alerting us. As a "Fence Sitter", this is certainly warrants serious research.

 

[peakbagger]

This capability apparently is a requirement to get incentives in Japan and this model was originally designed for Japan but given the storm along the Northeast coast last year they have come out with a US unit. The smallest they make is 3 KW

I wouldnt be surprised if other firms offer similar inverters, although I think many are still scrambing just to supply units that have DC arc fault capabilities required for NEC 2011 states.

 

[Redbarn]

This is an example of one of the problems with installing PV. The technology is still changing quickly so no matter when you decide to do the installation, better hardware appears within weeks if not months.

 

[Grisu]

How does the unit handle changing current through uneven power generation? Let's say a cloud moves in front of the sun and your power generation drops significantly what does that mean for the load you had put on it? I always thought batteries were not just for power storage but also to deliver a constant current which the solar cells often cannot supply.

 

[jebatty]

The install I am planning is giving this consideration. I already have a 240v generator plug-in with transfer switch for house circuits, so a 240v UPS type system would be easy to plug-in.

 

[peakbagger]

"How does the unit handle changing current through uneven power generation? Let's say a cloud moves in front of the sun and your power generation drops significantly what does that mean for the load you had put on it? I always thought batteries were not just for power storage but also to deliver a constant current which the solar cells often cannot supply. "

I think the unit is either on or off. If the cloud comes over and there is not enough power to supply full amperage, I would guess it shuts down and then waits until the sun is back out. Its definitely not a critical load source, that's why the UPS option might help. The limited info I saw is that the unit only puts out about 2/3rd of its rated input so it has come droop capability.

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[Redbarn]

I have read the Sunny Boy user manual for the SUNNY BOY 3000TL-US/5000TL-US.
The 'Secure Power Operations' feature restricts output power to 1500 Watts, provided the solar array is producing sufficient power.
This is about 75% of the output of a Honda/Yamaha 2kw Genny.
Useful but is it really a game changer ?

 

[peakbagger]

I agree its not a major power output, I think the intent was to be able to plug in cell phone to recharge and maybe keep a fridge running intermittently. For many the price bump of $300 minus 30% fed credit is worth it.

 

[begreen]

1500W is pretty close to the usable running output for the Honda EU2000i generator (120V 2000W max. (16.7A), 1600W rated (13.6A)). With load management you can run a fair amount on 1500w, but that is only while the sun is shining.