[RE-wrenches] Outback AC coupling Sunpower?
Ryan
ryan at kb1uas.com
Wed Jul 31 11:16:03 PDT 2013
Ray
You did not mention the XW, it frequency dithers so it is a pretty
straight forward setup. It also comes in 4, 4.5 and 6KW
Ryan
On 7/31/2013 2:04 PM, Ray Walters wrote:
> Hi Kelly;
>
> I agree the Radian system is appealing. Its basically uses a circuit
> breaker that can be controlled like a relay as well, and just
> disconnects the GT inverter.
> I'm going to offer a brief table of what I've found for my choices:
>
> Brand
> Control Method
> Pros
> Cons
> SMA Sunny Island
> Frequency shift to disconnect GT inverter
> simplest wiring, Trusted GT industry player
> most expensive, Freq shift can cause other problems
> Outback Radian
> Remote controlled Circuit breaker disconnects GT inverter
> fairly simple wiring, relay and breaker are combined, better control
> of battery charging
> still expensive, not available in smaller than 8 kw model
> Magnum
> Diversion load controls for battery regulation (soon to offer AC
> load control)
> lower cost, proven technology, freq shift control offered as fail safe
> most complicated wiring, diversion loads not always reliable or
> available
> Modsine Backup system
> no AC coupling, just an old fashioned backup system
> low cost
> complicated, needs customer interaction, not as efficient, GT PV not
> used, dedicated PV modules only charge backup system
> Generator
> No AC coupling, generator runs backup loads
> lowest cost, backup power available for as long as outage (no batteries)
> best for week long outages that only occur every few years
> Not Renewable, fuel storage issues, doesn't switch fast enough to
> maintain computers, etc.
>
>
>
> I'm still pricing out the options, but the SI and Radian seem a bit
> overkill for smaller systems. Backup inverter power of just a couple
> thousand watts is all that most people need. The Magnum is
> appealing, but I have quite a bit of experience with load diversion
> controls from wind and Hydro systems, and I really feel that its
> overly complicated for the less than 1% of the time that the grid is
> out. Keeping the battery from being damaged is what's important, but
> maintaining full 3 stage charging for a couple of days a year is not.
> The batteries can be properly charged once the grid returns. May be
> able to use Outback's ROCB with the Magnum? That might get the best
> of both worlds.
> If I was building the entire system to start, I'd just use a single
> Outback GVFX with its own PV array, and add GT inverters and array
> that were independent for the rest of the GT requirements. This
> project however is retrofitting an existing GT system.
> I've done many backup systems in the days before Grid Tie, and they
> work fairly well. Basically either the modules are not used much of
> the time, or the customer has a few circuits that are on the backup
> system (off grid) all the time. They operate it just like an off
> grid system, the only difference is that when its time to run a
> generator, they can just switch to the grid. These are not for your
> average customer, but can work well for someone that likes to save
> money and tinker.
> Another consideration is that if the battery bank is large enough
> relative to the array, over charging becomes less of an issue;
> especially with flooded cells that can stand a bit of over charging
> ("equalization") every now and then. However, I can see that the
> average small sealed battery bank hooked up to several KWs of PV could
> get ruined in a day.
> I'll close with a quote from Joe Swartz in his 2012 Solar pro magazine
> article :
>
> "AC coupling is still the Wild West of renewable energy applications"
>
> R.Ray Walters
> CTO, Solarray, Inc
> Nabcep Certified PV Installer,
> Licensed Master Electrician
> Solar Design Engineer
> 303 505-8760
> On 7/30/2013 11:37 PM, Kelly Keilwitz, Whidbey Sun & Wind wrote:
>> Ray,
>> The battery-based inverter in an AC-coupled system should not be
>> grid-interactive. The grid passes through the BB inverter to the
>> grid-direct inverter(s). The BB inverter is there to create a stable
>> grid-like signal for the grid-direct inverters when the grid is not
>> present, and to manage the batteries. Thus, the pass-through AC
>> capability of the BB inverters normally (there is a complicated
>> work-around) must be able to handle all of the PV AC output, when
>> loads are low.
>> You probably are aware, but to make it clear in this thread: the
>> system needs to have some method to protect the batteries from
>> overcharging, as a result of the grid-direct inverter output when the
>> grid is down and loads can't use all the solar energy available. With
>> the Sunny Islands it's done by a signal that reduces output from the
>> Sunny Boys without disconnecting them. With Outback and others it's
>> done with a installer-designed relay that disconnects the grid-direct
>> inverter when the battery voltage gets to a set point. We haven't
>> done an AC-coupled system with the Radian, yet. Sounds like the
>> remote controlled breaker is Outback's approved and listed way to do
>> it. About time.
>>
>> -Kelly
>>
>> Kelly Keilwitz, P.E.
>> Principal
>> Whidbey Sun & Wind
>> Renewable Energy Systems
>> NABCEP PV Installation Professional
>> WA Electrical Administrator
>> kelly at whidbeysunwind.com <mailto:kelly at whidbeysunwind.com>
>> PH & FAX: 360.678.7131
>>
>>
>>
>> On Jul 30, 2013, at 4:23 PM, Ray Walters <ray at solarray.com
>> <mailto:ray at solarray.com>> wrote:
>>
>>> The Outback rep got me some good info, and I'm liking the Radian
>>> with the Remote controlled breaker to control the GT inverter when
>>> the grid is out. I've heard of quite a few problems related to the
>>> Sunny Island frequency controlled system.
>>> My question is can off grid inverters like the Magnum be AC coupled?
>>> I'm trying to get the price down, and still handle the 240 vac
>>> input from the GT inverter.
>>> I penciled out the Radian and I was topping $10k before
>>> installation. This customer is hoping for a solution under $10k,
>>> and closer to $5k if possible. I think an elegant lower cost
>>> solution for Grid tie with battery back up is in order. A Radian Lite?
>>> For backup, it could even be mod sine, as it wouldn't be much worse
>>> than generator power or the average UPS setup.
>>>
>>>
>>> R.Ray Walters
>>> CTO, Solarray, Inc
>>> Nabcep Certified PV Installer,
>>> Licensed Master Electrician
>>> Solar Design Engineer
>>> 303 505-8760
>>>
>>> On 7/30/2013 2:59 PM, Ray Walters wrote:
>>>> Hi All;
>>>>
>>>> I know AC coupled systems have been covered before, but I have a
>>>> new issue: positive grounding. A customer with an existing 8kw
>>>> Sunpower system wants to add backup. He was put off by the high
>>>> cost the Sunny Island, so I was steering him towards a single
>>>> Outback VFX coupled to just one of his 3 inverters. The issue is
>>>> how will the VFX work with positive grounded inverters. I'm
>>>> assuming that since the two inverters will only be connected by AC,
>>>> that the positive vs negative grounding of their separate DC
>>>> systems will not matter. Any experience with this particular
>>>> scenario: Sunpower system AC coupled to an Outback?
>>>> Also, would I even need a GVFX, since the inverter would only be
>>>> used during outages (which might allow a generator to be used
>>>> later as well) A VFX should still AC couple to the GT inverter
>>>> during an outage, right?
>>>>
>>>> Thanks as always,
>>>>
>>>
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