Recommendations for an expandable hybrid system controller

[Rhys79]

I'm looking for recommendations for a system controller for US 120/240v split phase service. Fairly specific needs, and not out of the question to design my own if needs require. I have the knowledge, experience, and tools to do so, if necessary, but would prefer something off the shelf so I don't have to fight with the local code officer....

I live in an area with relatively frequent and sometimes prolonged grid outages. As in 3-5 times a year on average, and sometimes upwards of a week without grid power. Historically, a portable generator had been used (5KW) with extension cords to power critical items in the house. Since moving in, I have added a proper 50A rated generator inlet, and am in the process of adding a natural gas hookup, converting the gen set to run on natural gas, and building a control system so gas supply and gen set can be managed without going outside. Eventually, as funds allow, I'll upgrade to a proper standby generator, but I'd like to get started on a solar system first.

I'd like to start small, as funding is tight. The house needs a LOT of work, it's only tried to kill us three times in the last few months. Just finished overhauling the meter pan and service panel as the pan tried to catch the house on fire ?. Expensive and unexpected, but everything is freshly wired with brand new 200A service equipment and feeds.

What I would like suggestions on is a relatively inexpensive hybrid solar grid-interactive battery storage generator augmented system controller. I intend to use microinverters on the panels, as I want to be able to build the system out starting with one or two panels, and add panels as I can afford them, up to the point the solar and batteries can handle the full energy needs of the house with a net export to the grid. The controller will need to sync the solar/battery system to the grid for normal grid tie use, but also handle transitioning to off-grid when the power is out. Off-grid operation would be solar/battery first, then auto-switch to gen set as needed to power the house and charge the batteries when solar is unavailable. Once the grid is back up, the system would need to automatically bring the system back to solar/battery, shut down the gen set if it is running, resync to the grid, and go back into grid-tie net export mode.

As a bonus, would be even better if the system can also handle the possible addition of a wind turbine if I can get it approved by the city. Additional bonus if the controller can handle coordinating and phase locking multiple gen sets. I can pick up used 5kw electric start gen sets all day for $200ish around here, whereas a single 20+kw standby generator is north of $5k. I know some of that control would be on me to build, as there's nothing I can find off the shelf for that, but it is doable.

I know this is pretty far off the beaten path, and there isn't likely anything commercially available that will do even half of what I want, but any information or resources would be much appreciated!

 

[MisterSandals]

I intend to use microinverters on the panels, as I want to be able to build the system out starting with one or two panels, and add panels as I can afford them, up to the point the solar and batteries can handle the full energy needs of the house with a net export to the grid.

Starting with micro inverters is a good first step that is scaleable. It likely will not provide power when power is out as there are only a couple that do that (anaphase comes to mind but are not cheap).

Adding a controller that creates a micro grid when power is out is fairly rare too unless you have batteries. This will be a very expensive part of your build. I expect more and more products to become available and at better prices (because of competition) in the next couple years.

Regarding wind, unless you live in a wind tunnel, is rarely anywhere close to practical.

What is your budget to start with and when do you expect to have power in grid down situations?

 

[Rhys79]

I've noticed most of the micro inverters only seem to be meant for grid tied. I figured they'd be less expensive to get started, but if stackable central inverters are a better option for my use case, that's acceptable too.

I expected to need batteries, but I'm ok with just enough battery capacity to auto-transfer to micro-grid when the power goes out and keep things running long enough for the generator to be brought online.

Wind was an optional throw in, I haven't done any analysis on wind patterns at the house yet to determine if it's feasible or not. I live in the northern Midwest US. Wind is generally steady and available at or above 10mph, but I live in a valley between two hills, so wind may not be an option at my specific location. There are a LOT of wind farms around here lol.

Budget is the minimum I can spend at any given time. Hence the scalability need. I typically will only have a few hundred dollars at any given time to put into components, and would build the system in pieces over time. I have no interest in financing a large system up front and making payments, and would rather not have to try to save a large sum to spend all at once. The idea is to start small to initially get things setup in a manner that will cover power outages and reduce the electric bill, and slowly scale the system to eventually reach a net export.

I have been doing research on inverters and control systems as I have time, and I've found a few inverters that are small (1kw-5kw), inexpensive (well under $1000), stackable up to at least 20kw total output, support batteries as well as grid/generator input, and seem to be able to transition back and forth between grid-tied and island mode. They are mostly chinese crap on Amazon though, so no idea as to how robust or well supported they are.

I honestly don't get why there seems to be so little interest in a system like this. It what makes the most sense to me, especially with how rapidly the US power grid is going downhill. The grid works great when it works, but problems are becoming more frequent, and most power companies are allowing some level of grid-tie power export, at least up to a net zero bill if not net export.

 

[MisterSandals]

I honestly don't get why there seems to be so little interest in a system like this.

I think there is a LOT of interest in systems like this. I waited a couple years to find a top tier product that does "most" of that. I think that there is a big but sloooow push towards developing such self consumption systems.

I cannot imagine how one would work to this end with a couple hundred bucks at a time. I'd look at the smart micro inverters (Enphase comes to mind). I think they can be put to use one at a time for instantaneous use or sellback. Then with the Enphase main unit, can create a local grid (without batteries?) with sufficient number of micro inverters and sun. And Enphase also makes (proprietary?) batteries to complete the system.

Sorry, thats all i have.

 

[Rhys79]

I've looked at the Enphase equipment. Once you piece everything together, it actually suits most of my requirements. However, the price is quite exorbitant, and it misses on a couple of items. Primarily, the need for a massive 20KW+ standby generator for it to work in backup power micro-grid mode. Also misses on the $5K+ for the controller system. I'd need to be able to drop $5k-$10K at a time to piece that system together beyond the grid-tied solar panels with microinverters.

I'm finding a bunch of 3K-5K stackable inverters for around $400-$500 each, that have most of the functionality I want with the simple addition of an ATS to handle powering up the gen set(s) when the grid goes down and switching between gen/grid mains. However, they seem to all be 230v single phase for the civilized world. As soon as you add in the Cro-Magnon requirement for the wonky "good old US of A" 240v split phase system, they jump to 10KW+ inverters at $1200+ ?

Very frustrating. I'm actually beginning to seriously consider designing my own inverters based on one of the various inverter controller boards I have been seeing lol

**edit** Have I mentioned the absolute insanity of the US's refusal to follow the rest of the worlds standards, especially when it comes to anything engineering related, frustrates the ever living hell out of me ?