Hybrid Inverter

Work Doc

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Grid Tie Costs

• $800 for 6kW grid tie [1].
• 10kW grid tie is $1400 [2]

But That is Ridiculous

If the grid goes down, so does your solar power! That's not acceptable for critical operations during the day. There is a complex solution: essentially set up another off-grid inverter system that powers your on-grid inverter without grid. Ridiculous and expensive. [3] and [4]

Solution - OSE Hybrid Inverter System. No batteries, up when sun is up, no grid needed.

Disadvantage: power is available only when sun is out.

Advantage: no batteries needed, switch back to grid as needed.

Key: have enough PV to run everything that you need, and to shut off loads via a smart controller. Using cheapo 63A automatic transfer switches with Arduino will work. Get out the CNC circuit mill and build circuits as needed.

Hybrid Inverters

• Have a small battery bank and can operate without grid. [5]
• Not clear how the solar mode operates - does it put out the full power of the panels?
• $1600 - hybrid 6kW solar inverter (450VDC input max)- does it work at full PV output without batteries? Does it work at full PV output when grid is down, and sun is available, on a small battery? [6]? Does it work at full PV output when grid is down and there is no battery? If this thing can work full PV output - with grid signal (not using grid) - then this meets our needs. Or, does it switch 100% to grid whenever it's overloaded
  • On-grid - it's not pass-through - max grid power it puts through is 6kW - [7].
    • This would be impractical for most homes if they are not energy-efficient smart homes. Does not leave chance of higher power use, such as heavy power tools
  • Hybrid inverter allows battery-only, grid-only, and solar only modes, but limit in all modes is 6kW:
• This inverter appears to be stackable, but requires grid + PV connections to make this happen - up to 9 inverters, 54kW. Each inverter connects to the same battery. For single unit use- battery can be avoided all together. This means that small buffer battery should also work for up to 54kW?

• There is a cheaper $1350 model, not split phase, but 2-stackable to split phase 240, and 3-stackable to 3 phase, and stackable up to 6 units - but input voltage is a bit lower at 250V [8]
• There are cheapo hybrid inverters on Ebay - $700 6kW - not stackable? Are they also PV-only capable without battery? [9]
• $700 6.2kW - no battery capable? Yes. Stackable?. Only 230 AC not split phase? [10]

Mode of Interest: As Much Solar as Possible, Tapping Grid Only to Top Off What is Needed

• This is called Inner Limiter, or Double Conversion. Inner limiter - say 3kW solar + 1 kW grid. Double conversion - same, but inverter transforms grid to DC first, before sending it out as AC. [https://diysolarforum.com/threads/hybrid-inverter-output-priority.25954/
• The Sungold SUB mode appears to top off solar with grid [11] - Dear customer, in the SUB mode, solar energy provide power to the loads as first priority. If solar energy is not sufficient to power all connected loads, Utility energy will supply power to the loads at the same time.
• The single phase only (need 2) - is UL listed [12]. Price out of range because need 2.
• This shows SUB mode work on Voltronic Axpert 1000 1 kVA VM MPPT 12V - bat/grid only tops off [13]. It implies SUB on Growatt
• SBU and SUB, and SOLar modes should work - they all top off PV as necessary, don't cut the PV off by switching fully to another source. [14]
• SPH series Growatt inverter seems to work properly, topping off solar with grid as needed [15]. Appear to be single, not split phase.
• Hybrid split phase - starts at $3k for 7 kW [16]
• Grid priority inverter - split phase 6kW but not clear if it does solar only [17]
• Magarevo - UL 1741, split phase [18]

Shopping 2023

• Opsolar - this one appears to be hybrid for batteryless, but it's only 120V [19]

Shopping 2022

• Sungold split phase stackable 6kW $1365 [20]. Manual - [21]
• Sungold split phase 6kW [22]
• Has SUB and UL1741, $1249, 6.5kW, 500VDC input. But only 120VAC output. [23]. Manual [24]. 5 kW transformer $170. [25]. QA here says it's single phase [26]
• Has SUB - manual POW-HVM5.5K-48V. 450VDC input. [27]. PowMr $700 hybrid but single phase 230V [28]
• No need for UL listed when not feeding power to grid? Depends on jurisdiction?
• 24V 110AC nonstackable, 2.4 kW $300. Seems to work without bats (bats too low - meaning not using bats, or disconnected bats. If it requires bats, a placeholder low voltage source may be used?). [29]. Looks like it has SUB mode [30]. No, looks like SBU see p 17 [31]. SBU appears to not allow any solar when solar is insufficient, while SUB allows partial solar. [32].
• UL1741 8kW $1800- [33]
• Listed 2.4 kW stackabe, $2k [34]
• Sungold 10kW UL listed $2245. 48VDC, and 155VDC max array. [35]
• 5.5kW, max input 500VDC - $600, doesn't appear to be split phase. [36]
• Sungold 12kW UL split phase, 48V, max input 450VDC [37]
• Use hardieboard to handle fire risks for PV cabinet? Video at [38]
• Split phase 6kW ETL to UL1741 $2k [39]
• Sungold $1350 UL 120V - [40]

Split Phase vs Single Phase

• Conversion of Power Jack to split phase - [41]

Legal

• This article is nonsense: [42] - the special case of hybrid inverters (SUB, SBU priority) are not covered, nor is a hybrid hybrid system with transfer switch, allowing full grid power, and grid-augmented off-grid power - without grid feedback. That is the realm of operation of the OSE system. Anything else is a sellout: not being able to use PV when there is light, when the grid goes down.
• UL1741 appears to cover standalone and grid-interactive systems, but is hybrid SUB mode considered to be standalone or grid-interactive? Hybrid is not standalone, and hybrid is not grid-interactive - it is a mix. Thus, do hybrid inverters need to be UL1741 listed? [43]. Is grid-interactive defined as feedback to grid? Or is feedback to grid considered parallel operation?

Communications

Hi,

Thank you for talking.

We would like to install this solar (PV) system on new construction. Please take a look at 2 slides here:

https://docs.google.com/presentation/d/1jRwADE9tkk9A0Y71_JJ2KlpxmCiU2fiXvOWPrgnApOo/edit#slide=id.g136ca38b9a6_1_0

Would you be able to help us implement the design consistent with the stated design requirement? The layout is on the second slide.

Links

• Sungold 6kW Hybrid Inverter
• Sungold 8kW Hybrid Inverter.