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Hybrid solar with grid tie on Hawaii?

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  • #16
    Originally posted by BenHawaii View Post

    This is worth a look --good videos!. One problem could be the dreaded Amazon message "This item cannot be shipped to your selected delivery location. Please choose a different delivery location." which we receive for any lithium batteries now, but not products with a lithium battery, like lawn trimmers etc.
    buy the batteries from china and wire them up yourself. Amazon is a joke. get some 272a or 280a lifepo4's you'll need 16 for a 48v system.

    lifepo4 china lishen - YouTube

    you can diy a hot water heater for a few hundred bucks. Black HPDE PIPE IN A coil would probablay work for most of the year in hawaii.


    • #17
      Now that HI has mandated solar thermal for new construction, it has become very expensive. I was quoted $17k for a two panel solar thermal system on Kohala Coast.

      Rainfall and cloud cover vary widely on the Big Island, especially around Hilo. You might want to identify a neighbor with solar and compare his average annual production with what PVWatts predicts.

      Another consideration would be to switch to TOU rates, load shift as much as you can to 9a-5p ($0.2/kWh cheaper than residential rate), load battery(s) from 9-5, run off battery from 5p-9a. I don't think PW2 can be loaded from grid. LG Chem batteries can but they would need a hybrid inverter.


      • #18
        Much of Hawaii is Zero Export for Grid Tied Systems. Check with your utility. If that is the case, batteries and self consumption make the most sense. Consider a Generac system



        • #19
          To the OP, do a lot of research before selecting a Growatt Hybrid Inverter.
          There is a 4 page thread on another forum with guys saying that the Growatt is having an issue with maintaining PV power in the day after it has charged the batteries. It seems like once the batteries are charged, for eg by by 2pm, it then switches off the PV and runs on battery power alone for hours until the batteries discharge enough that the PV is switched back on. Seems like a lot of out reach has been made to Growatt and they seem to indicate that it's a problem if you use Lithium Iron Phosphate batteries that are not Growatt branded and do not have closed loop BMS communication with their inverter.
          I am not saying anything is wrong with Growatt but it would be nice to see these guys get some sort of resolution to their problem or add support for more battery packs to their closed loop system.
          Last edited by robbyg; 06-06-2021, 09:09 PM.


          • #20
            Thank you for the suggestions KhanhDam and RobbyG. I’ve spent the past 5 months further educating myself and doing more research on our needs for a hybrid system. I now have a better technical understanding of off grid/hybrid solar technology and our usage. Based on KillaWatt plug in meter, the Energy Star appliances we invested in truly are energy saving. While finding that some older devices, like my 10+ year old Apple Cinema Display, is drawing about 100 watts.

            Clarifying my original post, power outages are not a regular issue. In fact, I can’t even recall the last time the grid power was out. We have a generator just in case. Goals, in order of priority, reduce grid energy bill, reduce greenhouse gas emissions, minimize effects of fuel price increases since 85% of our power plant petroleum is refined in continental U.S. then has to be transported to Hawai’i.

            A handyperson we hired for some carpentry work,has also installed off grid solar systems, using a Growatt inverter and LifePO4 batteries that they imported from China. Handyperson said 16 - 3.2V Grade A LifePO4 cells will cost $3,500 (cell cost + shipping+ port fees +customs) and a loooong wait. Plus, still need to build LifePO4 battery bank adding BMS etc. A couple of Growatt inverter/charge controllers wired together is an initial cost saving, but an Outback hybrid inverter appears to have more hybrid auto power management and seems to be more reliable. Handyperson also tends to show up when they have time, so who knows when they could install and help with problems. There are a couple of nearby established off grid/Hybrid system installers that use Outback equipment and they (installers) have good reputations and fair pricing.

            Our current electric bill shows 17 Kwh average daily use. This coincides with energy audit of AC devices. Non daylight estimated use over 12 hours is 9,000 watts. Full load wattage is 8,800, but with two people living in home all devices on at the same time scenario very unlikely. Insolation map shows 4.2 for 10 months of year and 3.8 for Dec/Jan. Planning on 7,000 watt solar array. Probably more than required. However, we have periods of 4-5 rainy/cloudy days with a couple of hours of clearing and sun on these days. A 10Kwh useable power AGM battery bank is about $3,500 and readily available on island.

            Would like to get some feedback on current needs, equipment and availability. Mahalo