Hybrid solar with grid tie on Hawaii?

[BenHawaii]

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

[robbyg]

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.

[PVAndy]

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

Andy

[Steeler.Fan]

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.

[khanh dam]

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.

[BenHawaii]

david poz growatt - YouTube
watch above videos. if you are paying $.34/w you can diy your own battery and soalr set up and it will pay for itself in several years. dont use agm batteries lifepo4 is chepaer in long run.

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.

[BenHawaii]

I thought hawaii was a no brainer for solar hot water panels? maybe being on the rainyside means less sunshine? but I'd switch to solar insteads of propane for water heating

Yes, it's in the plan for future. A few people I know had solar hot water heaters installed on their roofs. But at a cost of $ 8,000. I know this isn't the only solution. We are only spending $40 a month for propane for hot water, stove, and dryer.

[khanh dam]

I thought hawaii was a no brainer for solar hot water panels? maybe being on the rainyside means less sunshine? but I'd switch to solar insteads of propane for water heating

[khanh dam]

david poz growatt - YouTube
watch above videos. if you are paying $.34/w you can diy your own battery and soalr set up and it will pay for itself in several years. dont use agm batteries lifepo4 is chepaer in long run.

[BenHawaii]

If you need 8.5kWh for the evening and night, given you may also need some for early morning, you probably need at least 10kWh of battery or more like one Powerwall for 13kWh I believe.
Then you need to answer the other questions about outage duration, season, period, weather.... so you can get an idea of what is the worst case scenario for solar production on days of outage.

You also to evaluate minimum daytime needs, for outages lasting longer than an evening like a day or more if they occur.
IF the outage lasts over a day, and that happens top be days with heavy clouds, solar production may not be enough to recharge the battery and satisfy daytime needs.



Are you saying you would want to be off grid all the time except when you need more power that solar/battery can provide?
Because I don't know that there are any inverters that can manage that automatically.

The usual scenario is that you are tied to the grid all the time. then, assuming your inverter has a self supply mode, in that mode, it will use Solar and battery before using the grid. But this has a drawback, is that you could be hit by an outage after having depleted the battery.
To alleviate that, you can define a minimum reserve to keep in the battery while in self supply mode, and that means you strike a compromise on using the grid more often (using less battery), in order to keep more reserve in the battery in case of an outage.

Yes, the "usual scenario" of remaining on grid and inverter with self supply mode (solar and battery used before switching over to grid). For this investment to have value the goal would be to reduce grid bill as much as possible, while maintaining battery longevity. If there was an outage we also have a generator and would adjust power usage to shift as much as possible to daylight (fingers crossed for sunny days), and minimal evening usage.

One way I am looking at this is that if we save $2,000 a year in grid bills, use AGM batteries with most lasting 7 years, we would look at the system "paying for itself in about 7-9 years or so. Although, there is added value in having backup and self sufficiency and protection from rate increases.

Thank you
Ben

[Mike90250]

Don't forget that a hurricane may blow all your carefully planned panels away, or you may have clouds for a day or two afterwards.

[scrambler]

Apologies, will be more careful with terminology. My inventory shows that in the evening I might have 1,700 watts of lights, appliances, TV, phone chargers, fans on for 5-6 hours. Hope this is a correct way to communicate this.
Ben

If you need 8.5kWh for the evening and night, given you may also need some for early morning, you probably need at least 10kWh of battery or more like one Powerwall for 13kWh I believe.
Then you need to answer the other questions about outage duration, season, period, weather.... so you can get an idea of what is the worst case scenario for solar production on days of outage.

You also to evaluate minimum daytime needs, for outages lasting longer than an evening like a day or more if they occur.
IF the outage lasts over a day, and that happens top be days with heavy clouds, solar production may not be enough to recharge the battery and satisfy daytime needs.

Wanting to install a grid tied hybrid system, with inverter switching over to grid if power needs require it.
Ben

Are you saying you would want to be off grid all the time except when you need more power that solar/battery can provide?
Because I don't know that there are any inverters that can manage that automatically.

The usual scenario is that you are tied to the grid all the time. then, assuming your inverter has a self supply mode, in that mode, it will use Solar and battery before using the grid. But this has a drawback, is that you could be hit by an outage after having depleted the battery.
To alleviate that, you can define a minimum reserve to keep in the battery while in self supply mode, and that means you strike a compromise on using the grid more often (using less battery), in order to keep more reserve in the battery in case of an outage.

[Ampster]

My brother reports that HECO woke up to the fact that they were facing significant grid departure and may have eased up on the stonewalling that they were doing historically. That may bode well for your application for grid tie.

Reportedly the biggest problem is that there is so much solar on different parts of the islands that some substations are seeing reverse flow during the middle part of the day.

[BenHawaii]

I assume you mean 8.5kWh (not kW) of energy during a single evening night period?
If so, that is a lot, wonder what you are running at night beside fridge, lamp and TV...

Are you thinking of an OFF grid system or a Grid Tied system?

Apologies, will be more careful with terminology. My inventory shows that in the evening I might have 1,700 watts of lights, appliances, TV, phone chargers, fans on for 5-6 hours. Hope this is a correct way to communicate this. Wanting to install a grid tied hybrid system, with inverter switching over to grid if power needs require it.

Thanks
Ben

[scrambler]

Evening usage is 8.5 Kw (which includes fridge and chest freezer that don't run constantly), with inverter that will auto switch over to grid if batteries can not supply power needs.

I assume you mean 8.5kWh (not kW) of energy during a single evening night period?
If so, that is a lot, wonder what you are running at night beside fridge, lamp and TV...

Are you thinking of an OFF grid system or a Grid Tied system?