Solar Quote Oahu Hawaii

[bcroe]

Power management problem

The only way we have found a good resolution is moving the
house to off grid, and using a transfer switch to isolate from Heco, and use the off
grid system as the primary source, Heco as the secondary source.

Using a transfer switch twice a day sounds difficult. Can this be done without
batteries, or at least with very few batteries? Is it all automatic, equipment for
this sort of service available? Inverters on all the time waste a lot.

Its a huge power management problem. Without a grid tie, a LOT of PV energy
may not get utilized when available. I am imagining your whole load system
being designed around the time of day. Perhaps the primary problem is getting
through each night; here its a matter of getting through winter. Bruce Roe

[boostinsteve]

Using a transfer switch twice a day sounds difficult. Can this be done without
batteries, or at least with very few batteries? Is it all automatic, equipment for
this sort of service available? Inverters on all the time waste a lot.

Its a huge power management problem. Without a grid tie, a LOT of PV energy
may not get utilized when available. I am imagining your whole load system
being designed around the time of day. Perhaps the primary problem is getting
through each night; here its a matter of getting through winter. Bruce Roe

There is no way else to do it currently for my area. They will not issue permits or interconnect agreements. We can start talking about the efficiency of the systems all day long, but the utility has a real problem with all the extra generation occurring.

The only time that the transfer switch would need to operate is when the battery falls below a threshold. Just like using a gen autostart to recharge the batteries.

[Naptown]

Not having thought all the way through this it is most likely possible.
You would need to use something like a Xantrex XW series inverter set to load shaving (not in sell mode)
The only issue I haven't worked around is keeping the battery sensor from reading the higher voltage when it is in charge mode and keeping it off till the batteries reach at least absorb state.
Opportunity loads could be introduced also like the diversion on a wind system to preheat water when system is producing more than is being used.
It is going to be expensive no matter how you look at it.

[shaka]

Just had another estimate today with a guy that matched an LG270 with an Enphase M215. The PTC for LG270 is 245.1w which is well over the 225w max that I've read others clip at with this inverter. Am I missing something here or is this a bad combination?

[silversaver]

Just had another estimate today with a guy that matched an LG270 with an Enphase M215. The PTC for LG270 is 245.1w which is well over the 225w max that I've read others clip at with this inverter. Am I missing something here or is this a bad combination?

It might clips depends on your orientation, pitch or shade.

[bcroe]

Power management problem

There is no way else to do it currently for my area. They will not
issue permits or interconnect agreements. We can start talking about the efficiency of the
systems all day long, but the utility has a real problem with all the extra generation occurring.

The only time that the transfer switch would need to operate is when the battery falls below a
threshold. Just like using a gen autostart to recharge the batteries.

So I think you are saying, you are going for an essentially off grid system. If all your energy
flows in and out of batteries, the cost is going to be even more than your electric rate. If a lot
of PV power will flow directly to the load, the battery costs are reduced, but your power
management problem balloons. I was hoping to see details of equipment, loads, numbers.

You could simply use a battery charger to maintain a minimum level, no need to transfer.
Bruce Roe

[shaka]

In reality, they can't stop you from going off grid. HECO tried a couple years ago to keep people from doing just that, but they failed. Not sure about Ewan, but they already stopped issuing permits for Waianae for grid tie application PV.

Did you still need HECO approval to use the batteries? One of the companies I got an estimate from said HECO still needs to approve your battery backup.

[wwu123]

Just had another estimate today with a guy that matched an LG270 with an Enphase M215. The PTC for LG270 is 245.1w which is well over the 225w max that I've read others clip at with this inverter. Am I missing something here or is this a bad combination?

My crude understanding is the PTC is only achieved under the test conditions but also when the sun is perfectly perpendicular to the panel's flat plane (i.e. "straight above"). 225/245 = 0.92 which means you'd only clip if you came within 23 degrees of the panel's vertical axis. So if for some reason you could only mount your panels facing straight up on a flat roof, at your latitude 21 deg you'd only be clipping for a few hours on a few days in June. Or if you were tilted but on a north, west, or east roof, you might not come within 23 deg to clip significant through the year.

But if you're south-facing tilted towards your optimum of around 21 degrees, it seems you'd be clipping during peak generating hours mid-day for significant periods of the year.

[russ]

Did you still need HECO approval to use the batteries? One of the companies I got an estimate from said HECO still needs to approve your battery backup.

Battery backup means grid tie

[shaka]

Ok, I limited my choices to the following systems below. I plan on having Vendor 1 to install my solar hot water system. Another thing is they need 1K deposit to be put in the HECO NEM queue. Vendor 2 has been pretty responsive after we met. No deposit needed to be added to the NEM queue. Also my neighbor an installer with the company.

Only difference between the Systems 1 & 2 for Vendor 2 are the inverters.

Your advice is greatly appreciated!

Vendor 1

System 1
8.37kW
(31) Solarworld 270
(31) Enphase M250 Microinverters
Price Per Watt - $4.00
Total Price - $33,480.00
Price after Federal & State credits - $13,718.00

System 2
8.25kW
(30) Solarworld 275
(31) Enphase M250 Microinverters
Price Per Watt - $4.00
Total Price - $33,000.00
Price after Federal & State credits - $13,550.00

Vendor 2

System 1
7.95kW
(30) LG 265
(2) SolarEdge 3800
Price Per Watt - $4.01
Total Price - $31,895.06
Price after Federal & State credits - $11,902.56

System 2
7.95kW
(30) LG 265
(30) Enphase M250
Price Per Watt - $4.04
Total Price - $32,128.34
Price after Federal & State credits - $13,317.20