Help with PV system for the USVI

[Kachael]

Hello from a long time reader of these forums, I'm planning to move the USVI in a few months to break ground on a retirement home.

After several visits spanning several years to plan the construction and reading these forums I have a couple of questions.

Previously there was a cap on new grid tie installations, I understand that new connections are being allowed again since 2016.

Electricity is expensive running about .32 to .34 KWH from the VI power company WAPA. Second a lot of home do have solar installations, but almost all are grid tied. WAPA is not the most reliable power supplier on a good day either, normal wind or rain storms will interrupt the power on the island. Current sun hours run about 5.5 to 6 hours per day.

Some island solar installations have generators with grid disconnects, several friends with solar have been on generators since Maria hit the islands in September 2017 until just a few weeks ago.

Currently this is what I have come up with so far, daily home power usage would consist of two refrigerators, cistern pump and pool pump as the major loads. smaller loads would be the LED TV's and lighting.
Additional loads would be four 5000 to 10000 BTU a/c split units.

Plan the electrical service during the construction to allow the installation of solar grid tie, battery back up and generator back up? rather then adding later as needed?
Size the battery and generator to the electrical loads less the a/c split units, taking those off line when the power is interrupted

Hook up to the grid and watch the actual usage over several months and size the PV system at that time?
Current roof design allows for 20 standard panels minimum.

Would prefer a bullet proof system that is easy to service and upgrade the electronics. Panels would need to be wind and storm rated for HVHZ. 150 MPH

Would a "Power wall" type battery installation be a better choice for energy storage if the grid is down for several days to weeks rather than running the generator all the time?

Just thinking of the cost per run hour "Power wall" vs generator when the grid is down for days to weeks.

If the forum could help with a rough idea for a PV system and then I can get some quotes from the local contractors to see what they are recommending for panels and inverters.




Thanks for any thoughts,

[Mike90250]

Sadly, i think most panels top out at about 100 mph wind. You also have flying debris, 1 lawn chair at 60 mph will clean all the panels off your roof

Maybe members in Florida, that are faced with the wind problem. will chime in.

For both Grid Tie and Battery (off gird or grid failure) you would want the trade calls a Hybrid Inverter, like the Schneider Conext XW-6548

https://solar.schneider-electric.com/product/conext-xw-na-solar-inverter/

datasheet : https://41j5tc3akbrn3uezx5av0jj1bgm-...-Datasheet.pdf (yes it's a goofy link, but it's real)
You would pair it with the Combox for control & monigtoring, and the 600v solar charge controller to get from the panels to the battery

https://solar.schneider-electric.com/product/conext-combox/

https://solar.schneider-electric.com/product/conext-mppt-80-600/

https://solar.schneider-electric.com/product/conext-mppt-60-150/

I like the Midnight Solar E-Panel better than the Schneider epanel

[Kachael]

Hello, Mike thanks for the reply, great links for the Schneider equipment.

As far as the PV mounting, the house is 150 feet below the mountain top with the south facing roof against the mountain and the house is set back 1/4 mile and 120' feet above sea level. so the exposure is greatly reduced from direct wind loads.

We are lucky as there are only 5 existing homes in the subdivision and there are protected lands to the east of the subdivision.

I would like to get some feedback from anyone in Florida on the types of rail mounting that are used for panel mounting.

Any ideas on using one of the "Powerwall" battery back ups to allow use of the PV system if the grid is going to be down for weeks or months?

Thanks,
Chris

[Mike90250]

Instead of an expensive powerwall, I'd suggest the hybrid inverter and 8 Golf Cart batteries for your emergency backup. That would be about 9,600wh of storage, 7,000 usable in a annual emergency. Run time would depend on the loads, it should run a single, efficient fridge for about 4 days of no sunlight. Add some lighting, radio, computer, fan, you would get 6-8 hours of power from it, The powerwall is rated 10,000wh of storage, just a little bit more, but a lot more $$

[Kachael]

Hello Mike,

I will need to check into the golf cart battery set up, at least from what iv'e read the lead acid batteries are more tolerant to abuse than the Power wall type systems. Depending on battery manufacture there is a wide range of prices and specifications on these items, so i will need to read up on these subject.
Is there any preferred battery voltage and amp hour rating that would be best?

If I would suffer and any storm damage to the PV panels and would need to replace them that cost isn't too bad considering that most of the system cost is in the electronics and the batteries. any those items are protected from the weather.

Would it be easier to have the electronics prewired before installation and installed as a "plug and play" or just mount and wire on site?

When buying the panels is it best just to shop using total watts and price per panel and not just by brands?

Thanks,
Chris

[Mike90250]

Well, you have a big job ahead, to educate yourself enough to not get scammed.
Panels, yes, they are basically now, a commodity. Many brand names will fail in 5 years (company fails, Panels still work OK), only a few, that are one product of many, from a large company (like Panasonic) will very likely be around for warranty replacement.
There is a book Solar Power your home for Dummies, that will cover a lot of the basics you need to know.

[carsantini]

Kachael I live in Puerto Rico. Maria impacted the Island with 180 mph sustain winds and 210 wind gusts. I have researched hundreds of modules available in the marked today. So far, the only panels in the market, including the ones for commercial or utility scale, that can withstand loads more than 5000pa (201 mph) are the LG NeOn R panels rated @ 6000 Pa (221 mph) front load, and a rear load up to 5400 Pa (209.80 mph). You wont find better panels that can endure such a higher front load that this ones, at least on paper. They are expensive thou. Don't forget the appropriate racking needs to be considered too. Im considering galvanized standard struts for my installation.

[Mike90250]

Be aware that wind blown debris, lawn chairs, tree branches, stuff like that, will likely damage panels before the raw wind damages them, so absolute wind specs can be misleading. But if debris is not a hazard in your area, then wind load (and racking and attachments to roof) becomes the driving factor.

[carsantini]

Thank u for pointing that out. My location is a penthouse, the 10th floor of a building. No issues with debris.

[Kachael]

Carsantini, good morning, Yes I was wondering about the experiences of the Caribbean solar owners with the hurricane force winds in this region..

I'm not sure how many systems were installed before Hugo in 1989, but just looking at the videos from Maria and Irma it seems that it all depended on your location and PV mounting system, roof or ground mount if you sustained damage or not during the hurricane.

I have to balance out the cost of going with a LG panel or just going with the cheaper cost per watt panel and bank the cost difference for the once in 20 year storm that would damage the PV panels.

It seems that the prices in the electronics have basically stayed flat compared to the PV panels, which have been slowly been gaining more watts per panel and lower costs per watt.

As for roof mounts I was leaning towards aluminum, coated steel in the tropics is a problem with the salt air as the coating is sacrificial in nature compered to the aluminum.
I wish I could get stainless steel

Chris

[carsantini]

Kachael agree, but beware of aluminum, some aluminum systems also failed. Check out this article from Sollega https://goo.gl/ar1bYs

Screen Shot 2018-03-07 at 6.49.00 AM.png

[bcroe]

Stainless Steel is available, but extremely expensive. I have been using 6061 alloy aluminum and
18-8 SS bolts which show absolutely no corrosion after 5 years. But your sea air may be more
corrosive than mine.

Survival, I suggest a really strong mount with cheap panels. After a max storm, just put new panels
on the built to survive mount, that is the plan here. Bruce Roe