Grid tied solar system.

[posplayr]

This is the PVwatts output. Based on a 50% probability I get 12 and 10.5 hours of 3K watt SPS daily for June and July respectively. We have had relatively cloudy monsoonal weather for most of July.

[posplayr]

I would not rely on getting the full 3kw from SPS from 10AM to 6PM. Maybe if there are no clouds and it is Summer you might get that for 5 to 6 hours but not 8.

Well that is the stressing case, however you overlooked that this is Tucson and I would have a tracker with 45 degree tilt capability.

Further, perhaps the diagrams are confusing, but there is no reliance on the SPS. The Gen set provides for a flexible switch over capability.

[bcroe]

I would not rely on getting the full 3kw from SPS from 10AM to 6PM. Maybe if there are no clouds and it is Summer you might get that for 5 to 6 hours but not 8.

Assuming you work out the other issues, I would expect your solar power availability to be centered around
solar noon. Only a couple hours are going to give max power. Since you have gone to so much trouble
already, you could widen that a lot by adding some east facing and west facing solar panels. This is the
power curve that provides here. Bruce Roe

[SunEagle]

This is what I have been thinking about for a relatively low cost contingency stay alive system for 30-45 days.

The idea if for a Grid tied 10 Kilowatt system using SunnyBoy TL inverters and Secure Power Supply (SPS) 1500 watt outputs. I would split the 36 panel array into two separate 5 Kwatt systems of 2 each strings of 9.

In order to bolster the SPS surge capacity I would use 3KWatt UPSs with some LA 48V battery combination for the main part of the day.
There would be two SPS ports each with 1500 watts. I could back feed the breaker as if it was 240 although the phasing will be random. It would not matter it would still provide 120V loads just not any 240 V loads which would overwhelm the system anyway. It would be rated at 2x12=24 amps @ 120V

If all else fails and it is too hot then the 7Kw Generator can be kicked in for a few hours morning and evening.

After turning off the generator, and you turn in for the evening. The UPS would putter along on subsistence loads. Either size the batteries to keep the refrigerators going at nite or shut all down except for LED lighting.

When this setup is not in contingency mode the UPS batteries remain topped off as the are plugged into one of the house 120V outlets and are only plugged into the SPS 120V solar when in that mode.

I would not rely on getting the full 3kw from SPS from 10AM to 6PM. Maybe if there are no clouds and it is Summer you might get that for 5 to 6 hours but not 8.

[posplayr]

EDIT: 7/13/2015: Rather than just remove this post, I will detail what is wrong with it in case someone is asking about something similar.

First the transfer switch in this diagram probably has no practical way of providing an interlock between GRID power and the internal (solar, generator) power sources and so it is in violation the NEC.


This is what I have been thinking about for a relatively low cost contingency stay alive system for 30-45 days.

The idea if for a Grid tied 10 Kilowatt system using SunnyBoy TL inverters and Secure Power Supply (SPS) 1500 watt outputs. I would split the 36 panel array into two separate 5 Kwatt systems of 2 each strings of 9.

In order to bolster the SPS surge capacity I would use 3KWatt UPSs with some LA 48V battery combination for the main part of the day.
There would be two SPS ports each with 1500 watts. I could back feed the breaker as if it was 240 although the phasing will be random. It would not matter it would still provide 120V loads just not any 240 V loads which would overwhelm the system anyway. It would be rated at 2x12=24 amps @ 120V

If all else fails and it is too hot then the 7Kw Generator can be kicked in for a few hours morning and evening.

After turning off the generator, and you turn in for the evening. The UPS would putter along on subsistence loads. Either size the batteries to keep the refrigerators going at nite or shut all down except for LED lighting.

When this setup is not in contingency mode the UPS batteries remain topped off as the are plugged into one of the house 120V outlets and are only plugged into the SPS 120V solar when in that mode.

[bcroe]

A conventional freezer or refrigerator compressor does have a significant starting
surge, and the SMA SPS does not really have surge capability.

If you have a soft starting inverter type compressor (not found in standard units) then you might get away with it. But rather than deliver max current and drop the voltage to match the SPS will simply shut down on overload.

That is a shame, because the top items I'd like to back are the fridge in summer, and the furnace blower
in winter. Both are motors with starting surges. Maybe the feature could be offered with a super cap on
the panel side for the surge, and a big surge capability in the DC to AC conversion. Bruce Roe

[inetdog]

Talked to a company that sells the SMA TL inverters and they say that the 1500 watt plug it has wont produce enough for the start power requirements for the fridge or freezer. Any input?

A conventional freezer or refrigerator compressor does have a significant starting surge, and the SMA SPS does not really have surge capability.
If you have a soft starting inverter type compressor (not found in standard units) then you might get away with it. But rather than deliver max current and drop the voltage to match the SPS will simply shut down on overload.

[SunEagle]

Talked to a company that sells the SMA TL inverters and they say that the 1500 watt plug it has wont produce enough for the start power requirements for the fridge or freezer. Any input?

Unfortunately those SMA inverters while are good quality were only designed to provide some "emergency" power for small critical loads. Refrigerators, freezers and even some window AC systems were not on the list when they sized this system.

[North Texas]

Sma tl

Talked to a company that sells the SMA TL inverters and they say that the 1500 watt plug it has wont produce enough for the start power requirements for the fridge or freezer. Any input?

[ButchDeal]

Will the SMA TL inverter thing work for a slow steady output on sunny days without grid? Do I have to have 2? The TL line doesnt seem to start until 7000 Watt. That would be 2 big inverters. Thinking of doing this and propane generator. looking between a 7kwh and and 11 kwh. Have to go up to 11KWH to get 200 amp service I think? What peoples opinions on this?

it starts at the 3000 up to 7700

http://www.sma-america.com/products/solarinverters/sunny-boy-3000tl-us-3800tl-us-4000tl-us-5000tl-us-6000tl-us-7000tl-us-7700tl-us.html

[North Texas]

Will this work?

So i could do this without getting a full battery system ( just one or two batteries?) and add batteries later? Would lack of a full battery bank kill that battery quick?


This may be the way to go! I dont care for much power, mainly just for food. I'm not good with math in electricity, does my numbers add up? I thought all grid tied solar systems became usless in a power outage? Is this capable only cause of the inverters?

Will the SMA TL inverter thing work for a slow steady output on sunny days without grid? Do I have to have 2? The TL line doesnt seem to start until 7000 Watt. That would be 2 big inverters. Thinking of doing this and propane generator. looking between a 7kwh and and 11 kwh. Have to go up to 11KWH to get 200 amp service I think? What peoples opinions on this?

[DanS26]

Zero out your bill with a grid tie system

Spend your battery money on a generator

If winds take out your local wires, the debris will take out your solar panels (glass, outside, in the wind) and your batteries are flat and you will need to run the generator anyway. Work up a safe fuel storage scheme, there are many ways.

++1...this is good advice.

Instead of spending money on batteries and all of what that entails, just go out and buy a 500 or 1000 gal propane tank and bury it in close proximity to your propane powered generator. You will save enough money to buy a second backup generator and still have months or more of backup power and much cash in your pocket.

After a few years those batteries will be toast as opposed to that LP tank which will probably outlive you.

[ButchDeal]

For grid tied only? Or for for grid tied battery back up?

Outback is Grid tie battery backup

[North Texas]

Usage

Found usage on frig and freezer. Total for both is 89.5 kwh per month, 2.98 kwh per day. Published numbers, am in the middle of measuring with a kill a watt.

[North Texas]

On the second sort of, you can get a full hybrid system and us that AC couple a grid tie system but it would need batteries and costs would be even higher.

So this would be just a grid tied battery system?

An OutBack Flexpower 2 would make a perfect fit for you with an 8kw system.

For grid tied only? Or for for grid tied battery back up?