Installation of a Redundant Electricity Solution with Seemless Switching

[hussain]

Hi,

I live in Pakistan where power cuts have become unbearable. Usually there is no electiricity in my city from 6-12 hours each day.

I am looking to invest in solar solution however I am highly confused and come here in search of help.

What I want to do is to install a Redundant Electricity Solution with Seemless Switching between Solar, Battery and Grid. Basically What I want is to install a system which does the following:

1. Provide electricity from solar panels directly to my house and charge batteries.
2. During a Cloudy day or at Night when solar energy produced is less than power requirements of the house, the system should provide electricity directly from batteries.
3. In case the battery charge falls below 50% the system should switch to grid whereby the power requirement of the house are met by grid electricity. This is to ensure that if grid electricity also cuts off i always have battery backup available.
4. The tranistion should be seemless i.e. all electrical equipment should not loose power during switching.

All the high load equipment such as referigerator, Air Conditioners, microwaves etc shall remain on grid electricity while the remaining load shall be on the redundant system. The maximum load if all the rest of equipment are on at the same time shall be:

10 Fans = 150 X 10= 1500w
LED Lights = 15 X 30 = 450 W
3 TV's = 100 + 150 + 200 = 450 W
Centralized evaporative cooler = 900 W
Home Theatre System = PS3 + XBOX + BD Player + Projector + Audio Video Receiver = 200 + 200 + 100 + 100 + 360 + 840 = 1500 Watt
Total (max) = 4800 watt

So it seems like that a with 5000 watt inverter my load will never exceed the inverters capacity. My question here is which inverter should I buy as there is a lot of jargon which i don't understand such as off grid, on grid, tie grid etc.

Thanks
Hussain

P.S: Would also appreciate if somebody can tell me above what wattage would I need a three phase inverter instead of single phase inverter.

[Mike90250]

greetings

What you want is a Hybrid inverter, that has internal Transfer switches, battery connections, and AC Grid and Generator connections.

Some are able to run in "Grid Support" mode, where they will use "local" (solar) power while it exists, and fall back to grid at evening and night time. If the Grid fails, it will seamlessly switch to battery/solar/generator as long as there is power.
When the Grid returns, it uses it's internal charger to quickly recharge the battery for the next outage.

You want to use the grid as much as you can, to preserve the life of the batteries.

You need to decide what circuits are to be "protected", so you do not deplete the batteries needlessly. (When the grid fails, stop playing video games on the big screen TV, and stop using the microwave oven) so the ice cream in the fridge does not melt.

You would likely want a small generator (honda eu2000) for bad weather, or your whole house shuts down when the batteries go low.

All the high load equipment such as referigerator, Air Conditioners, microwaves etc shall remain on grid electricity while the remaining load shall be on the redundant system.

And keep in mind, that as more folks install systems like this, there will be huge loads when the grid returns, as all the batteries start recharging and the grid will fail again.

the inverter I use Schneider-Electric XW-6048 (used to be called Xantrex XW-6048) is now the Conext XW - inverter / charger XW6048-230-50 does all this. You will need an electrician to install it, and a battery room will need to be constructed along with a solar array & generator area.
The size of the battery bank will determine how long you can run fans and such.


LOADS
I suggest you switch off many more loads than you have listed, so the batteries run longer. What you have listed will require a huge battery bank that will have to be replaced every 5 years at great cost. When the grid fails, you want to be like a submarine, running on batteries, being very slow and quiet. While you have solar power, you can selectively run large loads in the daytime.

3-phase system is not advisable for home use. The basic wiring is not compatible with the existing wires in the wall.

Hybrid Inverter
Electrical box (midnight e-panel)
PV array & mount structure
PV combiner box
PV charge controller
Battery circuit breaker (150V 100A DC (not AC))
Inverter control panel
battery temperature sensor
batteries (8, 6volt golf cart batteries as a bare minimum)
battery cables
and a mountain of wires and DC circuit breakers to wrap it all up with.
source of distilled water to refill batteries monthly
power plant engineer (you)


I believe Outback & SMA also make hybrid inverters.

[hussain]

Thankyou Mike, very informative reply. I have a few more questions

1. What is the expected life of Gel based battery, when fully charged and left alone. I ask this because the power cuts are basically in month April-September. With minimum to zero power cuts from December-February.
2. To prolong batter life shouldn't it go through frequent charge/discharge cycles.
3. What is total number of charge/discharge cycles a GEL Based battery can undergo.
4. In terms of cost saving, isn't it better to go from solar->battery->grid.
5. Is there any inverter which goes from solar->battery till 50% charge -> grid i.e. switch to grid before batteries completely run out so as to ensure that batteries have some charge left if grid cuts out.

Thanks

greetings

What you want is a Hybrid inverter, that has internal Transfer switches, battery connections, and AC Grid and Generator connections.



I believe Outback & SMA also make hybrid inverters.

[Mike90250]

GEL batteries do not belong in a PV system.

http://jgdarden.com/batteryfaq/carfaq7.htm

AGM or Flooded batteries are ok

You never want to take the batteries below 50% charge except in an emergency

You want to use the grid as much as possible, using lifetime cycles from the battery costs more than the grid power does.

Expect no more than 5 years from the batteries, even if not used much.

Lots more to learn about care and feeding of solar batteries. Sulfation, stratification.....

Calculate your loads in watt-hours, then you can plan the rest of the system to supply that power.

[hussain]

The link you quoted does not state that GEL are not suitable for solar.

Would i loose my battery if doesn't undergo a charge/discharge cycle?

GEL batteries do not belong in a PV system.

http://jgdarden.com/batteryfaq/carfaq7.htm

AGM or Flooded batteries are ok

You never want to take the batteries below 50% charge except in an emergency

You want to use the grid as much as possible, using lifetime cycles from the battery costs more than the grid power does.

Expect no more than 5 years from the batteries, even if not used much.

Lots more to learn about care and feeding of solar batteries. Sulfation, stratification.....

Calculate your loads in watt-hours, then you can plan the rest of the system to supply that power.

[inetdog]

The link you quoted does not state that GEL are not suitable for solar.

Would i loose my battery if doesn't undergo a charge/discharge cycle?

Whether it was mentioned in that link or not, the biggest problem with GEL batteries is that they cannot accept a high charging current without damage.
For FLA you can safely charge at C/8 where C is the capacity in Amp Hours.
For AGM you may be able to charge at up to C if the manufacturer recommends it. Certainly C/4 will be OK.
For GEL you may need to stay below C/12, particularly when you are gassing. Event though the GEL cell has a chemical mechanism for recombining the hydrogen and oxygen gas generated during charging, too high a gassing rate can cause bubbles to form in the GEL separating it from part of the plate material, making part of the plate area permanently useless.

[hussain]

Whether it was mentioned in that link or not, the biggest problem with GEL batteries is that they cannot accept a high charging current without damage.
For FLA you can safely charge at C/8 where C is the capacity in Amp Hours.
For AGM you may be able to charge at up to C if the manufacturer recommends it. Certainly C/4 will be OK.
For GEL you may need to stay below C/12, particularly when you are gassing. Event though the GEL cell has a chemical mechanism for recombining the hydrogen and oxygen gas generated during charging, too high a gassing rate can cause bubbles to form in the GEL separating it from part of the plate material, making part of the plate area permanently useless.

Thanks.

1. What is the "shelf" life of battery if it is charged fully and then left alone.
2. For the load I listed should i go with transformer or transformer less inverter.

[inetdog]

Thanks.

What is the "shelf" life of battery if it is charged fully and then left alone.

That is a good question and it depends entirely on the self discharge rate of the battery, which will vary with the plate chemistry and the mechanical design.

For FLA I would worry if they went two months without recharging. For some AGM batteries they manufacturer claims that they can safely go four months or more without charging, starting at a high SOC. GEL I do not have any data for.

[hussain]

That is a good question and it depends entirely on the self discharge rate of the battery, which will vary with the plate chemistry and the mechanical design.

For FLA I would worry if they went two months without recharging. For some AGM batteries they manufacturer claims that they can safely go four months or more without charging, starting at a high SOC. GEL I do not have any data for.

Hi,

Actually you misunderstood my question, i want to install one of this system in my vacation home. The problem is that i don't go there often, sometimes not for 3 to 4 months. during this time, the solar will charge the battery but there will be zero consumption, i am worried that as battery won't be going through dischage and recharge cycle they will die.

Also is sunny boy that you own work on logic of solar->grid->battery.

[Mike90250]

I would expect a $100, 90ah deep cycle marine battery, to live 3-5 years, being used or not. They start to age and break down right after being built. They are OK with shallow 10-20% daily cycles, but the deeper the cycle, the shorter the life. But the basic plate material degrades no matter what, and I'd say plan for no more than 5 years.

[hussain]

I would expect a $100, 90ah deep cycle marine battery, to live 3-5 years, being used or not. They start to age and break down right after being built. They are OK with shallow 10-20% daily cycles, but the deeper the cycle, the shorter the life. But the basic plate material degrades no matter what, and I'd say plan for no more than 5 years.

But what if there are no cycles for 3 months, would the battery die?

Also can somebody point towards a good transformer less 5000 Watt hybrid inverter.

Transformer less are more efficient , right?

[Mike90250]

But what if there are no cycles for 3 months, would the battery die?

Even a new battery, on a float charger, will be next to useless, after 5 years.
if you just park a battery by itself, it will self discharge about 10% a month 2 Months, it will begin to be damaged internally
if you leave the solar charger connected, it will maintain the charge in the battery, but again after about 5 years, the battery internal parts will become age damaged anyway.

Also can somebody point towards a good transformer less 5000 Watt hybrid inverter.

I can't. I don't know which are which anymore - too large of a market.

Transformer less are more efficient , right?

Nope. Just saves a lot of weight and cost of copper. Transformer inverters are 95-97 % efficient, hard to be much better than that. Transformers are also pretty robust and can take a lot of abuse.