Advice off grid set-up

[bdsolar]

Hi

I have a property in an area where there is frequent load shedding. I am trying to design an off grid solar set-up with the battery bank as a backup power source for the lighting circuit.

Requirements:
If enough solar power available it should power the load.
If not enough solar power available then mains should power the load.
If mains not available then battery to power the load.

Battery charging:
When solar power is available it will charge the batteries otherwise use mains to charge the batteries.

I am not sure how such a set-up can be achieved. I have seen various diagrams for off grid set-ups but am not sure how they can be modified for above scenario.
The two obstacles, for me, are:
1. auto-selecting the source for the inverter &
2. charging the battery bank using solar & mains.

I am starting with the following off grid diagram.

off grid set-up.png

I believe in the set-up in the diagram a drop in solar power would be supplemented by the battery to power the inverter. Is this correct?

I cannot tie the system to the grid and additionally I need to store power in a battery bank.

Any help would be appreciated.

[russ]

The diagram is for off grid - a different thing.

You want a hybrid system to use both batteries and the grid - the most expensive combination.

What is your approximate location?

[bdsolar]

I'm in UK but the set-up is for a property in Bangladesh.

I was hoping to source the charge controllers / inverters here as opposed to local stuff.

Off grid set-up looked viable and easy to understand. Hence I thought with some modification and or custom electronics might get to what I want. Do hybrid system use different components altogether?

[russ]

Different inverter - Mike, Rich or one of the other guys can explain more accurately than I

[Mike90250]

You will need a "Hybrid" inverter. They have the Transfer Switch, smart 3 stage charger, and the brains, all in one box. The one I have, from Xantrex/Schneider has a 2nd AC input for the aux generator, so the one internal charger, can function from Grid or Genset. Outback also makes one, I don't recall if it will produce 240VAC, or if you need a pair of them or transformer.

The only difference from my setup to what your would use, would be: connect to the GRID via AC1 input.

powerplan-3b.jpg

I would suggest that you buy name brand gear, and ship it over in a container. PV panels, mounts, wires, fuses, everythign but batteries. May be easiest to locate a resort nearby and get golf car batteries, or fork truck batterys. Batteries don't have to have "solar" printed on them. And a source of distilled water too !
Don't forget a generator - something in the 4-7KW size should be good. Too large, and they never heat up and can die from that. (wet stack)

[bdsolar]

Mike thanks. I didn't know 'hybrid' inverters existed. I was Googling for "multiple input inverters" without luck!

[axis11]

Have you tried considering an inverter/charger and battery set-up? A few of my colleagues from pakistan and bangladesh use this system. The system mainly uses the grid to charge the batteries. When the grid fails, battery supplies power to the inverter and connects to your mains using an auto transfer switch or a manual switch. Its typically a bigger version of your computer UPS. Since power failures last only a few hours and power is available everyday, you will be guaranteed a fully charged battery everyday provided the system is properly sized.

[bdsolar]

I wanted to make use of some solar power as there solar panels are readily available there. But it seems the cost of a hybrid inverter is quite high.

I looked for inverter / chargers which are also sold locally. However they seem to be of dubious quality and last less than a year. I'm assuming they are putting together a simple charging circuit without much intelligence.

Can you recommend any brands that are available in Europe which I can take with me?

[Mike90250]

... Can you recommend any brands that are available in Europe which I can take with me?

Xantrex - Schneider Electric is global

I think Steca is in Europe

SMA & Fronius may be EU too.

What you are looking for, is a gadget that is always controlling LETHAL high voltage. Not like a Hi-Fi radio, but this will be producing high voltage, and when charging, controlling large amounts of amps, beyond what even a large truck powers itself with. And there is not a large volume market, these are only made in the thousands, not the millions in work camp factories. So they are going to cost a lot, but they do a lot.

This is an area where you get what you pay for

[axis11]

I am currently in the Middle East and doesnt have much info on the european market. Members from UK could comment on your query better.
To utilize PV for charging, you have to determine how long does the power shedding last each day. Also determine the loads you will be using during that period and determine the panel wattage you need. If you can afford the panels and gear, no need for a hybrid inverter.You can do with a pure sine wave inverter and a transfer switch (auto or manual). With the cost of a hybrid inverter, you can buy a lot of panels. Just add a simple AC charger to manually bulk charge the batteries during cloudy and rainy days.