2Kw Offgrid pumping system

[seza]

Hi all,

I am new to the solar business, I need advice to about a basic water pumping system:

:: Power needed is about 2Kw
:: Panels available 40v 300W (nominal) but it is capable of producing more.
:: Inverter is Sunnyboy 2Kw designed for grid connected system.

The system will be off grid installed in N Africa with plenty of sun, I have couple of questions:

1. How many panels do I need?
2. How are they to be connected
3. tracked vs untrucked system what is the power difference?
4. How to turn off system? ie what will happen to panels if I disconnect them from the load while they still exposed to sun?

Many thanks.

[Naptown]

Is this for a well?
And is there some sort of water storage for when the sun is down or cloudy?

[Mike90250]

Inverter is Sunnyboy 2Kw designed for grid connected system.

You NEED a grid, for a GT inverter, to dump excess power into, or else it will fault and shut off.

What does the electrical nameplate label on the motor for the pump say it requires ?
1 or 3 phase
120 or 240VAC
1/2 hp or 3 hp
500 watts or 3500 watts
Those are the numbers, along with the depth of the well, and the amount of water needed.
Also, the useable solar hours in a day is much less than sunrise-sunset hours.

[seza]

Thanks guys,

It is for pumping water from a borehole about 80m deep to a reservoir nearby.
we need 1 phase power.

Mike, you raised a good point about need a grid, for sure there will be NO grid any time soon and that's the reason for the solar project,
I somehow thought that Grid Tied inverter will still work even without a grid but you opened my eyes to that fact - thank you.

the inverter I got for the job is Sunny Boy SB2000HF-30.

So it seems back to the drawing board on the inverter front.

Assuming I will sort out the correct unit what will be the best configuration?

many thanks

[inetdog]

...the inverter I got for the job is Sunny Boy SB2000HF-30.

If you get good deals on SMA, their Sunny Island family is what you need. But there are a lot of other good manufacturers with competitive prices that offer off-grid-only inverters. The SI has the capability to be used in a hybrid (sometimes grid or grid support) situation, so it costs more than a basic off-grid-only inverter.
You will find lots of them discussed here in the off-grid sections.

If you can get away with pumping only when the sun is shining and storing the water, rather than storing energy to operate the pump at any time, there are DC input pumps (Grundfos is one supplier) that can be driven directly from the solar array or through a less expensive linear current booster.

You need to evaluate the cost of a DC pump versus the batteries needed to support an AC pump and inverter.

[ChrisOlson]

Have you given any thought to using a water pumping windmill instead? They have been used for over 3 centuries and we have one at our place that has been pumping water into a cistern for over 60 years. Ours is a 8 foot Aermotor with 2" cylinder on a lift of 175 feet, and it can pump 130 gallons/hr with wind speeds over 15 mph, and about 20 gallons/hr at 6 mph wind speed.

If you have a suitable location, windmills run 24 hours a day. And they are less expensive than solar panels and electric pumps.
--
Chris

[seza]

Thank you both,
Chris, a windmill is a good idea but there none to be found in the area, also wind is bit unpredictable whereas sun is reliable and plentiful.

[ChrisOlson]

When the solar deal turns out to be too expensive and not as reliable as you thought, check these out - they are sold in Africa. I believe a fellow by the name of Dr. Michael Mulder set some up in Darfur and Tanzania for remote villages.

http://www.aermotorwindmill.com/

In Bolivia they build their own mills with normal everyday hand tools:

http://vimeo.com/8367311

Our 8 foot Aermotor has been running on our place since 1954. In 13 years all we've done is to grease it and replace the leathers in the cylinder twice. There is no solar water pump devised by man that can match it for reliability and long term operating cost. Nor can a solar pump (at least one you can afford) match it for sheer volume of water pumped in a month.
--
Chris

[extreempv]

You can use your existing Sunny Boy inverter in this system but you need a SMA Sunny Island inverter/charger
There are bigger versions, but the small 24V 2kw sunny island will probably be sufficient. If you have an idea of how many kWh's per day you require it would help size the system.

Ken

[inetdog]

You can use your existing Sunny Boy inverter in this system but you need a SMA Sunny Island inverter/charger
There are bigger versions, but the small 24V 2kw sunny island will probably be sufficient. If you have an idea of how many kWh's per day you require it would help size the system.

Ken

This system will still require batteries to keep the SI happy, even if you only intend to run the pump when the sun is shining. Just not as large a battery bank as you would need for an off-grid inverter alone.