Convert dc to ac without transforming the voltage

It appears the inverter link should run your induction motor...

Many times, people do not run their pumps very long. A smaller AGM battery bank (AGMs have higher output/surge current) with heavy cabling from batteries to AC inverter + solar charge controller would probably be a straightforward solution:

https://translate.google.com/translate?sl=auto&tl=en&u=https%3A%2F%2Fwww.dwe-oss.nl%2Fproduct%2F24v-naar-230v-omvormer-2000w%2F

Problem is that induction motors can take upwards of 5x running current for starting. A 5x larger solar array vs battery bank+AC inverter+charger+panels may be a better solution.

A minimum of ~225 AH @ 24 volts AGM bank... Or 400+ AH for flooded cell lead acid 24 volt battery bank (aka golf cart batteries--4x in series by 2x parallel strings of 6 volt @ ~200 AH "GC" batteries).

This is not my area of expertise--Just a rough guess at sizing. Others here with experience can chime in with their recommendations.

How many hours a day do you pump (fraction of an hour per day vs hours per day for irrigation)?

-Bill

Average power vs starting/surge power is always an issue... If you assume 5x rated power for surge--you are generally pretty safe with induction motors and gensets/inverters.

Your sticker says 0.55 kW or 550 Watts. Motors are rarely operated at 100% of rated power unless they are built into an appliance (like a refrigerator compressor).

Also, power usage depends on your water pressure, pump type, and to a degree, what is the voltage is and what is the energy source (utility, genset, inverter).

For example, say you have a 2,000 Watt (4,000 Watt surge) inverter, but only need 550 or 300 Watts maximum, you can downsize the battery bank for the actual loads... However, if you want to run a worm drive saw on the inverter, you want the battery bank and wiring to supply every bit of 2,000 Watts and close to 4,000 Watt surge (or whatever your inverter is rated at).

What also makes it hit and miss on predictions... Every energy source behaves differently when operating with large/inductive loads (and other "non-linear" loads like large electronic power supplies and such). Say your small genset is an inverter genset (AC generator=>Internal AC inverter=>AC out)... These have very clean power, but not much surge (they will shutdown in faction of a second if hit with a heavy starting surge).

And a plain old genset--Hit with a heavy starting load may simply sag the voltage to 180 VAC or less (for seconds to minutes) until the load is "up to speed" (or a fuse/breaker is popped).

If you have equipment to play with--You can try to "optimize" the system. If I am trying to help you from 4,000 miles away behind a keyboard, I am going to be a bit more conservative and hopefully give you a solution that will work and you can try to downsize "pieces" (battery bank, solar array, AC inverter, wiring, etc.) and see if the "cost optimized" system will work or not.

Here is a good website with a lot of information about gensets/inverters/loads:

http://www.screenlightandgrip.com/html/emailnewsletter_generators.html#anchorSquare Wave Generators

Assuming you want to use the 2 kWatt inverter to its full capacity... We use a rule of thumb of 500 Watt of AC inverter per 100 AH @ 24 volt flooded cell lead acid deep cycle battery bank:

• 2,000 Watt inverter * 100 AH * 1/500 Watt inverter (of 24 vdc battery bank) = 400 AH @ 24 volt battery bank minimum (FLA battery)

FLA batteries are best discharged (continuous load) at C/8 to C/5 discharge rate (max starting surge around C/2.5). (discharge battery to dead in 8-5 hours) (note: ignoring other factors which will reduce run-time--just keep math simple for the moment).

AGM Batteries (you have to check their specifications) can be discharged as fast as C/1 discharge rate (take the AGM "dead" in ~1 hour).

Let's start with "golf cart" FLA batteries (cheap/easy). 4x 6 volt = 24 volts. 2x ~200 AH = ~400 AH for parallel strings.

When designing solar systems, we do two calculations. One based on the size of the battery bank (larger battery bank needs more panels), and the second based on hours of sun and loads usage per day.

Sizing the battery bank--5% to 13%+ rate of charge suggested... 5% for weekend/sunny weather usage can work. 10%+ recommended for full time off grid:

• 400 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 753 Watt array minimum
• 400 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 1,506 Watt array nominal
• 400 AH * 29.0 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,958 Watt array "cost effective" maximum

Then there is sizing the system based on your daily loads--And 2 days of storage (no-sun) with 50% maximum planned discharge (longer battery life). Knowing the actual energy usage of your loads is very helpful... 300 Watts for your pump I will use (using a Kill-a-Watt meter to estimate or similar)... 550 Watts nameplate is usually higher than actual energy usage:

• 300 Watt load * 0.5 hour run time = 150 WH daily load
• 300 Watt load * 1/0.85 AC inverter eff * 0.5 hour per day cycle * 2 days storage * 1/0.50 max discharge * 1/24 volt battery bank = 29 AH @ 24 volt battery bank

And here is an example of the issues of designing a "balanced" system... If this was powering an off grid cabin, the relatively large battery bank for hours of average loads + short term surge current support works out nicely.

In the is case, we have relatively large starting power (which FLA batteries are not "great" at) and relatively low energy usage (only need a "small bank" to run.

If you wanted to run an off grid cabin, I would go with the 400 AH @ 24 volt (or even a 600+ AH @ 24 volt if you are running a full size fridge).

If you are only running the pump, then AGM or LiFePO4 batteries (very good surge current) may be a better choice (these batteries tend to be "pricey"--So smaller is better with them).

Just to finish the calculations, sizing the solar array for your load of 150 WH per day. I don't remember if you said where the system is located, but let's assume Antwerp Belgium, fixed array, facing south (not a lot of winter sun there):
http://www.solarelectricityhandbook.com/solar-irradiance.html

Antwerp
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 39° angle from vertical:
(For best year-round performance)JanFebMarAprMayJun1.38
 2.20
 3.03
 3.83
 4.49
 4.29
 JulAugSepOctNovDec4.29
 4.23
 3.29
 2.38
 1.50
 1.07
 Let's toss the bottom three months (use genset in bad weather, or not occupied during winter):

• 150 WH per day * 1/0.52 off grid AC system eff * 1/2.20 hours of sun (February) = 131 Watt array (Feb "break even" month)

Obviously, not a good "match" between large battery bank and small (high surge/large inverter) load.

To finish the design and what the "larger system" is capable of... Assume 25% per day battery power (day of "no-sun"):

• 400 AH * 24 volts * 0.85 AC inverter eff * 1/2 days storage * 0.50 max discharge = 2,040 WH of "battery power" per day

Running the same February 2.20 hours of sun per day (generally >3.0 hours of sun is a "respectable" amount):

• 2,040 WH per day * 1/0.52 off grid system eff * 1/2.20 hours of sun (Feb "break even") = 1,783 Watt array (Feb break even load)

Here we are, a "poorly matched" large load (surge) with a (relatively) large AC inverter (and a large FLA battery bank to feed it)--And not really needing that much power.

Besides the "bigger than you need"(?) system--Looking at addressing your pumping loads is an option. For example, get a large cistern and pump once or twice a week into the tank--And use an RV (Caravan) Pump that takes something like 9 amps @ 12 volts (or 5 amps at 24 volts) to pull from the tank and pressurize the cabin (enough water for a sink/low flow shower, etc.).

Or, go with a "slow pump" to fill the tank/cistern, and the RV pump for pressure.

Lots of ways of addressing the needs... What do you think/need?

-Bill

Here is a typical RV style water pump:

https://www.solar-electric.com/2088-443-144.html

And even just one "automotive" size deep cycle battery (roughly 80 AH at 12 volts) and something like a single 140 Watt panel or so plus the DC water pump (12 or 24 volt models are available for not a lot of money) (have not done the calculations--Just trying to figure out what you need and why the 230 VAC 500 Watt pump and no other off grid electrical needs)...

Would this work for you or not (you can keep the pressure tank and even your 230 VAC motor as backup/for days when you need high water flow--Just fire up the genset for AM showers for when the family visits, etc.).

I am a bit unsure about your off grid power needs... Do you have utilty power and need backup power? Or do you not use any electricity except for water pumping?

-Bill

Sounds like a relatively small jet pump. I cannot think of any way of easily/cheaply converting to something else (without pulling the whole pump, pipes, and injector assembly).

The only way I can think of using solar is to use the main pump to pump to a cistern, and then use an RV 12 or 24 volt pump + smallish battery + solar panel + charge controller--Then you may only have to fire up the genset once, and then use the RV pump from the cistern to keep pressure in the place day/night.

-Bill