Solar to Power Water Pump

rscott7706

I am a newbie to solar. Really getting my feet wet now, and am excited about being a better partner to environment and saving bucks at the same time.

I have a Jacuzzi brand water pump (may or may not be for a Jacuzzi hot tub).

I want to use solar to power, and am confused about panel size needed (and other details).

Here are specs:

Emerson Motor Company
Model MB 899C (could not find in web search)

Vin 115/230
Amps 10.8/5.4
SF Amps 14.4/7.2

OK, basically I want to set this up with a deep cycle battery of some sort, and recharge it from the least expensive panel set up possible. My usage will be sporadic - maybe only about 30 minutes every day or if deemed necessary, every other day. I am only going to water outside plants (or lawn) with this setup.

I am in Lakeside, CA so get plenty of sunshine.

Question 1 - Do I need anything more then a panel that will recharge the battery after a cycle of use? (Again about 30 minutes a day or every other day).

Question 2 - How do i size my inverter? Is there a formula?

Question 3 - Would it behoove me to invest in a 12 volt motor instead of the 115/230?

I hope didn't ask too much, and I gave enough detail to get this started.

Thanks!!

Ron

icarus

Re: Solar to Power Water Pump

If you have grid power available, it is never going to be cheaper to pump water using a battery based solar system.

Just FYI, Grid tie PV solar systems run $5-10/watt.

Battery bases systems are easily double that. In addition, your battery system will run only ~ 1/2 as efficiently (at best) leading to a net/net 4 fold cost over grid tie. Even grid tie tends to be more expensive net/net than pure utility purchased power.

Your current pump, 120vac @ 10.8 amps will draw ~1300 running watts,,, perhaps ten times that to start! You are going to need a very big inverter and battery system to run that pump.

Please do some reading on this site and elsewhere,, (there are some very good water pumping threads here) before you buy anything. The biggest thing you need to avoid is the ready, fire, aim syndrome,

Good luck and welcome to the forum.

Tony

BB.

Re: Solar to Power Water Pump

rscott7706 wrote: »

I am a newbie to solar. Really getting my feet wet now, and am excited about being a better partner to environment and saving bucks at the same time.

Just to be clear, if you have utility power anywhere within practical wiring distance of the pump--solar is going to cost you more money.

You did not say if this was going to be a grid tied system (solar panels + GT inverter)--which is the best bang for the buck. Or off grid (solar panels + charge controller + battery bank + inverter).

Basically, with a grid tied system--you can get pretty close (or even cheaper) than utility power (a lot depends on where you live and your local utility rates). Off-Grid solar is going to cost you ~$1-$2+ per kWHour.

There is also an option to use a water pump that operates directly of solar panels (no inverters, no charge controllers, no batteries). Can be a very nice alternative setup (slow water pumping while the sun is up).

For the moment, lets assume off-grid + charge controller + batteries + inverter.

Emerson Motor Company
Model MB 899C (could not find in web search)

Vin 115/230
Amps 10.8/5.4
SF Amps 14.4/7.2

Your best bet is to measure your Voltage, current, average power, and starting current (if you can).

OK, basically I want to set this up with a deep cycle battery of some sort, and recharge it from the least expensive panel set up possible. My usage will be sporadic - maybe only about 30 minutes every day or if deemed necessary, every other day. I am only going to water outside plants (or lawn) with this setup.

Let's make some assumptions here... Assume starting current is > 14.4 amps at 115 volts:

• VA=14.4 amps * 115 volts = 1,656 VA starting energy

So, at the very least, you probably need a 2 kW inverter to start the pump (others may have a better idea than I--No experience with well pump on an inverter).

The average power may range between:

• 115v * 10.8 amps * 0.6 PF = 745 watts
• 115v * 10.8 amps * 1.0 PF = 1,242 watts

I am in Lakeside, CA so get plenty of sunshine.

Question 1 - Do I need anything more then a panel that will recharge the battery after a cycle of use? (Again about 30 minutes a day or every other day).

So, worst case average power usage by the motor would be:

• 1,242 watts * 0.5 hours per day = 621 Watt*Hours per day

Using the PV Watts program for San Diego CA, assume 1kW of solar panels (even number) and 0.52 overall system efficiency (0.77 for panels+charge controller, 85% for inverter, 80% for battery bank):

"Station Identification"
"City:","San_Diego"
"State:","California"
"Lat (deg N):", 32.73
"Long (deg W):", 117.17
"Elev (m): ", 9
"PV System Specifications"
"DC Rating:"," 1.0 kW"
"DC to AC Derate Factor:"," 0.520"
"AC Rating:"," 0.5 kW"
"Array Type: Fixed Tilt"
"Array Tilt:"," 32.7"
"Array Azimuth:","180.0"

"Energy Specifications"
"Cost of Electricity:","12.5 cents/kWh"

"Results"
"Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
1, 4.83, 72, 9.00
2, 5.35, 72, 9.00
3, 5.91, 88, 11.00
4, 6.52, 93, 11.62
5, 6.05, 89, 11.12
6, 5.98, 84, 10.50
7, 6.26, 90, 11.25
8, 6.62, 94, 11.75
9, 6.02, 84, 10.50
10, 5.88, 86, 10.75
11, 5.16, 74, 9.25
12, 4.67, 69, 8.62
"Year", 5.77, 994, 124.25

So, lets assume you do your pumping during the 8 months of the year > 84 kWhrs per month:

• 84 kWhr / 30 days = 2.8 kWhrs per day
• 621 WH per day / 2,800 Whrs per day per 1,000 watts of solar panels = 222 Watt panel minimum

Battery size--you can choose between 12, 24, or 48 volts DC -- but for a 1 HP motor, I would recommend 24 volt minimum.

Normally, we recommend 3 day of no sun, and 50% maximum discharge. Assuming 85% efficient inverter:

• 621 WH per day * 1/24 volts * 3 days no sun * 1/0.50 * 1/0.80 = 155 AH @ 24 volts

Now, the problem is that you should not have too heavy load on the battery... Using C/8 as the maximum continuous discharge rate:

• 1,242 watts * 1/0.80 eff inverter * 1/24 volts * 8 max rate = 518 AH @ 24 volts

As you can see, this is a pretty substantial system...

Normally, for pumping, it would be better to use a small pump and run it 5 hours per day on a solar system--and work at conservation to reduce your overall energy usage.

-Bill

rscott7706

Re: Solar to Power Water Pump

Both BB and icarus;

Thank you for the prompt and informative information. One factor I did not mention was trying to avoid the cost of running electricity to the pump area. It is +/- 250' from my house, and in much lower in elevation (probably a good 20' rise from pump location to house).

And, my panel, although considered to be more then sufficient when I built my house is a loaded 200 amp panel.

I have not gotten an estimate on what it would take to run a circuit that far with potential panel upgrade in mind.

It looks like I may be better off for the short term to go with a small gasoline engine to pump up hill to a secondary tank, then a pressure pump from there.

Again though I thank you very much for your great info, I am slowly investigating all alternatives.

Ron :cool:

Cariboocoot

Re: Solar to Power Water Pump

Just a note from a guy who used to work for Emerson: that is a pretty big water pump motor. Approximately 2 HP. That thing would draw about 2000 Watts running (while pumping) and the 'no load' start-up would exceed 3000. Are you sure that's a well pump? Methinks with the 'Jacuzzi' name on it that it was originally a circulating pump for a hot tub. In which case it wouldn't be suitable for pumping from a well (not designed for lift).

BB.

Re: Solar to Power Water Pump

I believe Jaccuzi has made well pumps (at least jet type) for decades... Here is a large list of Mfg. Model numbers--see if you can find a pump model number match there (as opposed to the motor model number).

-Bill