Equipment need for pool pump and cleaner without batteries nor grid tie

[RLW]

My pool pump and cleaner account for about 25% of my monthly usage (1,512KWh). I am considering options to reduce my grid consumption (my Austin TX power provider's net metering charges are higher for consumption over 1,000 KWhs).

My Jandy ePump is rated at 2.7 HP, 230V, 10.5A, 500 to 3,450 rpm. I have a note that the installer said it pulled 8.0A while priming and then 4.4A.
230V X 4.4A = 1,012 watts X 5 hours = 5.060 kwh per day.

The pool cleaner pump is 3/4 hp, SF 6.4A. Note: The Jandy epump must be running when the cleaning pump is running.
230 X 6.4A = 1,472 watts plus the Jandy epump @ 1,012 watts = 2,484 watts X 3 hours = 7.452kwh per day. I do not know the start up amps.

I'm thinking to keep cost down, I can run it during the day so I do not need batteries or a grid connection. There is room for about 6 panels on my shed.

1} As described, what equipment would I need?
2) If I used six Enphase M215 micro inverters and six 240w panels, would it produce enough to run either pump for a shorter amount of hours?
Thank you in advance.

 

[svetz]

Welcome to the forums!

I know the title says "no grid tie", but if you live somewhere with a good net metering agreement it can be a good deal as any excess power (you'll probably want to size for winter, so in summer you'll have excess) will save you money. Even if the net-metering is bad, you can typically run a hybrid at zero export and the "house" can use the excess. But the best bit about being grid-tied is you can truly skip the batteries (without some battery, every passing cloud would stall the system making it hard on the components, so even a small battery would be useful).

The Problem

1. 5 kWh/day needed over any arbitrary 5 hour period, + 2.5 kWh over 3 hours. A 1012W ePump and 1472W cleaner.
2. Austin Texas
3. No backup power, that is it doesn't run on cloudy days.
4. Have room for 6 panels

Questions

1. What Equipment do I Need ?
   Ground Array: Solar Panels ->SCC->(battery+LVD) or Capacitor->fuse/Breaker->Inverter
   Roof top Array: Solar Panels ->RSD->disconnect->SCC->(battery+LVD) or Capacitor->Fuse/breaker->Inverter
2. Can I use Enphase?
   No. If Microinverters don't detect a grid they won't turn on
3. Are 6x 240W panels enough?

#3 -- The Math This is a really hard problem to solve without using energy storage, so the calculations may be a bit off. But here's my take on it, YMMV. You need 5 kWh for 5 hours and 2.5 kWh for 3 hours. The problem is the sun is only full strength at solar noon. But, using the chart to the right we can get the % power based on the sun's altitude. The calculation below is a bit simplistic, so you'll probably want to add some margin on error. The earth rotates 360° in 24 hours, or 360/24 = 15°/h. 5 hours x 15° = 75%, split half way from solar noon call it 40°. 90-40 = 50° of sun altitude. From the chart to the right, at that sun altitude the maximum solar output is 75%. The winter vs. summer insolation is about 76%

So, to generate 1 kW at 50° you'd need to generate 1/.75/.76 = ~1.8 kW array optimized for winter.

3 hours to run the cleaner is 3x15= 45°. During that time the panels need to generate 1 kW ePump + 1.5 kW cleaner, or 2.5 kW needed.

Split halfway from solar noon, for 45/2 = 22.5°; or ~67° altitude, which is about 92% maximum power. So, 2.5kW / .92 / .76 = 3.6 kW array. Adding in the inefficiencies plus margin for the average hazy day and it would probably a 4 to 5 kW array.

> Are 6x 240W panels enough?
6x240=1.4 kW array, so the answer is no.

What about with a battery?
From an insolation calculator, the lowest insolation when optimized for winter is 3.91. So, to generate th 7.5 kWh/d AC needed is:
7.5 kWh/d DC / .9 inverter efficiency / .98 SCC efficiency / = 8.5 kWh/d DC
8.5 kWh/d DC / 3.91 = 2.2 kW array, so the answer is still no (at least for winter).

Hope that helps serve as some example math so you can play around with it.

 

[rogerdw]

Hi RLW, I'm new here too, just discovered the forum this morning.

You've already got some impressive maths from svetz and I can't argue or compete with that, but I can give you a real world example with a pool pump running on panels alone.

I'm not quite sure why you have two pumps, must be different to how they run pools here in Australia.

We do have two pumps, but the main one is used for circulating water through the filter and also for vacuuming etc ... and a second one to run water through the solar collector on the roof for a bit of extra warmth.

I also found the expense hard to cope with ... so with my experiment I ended up hooking a (supposedly 3hp) DC motor from a treadmill to the existing main pump motor (1.5hp) via a ribbed belt ... and connected 6 x 250 watt panels in series to it ... with no control electronics at all.

The pump can run all day, though of course early and late in the day it just idles along ... but it has done a pretty good job of the pool ... and of course my electricity bill is markedly lower.

The system rarely ever reaches the same pressure that the normal AC pump sat on ... probably runs at about 75% on good days and of course much lower on poor solar days.

The original setup was set to run the pump between 4 - 5 hours per day ... so the solar running lots more hours per day (but at lower speeds) still seems to maintain the pool perfectly ok. The pool experts here say it needs the hours of running, not so much for filtration ... but for circulation ... so it seems it does the job.

Having said all that, I'm sure that with another six series panels in parallel with the first lot ... the output would fairly closely match the original AC system. The trouble is that then I have to move all the panels up on the roof and make it more permanent ... and I'm not sure I want to go to all that trouble.

In my initial experiment, I used a much smaller motor and that only lasted about two weeks before a brush failed and badly overheated the commutator ... but the second motor has run for about 15 months so far, and the only real trouble I've had was that the belt wore out a couple months ago and I had to replace it.

I see your motor power requirements are much higher than mine also ... so I'm not sure what I'd do in your shoes.

I did a write up and photos about it on another forum, and I don't know what the rules are as far as adding links, so I haven't. I only just got here, I don't wanna get kicked off just yet.