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Hi all,

Name's Wynand and I live in Villiersdorp WC.

I bought two 100W solar panels yonks ago for my off-road caravan but have never used them and have since sold the caravan. I recently started a Hydroponic system in my backyard and was thinking of using the panels to power the hydroponics. I Ordered an Axpert VM1000/1000VA inverter/ MPPT regulator from Takealot which I am waiting for and which will be used for the hydroponics and intend to get two 100Ah batteries shortly. The system, when completed, will be totally off-grid. My hydroponic system will eventually consist of about 3 or 4 pond pumps (40W each). 3 or 4 fans (40/45W ea) 4 x CFL bulbs (10W each) and about 3 x 100W aquarium heaters but only the pumps will run continuously

I'm a qualified electrician but have absolutely now experience in Solar, so I joined here in the hopes that, if the paw-paw hits the fan, I'll be able to get some help and advice.

Cheers

Wynand

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10 minutes ago, WynandK said:

Name's Wynand and I live in Villiersdorp WC.

Welcome Wynand. lovely area, as a little boy I use to stay in Caledon. 

You have come to the right place. You will get the help you need, from quickly looking at your setup as described, you nee a couple more panels, the 2x100 watt wont keep up with the demand. If you can maybe share the run-times  of all the equipment , we will be able to help you correctly sizing your array and battery bank size. Please also mention if you want to run any of these equipment at night and for how long at a time. 

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4 minutes ago, Jaco de Jongh said:

Welcome Wynand. lovely area, as a little boy I use to stay in Caledon. 

You have come to the right place. You will get the help you need, from quickly looking at your setup as described, you nee a couple more panels, the 2x100 watt wont keep up with the demand. If you can maybe share the run-times  of all the equipment , we will be able to help you correctly sizing your array and battery bank size. Please also mention if you want to run any of these equipment at night and for how long at a time. 

Hi Jaco and thanks,

Well basically I have only one pump running continuously for now (40W) and 1 fan (45W) running during the day, but only when it is very hot inside the tunnel.

I will eventually have 3 pumps of which 2 will run continuously (night and day)and the third one will run every hour for about 15 minutes, during the day and maybe once every 3 hrs, for 15 minutes during the night.

I will eventually also have 4 fans (Normal oscillating fans) running during the day, but like I said only when it is very hot in the tunnel. I open up the sides of the tunnel for airflow but have a heat build-up high up, under the plastic covering

The lights are only used at night but very seldom as I try and do everything during daylight hours.

The aquarium heaters whilst on all the time, are controlled by thermostats and will probably only work in the winter months and then mostly during the night when temperatures plummet.

My nutrient reservoirs are buried in the ground, so the temp remains pretty constant.

My main aim for the solar system is to ensure nutrient flow to the plants during load shedding but running it completely off-grid is the ideal.

 

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1 hour ago, WynandK said:

3 x 100W aquarium heaters but only the pumps will run continuously

Wynand, can you measure the consumption of one of these over a 24 Hour period? I have made a quick calculation assuming these will run for 12 hours, but if its isolated well, it might be less., this 300 watt constant, has a big impact on the battery bank size.  

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Jaco, Thanks for your help.

Measuring their consumption now is not possible as the nutrient does not get cold enough for the heaters to work. The nutrient should ideally be kept between 20 and 26 deg C. During summer it is more likely to go up to 30/32 deg C so I have to put iced bottles into the reservoir.

In winter however it will be a different story but the fact that the reservoirs are buried will help to keep the temp. If I had to venture a guess, I would say they would probably work a total 2 - 3 hours per night, during the winter. They are set @ 22 deg C and would want to keep the temperature there. They will therefore switch on and off all the time but the total "on" time would probably not be more than 3 hours per night.

I think, work on your gut feel for now or disregard the heaters for now, as it is still far to winter. I can always add more batteries should it be necessary. I have in any case only got one hydroponic system going and am busy building the second one. The third one is still a way off.

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10 minutes ago, Antony said:

Welcome Wynand,

I went to boarding school there, (when bread was still 12 cents) stayed in Huis Du Raan and visited Huis Theresa quite often.

Hi Antony,

That was probably in the days when sex was safe and cars were dangerous? Been here 3 years now. Moved from Richards Bay.

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1 hour ago, WynandK said:

I think, work on your gut feel for now or disregard the heaters for now,

Basically comes to this. 

2 x 40 watt pumps for 24 hours = 1920 watts

1 x 40 watt pump for appr 5 hours = 200 watt

4 x 45 watt fans for 4 hours = 720 watt

Worst case max is 2840 watts for 24 hour period. 

Rest of calc, if you take "Cheaper" battery's and allow 30% discharge and allow for 2 days storage the result looks like this.

24V.JPG.f6f67716249371fc8d5c40b58408e34b.JPG 

So you will need at least 2 x 330 watt panels and 542 Amp hour battery bank. 

If you have Eskom available and you want to allow for 1 days storage the bank size drops to 360 Ah .

Either way, to use 100 ah battery's will just complicate everything. The aim is to try and reach the required AH in the least possible stings. Reaching 360 Ah will need you to connect 2 12 volt 100 ah (8 battery)  in series and four strings like that in parallel. Using 200 ah battery's are actually better. 2 strings of 2 in series. (4 Battery's) 

Just to give you and idea of what is needed at the end to go off-grid with your project. 

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21 minutes ago, Jaco de Jongh said:

Basically comes to this. 

2 x 40 watt pumps for 24 hours = 1920 watts

1 x 40 watt pump for appr 5 hours = 200 watt

4 x 45 watt fans for 4 hours = 720 watt

Worst case max is 2840 watts for 24 hour period. 

Rest of calc, if you take "Cheaper" battery's and allow 30% discharge and allow for 2 days storage the result looks like this.

24V.JPG.f6f67716249371fc8d5c40b58408e34b.JPG 

So you will need at least 2 x 330 watt panels and 542 Amp hour battery bank. 

If you have Eskom available and you want to allow for 1 days storage the bank size drops to 360 Ah .

Either way, to use 100 ah battery's will just complicate everything. The aim is to try and reach the required AH in the least possible stings. Reaching 360 Ah will need you to connect 2 12 volt 100 ah (8 battery)  in series and four strings like that in parallel. Using 200 ah battery's are actually better. 2 strings of 2 in series. (4 Battery's) 

Just to give you and idea of what is needed at the end to go off-grid with your project. 

Duisend dankies Jaco.

Dit het my oe bietjie oopgemaak. Sal maar vir eers dit wat ek het gebruik vir back-up as Eskom af gaan. Die behoort die sisteem (Pompe) aan die gang to hou vir 2,5 ure. Sal maar net 'n changeover insit sodat dit outomaties kan oorskakel

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In my opinion, the Axpert is not the right choice for this setup.

I would rather use a small puresine wave inverter. You get a 400W PSW for about R2.5K. This will power the pumps. Then use a couple solar panels and MPPT charger to charge and run the batteries. You can still use the calculations above but might find that you'll end up using less than that and will have some nice backup power when needed ;)

Edited by SilverNodashi
typo
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