Info: my solar-powered irrigation

7 posts

Member for

12 years 6 months
Last seen: 03/08/2018 - 21:05
Joined: 09/23/2011 - 16:27

Info: my solar-powered irrigation

I posted some time ago describing my initial experiments with a solar-powered drip irrigation for my farm at Elands, NSW. I've continued to improve the system each season and thought I'd give an update in case it's helpful for anybody else considering it.

I have two small hazelnut orchards of 100 and 50 trees respectively, for a total area of about 2 acres. I pump from a creek to a 5,000 L tank at the higher of the two orchards, and from there I pump out to a drip irrigation system.

This season I added a submersible pump to replenish the storage tank, but in previous years I had to do that manually with a diesel pump. Since I only visit the farm one or two weekend per month, it's important to me that the system can operate autonomously for at least a week, preferrably a lot longer.

The submersible pump has been a moderate success, but the creek is heavily shaded and I struggle to get enough sunlight on the solar panel. I've extended it a little, to a more sunny position. I'm about to extend it a lot, to a position that will give me about another three hours of useful sunlight. That will need another 100 m of cable, but the power loss in the cable is trivial compared to the extra hours of pumping. I'm using 4 mm cable and a 24 V panel/pump, to minimise power loss. Contrary to a fairly common opinion, this setup requires no battery and no controller. When there's enough sunlight, it pumps.

The drip system is powered by 12 V pumps rated at 17 L/minute (40 psi). I adjust them for a bit less pressure than that - around 32 PSI, as it slows down the on/off cycling when they pressurise the system.

The cycling has been the biggest headache. Those pumps are only itended for short-term use. I am abusing them by running for an hour. They use a mechanical pressure switch that shuts off the pump when it reaches operating pressure, which it does about every 1 1/2 seconds. Those switches are rubbish. My average time to failure was about 3-4 weeks. As the pump switches on-off quite quickly, the switrch arcs and burns out.

I supplemented the mechanical switch with a high-current electronic switch. The mechanical switch still senses pressure, but the electronic switch takes the burden of handling the pump current. This has been 100% successful. However the first time I tried this, I had the switch sitting on my shiny new deep cycle battery, and it got so hot it almost melted through the battery's case. I now have the switches mounted on a strip of aluminium to dissipate the heat.

A month ago I duplicated the pumps for the larger orchard - it has two pumps in parallel, but only one at a time operates. I have them on a 30 minute roster, to rest each pump (they get hot). It also gives me a bit of redundancy so I still get some pumping if one of them fails.

I use 100 AH deep cycle batteries - one per orchard. The larger one has a 200 W solar panel, and the smaller one a 100 W panel. This is easily enough to pump for one hour per day.

I use generic solar charge controllers that I bought online. They are "OK" but I've had a few failures. They are susceptible to moisture and ants.

Timing is the simplest and most reliable part of the system. I use programmable tap timers that I bought at the local hardware store. Exactly the same thing as most folks put on their garden drippers or sprinklers. The pumps are "on" all the time, but they don't do any work until the timers activate, which is one hour per day. I wish there was a controller that would take care of everything - solar charging and timing, and valve opening closing. I thought about making it but ... I'll put up with the existing system and add more redundancy. It's quicker and cheaper. I want to do farming, not electronics :(

The hardest part is getting the system "balanced" so that I pump enough water into the tank over the period of a week to ensure that it does not become depleted. So many variables, and I'm not there for long enough periods to observe it. So it's all trial and error. I've temporarily bridged the 20,000 L house tank into the irrigation system as an insurance.That's on a timer too - 15 minutes per day, but it's mains-powered and I get about 200 L transfered in that time. I don't *think" I need it, but I'm just not sure.

I was intending to attach a photo of the current setup, but it seems to be only possible to insert links to pictures on this forum?

Last seen: 09/17/2019 - 18:07
Joined: 11/23/2011 - 09:38

Hi,

I don't have solar pumps personally, but my friend does. To fill the tanks for irrigation and livestock, she had a float valve system installed. When the tank is full, the float valve switches the pump off. Usually it works fine. However, a couple of years ago, there was a lightning strike that burnt out the switch. You've guessed it, the pump just kept on pumping. The house was down hill from the holding tanks, which overflowed as the switch was burned out. Looked like the last flood in the house yard and took a couple of weeks to dry out. I think that now there is some sort of earthing system installed on the system. Had to share, even if it is a bit sideways to the subject.

 

Cheers,

Barb

Last seen: 03/08/2018 - 21:05
Joined: 09/23/2011 - 16:27

Hi,

 

Control of the filling will be my next project! The float switch is easy enough - in fact I bought one a year ago. However the submersible pump is a long way from the creek. The house tank that I bridged is even further. Too far to run wires.

I priced a wireless remote switch last week - it's over $500. That's expensive compared to everything else in the system. And I'd need two of them with my current setup. I'm putting this together on a shoestring, so 2 x $500 is s showstopper at the moment.

I also want to have a soil moisture sensor so the drippers don't come on when they aren't needed.

Last seen: 09/17/2019 - 18:07
Joined: 11/23/2011 - 09:38

Hi,

 

A soil moisture monitor control sounds like a great idea. Need rain here at the moment as it is very dry- but what's new? Thank Heavens there is plenty of water in my dams.

 

The distance to the storage tanks from the pump spear is only around 700 metres at my friends, so I guess that isn't too far. I do remember that the set up cost her quite a few thousand though. 

 

Cheers,

Barb

Last seen: 12/26/2018 - 09:21
Joined: 05/31/2011 - 09:44

Hi Frisbie,

Thanks for all the wonderful information, very helpful for anyone looking to set up a solar powered irrigation system.

You should be now able to upload an image,

- Click on the image tab in the tool bar

- Click browse server,

- Click upload,

- Choose the file from your computer,

- Click upload and then click insert file.

There was a technical gliche previously which is why this function was not working.

Regards,

Charlie

Last seen: 03/08/2018 - 21:05
Joined: 09/23/2011 - 16:27

pumping gear and the tank

This is the header tank and the solar pumping system. The tank holds about a week's worth of water without replenishment.

 

pump setup

 

More detail of the pump setup - solar chargers in the front (they also prevent over discharge of the batteries). Electronic switches in the middle and the timer to the left of them. Three 12 volt pumps and a small pressure accumulator. It's a mess :( But I have time to either make it work or make it pretty!

Last seen: 04/01/2016 - 23:06
Joined: 04/01/2016 - 22:44

Hey, thanks for the useful information you provided! Solar powered irrigation systems are definitely one of the things people should be thinking about when it comes to making their homes and gardens more energy efficient. After all, every normal irrigation systems uses lots of electricity and often uses more water than it should, which is not only unneccessary, but also costly. We planned on installing an irrigation system recently and we stumbled upon this company - http://www.gardeners-melbourne.com.au/irrigation-services/ . We were very surpriced to find out that there is more than 1 type of irrigation systems. There are all kinds of water and energy saving types, which are supposed to help you save resources. They also told us about the solar powered irrigation technology, but according to them it was still a work-in-process, and that in an year or so there will be a lot better versions. So now we are struggling what kind to get.

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