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?