Wednesday, August 5, 2015

Solar Power Drip Irrigation

I constructed a simple solar powered drip irrigation system to water the vines this year.  The system has two segments; the solar power generation/circuit and the water distribution system.

So the water distribution system works like this.
There are 150 vines on each leg of the distribution system.  The water pump is hooked up to a series of tanks (1500 gallons total) and pushes up to 180 gallons of water per hour and each of the 150 vines has a 1 gallon per hour drip emitter (so distribution for each leg is 150 gallons per hour).  So when the pump is running there is enough pressure at 180 gallons per hour flow to ensure the 150 gallons gets to the vines at approximately 30lbs per square inch of pressure.

The 12v pump is activated by a simple water pressure switch.  The switch activates when the pressure drops below 20 lbs per sq inch and shuts off when the pressure get up to 40 lbs per sq inch.

Each leg is on a timer.  I set the timer to go on for 1 hour every 3 days.  When the timer activates it opens up and the pressure in the line drops in the line below 20 lb per sq inch which activates the switch to turn on the pump.  The pump does its thing pumping up to 180 gallons per hour and because there is 150 drip emitters releasing water at 1 gallon per hour (so 150 gallons) on the leg it pushes the water out fast enough through the emitters so the pressure does not exceed 40lb per sq inch(so the switch doesn't turn off).  But after 1 hour the timer closes and the pressure behind it builds up to 40 lb per sq inch and the switch shuts off the pump.

I have added a pressure gauge in-line between the pressure switch and the timer to see how much pressure is in the line when it is running. When the pump is running it is usually at about 28 lb per sq inch. 

One thing to remember is that I have just enough drip emitters to keep the pressure at around 30 lb per sq inch otherwise if there were not as many the pressure may be too high in the line and the switch would turn off the pump. I had anticipated this and hooked up a hose at the end of the leg of the drip emitter line that could be partially closed off manually and thus set to regulate the pressure. The line loops back tot the water tank putting the excess water back into the tank.  Fortunately I did not need to use this.

I can run this 4-5 weeks without having to refill the water tank.

The solar generation/circuit works like this;
The solar panel is 125 watt 12volt panel that charges a 12 volt battery though a 7.7amp charge controller.  The pump is wired to the battery through the pressure switch.  The pressure switch is the 120 volt model used on a pressure tank in a house but you can run 12v though it as it is just a switch.

Here is some pictures;