Saturday, January 10, 2015

Simple Solar Irrigation System

In 2009, we bought an acre of land in Homestead, Florida , about 35 minutes south of Miami.  Since the parcel had no electricity or structure to accommodate a large solar array and the related inverters and water pump for a full scale sprinkler system, I settled for a drip irrigation system.

I wanted it to be as simple as possible with the least demand for equipment.  The solution that I settle for  was to use a 275 gallon plastic tank like the ones used for mobile car wash ($60 locally, you have to rinse it as it usually contained vegetable oil or something in that line), a 2 inch electric valve ($160 ebay) to release the water and an electronic timer ($16 ebay).  Electricity is supplied via a Unisolar PV136 module on the ground ($110 ebay).  The charge controller is an LCD30 ($79 ebay).

The water pump is a 24V 4 inch, 1.6 gallon per minute Chinese well pump inside the 6 inch well hole or shaft ($135 ebay).  I have read reviews of people complaining about the quality of these pumps but I have had mine for over a year working several hours everyday and so far it has not given me any trouble.  There is no reason to worry about overheating as the pump is submerged in the well in cool water.  The battery storage are two car batteries in series ($65 each at Walmart).  Now I'm a fan of using Walmart batteries as they are reasonably priced and if you ever had problem you can just take them back for a replacement if they are 3 yars or less old or prorate of they are under 5 years.  No questions asked or even a receipt necessary.  I have not had problem with them yet and I don't expect to have later.  I have had problem once with a car battery in my wife's car and they replaced it after a little over 2 years free of charge.  I don't like exotic and expensive batteries as they are well, expensive and they don't rotate fast at the distributor and might not be as fresh when you buy it.

The water tank has a 2 inch manual valve with standard npt threads to goes into the 2 inch electric valve.  Now some people might ask why an expensive $160 brass electric valve when there are some plastic npt valves for less money like the ones used on sprinkler systems.  The reason is that those cheaper valves are designed for pressurized sprinkler systems with large pumps or city water lines with good pressure.  Since my system works with gravity, the pressure is not enough to open them properly and sometimes it might work and sometimes not.  Or it might work halfway.  This particular type of brass valves works with 0 pressure and works every time.  You can use a different diameter valve depending on your system like size of the valve on your water tank and number of trees to be irrigated.  If there is less then you can use a smaller diameter valve which in turn are much less expensive.

After the 2 inch brass valve it goes into 2 inch PVC pipes.  I recommend you to buy the irrigation pipes instead of the one for potable water as the irrigation type are cheaper as they are thinner and thus allows more water.  Comes in sections of 20 feet instead of 10.  And one end is bigger to fit into the next tube saving time and money in adding a piece of joiners.  At 25 foot length on the 2 inch PVC pipe there is joiner with a 3/4 outlet thread on the top where a 3/4 T in inserted for the 3/4 irrigation tubing.  And a barb for 1/4 tubing is inserted at the appropriate length for each tree.  For 10 minutes of irrigation, each of the 82 tree receives about 1.5 gallons of water and take the pump about 2 hours to replenish the used water.   Oh!  The pump is activated via a float switch ($10 amazon) that activates when the water level drops and stops when the water tank is full to the switch level.  A 24V relay ($10) is needed as the float switch is of low amperage and can not be used directly to run the pump.  The time switch can be used to run the electric valve as it can handle 15A and is way more than the valve consumes which is about a little over 1 Amp. 

 Timer that controls the watering and the relay connected to the float switch that controls the water pump.
 This is the 2 inch electric release valve coming out of the water tank and into the 2 inch pipes.
 Ending of one extreme of the pipe where a 3/4 T is coming out and connected to the 3/4 plastic irrigation hoses.


 The good thing about drip hoses is that you can puncture it anywhere and install a barb to get a water outlet.  You are not constrained like with rigid pvc pipes.  If you don't need it anymore you just put a plug in it or bend the 1/4 tube and tie it.
 As you can see, you can insert the barbs anywhere you need water.
 This is the float switch that controls the water pump.  When the water is released via the electric valve, the float activates the water pump and stops once the level has gone back to normal.  This model has two floats in case you want different levels.  The floats can also be reversed to it activates when the level goes up and deactivates when the level goes down.
3/4 T barb installed for the flexible secondary hoses that supplies the trees.




No comments:

Post a Comment