New technology for small field irrigation:
In today’s market there are a number of full sized centre pivot irrigators designed for larger fields.
Mini pivots, available from, Hardwick Irrigation Supplies, have been developed for irrigation on smaller sites under 250m radius.
They come towable as standard and can save labour costs and your time compared to other forms of irrigation. These pivots run with 100 watt 48 volt DC powered electric motors, enabling low power requirements to drive the machine.
This is equivalent to a 100 watt light globe, which is a distinct advantage to conventional centre pivots.
Mini pivots can be driven by a water turbine. This relies on the power of water passing through a turbine to drive a DC generator charging a set of batteries.
The battery pack is large enough to operate the machine for 12 hours without water - enabling the mini pivot to be manoeuvred for towing if it is to irrigate a second site
Using the mini pivot and water turbine:
A 6 span towable mini pivot which is 246 metres long (covering 47 acres) per site is quite common.
This requires a peak power load of fewer than 600 watts, less than a small electric drill. The only difference is when irrigating, the machine will only operate the motors for 20% of the time (for example when applying 30 mm of water).
This equates to an hour is less than 120 watts.
If mains power, 240 or 415 volt is available then power supply is straightforward for the mini pivot.
If a generator is required a common problem is durability due to the low power loads. A cheap unit running at high speed (3000 rpm) will not last long; nor will a 4 pole unit running at 1450 rpm – due to glazing of the motor due from low loads.
Example of the water turbine in use:
David Barron has installed a mini pivot at Cooma, it is 267 metre long and irrigates 55 acres per site.
The pivot works two sites and the water is drawn from a river with a diesel powered pump. Since there is no mains power available the turbine is bolted to the inlet manifold of the pivot and the battery pack is attached to the pivot point frame.
This allows a tractor with a 3 point linkage to pick up the pivot point frame and tow it from one site to the next.