Harnessing the power of the sun
New off-grid solar water pumps could be the pot of gold at the end of the rainbow for farmers, saving them time and money. By Steve Mcmillan.
Achance encounter at the Central District Field Days a few years back resulted in a Ōhingaiti sheep and beef farmer plumbing in four solar pump units on 600 hectares, 55km north-east of Bulls.
Bryan Rendle, a rural bank manager, says the capital investment has ensured his 2000 Coopworth X ewes and 600 Angus and Dairy Beef cross breeding and fattening cattle have access to constant water sources in somewhat remote locations – ensuring good animal health and reducing farm input costs.
It was after a conversation with Perkinz manager Wayne Perkins that Rendle began investigating solar pumping options.
“We have three React pumps and one Perkinz Solar Submersible pumps and all our systems are working great,” Rendle says. “Solar is magnificent because with four panels on each of the pumps, it’s incredible how they tick away – even on very grey days.
“People who ask me about them get hung up on the fact they don’t pump at night, but that has never been an issue for us, we have plenty of storage so that water storage acts as a battery.
“The solar sub pumps from a spring, works brilliantly and pumps way more water than the specifications say. In the height of summer we move 15,000 litres of water per pump, per day – no worries.
“I did notice it slowing up at one point and replaced the screw after four months and that fixed the problem. It was relatively easy to replace once I’d watched a couple of Youtube clips.
“The beauty of both pump types is they are simple and I can replace seals and do maintenance myself, so I am not reliant on tracking down a tradie,” he says.
Perkins says most clients who adopt the solar pumps require about 8000 to 10,000 litres of water per day.
“You can pump to virtually unlimited distance and the majority of systems we have installed pump to a height of 50 metres to 120m, with the largest being 260m which is a fair old lift,” he says.
“As always, the inside diameter (ID) of the pipe used depends on the distance water is being pumped. The further the distance, the larger ID required to cut down on friction losses. At 200m you could get away with 25mm but at 1km you probably need to go to 40mm.
“In general, for a total turnkey kit cost of about $7000, our units can pump 15,000 litres of water per summer day to a height of 50m, or 9000 litres per summer day to a height of 100m.”
Rendle says the best way to mitigate the inconsistencies of the sun is to pump more water daily than you need to a storage tank or reservoir, allowing you to have a bank of water in the system that can accommodate the down days, effectively turning your tank/reservoir into a battery.
“Farming practices and the type of farm also impact solar water pumps because farms with a larger livestock population require more water and, therefore, more energy to pump water.
‘‘Moreover, farms located in remote areas may not have access to grid electricity, making solar water pumps the only viable option.
“As the world population grows, so does the demand for food. Livestock farming ... is still one of the most important sectors in the New Zealand and Australian agricultural industry. Consistent water supply is crucial to good animal health and good farming practices.”■