Solar trial works wonders
Solar irrigation means the best of both worlds
WHEN growers try to reduce pumping costs by irrigating at night, there can be significant impacts not just on productivity, but on the grower’s health and wellbeing as well.
Feeling constrained to night irrigation times to reduce electricity costs means growers often delay irrigation and frequently do not apply the quantity of water required to maximise productivity in a supplementary growing region such as Bundaberg.
Chasing water winches at night also disrupts sleep and can be dangerous.
To overcome these problems many growers have looked for and implemented alternative irrigation systems.
While solar energy has significant advantages and potential cost savings, stand-alone solar systems can have operational limitations.
A new three-year renewable energy project in Bundaberg, which is funded by the Australian Renewable Energy Agency (ARENA) and administered by the Bundaberg Regional Irrigators Group (BRIG), is investigating the feasibility of using a unique hybrid solar and grid energy system to provide all the convenience of grid electricity and the savings offered by solar.
Bundaberg Sugar Services special projects officer, Maurie Haines, said the solar array at the demonstration irrigation site had been living up to expectations since it was commissioned in mid-January this year.
“This system is designed to be a hybrid irrigation system that blends solar and grid power to maintain seamless operation between clear or cloudy daytime conditions or night-time operation,” he said.
“Unlike most solar farms, this system does not feed solar energy into the grid. All the decisions the grower makes are based on whether the crop needs water, and not how much it will cost.”
During peak solar radiation conditions, the solar panels can power the pump without drawing on the grid supply.
In the early morning and late afternoon, the system draws as much solar energy as is available and draws the rest from the grid. In the evening, the cheaper night tariffs are used if required.
The demonstration site is located on the Killer family farm at Sharon, west of Bundaberg.
Rodney and his son Josh have 58 hectares of cane on this block and use highpressure water cannons to irrigate.
Other options, such as low-pressure lateral booms, are not a feasible option for the undulating and oddly shaped farm.
Josh said the new pump system had given them a much greater incentive to water when they knew it would be beneficial, without worrying about the cost of electricity.
“This year we have irrigated ratoons much earlier than we usually would and we are confident that looking after them during the dry winter and early spring will pay off in higher yields at harvest next year,” he said.
The other big benefit for Josh has been the reduced work stress surrounding irrigation. Josh lives about 45 minutes from the farm with the solar demonstration so starting and stopping pumps and checking water winches was time consuming.
“Before the solar system was operating I would need to get to the farm early to shut the pumps off and stay late in the afternoon before starting the pumps so that we only watered on the night tariff,” he said.
“Now I can turn the pump on and off remotely, knowing that there is a safety mechanism to shut everything down if there is a problem.
“I can really manage my time a lot better between our two farms and can get the most out of every day.”
The Killers are now able to irrigate all day and all night if necessary during peak water use periods, to keep their crops growing and make the most of the available sunshine and warmth in spring and early summer particularly.
They are also using the extra flexibility with irrigation to water in fertiliser so they eliminate volatilisation losses and get the full benefit of the applied nutrients. Josh has found that the solar system has changed their whole
mindset when it comes to the application of water.
The equipment installed at the site includes a 240-panel solar array (81.6kW), 45kW electric motor and centrifugal pump designed to operate at varying speeds, and a VSD Ecodrive controller to manage both solar energy (DC power) input as the priority energy source with grid supplied (AC power) as a supplementary source. The Ecodrive controller also manages the input water pressure to maximise pump efficiency.
A new pump was installed as part of the demonstration project but it has the same capacity as the one it replaced.
The changes have centred on improving pump efficiency.
The before-and-after energy usage comparison shows the solar/grid pumping demo system uses approximately 78 per cent less energy than the grid-only system it has replaced.
The VSD Ecodrive power blending system monitors the water inflow pressure and manages the motor speed to maintain a constant pressure to the winch irrigator.
This means the pump is always operating at maximum efficiency and not wasting power, unlike the previous system, which relied on a check valve to control pressure to the winch while continuing to operate the motor at maximum speed and energy use.
“Unlike some solar systems, this one never cuts out and does not simply switch to the grid if the solar input drops below the threshold required to run the pump,” said Maurie.
“The priority-solar with grid back-up system maximises the benefits of solar electricity.
“Given that many growers in the Bundaberg area only use 50 per cent of their water allocation, due in part to concerns over pumping costs, there is plenty of room for additional productivity from the current crop area,” he said.
“Avoiding crop stress in July and August and taking advantage of longer days in summer will both pay off in extra yield.
“The more the grower uses a system like this the better off they will be.”
The modular design of this demonstration solar farm is one of the key features that makes it a viable option for other growers.
It is possible to start small, installing the Ecodrive system to initiate greater pump efficiencies and then add extra solar panels as funds permit, until the array has the capacity to run the pump on solar energy alone during clear daytime conditions.
Over and over again, Maurie has seen the effect of growers making a change to their irrigation practices and reaping the double benefit of better productivity and reduced costs.
“It is so often the case that the productivity gains even outweigh the savings in energy costs,” he said.
To assist with irrigation scheduling, there are soil moisture probes and an automated weather station installed on the Killers’ property. These also contribute data to the area-wide weather monitoring system in Bundaberg, providing growers with more localised weather information.
This demonstration project aims to provide growers and their lending institutions with reliable and field-tested data to support investment in similar systems.
“These systems involve large capital outlay and growers need to be confident that they will deliver productivity gains and cost savings,” Maurie said.
“Another component of this project is to collect local information about how much solar energy is available throughout the year and how that might vary across the district. This will help growers determine if they can expect the same outcomes or better than what we are achieving at the demonstration site.”
All the data collected through the three-year project will be available on the BRIG website (www.brig.org.au), including how much solar and grid energy is consumed for each megalitre of water pumped and all operational costs.
“This information will be of enormous benefit to growers if they get Bundaberg Sugar Services Ltd to conduct a Farm Energy and Irrigation Information Audit for their farm,” Maurie said.
“This will create a powerful decision-making tool for farm energy and farm water use planning in the lead-up to the 2020 tariff changes and beyond.”
STEPPING UP: Rodney Killer and his son Josh were on board with the trial.
HIGH-TECH: The equipment installed includes a 240-panel solar array (81.6kW), 45kW electric motor and centrifugal pump designed to operate at varying speeds.
The solar pump on the Bundaberg property.