Offgrid energy, water and effluent delivers true agricultural sustainability

When David Travers purchased his 45-hectare property ‘Siostra Springs’ in the Clare Valley in 1995, he bought agricultural land without any major utility connections.  

No connection to the (then ETSA) electricity grid, no connection to SA Water’s grid and no sewage connection to the local council’s common effluent drain.  Fortunately it wasn’t a new situation for David, whose family had a century of farming broadacre sheep and wheat properties on Eyre Peninsula; including more than 1000 ha of farms without these same common utilities.  

But Siostra Springs has become a model for what is possible in combining emerging technologies with genuinely sustainable living.   Over the past 20 years David has built three interdependent utility grids.  A fully offgrid 140m-long solar micro-electricity grid, 1.2km of internal high pressure water grids and an aerobic effluent system, producing irrigation water for horticulture.  All powered by solar PV, with gel battery storage and supported by 8kW of conventional diesel backup.

While none of those technologies are particularly unusual in isolation, the project’s uniqueness comes from its full integration and collective independence from any utility scale support.

“For us, achieving economic, environmental, technical and social goals is genuine sustainability.  A lot of projects fail because they don’t achieve this balance.  It’s like a four-legged chair.  If you take one leg away, your chair will tip over when you really put some weight on it,” David says.

“It doesn’t matter how honourable your environmental goal, if the technology doesn’t work reliably in the field, your project will eventually fail.”

In 2014, noticing more frequent summer heatwaves and following two significantly dry springs, David began to seriously investigate the option of installing supplementary irrigation for his unirrigated ‘Single Vineyard’ shiraz block.  The majority of which is contracted to Penfolds (Treasury Wine Estates, ASX:TWE).

“We were conscious of ensuring we did not lose quality in adapting this dry grown vineyard to one with supplementary irrigation,” David says.

After consulting with Dean Willoughby, his Grower Liaison Officer at TWE, David set out to design an irrigation system that would meet the winery’s fruit quality needs and then worked backwards to match an energy system that would power the irrigation pump.

The key challenge was an irrigation system design that required a 4kW vertical pump to provide enough power to lift water to a 50m head, while maintaining sufficient pressure over irrigation schedules of up to six hours.  Obtaining the necessary starter motor power from solar required some key customisation.

“A lot of people said what we were trying to achieve was impossible.  But working with Offgrid Energy, Grundfos and Mid North Irrigation we overcame the need for three-phase power, by customising a CR multistage 240V x 3 Grundfos starter motor,” David says.

“At about the same time we were also building a cottage at the property and wanted to combine further renewable and sustainable benefits.”

Working closely with his engineering builder-brother Peter, owner of Travers Construction http://www.traversconstruction.com.au/, the two used computer-aided design (CAD) to achieve a range of energy saving elements, including:

  • 2.7m ceilings, allowing 2.4m north facing windows for large amounts of natural light
  • Specific due north orientation with a precise 3000mm wide veranda to keep hot summer sun out of the house, but allowing warming winter sun in
  • A western wall that contains only 0.5m2 of window space, minimising glass conduct in western summer sun conditions
  • Optimal use of 4 watt downlight LEDs throughout
  • Carefully oriented louver windows to allow passive gully airflow to cool in summer
  • Recycled foam waffle pod saving earthern foundations, and a polished-concrete slab finish
  • Hebel™ wall panels (three times the thermal properties of brick veneer and 30% less CO2)
  • Timber gables, allowing natural contraction, and thus airflow, in summer, and expansion, and thus closure, in winter.

David says anyone can develop lasting sustainable energy solutions if they are focussed on long-term success and have a broad systems approach.

“There’s a lot of hype about creating ‘sustainable’ living – environmentally sustainable in particular. Unfortunately many ambitious tree-change projects forget true sustainability means achieving lasting economic, social and technical measures – not just ecological ones,” he says.

SIOSTRA SPRINGS’ KEY TECHNICAL FACTS:

ENERGY SYSTEM

Offgrid energy system http://www.offgridenergy.com.au/
10 x thin film PV solar panels. LG 300W Neon Monocrystalline (3kWp)
24 x gel batteries.  PVV 660 BAE VRLA Sealed Gel (686Ah = 32kWh@C100)
48V Sunny Island Inverter/Charger
Solar MPPT Inverter. SMA SB.  3000TL
Inverter voltage and frequency are 230V, 48-52Hz
Battery Inverter/charger delivers 6kW continuous power output; 8kW 1/2hr; 9.1kW 5mins; 11kW 3sec (~20kW ms).
J108 Kubota diesel 8KVA generator (backup for system)

WATER SYSTEMS

(1) HIGH PRESSURE IRRIGATION
240v input into the MPC-EC control panel
4.0kW Grundfos motor (3 x 240v starter)
1km x 80mm PVC mainline, 40mm + 50mm PVC sub-mains
50mm hydraulic pressure reducing valves

(2) RAIN WATER
3 x 22,500L (total 67,500L) of rainwater, extensive gravity feed.

EFFLUENT SYSTEM

3250L, five chamber, aerobic Ri-Treat waterwater system. Produces chlorinated irrigation water and powered by 1 x 1000-watt submersible pump with float switch and 1 x 100 watt biocycle oxygenation pump.  https://www.ri-industries.com.au/