Energy Savers
South East

Toowoomba Nursery

Implemented
47
Energy Savings
11.9
Savings
4,100
Industry
Nursery
Product
Fruit trees and native plants
Irrigation
Solid Set
Pumps
Bore, Booster
Technology
Pump upgrade, Heating, Air Conditioning, Solar Photovoltaic
Capital Cost
$47,323

Summary

A South East Queensland nursery growing fruit trees and native plants has saved money and reduced energy consumption after implementing the recommendations from a recent Energy Savers Audit. The recommendations installed included pumps, heating, and air conditioner upgrades as well as a solar PV system.

The 4.3 ha farm with current production covering 0.5ha utilises automated propagation and irrigation systems operating 24 hours per day year-round producing around 300,000 units per ha per year. Energy consumption varies with the seasons, with the highest peak demand in winter due to heating operating overnight. As the nursery is planning to expand, production and electricity requirements are expected to increase by 15% per year over the next three years. 

The annual energy consumption for the site during the 2018-2019 period was 26,953kWh at a cost of $6,500, and energy consumption on the farm consists of: 

  • Irrigation: including a booster pump and a bore pump. 
  • Propagation system: includes a hydronic heating system with a timer installed.  
  • Other minor uses: an office and staff facilities.  

A recent energy audit showed how improving the current systems can lead to energy and cost savings, even with the projected increase in production. The audit recommendations are: 

  • Irrigation Pump Upgrade: replace the booster pump with a twice-size multistage Variable Frequency Drive (VFD) controlled unit and replace the mainline with a 90mm pipe, to increase the flow rate and meet the future irrigation requirements as the nursery expands.  
  • Bore Pump Upgrade: replace the bore pump with a double-flow rate unit to reduce the runtime to half (6 hours), allowing it to operate during the peak solar generation period in the future, reducing electricity demand from the grid. 
  • Hydronic Heating System Insulation: insulate the pipes and install a 250L hot water storage tank to increase the storage of an existing system. 
  • Replace Air Conditioner: replace the old office AC with a reverse cycle split system, improving its efficiency. 

AC ES013

  • A 30kW Grid Connected Solar PV: to match solar generation with the projected increase in energy consumption, including heating the water for the initial period, thereby reducing the overnight electricity demand given the use of the hydronic heating system. 

Table 1. Costs and savings from audit recommendations. 

Recommendations  Annual Energy Savings (kWh)  Annual Costs Savings ($)  Emission Savings 

(tCO2-e) 

Capital Cost ($)  Payback Period (Years) 
Irrigation pump and system upgrade  3,567  1,116  3.5  7,525  6.7 
Bore pump upgrade  3,931  1,230  4.6  3,888  3.2 
Heating system upgrade  1,356  406  1.3  1,111  2.7 
Air conditioner (AC) replacement  1,084  340  1  1,599  4.7 
30 kW Solar PV  44,695  10,488  15.1  33,200  3 
Total  54,633  13,580  25.5  47,323  3.5 

 

The nursery has started implementing all the recommendations and at the time of writing, had upgraded the air conditioner and installed the Solar PV system. The savings made have been measured in a Measurement and Verification (M&V) process, as outlined in Table 2. 

 Table 2. Estimated and Actual annual energy and costs savings. 

Metric  Audit estimation  M&V calculation  Variation (%) 
AC  15kW Solar  AC  15kW Solar  AC  15kW Solar 

Energy Savings (kWh) 

1,084 44,695 916  13,724 -15 -69

Cost Savings ($) 

340 

10,488 255  3,855 -25
-63

 

The solar system is being implemented in 2 stages, with a 15kW array and 27.6kW inverter already installed and another 15kW array to be added to the system in the coming years. The lower solar generation (less than 50% of the expected) has been mainly caused by incorrect inverter settings, which were fixed during the M&V process. 

The mainline irrigation upgrade will occur in mid-2021 which will reduce the irrigation run time and allow it to be matched with the solar generation curve for better utilisation. On the other hand, the new bore pump still requires the spray nozzle upgrading used in the tank to aerate the water, allowing reduced operating hours to match pump use with the solar generation period.  

The new larger bore pump without the required spray nozzle upgrade has increased energy use by 900 kWh per year and the heating system has increased its annual energy consumption by 1,800 kWh given lower temperatures during night-time. The energy consumption on farm during the 2020 period was 15% higher than in 2019, in line with the projected increases.  The M&V determined that 5% is due to the expansion of the farm, 7% is driven by climatic factors and 3% is because of the incomplete upgrades of the irrigation system. Since the audit, the owner has also reconditioned the abandoned greenhouse which will be operative in 2022, increasing the irrigation requirements and energy consumption. 

From the partial implementation of recommendations in the audit, the business has reduced energy consumption by 47% and costs by 52%, with Carbon emission savings of 11.9 t/CO2-e per year. With the remainder of upgrades and inverter settings corrected, savings are expected to improve to 96% by 2021. 

Table 3. Pre and post implementation energy consumption, costs, and energy productivity improvements. 

Metric  Pre-implementation (2020)  Post- implementation  Reduction (%) 
Energy Consumption (kWh)  30,944  16,304  47 
Cost ($)  7,986  3,786  52 
Energy Productivity (kWh/ha)  61,888 32,608 47 

 

An energy audit is a good investment 

An energy audit is a great first step in moving a business towards a more efficient future by reducing energy use, costs and carbon emissions onsite.  

An energy auditor will review your past energy bills, your equipment and the way your business operates. They’ll show you where you’re using excess energy and explain what you can do about it. Find out about what’s involved in an energy audit HERE. 

See our range of agricultural energy efficiency case studies HERE and Subscribe to our bi-monthly energy e-news HERE  

If you have any energy efficiency related questions for the team get in touch at energysavers@qff.org.au.  

The Energy Savers Plus Extension Program is delivered by the Queensland Farmers Federation with support and funding from the Queensland Department of Energy and Public Works. 

 Capture