Energy Savers
Atherton Tablelands

Mareeba Nursery

Implemented
53
Energy Savings
21.9
Savings
7,189
Industry
Nursery
Product
Ornamentals and Fruit Trees
Irrigation
Solid Set
Pumps
Bore
Technology
Solar Photovoltaic
Capital Cost
$33,000

Summary

An Atherton Tablelands nursery growing ornamental plants and fruit trees has saved money and reduced energy consumption after implementing the recommendations from a recent Energy Savers Audit. The recommendation installed included an additional 20 kW Solar PV system.

The farm consists of 8 ha with a production area covering 4ha, which are irrigated all-year-round producing around 500,000 units per ha per year.

The annual energy consumption for the site during the 2018-2019 period was 37,653kWh, with 12,121kWh generated by the solar system and 25,532kWh supplied by the grid at a cost of $10,648. The farm has a 10kW solar system installed on a shed roof since 2014.

The energy consumption on the farm consists of:

  • Propagation system: including a LED lighting system and a seeding line used 1-2 days per week, with seed storage refrigeration operating 24 hours per day.
  • Potting system: includes an air compressor and new potting machinery operating 2 days per week, depending on the season.
  • Office: several computers with screens switched on 24 hours per day.
  • Staff facilities: including a refrigerator and urn.
  • Irrigation: automated pump to operate during non-business hours.
  • Other minor uses: including irrigation controls and workshops.

The auditor identified that the solar system was producing around 75% of its potential due to the suboptimal orientation of the panels and the need for cleaning. Pump efficiency was calculated at 6.3 kWh/ML/m head, lower than the industry benchmark as the operating pressure has been set at a lower point to minimise breakages in pipelines due to low pressure in some areas of the mainlines.

Upgrades to improve irrigation efficiency are planned, which will result in an estimated 4,400 kWh increase in electricity consumption per year due to the energy required to pump more water at higher pressures, with consequent increases in pumping costs and improvements in plant growth.

A recent energy audit showed how improving the current systems can lead to energy and cost savings. The audit recommendations are:

  • Automation: install a time clock on staff urn to only heat prior to breaks.
  • Additional 20kW Roof-Mounted Grid Connected Solar PV: to give 30 kW of total generating capacity, being able to offset most of the nursery energy consumption without requiring network upgrades or special permission from the electricity distributor.

The auditor also identified some immediate no cost or low-cost maintenance measures as follows:

  • Annual cleaning and maintenance schedule for on-site solar PV array to improve system lifespan and efficiency by 6%/year, increasing energy generation.
  • Turn off equipment’s when not in use and activate energy saving settings on the office and other equipment.

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)
Time clock on urn 728 196 0.2 25 0.1
20 kW Solar PV 31,900 9,730 30.6 33,000 3.4
Total 32,628 9,926 30.8 33,025 1.8

 

The nursery has proceeded with the implementation of the 20 kW Solar PV. The savings made have been measured in a Measurement and Verification (M&V) process, as outlined in Table 2.

Table 2. Estimated and Actual energy and cost savings from the 20kW Solar PV.

Metric Audit estimation M&V calculation Variation (%)
Energy Savings including exports (kWh) 31,900 27,019 -15
Cost Savings  including exports revenue ($) 9,730 7,189 -26

 

Energy savings have been reduced by 9% given an orientation of the panels, which have been arranged on a roof facing west, and additionally, it has been influenced by an 11% decrease in the average solar radiation received at this location, which has also limited. The lower feed-in tariff offered in 2020 compared to the evaluated in 2018 has also reduced the estimated cost savings of the system.

The farm’s energy consumption increased by 35% during 2020 from an increase in production and the addition of a second pump to support it. Of that, 26,068 kWh at a cost of $6,063 are sourced from the grid.

From the energy generated by both solar systems,  24,595 kWh are being used onsite – 68% of total generation – valued at $5,720, and 11,516 kWh are being exported to the grid with a revenue of $905. Considering that 52% of the total energy used onsite is being imported from the grid, there are significant potential savings from shifting consumption into the solar generation period. The total power balance of the farm, including solar exports, is shown in the following figure.

ES056

The next step for the farm is to adjust energy usage to offset all the energy consumption from the grid which would lead to further cost savings. The revenue from feeding into the grid is lower than the cost of using energy from the grid. If the farm were to shift 5,000kWh of energy consumption per year to coincide with solar generation times, they would save an extra $770 per year.

From the implementation of recommendations in the audit, the farm has reduced energy consumption by 53% and costs by 61%, including feed-in revenue, with Carbon emission savings of 21.9 t/CO2-e per year.

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

Metric Pre-implementation Post-implementation Reduction (%)
Energy Consumption (kWh) 50,664 23,645 53
Cost ($) 11,783 4,594 61
Energy Productivity (kWh/unit) 0.024 0.011 53

 

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 the rest of the 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.  

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