The site is 50 ha with a production area covering 8 ha consisting of growing areas, a propagation facility that is used 6 months of the year, and a potting area. The irrigation system operates during the day all year-round producing an average of 7,500 units per ha per year.
Energy consumption varies with the seasons, with the highest peak demand in summer due to irrigation requirements. The highest energy consumption occurs between 11 am and 2 pm. As the nursery is planning to expand the range of plants, production and electricity requirements are expected to increase.
The annual energy consumption for the site during the 2019-2020 period was 16,925kWh at a cost of $5,482, and energy consumption on the farm consists of:
- Irrigation: two bore pumps and a booster pump with Variable Speed Drive.
- Propagation facility: includes 2 heat mats and a small water pump.
- Potting system: consisting of a new potting machine.
- Other minor uses: a workshop, irrigation controls, and staff facilities.
A recent energy audit showed how improving the current systems can lead to energy and cost savings. The audit recommendations are:
- Tariff Change: Change from transitional tariff 65 that will be phased out during 2021 to optimal Time of Use tariff 20.
- A 15kW Grid Connected Solar PV: to offset all the electricity required from the grid and be able to feed into the grid when possible.
Table 1. Costs and savings from audit recommendations.
||Annual Energy Savings (kWh)
||Annual Costs Savings ($)
||Emission Savings (tCO2-e)
||Capital Cost ($)
||Payback Period (Years)
|15 kW Solar PV
The replacement of heat mats with more efficient systems was considered, but given the intermittent use of this equipment and the small heated area, the solution was considered uneconomic with a long payback period and a small return on investment. However, the auditor suggested replacing the heat mats if they fail over time.
The nursery has proceeded with the installation of a slightly smaller 12-kW solar PV system The savings have been made have been measured in a Measurement and Verification (M&V) process as outlined in Table 2.
Table 2. Estimated and Actual energy and costs savings from Solar PV.
|Energy Savings including exports (kWh)
|Cost Savings including exports revenue ($)
* Extrapolated from 9 months of measured data.
Lower savings have been achieved which is consistent with the smaller system implemented compared to the recommendation. The cost savings achieved have also been influenced by changes in solar energy use. Only 8,200 kWh are being used onsite and around 13,200 kWh are being exported to the grid, however, offsetting all the energy consumption from the grid would lead to further cost savings as the revenue from feeding into the grid is lower than the cost of using energy from the grid.
Although the farmer opted for a solar system that was 20% smaller than the one recommended in the audit, the energy savings and cost savings were not 20% less, so the farmer is getting more than expected from the new system.
The next step for the farmer is to identify opportunities to utilise more of the solar energy generated onsite to reduce the amount of grid energy used and solar energy exported. The auditor recommended reviewing electricity use and changing use patterns to reduce the small peaks in daily electricity consumption, being able to match energy consumption with solar generation. See HERE a similar case where better solar utilisation can lead to great energy and cost savings.
From the implementation of recommendations in the audit, the farm has reduced energy consumption by 127% thus becoming a net exporter of power. Costs have been reduced by 74%, including feed-in revenue, with Carbon emission savings of 17.3 t/CO2-e per year.
Table 3. Pre and post implementation energy, costs, and energy productivity improvements.
|Energy Consumption (kWh)
|Energy Productivity (kWh/ha)
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 firstname.lastname@example.org.
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.