Cecil Plains Cotton Farm
Energy Savings: 42% | Cost Savings: $11,200 | Capital Cost: $67,726 | CO2 Savings: 43.8 tCO2-e | Project Status: Proposed
Industry:
Cotton
Location:
Southern Downs
Pump Type:
Submersible
Irrigation Type:
Flood
Technology:
Solar Power and Renewables
The Farm
The farm produces cotton during the summer months and mixed grains during the winter months. Irrigation water is sourced from groundwater using a submersible pump which discharges interchangeably into two channels and a dam. The pump was installed in 2009 and has been unfrequently inspected and serviced.
Average yearly pumping energy is 121,191.8kWh (data from 01/07/2022 to 30/06/23) with an associated cost of $45,704. Pump usage depends heavily on rainfall and is strongly seasonal, typically used 2 -3 months per year. There is a high annual variation in energy consumption at the site as a result.
A key focus of the assessment was to consider opportunities to reduce energy consumption for the pump to below 100,000kWh per year so that the pump could access Ergon’s Small Customer tariffs to reduce energy costs, particularly peak demand, and network charges.
Pump performance indicator.
Electricity consumption per megalitre of water per metre of lift (kWh/ML/m head) is commonly used to ascertain the pump efficiency and can be used to benchmark for comparison of pumps economic performance.
A target electricity usage of 3.80kWh/ML/m head is commonly recommended. The electricity usage at the bore in this farm, was calculated at between 5.04 and 5.29 kWh/ML/m, which indicates that the pump is underperforming.
Bore Pump Maintenance
The power consumption indicated that the pump is correct for the task, though delivering between 21% and 30% less water than expected for its different duties.
The pump has not been removed since 2006, which means that no maintenance has been conducted on it in 18 years. The reduced water flow rate could therefore be attributed to either general wear and tear on the pump, or damage to the bore casing causing loss or recirculation of water.
It was recommended therefore, to remove the pump, inspect the bore casing, repair as necessary and clean the screens.
The audit estimates a flow rate increase of around 20% might be achieved which would reduce the run-time required to deliver the same amount of water by around 400 hours per year.
It was estimated that energy savings would be around 28,000kWh per year, with a potential demand saving of 4kW.
Solar system for the Pump
Three solar options were assessed to determine the most suitable arrangement that provides effective utilisation with the shortest payback period: 10kW, 20kW, and 30kW.
Considerations in the sizing of the Solar PV System and future generation include that:
- Large Customers (using over 100,000kWh/year) are not eligible for the regional feed-in tariff for any exported power so would not earn a revenue for any excess power.
- Solar Systems with an inverter capacity greater than 30kW are not eligible for the regional feed-in tariff.
- Whether the electricity network at that location could accept 30kW of exported power (not assessed).
Because the pump use is strongly seasonal, the solar system will be underutilised while the pump is not in use because the site is ineligible for the feed-in tariff. The recommended maximum of a 30kW inverter on the solar system was set so that the site will be eligible for the regional feed in tariff in the years that it is a small customer.
Therefore a larger solar system may assist in reducing consumption during the short time that the pump is in use, but would not be eligible for the regional feed-in tariff even if the site became a small customer as it would have an inverter capacity greater than 30kW.
The 30kW solar system was considered to be the most suitable. It would offset 23,456kWh, saving around $4,825.19 while the site is a large customer, with an additional saving of $5,254 when the site is a small customer and receives the feed-in tariff.
Summary of recommendations:
The recommendations from the audit have been summarised in the table below:
Recommendation | Annual Energy Savings (kWh) | Annual Costs Savings ($) | Emission Savings (tCO2-e) | Capital Cost ($) | Payback Period (Years) |
Pump and bore maintenance | 28,173 | 6,375 | 24.8 | 30,000 | 4.7 |
30kW Solar System | 23,456 | 4,825 | 19 | 37,726 | 7.8 |
TOTAL | 51,629 | 11,200 | 43.8 | 67,726 |
The savings and payback for the 30kW solar system above are based on the site remaining a large customer and earning no feed-in tariff revenue.
Implementation of both measures may assist in reducing the site’s annual energy consumption below 100,000kWh, though in some years with little rainfall and high pump usage, the site would remain a large customer.
In fact, implementation would likely mean that there are more years where the site is a small user.
Energy Audits. The farm had a Type 3 energy audit as a participant in the QBEST Ag program.
The QBEST program is being delivered by the Queensland Farmers’ Federation and is funded by the Queensland Government.