Nick Veenstra recently conducted an analysis of energy consumption at a dairy farm in South East Queensland and modelled the viability of a number of solar PV and battery options to determine the optimum system for the farm. The analysis was conducted as part of Mr Veenstra’s requirements for his Master of Sustainable Energy thesis.
The dairy consumes between 300kWh and 410kWh per day, with higher consumption during the summer months reflecting a higher cooling load. The dairy uses a diesel generator to ensure reliable power is available if milking is occurring during stormy conditions. The farm has other connection points for irrigation and other uses.
It was important that the farm remain connected to the grid, so hybrid systems were selected for the analysis. Performance and financial modelling software for renewable energy systems were used to analyse the selected hybrid systems, providing key performance and financial metrics to test their viability. Discounted payback periods were used as the basis for testing viability. This approach is more accurate than using a simple payback period because it considers interest, inflation and the decrease in performance of the system over its lifetime.
The study found that whilst solar PV and battery systems are technically capable of reducing energy bills and vulnerability to grid reliability issues, only solar PV is currently an economically viable option at the farm.
Some of the reasons for this are:
- The highly variable electricity load throughout the day with two milking cycles;
- Current up-front Small Scale Technology Certificate (STC) incentives for solar PV installations less than 100kW, more information HERE;
- Costs of battery energy storage, noting that these costs are reducing rapidly; and
- Significant network costs and export charges for connecting Solar PV larger than 30kW.
The four options were analysed for the dairy and the results are summarised below:
|System:||30kW Solar PV only.||100kW Solar PV only.||30kW PV + Battery: 60kW / 67kWh||100kW PV + Battery: 60kW / 216kWh|
|Cost||$55,009 -$73,320||$183,300 – $244,400||$281,009 – $349,320||$667,730 – $778,730|
|Network Cost||–||$53,995 – $104,995||–||$53,995 – $104,995|
|Network Export Charges||–||$228,125 ($25 per day over 25 years)||–||$228,125 ($25 per day over 25 years)|
|Annual Cost Savings||$15,000||$36,000||$14,000||$32,500|
|Net Present Value||$128K – $113K||$209K – $113K||($134K)||($440K)|
|Discounted Payback Period||3.9 – 5.7 years||9.9 – 15.8 years||–||–|
Note – Values were not calculated using upper bound initial costs when the lower bound initial cost of systems generates a negative net present value.
Whilst this study focussed on generation and storage, there may be energy efficiency opportunities available to Dairies, including cost effective water heating. Find more information HERE and read about how a Brookstead cotton farmer is saving money and has improved pumping reliability with a grid-connected solar PV system HERE.