Energy audits are an excellent way of measuring farm energy use and potentially saving money on electricity bills. Audits are expensive, in the order of $10,000 for a detailed level 2 audit of a large-scale vegetable farm, but savings can be considerable, and the pay-back period is commonly about 1-2 years. In addition, there is funding assistance available. Applicable programs include:
- Low Carbon Australia with loans or other financial assistance to upgrade key equipment, such as cool rooms and electric pumps, to increase energy efficiency (section 5.5.3).
- State-based programs – most States have grants available for making improvements in energy efficiency. Refer to section 5.6 for details.
A recent project that audited nine irrigation farms in Tasmania made the following conclusions:
- Total energy bills (electricity + fuel) varied from $35,000 to $156,000 per year, with the average being just over $80,000 per year. Electricity bills accounted for an average 64% of the total energy bill or nearly $52,000 per year.
- Irrigation accounted for 70‐80% of farm energy costs.
- The average energy index for irrigated areas was 1,268 kWh/ha ($216/ha).
- For those irrigation systems with flow meters installed, energy indices were calculated at between 200 kWh/ML and 500 kWh/ML, or about $35/ML to $85/ML. Variations depended on pump/irrigation sets efficiencies and the Total Dynamic Heads for those pumps.
Improving energy efficiency may be one of the fastest, cheapest and easiest ways to reduce farm energy expenditure and greenhouse gas emissions.
Types of energy audits
There are three main types of energy audits used for assessing farm energy use:
Energy Audit Method Level 1: Preliminary Audit
(Overview of the Total Energy Consumption On-site, Whole Farm Approach)
This is the simplest and cheapest form of energy audit. A whole-of-farm approach is usually adopted. This involves collating all the energy use data from the farm, including the total fuel (diesel, petrol and other fuels) and the total electricity energy consumed. It is generally expected that these figures will be available from the farm receipts. The total energy uses are then divided by the total farm production to derive the energy insensitivities of the site. Usually no additional tools are required for this level of audit.
Energy Audit Method Level 2: Standard/General Audit
(Itemised Farm Approach)
Level two energy audits generally involve breaking down the total energy usage on the farm into energy used in each farming operation. A level 2 will usually consist of a bowser and electricity meter-box type measurement for all processes, and with specific “spot” measurements for the key processes. It may also involve in-depth farmer interviews to identify the major energy usages.
Energy Audit Method Level 3: Detailed Audit
(Specific Operation Investigation)
The aim of level three energy audits is to investigate ways to improve the efficiency of a specific operation. Typically, level 3 audits would focus where the greatest energy consumption has been identified from level 2. This will usually involve a range of different sensors to measure the performance of different machines. Examples of sensors used may include (irrigation head) pressure, flow rate, engine RPM, tractor travel speed, torque, load and temperature etc. A data logger may be required to record the data over a considerable period of time. A level 3 energy audit may be necessary to certify a product/farming operation and to establish the energy-star rating and labelling scheme.
Tools available to assist with energy audits
EnergyCalc was developed for cotton/grain production by the National Centre for Engineering in Agriculture, University of Southern Queensland. It is a software tool originally developed by NCEA to quantify operational/direct energy inputs on farm and to determine greenhouse gas emissions due to energy uses. EnergyCalc assesses direct on-farm energy use, costs and the greenhouse gas emissions (GHGs) associated with diesel, petrol, LPG and electricity consumption. Energy use is examined across key processes within a production system and can be used to evaluate farming practices such as tillage, spraying, irrigation and post harvest. It is most useful in a level 2 energy audit.
Nursery industry energy calculator
The Australian nursery industry in collaboration with the University of Southern Qld has developed a Renewable Energy Calculator based on the EnergyCalc tool. The calculator is available online via the NGIA website. Although designed for use by the nursery industry, it could also be useful for vegetable growers. The tool will help calculate the current energy load within a business and calculate the renewable energy required to offset the energy cost.
Energy Self Audit Tool
Hydro consulting Tasmania has produced a booklet which aims to help Tasmanian farmers conduct a self audit of energy use on their farm. It also allows them to establish their historical energy use, develop energy use benchmarks, set energy-saving targets, and identify and implement energy-saving measures to meet those targets.