Heating water in dairies accounts for between 10 per cent and 40 per cent of energy consumption – the hot water is used primarily for cleaning and wash-down. Energy monitoring has been undertaken at a number of dairies under the Energy Savers Program.
An energy audit considered the most efficient hot water option for a Southeast Queensland dairy farm.
The farm uses approximately 24 per cent of its energy for hot water production and with rising electricity prices, there is potential to save energy and money by upgrading the system.
The farm uses around 800 litres of 90°C water per day for cleaning milking machines and an additional 300 litres of 70°C water each second day for vat cleaning. Because of the milking times, half of the daily hot water is used in the morning and the other half later in the afternoon, with heating occurring during the day, and vat water able to be heated during off-peak periods.
Four hot water options were considered for the dairy including:
- Adding 800 litres of extra water storage tanks to enable more heating to occur during off-peak periods;
- New solar thermal collectors (solar hot water system) and 1,500 litres of extra water storage;
- New heat pump powered by a new PV system with 1,500 litres of extra water storage; and
- Adding a new electric heat pump only.
A solar system provides some energy to the farm and exported solar power earns a Solar Bonus Scheme feed in tariff of 44c/kWh so that any power that can be saved during the day may be exported at that higher rate.
The energy savings and simple paybacks for each of the options were considered as follows:
|Item||Larger Water Tank – 800 litre||Solar Hot Water including 1,000 litre tank.||Electric Heat Pump, 1,500 litre tank and Solar PV||Electric Heat Pump|
|Energy Saving (kWh per annum)||0||27,396||29,851||21,773|
|Energy saving for hot water %||0||89||97||71|
|Capital Cost $||6,500||35,000||48,785||31,000|
|Annual Cost Savings ($/annum)||422||7,794||8,550||6,194|
|Payback period (years)||15.4||4.5||5.7||5.0|
The farmer is now considering whether to install the Solar Hot Water system, including options to finance efficiency and renewable energy projects.