Farm Ireland

Tuesday 17 January 2017

Take action to cut your electricity bill

John Upton and Michael Murphy

Published 11/01/2012 | 06:00

Like any other outgoing on a modern dairy farm, electricity costs should be monitored and managed. Corrective action can then be taken to bring them back in line. However, many farmers feel it is out of their control. Our research proves that this is not the case.

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It is easy to put a rough estimate on current energy costs. The first step is to add up the electricity charges over a year, excluding taxes and standing charges. These figures can normally be found on the reverse of the electricity bill. Dividing this figure by the total number of litres sent to the milk processor over the same period will give the electricity cost in euros per litre. Multiply this by 100 to get cent per litre.

These figures can then be compared with the results of Teagasc energy audits, which are outlined here. This calculation will be quite accurate if the dairy business has its own metering point. However, it is common to find the farmhouse included in the same bills. Domestic energy use will vary according to occupancy levels and heating type, but this can generally be accounted for by subtracting 10-15pc.

Data collected from 21 commercial dairy farms in 2010 as part of the DairyMan project is summarised in figure 1 (right).

Detailed energy audits were carried out on these farms from May to October 2010 to quantify the electricity consumption attributed to the dairy and milking operations. There was a large variety within the group in terms of herd size (46 to 170 cows) but the average herd size was 106. Milking parlour size varied from eight units to 20, with contrasting levels of automation and management practices. These variations inevitably led to a wide range energy cost per litre, from 0.23c/l to 0.76c/l produced. These costs are exclusive of taxes and standing charges.

If your farm's energy costs are towards the high end of the scale then it is certainly worth investigating further.

Milk cooling is the biggest consumer of energy and it is also an area where the biggest efficiency gains can be made. Effective plate cooling relies on adequate supplies of cold water. Water temperature can vary from 7°C to 14°C depending on the time of year and the depth of the supply. Effective plate cooling can be defined as cooling milk to within 3°C of incoming water temperature.

The recommended ratio of milk to water in the plate cooler is 1:2. This is rarely achieved at farm level due to poor water infrastructure or unsuitable milk pumps. Sub-standard plate cooling means that the bulk tank will consume more electricity. Tackling this area can save 30pc in cooling costs.

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Water heating costs can spiral out of control if the system is not set up correctly. Electrical water heating is the most common system on Irish farms. The cost of heating 100 litres of water can jump from €1 to €2.03 if night-rate electricity is not installed.

It is common for water heaters to become out of sync with night-rate hours, which are 11pm to 8am during winter and midnight to 9am in summer. Time clocks should be checked regularly. Treating water for hardness and insulating hot water tanks and pipes are essential measures for improving the efficiency of water heating systems.

Vacuum pumps are another big cost. However, there are technologies available to reduce their running costs. Most milking machine manufacturers offer variable speed vacuum pumps as an extra, which can save 60pc on electricity consumed by the pump's motors. Savings for this particular modification are more convincing for large, modern milking machines (greater than 16 units) than for older existing ones.

The benefits of reducing electricity consumption are two-fold. Reducing milk production cost is an obvious benefit but also 531g of CO2 are produced for every kWh of electricity used. Hence reducing electricity consumption will also reduce the industry's carbon footprint.

John Upton and Michael Murphy work with Teagasc at the Moorepark Animal and Grassland Research and Innovation Centre

Indo Farming