Reducing dairy electricity costs

John and Anna Booth from Rhual Dairy, along with NFU Energy’s Jon Swain and Jonathan Sandercock, explore the basic principles of good energy efficiency and the practicalities of different strategies to improve your energy efficiency.

Energy insight at Rhual

Electricity usage has always been high at Rhual Dairy. The average cost is of energy is 0.8ppl and annual electricity cost is £20,000.

Two years ago they installed 16kW solar panels. These have generated approx. 14,000kW since installation – only about half what it should have.

Their grid electricity usage has gone up since 2017, even with solar panels – was 344 kWh in 2017 and 367 kWh in 2020.

The farm use solar thermal panels to heat water and use an ice builder tank with 4,000 litre capacity. They use bore hole water for the plate cooler and a 2 stage plate cooler – flow rate 1:1 litre of water:milk.

They want to lower electricity usage on farm – want to reduce costs without expenditure first, then look at what equipment needs upgrading to reduce costs further.

The farm is taking steps in the right direction but have had a not so positive experience with renewable energy so far.

Steps to reducing energy costs

Buying better – when it’s cheaper

• Traditionally dairy farms benefitted from E7 type tariff, but consider:
  • Consumption pattern
  • Changes in electricity cost
• Rhual Dairy have night rate usage of 33%
• Single rate equivalent is(daily cost/units used = £55.70/367 = 15.2p/kWh

Load matching/shifting

• Don’t forget your time-switches – turn things on and off depending on period they are programmed for
• Check time-switches regularly to ensure correct operating hours

Renewable energy

Maximising energy production to suit usage profile is key

• Wind power – small scale wind turbines may start to make a comeback if planning restrictions relax
• Hydro (specific to Wales/Scotland) – constant energy generation, great if the install is reasonably priced
• Solar (PV and Thermal) – get the best payback when matched to daytime load profile
• Biomass – used best for heating water in conjunction with other heat uses around the farm
• Heat pump – may become more popular going forwards if unable to recover heat from compressors

Energy efficiency is important, as money spent saving energy will payback faster than most renewable energy systems, and also immediately reduce carbon emissions.

Recommendations for Rhual Dairy

Current compressors at Rhual Dairy are 35 years old. Currently struggle to recharge ice builder between milkings in summer. Scroll compressors are an ideal upgrade path:

• More efficient than screw/reciprocating varieties in the 5-10kW range
• Reliable and quiet
• Bulk tank DX system will run less

Heat recovery can provide the majority of your hot water needs. Rhual Dairy can still take advantage of heat recovery: 

• Saving up to £2800 per year
• Financial payback within 5-6 years
• Equipment should last 10+ years if well maintained

 Potential pump savings:

• Recently installed two Fullwood Q4 pumps with approx. running cost of £2,500 per year
• Some farmers see up to 50% energy savings with variable speed drive (VSD) installed
• Cost saving of up to £1264 per year
• Payback in as little as 3 years

Estimated benefits for Rhual Dairy

Rhual had a £20,000 annual electricity bill in 2020. Three sololutions suggested:

1. Heat recovery
2. Variable speed drives on pumps
3. New higher efficiency compressors

There is Potential for £5,400 annual saving along with 9300 kg CO₂/year. The next step is to get firm quotes to assess payback period.